CENTRE FOR AGRICULTURAL RESEARCH IN SURINAM
CELOS, P.O. Box 1914, Paramaribo, Surinam
C O N T E N T S
Scientific staff 4
9. Hand tools in agriculture 23
10. Hydrology 25
12. Plant breeding 30
14. Silviculture 35
16. Soil fertility and plant nutrition 37
17. Tillage 39
Visiting staff members
DR. 1R. J .H.A. BOERBOOM, Silviculturist** (Dept. of Forest Management, Forest Mensuration, and Silviculture and Forest Protection in the Tropics, Agric. Univ. Wageningen)
IR. N.R. DE GRAAF, Silviculturist* (Dept. of Forest Management, Forest Men­ suration, and Silviculture and Forest Protection in the Tropics, Agric. Univ. Wageningen)
IR. H.J. HOEFMAN, Agricultural Economist** (Dept. of Agricultural Economics of the Tropics and Subtropics, Agric. Univ. Wageningen)
IR. C B . HOUTMAN, Agricultural Economist* (Dept. of Agricultural Economics of the Tropics and Subtropics, Agric. Univ. Wageningen)
IR. P.J. HUMMELEN, Entomologist (Dept. of Entomology, Agric. Univ. Wage­ ningen)
DR. IR. B. H. JANSSEN, Soil Scientist* (Dept. of Soils and Fertilizers, Agric: Univ. Wageningen)
IR. R.W.R. KOOPMANS P H . D . , Hydrologist (Dept. of Land Drainage and Land Improvement, Agric. Univ. Wageningen)
IR. J.K. KOUWENHOVEN, Agricultural Engineer** (Dept. of Agricultural Engineer­ ing, Agric. Univ. Wageningen)
DR. IR. G. A.M: VAN MARREWIJK, Plant Breeder (Dept. of Plant Breeding, Agric. Univ. Wageningen)
IR. T. VAN DER SAR, Agricultural Engineer* (Dept. of Agricultural Engineering, Agric. Univ. Wageningen)
DR. G. STARITSKY, Botanist** (Dept. of Tropical Crops, Agric. Univ. Wageningen) IR. F.J. STAUDT, Forest Engineer (Dept. of Forest Utilization, Forest Policy and
Tropical Forest History, Agric. Univ. Wageningen) DR. IR. J.F. WIENK, Agronomist (Dept. of Tropical Crops, Agric. Univ. Wage­
ningen)
1. DIRECTOR'S REPORT
1.1. GENERAL
Due to a revaluation of opinions and the rapidly increasing number of students en­ rolled in the State Agricultural University (Wageningen, the Netherlands) less scientific staff than expected could be seconded to CELOS. As a result, during the year under review the further expansion of the Centre proceeded not as fast as had been planned.
In 1971 the aggregate number of months the various scientists worked at CELOS increased from 128 in 1970 to 139. The corresponding student figure was 101, versus 99 in 1970.
Work in several new disciplines was started. In some others it was closed or had to be interrupted because of the departure of the scientists concerned without their being replaced in time.
As a part of its efforts to put into use Surinam's almost uninhabited interior the Government instituted an organization responsible for the establishment and main­ tenance of experimental gardens in that region. The Centre was invited to participate in the reconnoitring research to be carried out at those stations. Preparations were made to tackle this new line of work in 1972.
1.2. SCIENTIFIC STAFF
Dr. G. Staritsky, botanist, returned to the Netherlands on 12 May, and has not yet been replaced.
Ir. H.J. Hoefman, agricultural economist, completed the field work of his study on the contribution of agriculture in the Nickerie distria (West Surinam) to the national and regional economy, and left Surinam on 26 May to resume his duties in Wageningen. His successor, Ir. C.B. Houtman, arrived on 19 February:
Dr. Ir. J.H.A. Boerboom, silviculturist, who started the Centre's research on forest ecology and silviculture, returned to the Netherlands on 30 June. He deputed his task to Ir. N.R. de Graaf who arrived in Surinam on 19 January.
Ir. J. K. Kouwenhoven, agricultural engineer, left the country for Wageningen on 8 October, after transferring his duties to Ir. T. van der Sar, in Surinam since 9 Fe­ bruary.
Dr. Ir. B.H. Janssen joined CELOS as a soil scientist on 26 March. Ir. E. Bessems, who in the years 1969/70 at CELOS investigated nitrogen fixation
in the phyllosphere of grasses spent the months June and July at the Centre for some additional research.
1.3. STUDENTS
Twenty-three students of the Agricultural University were attached to the Centre a? against 22 in 1970. After conclusion of their period of practical work six of them
carried out research projects for their main subject, viz. crop production, plant breed­ ing, hydrology, water purification or nature conservation. For many other students, like in previous years, posts were found in government services and private enterprises.
1.4. LAND AND BUILDINGS
During the year the second unit of the main building was completed by adding to the part constructed in 1967/68 two office and laboratory wings and a central section housing common facilities.
One of the greenhouses built in 1969 had a roof of polyester panes. Unfortunately the material turned out to be defective, resulting in a rapid decline of light trans­ mission. For that reason the polyester was replaced by hammered glass.
1.5. REVIEW OF RESEARCH
In the field of crop botany experiments were carried out to study the effect of spacing on production and distribution of dry matter in food crops, this time grain sorghum and cowpea. In the former also the effect of spacing on inflorescence ini­ tiation and differentiation as well as panicle size was investigated. A growth analytical comparison of IR 8 and the new Surinam rice variety Acorni showed a more rapid development of IR 8 during the early stages, but eventually Acorni reached a higher total dry weight and a higher grain yield.
Crop production research was limited to several comparative yield trials with sweet potato, cowpea and groundnut.
Entomological research remained focussed on the two major rice borers, Diatraea saccharalis and Rupela albinella. Life history studies of both species were continued with the main purpose of achieving a better insight in the plagues' development throughout the year. Emphasis was also on the collection, identification and study of their indigenous parasites and predators.
In Surinam, like in many other developing countries, the production and marketing structure of vegetables and fruit is a rather confusing affair. In an attempt to make the production side more transparent a farm management study was started cover­ ing 150 farms of various sizes and involving frequent on the spot collection of all relevant input and output data.
In addition to the succession studies in the lowland rain forest already in progress, forming the body of forest ecology research, an investigation into the natural propaga­ tion of Cecropia spp. was undertaken. Evidence was obtained that seeds of these species, being very typical for the secondary vegetation following clearing of the original high forest, may survive for a prolonged period in the forest soil.
In forest exploitation research emphasis was on work physiological studies. Various types of measuring equipment were tested to find suitable methods of determining the physical effort involved in tree felling with axes and hand and power saws.
Research in the field of genetics and cytogenetics was again focussed on the sex mechanism in pawpaw and the genetical basis of some seed coat characteristics in cowpea. Definite conclusions cannot yet be drawn.
It is no exception that in Surinam hand tools, though being indispensable on any farm irrespective of its degree of mechanization, do not receive the attention they deserve. To make up for this a comparative study was started to determine for various types and models of tools the durability, the quality and quantity of the work done
and the physical effort involved in using them. First tested were mowing and weed­ ing tools.
Hydrology research was more diverse than in preceding years. Rainfall measure­ ments at different levels over the ground failed to demonstrate differences under the local climatic conditions. The time consuming installation of a weighable lysimeter was nearing completion. An experiment concerned with the possibilities of subsurface drainage in a heavy clay soil produced the first results. Last but not least a water budget study of the CELOS-polder was undertaken.
In support of the above mentioned management study on farms producing veget­ ables and fruit, investigations were started into their marketing and consumption. The former include direct observations on the central market of Paramaribo and talks with traders, the latter a study of consumer behaviour in relation to supply and prices.
In plant breeding research the studies of fruit setting in sweet potato as affected by incompatibility and sterility and of cytoplasmic male sterility restoration in sorghum were continued. Breeding work to arrive at synthetic varieties of maize made good progress.
Like in the year before progress of the multidisciplinary research project on content and quality of protein in major tropical food crops was hampered by difficulties met in having the numerous samples analysed. To make up leeway in the laboratory the field work was slowed down.
Studies on the natural regeneration of worked-out areas of the lowland high forest under different tending regimes were continued. Though a remarkable decrease in average girth increment was noted, presumably as a result of severe drought in the second half of 1969, this did not eclipse the marked reaction of the vegetation to differences in tending regime. Other silvicultural work included new studies of the root system of Caribbean pine.
Soil science and plant nutrition research is a new topic in the Centre's programme. Several experiments concerned with laboratory procedures were carried out. In addi­ tion work was started to test the suitability of a new pot experiment technique as a method for quick identification of the nutrient status of soils in areas not yet well known.
In the year under review upland rice and Croialaria sp. (long wet season) followed by maize and soyabeans (long dry season) were grown in the long-term field trial started in 1970 to study the effect of tillage and non-tillage on a heavy clay soil under permanent cropping. In addition to this experiment a similar trial was begun on a light sandy soil in the savannah zone of Surinam.
Wood technology research remained focussed on specific gravity and moisture con­ tent in different sections of the stems of standing Caribbean pine.
16. CONTACTS
The large number of authorities and scientists visiting the Centre included Dr. J. Sedney and Dr. Ir. F. Essed, the Surinam prime-minister and minister of natural resources respectively, Dr. A. H. Boerma, director-general of the FAO, Dr. T. S. B. Aribisala, director of the agricultural services division of the same organization, Ir. P. van der Schans, director of agricultural education in the Netherlands, Ir. G. P. Tiggelman, president of the International Agricultural Centre at Wageningen (the Netherlands), and Ing. R. Canet Pellicier, director of the Rice Research Station of the University of Havana (Cuba).
