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Communications in Soil Science and Plant Analysis

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Response of Food Barley (Hordeum Vugarae L.) ToBoron Blend Fertilizer Rates on Alisols in SouthernHighlands of Ethiopia

Eyasu Elias , Beyene Teklu Mellisse , Getachew Agegnehu & Desalegn Ayele

To cite this article: Eyasu Elias , Beyene Teklu Mellisse , Getachew Agegnehu & Desalegn Ayele(2020): Response of Food Barley (Hordeum Vugarae L.) To Boron Blend Fertilizer Rates on Alisolsin Southern Highlands of Ethiopia, Communications in Soil Science and Plant Analysis

To link to this article: https://doi.org/10.1080/00103624.2020.1813752

Published online: 02 Sep 2020.

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Response of Food Barley (Hordeum Vugarae L.) To Boron Blend Fertilizer Rates on Alisols in Southern Highlands of EthiopiaEyasu Elias a, Beyene Teklu Mellisseb, Getachew Agegnehuc, and Desalegn Ayeled

aCentre for Environmental Science, College of Natural and Computational Sciences, Addis Ababa University and BENEFIT CASCAPE Manager, Addis Ababa, Ethiopia; bWondo Genet College of Forestry and Natural Resources, Hawassa University, Awasa, Ethiopia; cEthiopian Institute of Agricultural Research, Ababa, Ethiopia; dCASCAPE Project: Hawassa University, Hawssa, Ethiopia

ABSTRACTContinuous use of only N and P containing fertilizers are claimed to be the causes of other secondary and micronutrients depletion, resulting in low crop productivity in Ethiopia. In this study, on-farm trials were conducted to compare the effect of multinutrient blended fertilizer – also called boron blend (NPSB: 18. 1 N – 36.1 P2O5 – 6.7S – 0.71B) on the yield and yield components of food barley grown in Alisols in southern Ethiopia during 2017 and 2018 cropping seasons. Seven treatments involving five levels of born- blend fertilizer (50, 100, 150, 200, and 300 kg NPSB kg ha−1) were compared against a compound fertilizer (100 kgha−1 NPS) and the conventionally used 150 kg ha−1 di-ammonium phosphate (DAP). The seven treatments were replicated five times using farm fields as replicates and arranged in rando-mized complete block design (RCBD). Results revealed significant yield advantages of applying micronutrient containing fertilizers compared to fertilizers without micronutrients. The marginal rate of return analysis showed that the application of 100 NPSB kg ha−1 was the most profitable and agronomically efficient. Season and the soil fertility variation among farmers had a significant (p < .001) effect on food barley yield. Application of Boron blend fertilizer had 500 kg ha−1 grain yield advantage compared to equivalent amount of DAP that was highly promoted by the extension system. B-blended fertilizer was advantageous when applied during good rainy seasons in Alisols of Ethiopian highlands. For good performances of B-blended fertilizers, taking into account the soil moisture availability is advised for both better productivity and agronomic efficiency.

ARTICLE HISTORY Received 15 January 2020 Accepted 9 April 2020

KEYWORDS Agronomic efficiency; Alisols; blended fertilizer; economic feasibility; food barley

Introduction

In Ethiopia, food barley (Hordeum vulgare L.) is the fifth important staple cereal after teff (Eragrostis teff Zucc), maize (Zea mias), sorghum (sorghum bicolor) and wheat (Triticum aestivum) in that order (CSA 2018a). Barley is grown in wider environmental conditions, covering a total area of about 951,993 ha from which more than 3 million smallholder farmers drive their livelihood (CSA 2018a). Cultivation of barley has a long history, which is believed to be coincided with the beginning of plow culture in Ethiopia (Teshome 2017). In the highlands of Ethiopia, barley is predominantly cultivated in altitudinal ranges of 2000 to 3000 meter above sea level (m.a.s.l), but it can also grow from 1500 to 3500 m.a.s.l (Teshome 2017). For smallholders of Ethiopian highlands, barley grain accounts for 60% of their food (Alam, Haider, and Paul 2007) and barley straw is crucial component of animal feed especially during the dry season (Zemede 2000). Barley straw is also used for the construction of traditional huts and grain stores as thatching or as a mud plaster, as well as for use as bedding in the