Dr. Boerboom was again a visiting lecturer to the Forestry Faculty of the Andes University (Mérida, Venezuela), this year from 26 January to 3 March. Dr. Wienk attended the 'conference on the intensive management and use of forage crops in the tropics and their utilization by ruminants' held in Guadeloupe during the last week of May.
CELOS was host to the scientific sessions of the 'meeting of experts on the mechanization of rice production and processing', an international conference held from 27 September to 2 October and organized by Surinam, the Netherlands and FAO.
1.7. PUBLICATIONS AND REPORTS
The following CELOS Bulletins were published : 13. Report for the year 1970 of the Centre for Agricultural Research in Surinam
(English; Portuguese and Spanish summaries). 14. VAN MARREWIJK, G.A. M. Algemene aspecten van de veredeling van eenjarige
tropische gewassen (Dutch ; English summary). 15. RUINARD, J. Nature and assessment of losses caused by sugarcane borers (English ;
French summary). Like in previous years mimeographed "CELOS Quarterly Reports" and "CELOS
Reports", both in Dutch, were issued. The latter comprised the numbers 44 to 60 and dealt with root rot of Caribbean pine, various siivicultural and forest ecological topics, investigations in the field of forest exploitation and wood technology, miscellaneous studies on the rice borers Diatraea sacchardtt and Rufiela dbmella, growth analytical work in sorghum and cowpea, a comparison of several tillage and zero-tillage systems, soil drainage by means of plastic tubing and other hydrological studies, sterility and incompatibility research in sweet potato, inheritance of some seed coat characteristics in cowpea, and the contribution of agriculture ia the Nickerie district to the regional and national economy.
1.8. ACKNOWLEDGEMENTS
We are gready indebted to Dr. José H. da Costa Ferreira for translating the sum­ mary of this annual report into Portuguese.
2. CROP BOTANY
2.1. PRODUCTION AND DISTRIBUTION OF DRY MATTER IN Sorghum bicolor (L) MOENCH cv. MARTIN AS AFFECTED BY SPACING (70/17)
The effect of spacing on the production and distribution of dry matter in the semi- dwarf sorghum cultivar Martin was studied by regular sampling of a field trial in which three spacings were compared, viz. 20 x 20, 30 x 30 and 40 x 40 cm. The treatments were arranged in a randomized block experiment with four replicates. Samples were taken in the period 39-97 days after sowing at roughly weekly inter­ vals, and consisted of 4 x 12 plants per spacing. The final harvest took place 108 days from sowing. The trial was planted at the onset of the short rains. Weather condi­ tions appeared most unfavourable for sorghum. Over 730 mm of rain were recorded during the growing period of which 320 mm fell during the first 40 days. As a result crop growth was adversely affected.
At the time of the first sampling there were no clear differences in total dry weight per plant between the three spacings. Total dry weight in the period 39-81 days after sowing increased almost linearly. Straight lines were fitted to the treatment means using the method of least squares. Regression coefficients for the 20, 30 and 40 cm spacing were 0.584 ± 0.028, 1.006 dt 0.050 and 1.023 ± 0.061 respectively, cor­ responding with crop growth rates of 146, 112 and 64 kg/ha per day. During the entire growing period differences in dry weight per plant between the widest two spacings were small and not significant.
Maximum LAI values, recorded 53-57 days after sowing, i.e. before heading, were 3.54, 1.97 and 0.98 for the 20, 30 and 40 cm spacing respectively. Leaf area per plant rapidly decreased thereafter, the decrease being virtually linear at all spacings.
Net assimilation rates were calculated by using the regression equations for total dry weight and leaf area per plant. After heading the rates increased with decreasing leaf area, the increase being highest at the closest spacing. The wider the spacing the higher the net assimilation rate.
Panicle weights at the final harvest were 47.6, 81.9 and 89.3 g/plant for the 20, 30 and 40 cm spacing respectively. The differences could be entirely attributed to number of grains per panicle; 1000-grain weight was not affected. Final yields were 2.98, 2.26 and 1.40 ± 0.29 tons/ha on a basis of air-dry weight.
2.2. INFLORESCENCE INITIATION, INFLORESCENCE DIFFERENTIATION AND PANICLE SIZE IN Sorghum bicolor (L) MOENCH cv. MARTIN AS AFFECTED BY SPACING (71/6)
In spacing experiments with sorghum normally the size of the panicle is negatively correlated with plant density suggesting inter-plant competition at early growth stages. To investigate the effect of light on inflorescence initiation and differentiation, ex­ cluding possible competition for water and nutrients, a pot experiment was conducted in which the spacings 15 x 15 cm and 30 x 30 cm were compared in a randomized
block design with four replicates keeping pot size the same for both treatments. Plots were sampled daily for a period of 10 days starting 19 days from sowing, the fre­ quency of sampling being reduced to once every two days thereafter. Each sample consisted of a total of 12 plants which were examined microscopically for inflo­ rescence initiation and differentiation. Furthermore dry weight and leaf area were determined.
Parallel to the pot experiment a field trial was run in which the effect of the two spacings was investigated on the amount of sterile spikelets and on the size of the panicle. The field experiment, which comprised eight replicates, was planted towards the end of January, i.e. during the short rains.
At the first sampling of the pot experiment all plants were still completely vegeta­ tive. Differences in dry weight and leaf area did not occur until 30 days from sowing, when the LAI had reached values of 1.00 and 0.24 for the 15 and 30 cm spacing respectively; inflorescence initiation had taken place a few days before. Dry weight and leaf area curves for both spacings clearly diverted thereafter, the growth rate of the 30-cm spaced plants being higher than that of the 15 cm ones.
Data collected on the size of the inflorescence primordia have been insufficiently processed to be able to decide as to the exact stage at which the inter-plant compe­ tition exerted its influence on the development of the young panicle.
Due to adverse weather conditions plant growth in the field trial left much to be desired. Nevertheless, at heading the number of sterile spikelets appeared much higher at the narrow spacing than at the wide one. There was also a marked difference in total plant weight. At ripeness relatively more dry matter appeared to have been stored in the panicle at 30 x 30 cm than at 15 x 15 cm. Differences in panicle weight were found to be entirely due to differences in grain number ; the heads of plants at 30 x 30 cm contained over three times the number of grains of those at 15 x 15 cm; 1000-grain weight had not been affected.
2.3. A GROWTH ANALYTICAL COMPARISON OF THE RICE CULTIVARS IR 8 AND ACORNI (71/7)
The promising Surinam rice cultivar Acorni was compared with the cultivar IR 8 in terms of production and distribution of dry matter. The study comprised a pot experiment to compare the growth during the first 30 days and a field trial for the remainder of the growth cycle.
The pot experiment was sampled every three days starting three days after sowing. Sowing took place with seeds that had been soaked for 48 hours. The first five samples comprised 250 seedlings per cultivar, this number being reduced to 50 in the period thereafter.
The field trial was of the randomized block design with six replicates. Plants were raised in a nursery for a period of 25 days before being transplanted to the field at a spacing of 20 x 20 cm, one plant per hill. Sampling was done at weekly intervals starting 11 days after transplanting. The last samples were taken 90 days after trans­ planting for Acorni and 97 days for IR 8. The final harvest took place 9 respectively 14 days later.
During the first two weeks total dry weight in the pot experiment was greater for Acorni than for IR 8, the difference being due to the larger grains, which were included in the plant weight. After three weeks plants of IR 8 were heavier and had more leaves and stems than those of Acorni. Total dry weight of IR 8 plants increased
10
more or less linearly with age. The rate of increase in dry weight of Acorni descreased with age so that at the end of the pot experiment the plants weighed less than half those of IR 8. Also its number of leaves and stems was 50 percent less. Plant height was not affected.
At the first sampling of the field trial plants of IR 8 were already heavier than those of Acorni. The former also had more leaves and more stems, a difference that was maintained during the entire experiment. The difference in plant weight was in faveur of IR 8 up to 113 days from sowing. Total dry weight of Acorni increased virtually linearly up to the last sampling. That of IR 8, however, increased very little after 92 days so that Acorni eventually reached a higher total dry weight. At the last sampling Acorni plants weighed 46.6 g as against 37.8 g for IR 8.
Leaf number reached a maximum 78 days after sowing when 77 leaves per plant were recorded for IR 8 and 49 for Acorni. Leaf number decreased very rapidly there­ after, the rate of decrease being largest for IR 8. Maximum LAI values were 6.5 for IR 8 and 4.5 for Acorni. At the last sampling the LAI had dropped to 2.8 and 2.6 respectively.
Relative light intensities measured below the crop showed that the reduction in light intensity below IR 8 was 40-50% more than that below Acorni.
Heading in Acorni was observed 85 days from sowing, i.e. 5 days earlier than in IR 8. Panicle weight was first determined 92 days from sowing. It increased linearly for both cultivars during the next two weeks. For Acorni the increase in panicle weight then remained constant up to the last sampling. For IR 8 the rate of increase clearly decreased so that panicles of IR 8 eventually weighed least, i.e. 16.6 as against 19.9 g. Though not statistically different the grain yield at 12% moisture content was higher for Acorni (4.80 tons/ha) than for IR 8 (4.06 tons/ha).
2 4. PRODUCTION AND DISTRIBUTION OF DRY MATTER IN THE COWPEA (Vigna unguku- lata (L.) WALP.) CULTIVARS AFRICAN RED AND PI 221731 AS AFFECTED BY SPACING (71/17)
Two morphologically distinct cowpea cultivars, African Red (AR) and PI 221731 (PI), were compared in terms of production and distribution of dry matter at different spacings, by regular sampling of a 3 x 2 split-plot experiment with four replicates planted at the end of the long rains. Spacings were 20 x 20, 30 x 30 and 40 x 40 cm. Samples were taken from 27 days after sowing onwards until pods were dead-ripe, and consisted of 12 plants per sub-plot. The frequency of sampling was twice a week in the period 27-55 days after sowing, the interval between samplings increasing to 5 or 7 days thereafter. Entire plants were harvested. Rainfall registered during the crop's growing period amounted to 275 mm.
In the period 27-55 days after sowing total dry weight of both cultivars at all spacings increased virtually linearly. Straight lines fitted to the treatment means yielded regression coefficients for AR of 0.649 ± 0.046, 1.397 ± 0.063 and 1.967 ± 0.070 at the 20, 30 and 40 cm spacing respectively, corresponding with crop growth rates of 162, 155 and 123 kg/ha per day. For PI the regression coefficients were 0.626 ± 0.027, 1.380 ± 0.049 and 1.943 ± 0.058, and the crop growth rates 156, 153 and 121 kg/ha per day. In the period 27-55 days from sowing there was no signi­ ficant difference in total dry weight between cultivars at comparable spacings.
At the first sampling there were no differences in LAI between cultivars at com­ parable spacings. In AR leaf area per plant increased linearly up to 48 days from
11
sowing when maximum LAI values were reached of 6.24, 5.34, and 4.02 for the 20, 30 and 40 cm spacing respectively. Leaf area in PI increased much more slowly, the rate of increase decreasing with age. Maximum LAI values recorded in this cultivar were 3.04, 2.33 and 1.76 respectively, which were reached in the period 45-52 days from sowing. Once the maximum was reached LAI decreased more rapidly for AR than for PI, the rate of decrease in the former being higher with closer spacing.
Nearly all sample plants of AR flowered 45 days from sowing, i.e. one week later than for PI. Spacing had no effect.
Pod dry weight in the period 48-60 days from sowing increased more or less lin­ early, the rate of increase varying little between cultivars. Pod weight changed little thereafter, the changes being larger with wider spacing. Pod yields for AR were 2.75, 2.31 and 2.37 tons/ha dry weight for the 20, 30 and 40 cm spacing respectively. For PI these figures were 2.62, 2.40 and 2.32. Spacing had no effect on 1000-grain weight.
Net assimilation rates for AR were calculated using the regression equations for total dry weight and leaf area per plant. Because of the non-linearity of leaf area curves this was not possible for PI. However the much lower LAI values for this cultivar suggest a higher NAR. In AR the NAR decreased with age, the decrease be­ coming less as the crop became older. The wider the spacing the higher the net assi­ milation rate.
12
3. CROP PRODUCTION
3.1. COMPARATIVE YIELD TRIALS WITH SWEET POTATO, Ipomoea batatas L (LAM.)
(70/26; 71/3)
To obtain an idea of the yielding capacity of sweet potato under the conditions of the Surinam coastal area, 12 clones were compared in a randomized block design with three replications. Half of the plots were harvested 4Vi months after planting, the ether half one month afterwards. Each plot consisted of 54 plants spaced 30 x 100 cm, of which 26 served as guard plants. The results are presented in Table 1.
Table 1 - Average tuber yields (fresh weight ; ton/ha) of 12 sweet potato clones, har­ vested 4Vi or 5 Vi months after planting. Clones arranged in order of yield at the first harvesting date. The number at second harvest in brackets
months months
AVi
">Vi
(3) (2) (6) (1) (8) (5)
Jersey Orange Genjem 1 Butikatoka Blauwkop Willemsrank Egeida
m ±1.08 4.98 4.13 1.21 0.50 0.18 0.10
5VS
(7) (4)
(12) (9)
CV 41.9 77.5
Four clones amongst which the two local ones Blauwkop and Willemsrank produced very little at both harvesting dates. Of the best four producers at the first harvest three again ranked high one month later. With the exception of Genjem 1 and 2 all clones were most productive at the first harvest. This may have been caused by the very wet conditions between first and second harvest, bringing about decay of the tubers.
The five clones that appeared best in the above experiment at 4Vi months after planting were compared in a further trial planted during the short rains of 1971. To reduce intra-block variation the clones were arranged in a balanced incomplete block design with six replicates. The trial was planted on cambered beds of about 5 m wide. Harvesting took place 5 Vi months from planting, i.e. towards the end of the long rains.
As may be seen from Table 2 yields were extremely low. Most of the larger tubers had rotten away and some plants had no tubers at all. Judging from the yield differences
13
between record and guard plaints, the latter of which were mostly growing along the edges of the beds, excessive water in combination with the heavy soil may be res­ ponsible for the poor performance of the crop.
Tabel 2 - Adjusted mean yields (kg/ha fresh weight) of five sweet potato clones 5Vi months from planting
clone
record plants
± 54 1752 1536 1524 1103 800
3.2. COMPARATIVE YIELD TRIALS WITH COWPEA, Vigna ungukulata (L) WALP. (71/5 ; 71/16)
A number of morphologically distinct cowpea cultivars differing in characteristics such as type of branching, plant height and leaf size!, were compared in terms of yields. It was hoped that some of these attributes could be correlated with yielding ability and that types might be selected for further crop botanical research.
The first trial (71/5) was planted at the end of the short rains on a sandy soil. Six cultivars were compared in a randomized block experiment with six replicates. They comprised Capucijner 6101 of local origin, I.N. 593, Kwarra and Yebba from Nigeria, Blackeye 8152 from the U.S.A. and the South African PI 221731. Because of unfavourable weather conditions soon after planting, emergence in three replicates was extremely poor. They were subsequently written off. The trial was harvested within 70 days from sowing.
In the second trial (71/16) the three Nigerian cultivars were compared with African Red and Blackeye, both of local origin. The trial was of the balanced incomplete block design type, and was planted at the end of the long rains on a heavy loam soil ; there were six replicates. The trial was harvested within 66 days from sowing.
The yields obtained in the two trials are presented in Table 3. Generally yields were not high, as was expected from the moderate vegetative growth. In the first trial yield differences between cultivars were small, with the exception of PI 221731. This cul- tivar is characterized by terminal inflorescences and hence a limited vegetative growth. A slow early development in this cultivar results in a small plant with small yields, as was the case in the present trial (cf. section 2.4). In the second trial yields of the Nigerian cultivars were more or less the same as in the first. African Red produced little, the crop's stand leaving much to be desired. Again vegetative growth Was not abundant in this trial which was planted only a few days before 71/17 in which a much better vegetative development and far higher yields were obtained (cf. section 2.4).
The differences in morphological characteristics were not clearly correlated with yield differences.
14
Table 3 - Pod yields (tons/ha; 12% moisture content) of a number of cowpea cultivars as obtained in two different trials
cultivar
Yebba Kwarra I.N. 593 Blackeye 8152 Capucijner 6106 PI 221731 African Red Blackeye
trial 71/5
trial 71/16
1.05 1.27
3.3. A COMPARATIVE YIELD TRIAL WITH GROUNDNUT, Arachis bypogaea L, (71/15)
A comparative groundnut yield trial was conducted during the long dry season. The cultivars were Argentine, Natal Common and Spanish 205 introduced from Nigeria, and Matjan and 68056 of local origin. With the exception of the latter, a Valencia type, all cultivars belong to the Spanish group; they mature in about 100 days. The trial was of the balanced incomplete block design type with six replicates. The yields and some yield components are presented in Table 4.
Matjan clearly outyie'ded all other cultivars, both in terms of pod and seed yield. 68056 was the lowest producer, though the differences with the other three cultivars were not statistically significant. The three Nigerian cultivars differed little in yield, 1000-grain weight and number of seeds per ha. Both Matjan and 68056 produced considerably less seeds per ha than the Nigerian cultivars but in Matjan this was more than offset by the size of the seeds. This was not the case for 68056.
Table 4 - Pod and seed yields (tons/ha; 12% moisture content), 1000-grain weight (g) and estimated numbers of seeds per ha for five groundnut cultivars
Argentine
655
661
629
491
488
15
4.1. THE RELATIONSHIP BETWEEN RICE BORERS AND THEIR PARASITES (68/1)
The sampling of lowland rice plots at ŒLOS as mentioned in the previous annual report, was continued in the same way.
The percentage of infestation by Diatraea saccbaralis was nearly always below 1, with 5-35% of the borers being parasitized. For Rupela albinella these percentages were 2-7 and 20-40 respectively. The percentage of infestation by D. saccbaralis was lower, but that by R. albinella higher than the year before. As in 1970 a very clear peak in infestation was observed after the area's rice crop had been harvested. It occurred one month later than last year, the harvesting of the rice also being later.
Infestation by D. saccbaralis nearly always takes place when the rice plants are two months old; R. albinella starts one month later. One day old first-stage larvae of R. albinella are already found in the internodes, suggesting that this species requires a stem cavity for its development.
After the rice on the small-holders' plots in the neighbourhood of CELOS has been harvested, the borers appear to concentrate on the CELOS-fields there being no other rice left in the area. From that moment onwards the plants were very carefully examined to find also the small borer larvae. About 20% of D. saccbaralis larvae found were dead; for R. albinella this figure was about 15. Most of the pupae of D. saccbaralis were dead or nearly so when found, whereas for R. albinella this was about 25%.