CONTACT Beyene Teklu Mellisse beyteklu@gmail.com Wondo Genet College of Forestry and Natural Resources, Hawassa University, Awasa, Ethiopia

COMMUNICATIONS IN SOIL SCIENCE AND PLANT ANALYSIS https://doi.org/10.1080/00103624.2020.1813752

© 2020 Taylor & Francis Group, LLC

rural areas (Zemede 2000). In Southern Nationals Nationalities and People’s Regional States (SNNPR) of Ethiopia, barley is grown on a total area of 81,161 ha and the production is estimated to be 154,504 ton with mean yield of 1.9 ton ha−1 in 2017_2018 cropping season (CSA 2018a). In SNNPR barley is also the fifth cereal crop after maize, teff, wheat and sorghum from which more than half a million smallholder farmers drive their means of living (CSA 2018a).

However, in spite of long history of cultivation and livelihood importance of barley, its produc-tivity has never increased above 2.2 t ha−1, which is about one third of the potential yield of 6.0 t ha−1 obtained in experimental plots (Habtamu, Bobe, and Enyew 2014). The decline in the soil fertility driven by high rates of soil erosion (estimate 130 t ha−1 for cultivated fields), suboptimal fertilizer application rate, nutrient imbalance, and limited access to improved varieties are among the major limiting factors claimed for low food barley productivity in Ethiopia (Tarekegne, Gebre, and Francis 1997). Continuous application of DAP (18–46% N-P2O5) containing only nitrogen (N) and phosphorus (P) without due consideration of other nutrients is claimed for the depletion of other important nutrient elements such as S and micronutrients in soils (Abiye et al. 2004). Alisols that are strongly weathered, acidic soils having low base status clays with Aluminum (Al)-saturation in the soil solution cover about 3% of the total landmass of the Ethiopian highlands (4,800 sq.km) (Elias 2016). In these soils application of DAP is believed to have aggravated soil acidity and nutrient mining (Aboytu 2019). Such soils are most extensive in the high rainfall southern and south-western highlands where the soil is used for cultivation of cereals such as barley and high value crops such as tea plant (Camellia sinensis). According to soil inventory data, most of nutrients such as nitrogen (N), phosphorus (P), sulfur (S), boron (B), and zinc (Zn) are deficient in 86, 99, 92, 65, and 53% of Ethiopian soils (Ethio-SIS. 2016). Although micronutrient concentrations increase with decreasing soil pH, studies have found that B deficiency is particularly widespread in acidic soils of the southern highlands which limiting cereal yields (Elias 2019; Haque, Lupwayi, and Tadesse 2000).

Considering these problems, the Ethiopian government has been promoting the use of multi- nutrient blended fertilizer since the last few years along with liming (Simtowe 2015). The promotion of blended fertilizer was initiated after analyzing, identifying nutrient deficient soils and mapping the soil fertility status of these soils across the country (ATA 2015). Based on the soil fertility atlas, blended fertilizers consisting of N, P, K, S, B, Zn, and Copper (Cu) were recommended in different mixes and proportions for districts (Shiferaw et al. 2018). As part of the transformation of the soil fertility sector, introduction of the compound fertilizer – NPS (19 N-38 P2O5 −7 S) is used for blending with micronutrients such as Zn, B, Cu and sometimes potassium (K). Boron blend – NPSB (18. 1 N – 36.1 P2O5 – 6.7S – 0.71B) is the major blend formulations recommended in the study site based on the soil fertility atlas prepared for the region. This fertilizer is aggressively promoted among smallholder farmers through the extension system.

Applying multinutrient blended fertilizers are acknowledged not only for enhancing productivity but also nutrient use efficiency of crops (Redai, Tesfay, and Yemane 2018). Besides yield advantage, balanced fertilization has substantial role for sustainable crop production and soil fertility mainte-nance (Abiye et al. 2004). In spite of these general reports which narrate the beneficial effects of blend fertilizers over straight fertilizers, there are no sufficient information on the agronomically optimum and economically feasible rates of blend fertilizer on food barley. The extension system recommends 100 kg NPSB blend for all crops and soil types as a blanket rate in spite of wide differences in soil and crop types. Moreover, there is no enough informations on the impact of different types of fertilizers containing macro and micronutrients specially boron as it is reported to be the most limiting micronutrient in the southern highlands (Elias 2019; Ethio-SIS. 2016). Given the fertilizer trials involving multinutrient fertilizers are at its initial stage in Ethiopia, there is little information on the response of crops to blended fertilizers (NPS and NPSB) (Melkamu, Gashaw, and Wassie 2019). Thus, the current study was initiated with the objective of (1) to determine agronomically optimum and economically profitable rates of blend fertilizers for production of food barley in Alisols; (2) to explore the yield increasing effect of B-blend fertilizers as compared to the compound fertilizer without