Tricbogramma sp. and Telonomus sp. were reared from eggs of D. saccbaralis. Other parasites found were the same as those mentioned in the reports of previous years.
In 1971 weekly samples were taken in four lowland rice plots of small-holders. One plot showed some, the others virtually no infestation. However, this year rice planting took place very late.
4.2. THE BIOLOGY OF THE BORERS' PARASITES (70/32)
Agathis stigmaterus, the most important parasite of Diatraea saccbaralis in rice, is now being reared continuously in two ways : (i) First-stage larvae of Diatraea saccbaralis are placed on young potted rice plants
kept in cages. After 6-10 days, when larvae have reached stage L2-L4, a wasp is released into the cage. After a further few days the larvae are recovered and placed onto an artificial medium to await the wasps' development.
(ii) The wasp is reared entirely on an artificial medium. The larvae to be parasitized are 6-10 days old and are kept in Erlenmeyer flasks. The wasps are placed in the flasks where they parasitize the larvae through cavities the latter have eaten in the medium.
It takes 30-40 days for the wasps to develop. The maximum number of parasite larvae hitherto found in one borer is three.
16
<;
Dr. J. H. E. ferrier. Governor of Surinam, opens the 'meeting of experts on the mechanization of rice production and processing'.
Letting down the lysimeter tank into the cellar.
4 3. PREDATORS OF RICE BORERS (71/12)
Ants are important predators of rice borers. Although a number of species occur in lowland rice, Varatrechina {Nylanderiu) sp. is by far the most important one. It rarely if ever feeds on eggs of Duttraea saccbaralis but particularly eats the just emerged larvae. These ants make nests of clay and organic material between the stems of a rice plant just above the water level. There are small and large nests. The smaller ones, which are usually located between leaf sheath and stem, are made without clay. The larger ones may enclose the lower 10 cm of all stems of a plant hilL The contents of an ant nest may vary widely. If there are many winged ants there are virtually no eggs. The largest number of individuals found in one plant hill consisted of 2079 eggs, 1733 larvae, 834 pupae, 72 winged adults, 787 wingless adults and 7 queens. The average number of adults was 250 per hill. As a rule more than one queen is found per hill; it is not clear whether one has to do with one or more nests.
The maximum number of plant hills containing a nest that was found in lowland rice on the CELOS-fields amounted to 40%. The first nests are built near the dikes, 3-4 weeks after transplanting.
On small-holders' plots a maximum of 12% of the plant hills carried a nest whereas ants were found in up to 50% of the plants. After harvesting nests may be found for a long time in the straw remains.
It is striking that at the end of 1971 no ants were seen in the lowland rice at CELOS, whereas at the end of 1970 they occurred in large numbers.
4.4. THE BIOLOGY OF Rupela albinella (CR.) (70/20)
As rearing of R. albinella is extremely difficult, the number of larval stages was determined by measuring the width of the head capsule of larvae found in the field. Skins with head capsules are seldom encountered because they are eaten immediately upon moulting. An exception to this is the second-stage larva, which does not eat the skin and head capsule of the first-stage one. The first three larval stages can be easily identified. The Li has a head capsule that is 0.19-0.20 mm wide, L2 one of 0.30-0.45 mm and L3 one of 0.45-0.80 mm. As for the stages L4 and L5, these measurements overlap each other so that the width of the head capsule may be anywhere between 0.81 and 1.40 mm. Pupation was found not to take place until the head capsules were at least 0.95 mm wide. These larvae were probably all males.
The mean pupal weight of the female is 140 ± 5 mg, that of the male 63 ± 5 mg. The larva lives in the stem cavity and normally remains during its entire life in
one and the same internode. On!y when it entered the shorter internodes at the base of the stem, it may eat its way into one or two more internodes. Although various larvae may be present in one stem, never two larvae were found together in the same internode. An exception may be encountered among the first-stage larvae, but then only one is alive.
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5. FARM ECONOMICS
5.1. A FARM MANAGEMENT STUDY OF FRUIT AND VEGETABLE FARMS ( 7 1 / 1 3 )
Dependent on ethnical origin, the Surinamese spends 10-20% of the money that goes in food on fruit and vegetables. As compared with other food since 1953 the prices of these commodities have risen by 300-400%.
In order to obtain information on the underlying causes of these price increases a study was started on the production of fruit and vegetables, their marketing and the behaviour of the consumer in relation to these products' prices. This study comprises: (i) a farm management study of the faims producing fruit and vegetables ; (ii) a study of the marketing of vegetables (see section 11); and (iii) a study of the consumers' behaviour (see section 11).
The farm management study was started to gain an insight into : (i) the supply of fruit and vegetables ; among others in relation to season and type
of products; (ii) the important inputs such as land, labour, capital and know-hew ; and (iii) the farmers' reaction to prices, innovations, etc.
A total of 150 farms were selected in a stratified sample, the criterion being the total area under vegetables. A requirement was that most of the produce had to be sold. For the selection the data of the Agricultural Census 1969 were used.
In May of this year the field work was started with an inventory of the selected farms. From the beginning of July onwards data have been collected on labour, cost and yields. To this end the farms were visited three times a week. The work is to be continued until August 1972.
After having been checked and if necessary amended, the inventory forms were coded and sent to Wageningen, The Netherlands, where they have been processed for the electronic computer.
The "daily" forms are being summarized over two-week periods, and the totals coded and also sent to Wageningen for further computing.
In order to obtain some interim information, in February 1972 a first, simple analysis will be made of the commodities of which sufficient data are available. Final pro­ cessing and analysis will take place at the Department of Development Economics of the Agricultural University, Wageningen, The Netherlands, upon termination of the field work.
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6. FOREST ECOLOGY
The 1971 measurings of the forest succession plots (67/1) do not indicate an im­ portant change of vegetation development. The oldest plot, at Blakawatra, which has been described in previous annual reports, still shows the marked difference in vegeta­ tion between imperfectly drained and well-drained soil, i.e. savannah-like vegetation versus low secondary bush.
Some additional permanent plots were staked out for studying forest succession following shifting cultivation (67/3). Another study within the framework of this project, and already mentioned in previous annual reports, resulted amongst others in a classification in five age-classes of the physiognomy of secondary vegetations, to be used for terrestrial observation as well as for interpreting aerial photographs.
The vegetation in the permanent plots for studies of the virgin forest (67/4) was surveyed again. One of the plots (10 x 1 m) used for sampling undergrowth showed a remarkable increase in the number of seedlings established, which was most likely a result of an increase in incident light from openings in the canopy.
Germination tests with seeds of woody species, especially Cecropia (70/21), showed some interesting results. Bimonthly sampling of litter and topsoil from undisturbed forest, determining the viable seeds present by germination tests, showed the presence of large numbers of Cecropia seeds per m2 all the year round. Evidence was obtained that the Cecropia trees in secondary vegetations originate from seeds already present in the soil at the time of clearing the original forest. The investigations will be con­ tinued, and will include in vivo and in vitro tests on seed longevity.
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7. FOREST EXPLOITATION
During 1971 the research in this discipline concerned (i) work studies on, felling large-sized trees with power-chain-saws in the tropical rain forest of Surinam (71/1), (Ü) work physiciological studies (70/15) and tests (70/29), and (iii) measuring tech­ niques (71/11).
To increase efficiency and safety in felling with the power-chain-saw, the presently used techniques were analysed and a process and time study were made of the best gangs.
Work physiological research was restricted to the measuring of work load and the determination of the prescribed breaks during tree felling with axes, hamd and power saws, so as to obtain values for a fair day's work. The ergospirometer after Müller-Franz and the microgasanalyser after Scholander were used for measuring ventilation and oxygen consumption; cardiotachograms were obtained with the aid of a telemetric receiver and recorder.
The tests used to determine the work capacity of men were (i) a modified Harvard- Step-Test, (ii) the Lüngren-Step-Test, and (iii) the Ästrand-Submaximum-Test. Test per­ sons were recruited from amongst forest workers, CELOS gardeners and students.
Successful experiments were carried out with two types of stethoscopes, a normal one and a electronic one, in order to obtain heart rates during step tests and specialized foiest work, such as planting, weeding and thinning with axes. Both stethoscopes appeared to be useless, however, in combination with vibrating machines like power- chain-saws.
20
8.1. THE SEX MECHANISM IN Carica papaya L. (69/2)
In order to obtain information on the genetic background of sex in pawpaw a num­ ber of crosses between male (M), female (F) and three different types of hermaphrodite plants (Hi, H2, H3) had been made in 1969. Thirty-four progenies, comprising the combinations FxM, FxH3> FxH2, FxH^ HixM, HixH3, Hi selfed, H2XM, H2 selfed, H3xM and H3 selfed were selected and planted in the field at the end of the first quarter of 1970. Due to unfavourable weather conditions early growth was bad so chat in most plants flowering did not start until the end of that year. For further details the reader is referred to the annual reports for 1969 and 1970.
From December 1970 until July 1971 weekly observations were made, one to four flowers of each plant being described at each observation. Description included (i) position of the flower in the inflorescence, (ii) tube/lobe ratio of the corolla, (iii) ovary size, and (iv) number and insertion of stamens. Though the gigantic number of data obtained have not been fully analysed yet some remarkable features are already worth mentioning. Female plants showed no changes in sex expression during the observation period : among the several thousands of described flowers from ca. 300 plants only one showed stamens, all others having well-developed ovaries, and nearly free corollas but lacking completely male sex pans. Male flowers were only slightly variable with respect to the tube/lobe ratio. Hermaphrodite plants appeared highly variable for all characters under consideration. Both, the variability between and with­ in families was very striking. Besides, the sex expression of individual plants changed from week to week.
There are strong indications that soil conditions greatly affected sex expression. For instance hermaphrodite plants of progenies from all combination types tended much more to femaleness at wide than at narrow spacing.
Segregation ratios for the combinations FxM, FxH3, FxHi, H2 selfed and H3 selfed did conform to the expected ratios based on the hypothesis of Storey and Horowitz. However, marked deviations from the hypothetical ratios were found for the combina­ tions Hi selfed, HixM, HoxM and to a lesser degree for HixH3. In all these cases the number of hermaphrodite plants obtained surpassed the expected value.
8.2. INHERITANCE OF SOME SEED COAT CHARACTERISTICS IN Vigna ungmculata (L) WALP. (70/12)
The investigations into the inheritance of the seed coat colour and the seed coat pattern were continued. Special attention was paid to the nature of intensity gradations of "Watson", variability in the "Holstein" pattern, and to difference in size of "large eye" and of the concomitant degree of speckling. Besides, the segregation of a new pattern type "dark brown mottled" was analysed.
Progenies resulting from seeds classified as "dark" or "very dark" Watson were uni-
21
formly dark, whereas descendants from "normal", "light" or "very light" Watson se­ gregated into lighter and darker types. At least two intensity genes are thought res­ ponsible for this variation. In a similar way, Holstein parents having more than 50% of the seed coat surface coloured, remained constant for this characteristic ; variegated seeds with large uncoloured areas, however, segregated in several Holstein types. Again the results could not be explained by the action of a single modifying gene.
Even more complicated appears the analysis of the characters "eye" and "speckling". The classification of seeds into "large eye" and "medium eye" was particularly impeded by the differences in seed size. Nevertheless there are strong indications that there are genetical differences between medium eye and large eye. As for speckling it was found that this is highly correlated with eye size. Medium-sized eyes are seldom accompanied by large numbers of speckles; besides the speckles found are generally small. "Dark brown mottled" segregated into the parental type and solid brown, and the new patterns "dotted brown" and "mottled-dotted brown" ; mottling is monogenic dominant over non-mottling. The absence of both Holstein and Watson in the progeny is surprising. An explanation might be that the parents were homozygous for both W and H but heterozygous for the recessive epistatic dotting factors Di-di and I V d i In the first generation upon self ing 1/16 of the progeny will have the homozygous recessive con­ dition dididâdï and therefore be "dotted". Future work will have to prove this.
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9. HORTICULTURAL AND AGRICULTURAL HAND-TOOLS
This research comprises a comparison of traditional and newly introduced hand-tools that can be used in agriculture and horticulture in, Surinam. Basically the performance and the physical work load of the subject of experiment during work and the quality of this work are being compared for different tools. However, because of the simple device for measuring the work load this research can only provide a general impression.
During the long rainy season a comparison was made of the scythe and bush-knife (71/10). The work carried out (by fuil-grown men) was mowing grass vegetations of different ages. In young grass a scythe of 60 cm blade lenght was used, in old grass cne of 35 cm. The latter has a greater solidity and is therefore more suitable to mow the firmer stems of old grass. The bush-knife had a blade length of 54 cm and was used in young as well as old grass.
A 10 m swath was mowed in one run. The quality of the work, especially the stubble length, was about the same for the different tools.
In young grass the scythe appeared to perform better and was less tiring than the bush-knife. In old grass the differences were less marked. It may even be possible that the use of a bush-knife in old grass is preferable to that of a scythe.
In the long dry season a comparison was made of weeding tools in a crop of maize on a heavy sandy clay (71/10, 71/26). The row distance was 90 cm. The following tools were used : a traditional hoe, a long handled hoe, a scuffle hoe and a cultivator. Their measurements and weights are presented in Table 5. Many remainders of the last crop such as stems and roots were in the ground, which had an adverse effect on the results (Table 6).
Due to the many remainders in the soil the use of the scuffle hoe resulted in a rather high work load and small performance. The cultivator was hindered least by these remainders. In spite of the highest work load the number of workpulses per m2
for the cultivator was lowest of all tools. Also the quality of weeding was assessed (Table 7). It seems that with one tool
all types of weed were killed rather well, while another tool only killed broad-leaved weeds. However, more work is required to confirm these differences.
Table 5 - Measurements (cm) and weights (kg) of the various tools
, handle blade working . , t oo ! length width width w e i«h t
traditional hoe long handled hoe scuffle hoe cultivator (5 tines)
100 165 170 170
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Table 6 - Performance and work load of the subjects of experiment during the work with the various tools
tool
work- pulses per m2
31 33 37 44
17.22 18.16 22.68 13.99
32.0 31.0 32.5 32.8
77 77 70 67
•) "Workpulses" are defined as the difference between the number of heart-beats during work and at rest.
Table 7 - Quality of weed control expressed as the percentage of surface covered by weeds and as weed dry weight, 14 days after weeding
quality of weed control traditional hoe
longh. hoe
14 days after weeding
15.8 11.2 14.6
25.9 18.1 25.2
30.8 25.0 30.0
28.3 20.9 31.4
weed dry weight 14 days after weeding (g per m2) 6.6 11.5 15.2 16.3
The overall impression is that the traditional tools in Surinam agriculture (hoe and bush-knife) did not fall short of the expectations and performed very well in com­ parison to the newly introduced ones.
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10.1. MEASURING RAINFALL AT DIFFERENT LEVELS (70/22)
Rainfall measurements in a standard raingauge at 1.50 m above groundlevel are compared with measurements in a selfrecording groundlevelgauge. The latter has been briefly described in the previous annual report (CELOS Bulletins, 13, p. 29).
Only four times out of a total of 44 a difference per decade occurred of more than 1 mm; the decade levels varied from 45.1 tot 144.8 mm. The maximum difference per decade was 3.4 mm, which was observed on a total of 144.8 mm recorded in the standard raingauge. Generally differences per decade were below 2%. Over a period of 12 months in which a total of 1959.7 mm was recorded in the standard raingauges the difference amounted to only 5.0 mm.
Daily totals and decade totals over a period of almost 18 months of registration were statistically compared using a Student-test. In neither case significant differences were found.
From this study it may be concluded that the use of a standard raingauge at 1.50< m above groundlevel, does not lead to systematic inaccuracies when recording rainfall in the coastal area of Surinam.
10.2. THE DETERMINATION OF ÉVAPOTRANSPIRATION WITH A WEIGHABLE LYSIMETER
(70/23)
Except for rice, relatively little its known about the exact magnitude of the évapo­ transpiration of crops in Surinam. A knowledge of the évapotranspiration may be desired in connection with irrigation proposals, water budget studies etc. Lysimeters are the only instruments that can be used to make a direct measurement of the évapo­ transpiration. The weighable lysimeters currently used are weighed on the basis of various principles using different techniques.
At CELOS the hydraulic loadcell technique was chosen on account of its simplicity and, as reports in the literature indicate, its dependability. The lysimeter consists of an inner tank 1.80 m long, 1.50 m wide and 1.30 m deep, made of 6 mm steel plate, with internal strengthening of 4-cm I-beams. This tank fits, with only a few centi­ metres tolerance around, into a cellar with a reinforced concrete floor and walls of which the upper 0.62 m consist of 6 mm steel plate. Both cellar and lysimeter tank are watertight and are provided with drainage facilities. The lysimeter tank will be carefully refilled with the original soil, which consists of approximately 1 m heavy clay overlying fine sand. At the bottom of the tank a sloping concrete floor has been constructed on which a few thin layers of filter sand are placed to facilitate the drain­ age of percolating water. The amounts of run-off and percolating water are collected in reservoirs in which the waterlevel can be determined.
25
The weighing system consists of two interconnected hydraulic loadceils made of nylcn-butylrubberpipe*, an inverted-U-tube type manometer and a third loadcell. All loadceils are filled with water to which some Q1SO4 (0.5%) is added as an algae in­ hibitor. The lysimeter rests by means of two wooden blocks (Greenheart, Tabebuia serratifolia (VAHL) NICHOLSON) on the rubber loadceils. Pressures in the latter, which vary with the weight of the lysimeter, are measured in the manometer. Pressure offset is obtained with the third loadcell on which a constant load is applied by means of a lever. This compensating loadcell is placed in a second underground cellar which is in open connection with the lysimeter cellar. The manometer is placed above gxoundlevel at about 4 m from the lysimeter. Pressure differences are converted to depth of evapo­ ration on the basis of the ratio of total evaporating surface to bearing surface of the wooden blocks.
During the year under review construction proceeded to such a point that the lysi- metertank was placed on the loadceils and that the manometer system could be tested.
10.3. DRAINAGE BY MEANS OF PLASTIC TUBING — AN INVESTIGATION INTO THE POSSI­ BILITIES OF SUBSURFACE DRAINAGE IN THE COASTAL AREA OF SURINAM (70/24)
A drainage experiment was initiated at CELOS in order to investigate the possibili­ ties of subsurface drainage of a heavy clay soil of the Surinam coastal plain.
The construction of the trial field, which has been described earlier (CELOS Bulle­ tins, 13, p. 30), was finished during the year. After the field had been leveled, kudzu (Pueraria fhaseolokles (ROXB.) BENTH.) was sown.