2 E. ELIAS ET AL.

B (NPS) and the conventionally used DAP fertilizer hence generating evidence for extension promo-tion and agronomic nutrient use efficiency and economic advantages of using blended fertilizers.

Materials and methods

The study area

This on-farm trials were conducted at Malga Woreda in Sidama zone of Southern Nations Nationalities and Peoples Regional State (SNNPR) during 2017 and 2018 cropping seasons (July to December) (Figure 1). Melga is located at 06° 54ʹ 31”N latitude and 38° 42ʹ 30” E longitudes covering a total area of 206.74 square kilometers with 129,694 inhabitants (CSA 2018b). Most Kebeles (smallest Ethiopian administrative unit in Ethiopia) are classified as ‘rural’ (CSA 2018b). The rainfall distribu-tion is bimodal with a long (June to September) and short (March to May) rainy season. The altitude ranges in elevation from 1500 to 3000 m.a.s.l and receives 1200–1600 mm rainfall annually; the average annual temperature ranges from 12.6 to 20°C. The dominant soil type in the Woreda (district) is Alisol, characterized by loam to clay-loam textural classes.

Monthly rainfall distribution of the study sites

The Woreda received the highest rainfall in the main rainy seasons (June to September) while the lowest in the short rainy season (February to May) (Figure 2). The study area received more rain in the month of July and August in 2017 than other months of the year, which is the planting and crop establishment time for food barley, respectively (Figure 2).

Treatments and experimental design

Within Melga woreda, one kebele (Abiye jiru) was selected and within the kebele, five farm fields were considered as replications (Figure 1). The trial was conducted during the main growing seasons of

Figure 1. Study sites in Melga Woreda of Sidama zone, SNNPR.

COMMUNICATIONS IN SOIL SCIENCE AND PLANT ANALYSIS 3

2017 and 2018. The treatments consisted of five rates of NPSB blended fertilizer (50, 100, 150, 200, and 300 kg ha−1) to explore optimum rates of application; 100 kg ha−1 NPS and 150 kg ha−1 diammonium phosphate (DAP) to compare with 100 and 150 NPSB kg ha−1 whether the B-blend was superior over the NPS and conventional fertilizer respectively. These treatments were arranged in Randomized Complete Block Design (RCBD) with five replications (i.e. farm fields). The fertilizer levels and nutrient elemental composition of the various treatments are presented in Table 1. All blended fertilizer was hand drilled at the time of sowing while urea was applied one third at planting and the rest two third at 35 days after planting. Other agronomic practices were applied following the recommendation for the crop. Improved barley variety (HB-1307) was sown with a seed rates of 100 kg ha−1. The plot size of each treatment was 4 m × 5 m (20 m2) with 0.5 and 1 m space between adjacent blocks and plot was maintained respectively. Each experimental plot consisted of 16 rows each spaced at 30 cm. The trials were hand weeded two times during the cropping season.

Soil sampling and analysisInitial representative composite soil samples were collected at 0–20 cm depth from each experi-

mental site before sowing and were analyzed at the HortiCoop soil fertility laboratory. The samples were mixed manually and composite sub samples were grounded to pass through 2 mm sieve. Soil pH in water was determined at 1:2.5 (soil: water ratio) (Van Reeuwijk 2002); soil organic carbon (OC) by wet oxidation methods (Walkley and Black 1934); and total nitrogen by Kjeldhal method (Black 1965). Soil AP was determined by Olsen method (Olsen and Sommers 1982) while S and B were extracted by using the Mehlich_3 method (Mehlich 1984).

0

50

100

150

200

250

300

350

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Mon

thly

rain

fall

(mm

)

2017

2018

Figure 2. Monthly rainfall distribution of the study area.

Table 1. Details of treatments and nutrient composition of fertilizers.

Code Fertilizer rate (kg ha−1)

Nutrient composition

N P S B

T1 50 NPSB +100 urea 55.4 8.2 3.5 0.13T2 100 NPSB +100 urea 64.7 16.3 6.9 0.25T3 150 NPSB +100 urea 74.1 24.5 10.4 0.38T4 200 NPSB +100 urea 83.4 32.7 13.8 0.5T5 300 NPSB +100 urea 102.1 49.0 20.7 0.75T6 100 NPS + 100 urea 65.0 16.6 7.0 0.0T7 150 DAP + 100 Urea 74.1 30.0 0.0 0.0

Where N: Nitrogen, P: phosphorous, S: Sulfur, B: Boron, DAP: Diamonium phosphate

4 E. ELIAS ET AL.

Yield and yield components

Grain yield and straw biomass of food barley were determined from plants harvested from the four central rows (6 m2) each plot. The weight of biomass was determined in the field using spring balance. The samples were threshed manually to separate the grain and straw biomass and the fresh weight of grain and straw yields were measured in the field and the grain dry matter was adjusted to standard moisture content of 12.5% and finally converted to kg ha−1 for statistical analysis. Plant height, spike length, and number of kernels per spike were measured from five randomly selected plants. Harvest index was calculated from the ratio of the total grain yield to the total biomass yield.

Economic analysis

The marginal rate of return (MRR) was performed following the CIMMYT partial budget analysis (CIMMYT 1988). The variable costs associated with labor and fertilizer purchase were compared using partial budgeting, which included only costs that varied from the control, i.e. costs of variable inputs (fertilizer and labor). For the costs of blended fertilizer, DAP and Urea a price of 16.50, 16.00, and 10.50 birr per kg respectively were considered and calculated for each treatment depending on the amount applied and converted to per hectare bases. An average cost of 80 birr per person day was considered and calculated for each treatment depending on the number of labors required to apply different rates of fertilizers, harvesting, and threshing activities. The costs for seed and management that do not vary among the treatment were not included in this cost analysis. The price of all fertilizers was taken from farmers’ cooperative union who are engaged in supplying input for smallholder farmers. The grain yield was down adjusted by 10% with the assumption of variation in crop management, postharvest loss in farmer managed experiments compared to experiments managed by researchers. The income from grain and straw was calculated by multiplying the total yield per ha with the farm gate price. A price of 9.5 and 0.35 birr per kg was considered for grain and straw respectively.

The net benefit was calculated as the difference between the gross benefit (ETB ha−1) and the total costs (ETB ha−1). Following the CIMMYT partial budget analysis method, total variable costs (TVC), gross benefits (GB), and net benefits (NB) were calculated. Then treatments were arranged in an increasing TVC order and dominance analysis was performed to exclude dominated treatments from the marginal rate of return (MRR) analysis. A treatment is dominated if it has a higher TVC than the treatment which has lower TVC next to it but having a lower net benefit. A treatment which is non- dominated and having a MRR of greater or equal to 100% and the highest net benefit is said to be economically profitable (CIMMYT 1988). Benefit cost ratio was calculated by dividing gross benefit with total cost.

Data analysis

Analysis of variance (ANOVA) for grain yield and yield components was carried out using Statistical Analysis Software version 9.0 (Gomez and Gomez 1984). Whenever treatment effects were significant, mean separation was carried out using least significance difference (LSD) test at 5% probability level. Furthermore, agronomic nutrient use efficiency (ANUE) and partial factor productivity (PFP) were calculated using the formula developed by Fageria and Baligar (2003). ANUE indicated the economic production obtained per unit of nutrient applied.

ANUE ¼Gb � Gnb

Na(1)

PEP ¼GtNa

(2)

COMMUNICATIONS IN SOIL SCIENCE AND PLANT ANALYSIS 5

Where Gb and Gnb is grain yield obtained from plots fertilized with blended fertilizer and grain yield obtained from plots fertilized without micronutrient fertilizers respectively; Gt the total grain yield obtained from each treatment; Na is the quantity of nutrients applied. The fertilizers containing only NP (blanket recommendation) was taken as a control for this study as the intention is to shift from non-blended fertilizer which lack micronutrients to blended fertilizer with micronutrients.