In short it comprises five treatments, arranged in a randomized block design with three replications; each treatment consists of five drainconduits of 50 m long and at 4 m intervals. Discharge measurements were started soon after completion of the trial field and were carried out whenever possible. The rate of outflow of the five indivi­ dual rubes in each plot is determined simultaneously ; this is done by catching the water into calibrated buckets.
On account of high-intensity showers of short duration, which are common in Suri­ nam, the hydrograph of the plots mostly shows a peak very soon, i.e. 15-50 minutes after the discharge starts. The latter commences from 8 to 20 minutes after the be­ ginning of a shower of sufficient intensity and duration. The outflow seldom continues for more than 8 hours after it stops raining. It is therefore essential to start measuring as soon as possible after the beginning of a shower. Often it was not possible to measure the rising limb completely. A recording rainauge (see 10.1) makes it possible to compare the hydrographs with the intensity-duration curve of the rainfall.
The total discharge of each plot can be found by computing the area under the hydrograph and is expressed as a percentage of the precipitation.
So far only a limited number of successful measurements have been obtained. They indicate that tubes without coarse sand envelopes give better results, i.e. a faster res­ ponse than the same kind of tube in sand. Corrugated tubes give somewhat higher discharges than smooth ones ; the percentage discharge varied between a high 80% for corrugated tubes and a low 20% for smooth tubes in sand. At times the discharge of plots without sand envelopes peaked at 6 mm/hr.
* Carlisle Corp., Carlisle Pa. USA, distributed by Watersaver Co. Denver, Colo., USA.
26
10.4. A WATER BUDGET INVESTIGATION AT CELOS (71/9)
The greater pan (15.6 ha) of the CELOS grounds forms a polder which is suited to set up a water budget study. Such a study can be very useful, especially in connection with the lysimeter experiments (see 10.2). Moreover a water balance may yield a better insight into the distribution of rainfall over run-off and infiltration.
The various components to be determined for a water budget are : precipitation, evaporation, discharge, seepage and the change in the amounts of water stored in both soil and open water. Discharge and seepage may be positive or negative, meaning outflux or influx respectively. Negative discharge occurs when water is pumped into the polder for flood or sprinkler irrigation.
The period during which measurements were taken was from June 4 to August 13 ; this was during the wet season. Accordingly 659 mm of rain were registered during this period. By placing a propeller type flowmeter in the outflow pipe of the drainage pump it became possible to measure the (positive) discharge. The amounts of irriga­ tion water were computed from a registration of the running hours of the irrigation pump. Underground flow was estimated from groundwater observations which were carried out regulaily inside and outside the test area. The amounts of water stored in the soil were determined regularly by taking core samples, whereas the storage in open water courses was calculated from waterlevel registrations. As turned out later the moisture sampling had not been carried out with sufficient intensity so that a waterbalance per decade became questionable. Over the whole period, however, the accuracy was satisfactory.
Evaporation was computed by means of the Penman method but for comparison only, since evaporation was considered to be the unknown factor in the balance. The most interesting conclusion that may be drawn from this study is that évapotrans­ piration as computed from the water budget is considerably lower (about 25%) than the évapotranspiration computed according to Penman's method. Over the entire 70- day period the évapotranspiration was found to be approximately 200 mm whereas Penman's method yielded about 270 mm.
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31.1. A MARKETING STUDY OF VEGETABLES ( 7 1 / 24 )
As part of an overall srudy of the production and marketing of fruit and vegetables in Paramaribo and its surroundings (see section 5), an investigation of the marketing structure was initiated in October of the year under review, to obtain information on : (i) the sales and profits of the different kinds of wholesaler (commission-agent,
middlemen etc.) (ii) the sales and profits of the retailers at the capital's Gentral Market ; (iii) the farmer's position in selling his products; and (iv) the extent to which Government is involved in the present structure.
For one month observations were made of and talks held with the directly and in­ directly involved persons at the Central Market during wholesale hours (23.00-08.00 h). The data thus obtained have been checked and rechecked before being processed, after which the work will be repeated to be ab)le to confirm conclusions. At the same time about 50 retailers out of a total of 400 were interviewed during a 2-month period about the prices they paid, the amounts they bought, the time they bought at, and the persons they bought from. Where possible the quality of the products was noted. From these data and from consumer prices collected by the Ministries of Agriculture and Economic Affairs the range of profit margins can be worked out.
As to the farmer's position in selling his products conclusions cannot be drawn until the farm management study has been completed.
To study to what extent Government is involved in the marketing structure reports are being collected and talks held with officials of the above mentioned Ministries.
11.2. AN INVESTIGATION OF THE CONSUMPTION OF FRUIT AND VEGETABLES IN PARAMA­ RIBO AND ITS SURROUNDINGS (71/27)
Since an analysis of the problems of the marketing of fruit and vegetables is not complete without taking into account the consumer an investigation was started into the consumer's behaviour in relation to these commodities.
Only supplementary information was collected. In the years 1968-1969 a fairly thourough budget study has been carried out, the data of which provide most useful information for the investigation referred to. The supplementary data were collected for those population classes that had not been covered by the sample for the budget study.
The investigation was commenced with two classes, viz. the high-income group and the families the head of which was unemployed. Adding these two classes resulted in a coverage of about 96 percent of the people in the population area.
Because of lack of alternative sources like income tax data, the sample for the high- income group was obtained from the telephone directory ; nearly every subscriber has
28
an income of above Sf. 6000 per year. The sample for the group of unemployed was obtained through the employment bureau.
Every month about 24 families in each class are interviewed daily. If the inter­ viewed so wish they can write down the information themselves, the forms being collected twice a week. The questions asked are about prices paid, quantities bought and the places they bought. At the last day of the period of interview the consumer U asked about his income and the size of his family.
To obtain the first sample of 24 families in the "unemployed" group, 69 addresses were needed. Nineteen refused co-operation ; of the remaining 26 either the addresses proved wrong or the people could not co-operate for other reasons.
The sample for the high-income group was obtained by telephoning. Response here was good.
29
12. PLANT BREEDING
12.1. FRUIT SETTING IN SWEET POTATO, Ipomoea batatas (L.) LAM. (69/17)
Investigations concerning the role of sterility and incompatibility mechanisms in reducing fruit setting in sweet potato are in progress since 1969. In the year under review special attention was paid to the compatibility relations between various clones.
12.1.1. FIELD INVESTIGATIONS
A number of new clones entered the incompatibility programme viz. Copperskin Goldrush, Louisiana 3 and Louisiana 5 from the U.S.A., and Pono Rico, Putri Selatan, and Tox Paars from Indonesia. Also some additional material of Genjem 1 and 2 was introduced for comparison with earlier introductions the purity of which was doubtful. In addition some 80 Fi plants came in the field.
About 15,000 pollinations were made, 6,000 of them being intervarietal combinations; the remaining 9,000 were selfings of Fi plants or backcrosses to the parents. Of the parental crossings only ca. 120 fruits, containing 150 seeds, were obtained. Considering the fact that these fruits were derived from 70 parental combinations it will be clear that in most cases percentages of fruit setting were very low. This once more stresses the important role played by sterility factors. The idea as expressed by MARTIN & CABANILLAS (1968)* that once the sterility components have been identified the in­ compatibility might appear to be only an ignorable relic in relation to seed setting, is likely to be true.
Another complicating factor in determining the compatibility relation lies in the weather conditions. Certain combinations that were somewhat compatible at one mo­ ment completely failed to give seed setting some weeks later. Particularly showery weather seemed very unfavourable.
Fruit setting percentages have not yet been computed for the various Fi selfings and backcrosses. But, with the exception of a small number of very productive plants, the results were similar to those of the parental combinations.
In 1971 as well as in 1970 a correlation was found between seed weight and emergence. No emergence occured if seeds weighed less than 10 mg, while values of nearly 100% were found for seeds of 20 mg or more.
The germinative power also appeared to be affected by the maternal parent especial­ ly in the range 10 to 20 mg. Some of the seedlings from light seeds died immediately after emergence.
12.1.2. RELATIONS BETWEEN STYLE AND POLLEN
The study of pollen germination and pollen tube growth using the fluorescence technique, which had to be interrupted at the end of 1969, was continued in the year un-
• MARTIN, F. W. & E. CABANILLAS, 1968. Classification of sweet potato varieties for compatibility and sterility. Proc. Am. Soc. bort. Sei. 93: 502-511.
30
der review. The work completed so far concerns all combinations having one of the clones Djarak, Willemsrank, Blauwkop, Hopi, USA 130, White Star, Butikatoka, Brokopondo, and A 138 as maternal parent Analysis is greatly hindered by the large variation both within and between combinations that occurs in the number of pollen grains sticking to the stigmatic surface. Nevertheless some general conclusions can be drawn : (i) the number of germinating pollen grains seldom surpasses 50%, (ii) the number of pollen tubes penetrating the stylar tissue generally lies between 1 and 10, (iii) the number of tubes reaching the midstyle or even the micropyle four hours after pollination is very sinall. Concerning this point it has to be noted, however, that it often was very difficult to trace the pollen tubes in the stylar tissue nearby the ovary.
12.2. CYTOPLASMIC MALE STERILITY AND FERTILITY RESTORATION IN SORGHUM,
Sorghum bicolor (L) MoENCH (69/23)
As stated in CRT .OS Bulletins, 13, p. 33. a project was started "to trace the response of some widely accepted hybrids and their parents to Surinam conditions, and to ana­ lyse the genetical constitution of the various cultivars for their fertility characteristic".
In the 1970-experiment Martin and CK 60A had been used as the sterile parents, Tx4l4 and Texas 7078 serving as restorer lines for both of them. The segregation ratios obtained (F2 "> 15: 1 ; Bi </> 2 : 1 ) suggested a more complicated inheritance than advanced by MAUNDER & PICKETT (1959)* and Pi & Wuu (1963)*. Since little attention was paid to the degree of fertility, the experiment was repeated in 1971, using 35 progenies of the types (MSxR) selfed, MS x (MSxR), and [MS x (MSxR)] selfed. Each progeny consisted of two rows of about 50 plant hills. As a result of large differences in emergence, the number of plants per family varied from 40 to more than 100. Heads were bagged just before onthesis, evaluated for seed setting 14 days later, and then cut off to stimulate outgrowth of the tillers and side stalks. According to the amount of seeds set, heads were classified as — (no seeds at all), (—) less than 10 seeds per head, ± (less than 20% seed setting), (-|-) (20-70% seed setting), -f- (over 70% seed setting). Of each plant a maximum of eight heads will be evaluated.
Results obtained so far again indicate that more than one chromosomal factor plays a role in the restoration of fertility. In some genotypes an effect of environment on fertility expression was evident: successive heads of the plants concerned changed from partially fertile to sterile and vice versa.
As evaluation is still in progress segregation ratios have not yet been computed.
12.3. BREEDING SYNTHETIC VARIETIES IN MAIZE, Zea mays L (69/24)
In I969 a programme was initiated (i) to develop synthetic varieties as an alter­ native to the production of hybrid varieties and (ii) to compare different breeding methods for obtaining synthetics. Large numbers of introductions have been obtained since and many of them have been scrutinized for their suitability as a component in a synthetic variety.
MAUNDER, A. B. & R. C. PICKETT, 1959. The genetic inheritance of cytoplasmic-genetic male sterility in grain sorghum. Agron. ]., 5 1 : 47-49. Pi, C. P. & K. D. Wuu, 1963. The inheritance of cytoplasmic genetic male sterility in sorghum: Bot. Bull. Acad. Sin., 4 : 15-22.
31
During 1971 two groups of introductions were re-observed and selected, viz. (i) 104 Caribbean composites from the Centra Internacional de Mejoramiento de Maiz y Trigo (CIMMYT), Mexico City, and (ii) 82 inbreds (le) extracted from two Central American composites, that were handed over by the Agricultural Experiment Station, Parama­ ribo. Individual plants were recorded for general performance, number of days to tasseling and silking, plant height, circumference of the stem, ear number, ear length, mid-ear circumference, grain insertion, and weight, colour and shape of the kernels. Tassels and ears were bagged prior to flowering and plants were selfed or crossed within a line or composite.
Average plant height was over 200 cm for nearly all CIMMYT composites; most stems were firm and reached circumference values of 7 cm or more. Though there was a considerable variation in ear and grain characteristics, some general features can be summarized : (i) ears large, thick, and well-filled, (ii) grain insertion often irregular, (iii) grains large, alabaster white or ivory, more or less dent, sometimes shrinking and/or sensitive to bolting. As to ear length and circumference variation appeared to be large. Ear length varied from 10.9 to 21.8 cm, ear circumference from 10.6 to 17.2 cm. The distribution of average ear length and circumference for both CIMMYT composites and Central American inbreds is shown in Table 8.
As may be expected the average values are much smaller for the inbred lines, vary­ ing from 9.3 to 16.3 for ear length and from 90 to 13.4 for ear circumference.
Table 8 - Frequency distribution of average ear length and average ear circumference classes for CIMMYT composites and Central American inbreds
class (cm)
CIMMYT
length
104
composites
circumference
— — — —
— — — — — 82
circumference
— — — — — — — — 71
As found in 1970 the lines differed largely in average plant height - from about 100 to far over 200 cm -, and number of ears per plant. Seed charateristics were quite uniform and included : (i) orange or yellow kernel colour, (ii) regular insertion, (iii) scarse occurence of dent type kernels, and (iv) small kernel size.
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-S:
's
5
Studying root systems of Caribbean pine.
Many of the "lines" appeared not pure at all ; they were discarded, or only the most promising ears were saved.
Progenies of the top-cross and polycross tests of 1970 were sown in randomized blocks. Two replicates were planted on heavy clay soil at the Centre's grounds and four on a sandy loam at the Experimental Citrus Plantation Baboenhol, ca. 80 km south of Paramaribo. Each block comprised 30 plots viz. 10 progenies from each, the polycross, the non-emasculated top-cross, and the emasculated top-cross. The plots consisted of 6 rows of 15 plants spaced 30 x 90 cm. The two outer rows and two plants on both ends of the remaining rows served as guards, leaving 45 record plants.
Split application of fertilizer was used in all blocks. The replicates on clay received two equal doses of a complete fertilizer (400 kg/ha NPKMg—10+15+20+2), viz. at sowing and just before tasseling, and an extra nitrogen top-dressing of 120 kg/ha or urea 5 weeks after sowing. The blocks on sandy loam received three times the above amount of complete fertilizer.
Replicates on clay grew well and no conspicuous decay of the photosynthetizing organs was observed until the ripening stage. Plot yields were from 4870 to 8420 g, corresponding with 4000-6930 kg/ha. Of two lines polycross as well as the top-cross progenies yielded distinctly more than all other progenies. Great conformity as to the order of yields was found for the two top-cross procedures, but polycross pro­ genies were quite different in this respect.
As a result of low and ill-distributed precipitation and heavy borer attack, growth was poor for the blocks on sandy loam. Large within-block variation occurred with respect to number of surviving plants, ears per plot, and plot yield. Even when com­ puting the yield on a basis of 40 plants/plot, i.e. the mean value found in the clay replicates, average yields were 3-4 times lower than on clay soil. At first sight no clear line could be traced as to the sequence of yields of the various objects. The re­ sults of statistical analysis were not yet available at concluding this report.
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13. PROTEIN IN FOOD CROPS
For an introduction to this multidisciplinary research project, dealing with protein content arid protein quality in some major tropical food crops, the reader is referred to the annual report for 1969.
The experiments started in 1969 and 1970, and outlined in the previous annual report, were continued or not yet closed in the year under review. Again, however, progress was hampered by the difficulties met in having the samples analysed. It is hoped that with the recent completion of the Centre's own chemical laboratory this problem has become a thing of the past.
As yet no conclusions could be drawn from the preliminary trial (69/34) conducted in 1969 and 1970 to learn whether drying of tubers of sweet potato and grains of maize, sorghum and cowpea at relatively low temperatures (viz. 45, 65 and 85 degrees centrigrade) causes decomposition of proteins
The same applies to an experiment (70/1) concerned with the question whether the protein content and protein nutritive value of sweet potato tubers are affected by variations in growing season, fertilizing and age at harvesting. Field work in this trial came to an end in 1971.
Additional samples were collected, and sent abroad for chemical analysis, as a part of the investigations dealing with the relation between protein content and quality on the one hand and plant density (70/30) as well as type of variety (70/31) on the other hand.
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14.1. NATURAL REGENERATION
The research on this subject is mainly carried out in two projects, viz. 65/3 and 67/9. The first one concerns a field trial laid down in relatively lightly exploited high rainforest, and consists of two adjacent blocks of 10.88 ha, each with a different refinement as first treatment, i.e. poisoning of weed trees with diameter limits of 10 and 20 cm respectively. In each block 6 treatments are being compared in 8 repli­ cations. They comprise liberations of valuable poles with a girth above 100 mm, applied at different times over a period of 12 years. This year the usual records were taken, but treatment was delayed ; it will be done next year. No important changes in girth or height increment were found.
The second project (67/9), an experimental plot with 25 subplots of 1 hectare each, was laid down in 1967 in exploited high rainforest at Mapanecreek. The experiment has already been described in former annual reports. At last year's recording, as es- pected, the liberated plots showed a marked girth increment upon treatment (a mean girth increment of 25-45 mm per year). Trees in untreated plots grew at a mean rate of 8-12 mm girth increment.
A remarkable decrease in increment was noted for the period 1969-1970 for most of the trees measured. This decrease is most likely the result of the exceptionally dry weather in the second half of 1969.
14.2. PLANTATIONS
Since a few years research is being carried out on the morphology and develop­ ment of the root systeem of Pirtus caribaea MoRELET (66/2). Some results of root studies of 8 and 12 months old pines have already been mentioned in a former annual report. In the year under review some root systems of trees of 10 years and elder were excavated and drawn. A conspicuous characteristic of the root system is the marked separation between horizontal and vertical roots, which according to the literature appears to be normal for pines. Though the deepest roots were not reached by excavation, it is assumed that with trees of this age on well-drained loamy soils some thin roots may reach depths of 3-4 m. Differences in development of vertical roots, especially the taproot, between dominant and suppressed trees were not as evident as those of horizontal ones.
A number of rootgrafts (apparently resulting in callus growth on stumps) was found. Grafting was observed only where roots met that were some centimetres thick, or where a thin root was squeezed between bigger ones. It may be that these grafts play some role in the spreading of the unidentified root rot in pine plantations that locally results in the death of trees.
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15. SOIL AND CROP ANALYSIS
15.1. THE INFLUENCE OF EXPERIMENTAL CONDITIONS ON THE DETERMINATION OF CATION EXCHANGE CAPACITY AND EXCHANGEABLE CATIONS ( 7 1 / 2 5 )
At the close of 1971 the chemistry laboratory was nearly finished. However before routine analyses can be done, it is to be decided what procedures are to be followed. This is especially important for chemical analysis of soils, since the meaning and interpretation of results largely depend on the method used.
The ammonium acetate method, particularly the percolation procedure, was chosen for the determination of cation exchange capacity (CEC) and exchangeable cations.
Mixtures of quartz sand and the soil to be analysed are brought in percolation tubes and extracted successively with ammonium acetate, ethyl alcohol and calcium chloride. To select a procedure that is correct, simple, cheap and appropriate for as many soils as possible, the effect of the following variables is being examined : 1. Concentration of ammonium acetate : 0.5, 1.0 or 1.5 N 2. Amount of quartz sand with which the soil is mixed: 20, 50, 80 or 110 grammes; 3. Texture of quartz sand : coarse (unsieved) or finer than 600 microns ; 4. Amount of soil : 10, 25 or 50 grammes.
To start with two soils were used : a heavy clay and a loamy coarse sand. So far it was found that a concentration of 0.5 N ammonium acetate is too low
and that for the clay soil fine quartz sand is required. The work continues.
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16. SOIL FERTILITY AND PLANT NUTRITION
16.1. THE USE OF MAIZE (Zea mays L) FOR THE ASSESSMENT OF SUFFICIENCY QUO­ TIENTS (71/21)
Based on research in Australia (BOUMA, 1965*), a pot experiment technique has been developed for quick identification of the nutrients that are in short supply in soils (JANSSEN, 1970*). In these experiments, which take about three weeks, the follow­ ing procedure is used. A small pot with a gauze bottom is filled with the soil to be investigated and placed on a container with a nutrient solutioa Seeds are sown in the soil. After the roots have appeared through the gauze and have reached the nutrient solution, the plants can take up nutrients from both soil and solutioa If a nutrient is omitted in the solution, plants take up that nutrient from the soil only. In case of rich soils plants grow almost as well on a deficient solution as on a complete one ; however, if the soil is poor plant growth on a deficient solut'on will be retarded.
The availability of a particular nutrient in the soil is indicated by the "sufficiency quotient" (SQ), i.e. the ratio between the relative growth rates (RGR) of plants on deficient and those on complete solutions (e.g. SQN for nitrogen). SQ depends not only on the availability of the studied nutrient, but also on the length of the time interval over which the relative growth rates are measured.
Until recently there was no experience in this type of experiments with maize, a crop that appears very suitable under Surinam conditions. Hence a preliminary experiment was started to gain some experience and to establish the most appropriate time interval to assess relative growth rates. The experiment was carried out with three soils that were expected to differ widely in fertility, and comprised the nutrients N, P, K, Mg, Fe and Cu.
The interval between 9 and 17 days after sowing, i.e. between the four and eight- leaf stages, proved most appropriate for relative growth assessments and calculation cf SQ. The finer the soil texture the higher SKN and SQK- SQP was about the same on two soils and somewhat higher on the heaviest one. No shortage of Mg, Fe and Cu could be detected. There was a close correlation between plant N and SQN and between plant K, SQK and soil exchangeable K.
It was concluded that maize is suitable for this type of pot experiments, at least as far as they concern the detection of deficiencies of the main nutrients N, P and K.
• BOUMA, D., 1965: Growth changes of plants following the removal of nutritional stresses Thesis. Wageningen.
JANSSEN, B. H., 1970 : Soil fertility in the Great Konya Basin, Turkey. Arg. Res. Rep., CLD. Pudoc, Wageningen.
37
16.2. A STUDY OF THE NUTRITIONAL STATUS OF Pmus Caribaea MORELET BY MEANS OF THE TECHNIQUE USED FOR THE ASSESSMENT OF SUFFICIENCY QUOTIENTS (71/22)
Some growth difficulties of Pinus caribaea MORELET on the sandy soils in the Surinam interior are thought to be caused by shortage of nutrients. Since it is difficult and very laborious to establish in field trials the nutrients that are involved, it was thought worthwhile to investigate the possibilities of the pot experiment technique as des­ cribed above. It was hoped that some of the deficiency symptoms of the plants on incomplete solutions resemble the field phenomena, thus enabling an identification of the nutrients in short supply.
Young Pinus plants were transferred with soil from nursery bags to pots with a gauze bottom. The pots were placed on containers with different nutrient solutions : complete solution or solutions without N, P, K, Ca, Mg, Fe, B or Cu, respectively.
Very clear deficiency symptoms were obtained on the solutions without N, P, Mg, Fe or B. Less distinct were the responses to K, Ca and Cu.
The experiment is still in progress.
16.3. A SOIL FERTILITY SURVEY OF SOME SOILS IN THE INTERIOR OF SURINAM (71/28)
The results of the greenhouse experiments mentioned in section 16.1 need to be checked in the field on soils that vary widely in fertility. Until now little is known about the fertility of the Surinam soils. Though there are soil maps, it often is rather hazardous to use these for information on soil fertility. The criteria important for crop production cannot always be included in a soil map legend, either because it is impossible for them to be recognized in the soil profile or because the soil properties decisive for crop production are not known. A study on the relation between soil type and soil fertility appears therefore desirable.
Such a study has been planned for those Surinam soils that also occur in large areas elsewhere in the tropics. Since it is not possible to include all units concerned, the actual research is preceded by a survey to find out where the most interesting soils are, entailing chemical analysis of crop plants from trials and plantations, and the carrying out of small fertilizer trials.
The study started in December of the year under review. Grain samples were taken from sorghum at Baboenhol (70/28 ; section 17) and from maize at CELOS and at Baboenhol (69/24 ; section 12). Furthermore three field trials were laid dcwn on three different terrace soils at Victoria, about 100 km south of Paramaribo along­ side the Surinam river. Each trial comprises the treatments (i) no fertilizer, (ii) 120 kg N/ha, (iii) 120 kg N + 90 kg P205/ha, and (iv) 120 kg N + 90 P205 + 120 kg K2O + 12 kg MgO/ha. The crop was maize.
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17. TILLAGE
17.1. A COMPARISON OF TILLAGE AND ZERO-TILLAGE SYSTEMS ON HEAVY CLAY SOILS FOR THE CONTINUOUS GROWING OF ANNUAL CROPS ( 7 0 / 2 5 )
The trial as described in the previous annual report was continued in the year under review with rice and Crotalaria sp., grown in the period March to August, and with maize and soyabeans from September till December. (For details of the treatments che reader is refered to CELOS Bulletins 13, p. 40.)
The emergence of Crotalaria sp., which was sown in 90-cm rows, was very poor, probably because of the roughness of the seedbed and the very wet weather conditions prevailing at the time of sowing. Consequently this crop failed completely.
The rice (cv. Washabo), planted in 30-cm rows, was sown by hand in the period 15-20 March. Emergence and subsequent growth were good. Fertilizing took place on 8 April and on 15 May at rates of 250 kg NPK (15+15+15) and 85 kg urea per hectare respectively. The crop was harvested between 10 and 15 August, and threshed mechanically following some drying in the field. Some of the effects of the treatments on growth and yield are presented in Table 9.
Table 9 - Tillage operations and plant growth (rice, cv. Washabo)
rotavating ploughing zero-tillage
weed control (h/ha) plant height on 15 May (cm) yield at 15% moisture content (tons/ha)
The large number of hours required for weed control was caused by bad weather conditions and the presence of sedges (Cyperus spp.). Weeds were controlled by hand hoeing.
Tillage for the second period of occupation started at the beginning of September. The crops were sown mechanically on 8 September, maize being planted in 90-cm rows, soyabeans in 45-cm ones. Fettilizer was applied at the end of the month at rates of 250 kg NPK (15 + 15+15) and 250 kg NPKMg (10+15+20+2) per hectare for maize and soyabeans respectively.
Although the seeds were correctly placed, the emergence of the maize was only moderate in all treatments, and that of the soyabeans poor in the tilled treatments. Inadequate moisture supply and a very loose soil may have caused the poor per- formanse of the soyabean seed.
Weed control was by hand hoeing. The maize was sprayed once with Dipterex SP 95 against Laphygma frugiperda. Though the soyabeans were rather heavily attacked by Cerotoma variegata, control measures were not considered necessary.
The soyabeans were harvested by hand at the end of December, the maize at the beginning of January 1972. Both crops were threshed mechanically. Conditions for threshing were not ideal, however. Moisture contents of the cobs and pods were high, there being no facilities for artificial drying. Some effects of the treatments on the growth and yield are presented in Table 10. Overall yields were lower than usual, which may partly be caused by insufficient care during the first weeks after germi­ nation.
39
Table 10 - Tillage operations and plant growth (soyabeans and maize)
soyabeans weed control (h/ha)
— no sedges present — sedges present
number of productive plants per metre row yields (ton/ha; 15% moisture content)
maire weed control (h/ha)
— no sedges present — sedges present
number of productive plants per metre row yield (tons/ha; 15% moisture content)
rotavating
257 670
3.3 1.03
450 420
3.0 3.18
Because of the poor emergence of the soyabeans and the resulting low plant densities it is not possible to relate the yields to the tillage systems.
As for maize, though ploughing gave the best yield, it is not statistically different from the other two.
17.2. A COMPARISON OF TILLAGE AND ZERO-TILLAGE SYSTEMS ON SANDY LOAMS FOR THE CONTINUOUS GROWING OF ANNUAL CROPS ( 7 0 / 2 8 )
In January 1971 a field trial was started to investigate (i) the tillage systems for annual crops when continuously grown on sandy soils, and (ii) the response of the crops, the weeds and the soil to these systems.
The lay-out of t