Results

Soil properties of the study sites

The average soil pH was 4.85 (pH H2O) and the variation between farms were narrow (Table 2). The average soil organic carbon (OC) and total nitrogen (TN) were 3.61 and 0.34% respectively. The OC was below 5% for all farmers while TN was less than 0.4%. Although the average available phosphor-ous (AP) was 9.39% large variation between farms were observed. The soil available sulfur (S) and B were 28.65 and 0.30 mg kg−1 respectively. Available phosphorous varies from 7.42 to 13.05 mg kg−1

whereas AS varies from 24.27 to35.17 mg kg−1 between different farm fields.

Response of food barley yield and yield components to blended fertilizers

The responses of yield and yield components of food barley to the rates of B-blend fertilizer applica-tion and their interaction was computed using data combined over two cropping seasons. The analysis of variance indicated a highly significant (p < .01) effect main factor (year) on biomass, grain and straw yields, harvest index (HI), plant height, and kernel per spike (Table 3). However, the effect of fertilizer rates was significant only for grain yield and harvest index. The year with fertilizer rate interaction effect was not significant for most parameters except for harvest index.

The significantly (p < .01) lowest grain yield (2.6 t/ha) were obtained by the application of 50 kg ha−1 NPSB (Table 4). Although there were no significant differences for all higher B-blended fertilizer rates, higher grain yield (3.7 t/ha) was obtained by application of 100 kg ha−1 NPSB and the application above this rate showed a decline trend of grain yield. Significantly higher grain yield was obtained by application of 150 kg ha−1 NPSB than the same rate of the conventionally used DAP fertilizer (Table 4). Similarly, although not statistically different higher grain yield was obtained by application of

Table 2. Soil properties of the experimental site.

Farm fields (reps) pH OC (%) TN (%)

mg/kg

AP AS B

1 4.61 3.23 0.31 8.19 28.52 0.252 4.81 4.19 0.38 13.05 35.17 0.393 4.69 3.85 0.36 8.90 28.86 0.254 4.77 3.53 0.33 9.36 24.27 0.255 5.36 3.26 0.33 7.42 26.43 0.35Mean 4.85 3.61 0.34 9.39 28.65 0.30CV (%) 6.11 11.31 8.11 23.21 14.25 23.22

OC: Organic carbon; TN: Total nitrogen; AP: Available phosphorus; AS: Available sulfur; B: Boron

Table 3. Analysis of variance for food barley yield and yield components for two cropping seasons in Melga woreda (n = 56).

Sources DF

Yield Yield components

Biomass Grain Straw (HI) Plant height Spike length Kernel per spike

Year (yr) 1 *** *** *** *** * ns ***Replication (r) 4 *** *** *** ** *** ** **Treatment (trt) 6 ns ** ns ** ns ns nsyr*trt 6 ns ns ns *** ns ns ns

Significant at *p ≤ 0.05, **p ≤ 0.01, ***p ≤ 0.001; ns, not significant

6 E. ELIAS ET AL.

100 kg ha−1 NPSB than the same amount of fertilizer rate without B. Significantly lowest harvest index (HI) was also obtained by application of 50 kg ha−1 NPSB while application of 100 and 150 kg ha−1

NPSB gave higher HI. Application of NPSB fertilizer rates gave higher HI than the same rates of fertilizers without SB or B. This suggests the grain yield advantage of incorporating B and S in Alisols of Ethiopian highlands. Indeed, better response of B-blended fertilizer application were observed in good rainy seasons as higher mean biomass (16.1 t/ha) and grain yield (3.7 t/ha) were obtained in the year 2017 compared to the yield in 2018 (Table 4).

Effect of applying blended fertilizers on nutrient use efficiency of food barley

The highest grain yield per nutrient applied (41.7 kg kg−1) and agronomic nutrient use efficiency (ANUE) (5.0 kg kg−1) were obtained by applying 100 kg kg−1 NPSB. Application of NPSB fertilizers rates above 100 kg kg−1 showed a declining trend of both for partial factor productivity (PFP) and ANUE (Table 5). Higher PFP and ANUE were obtained by the application of 100 kg ha−1 NPSB than the same amount of fertilizer rate without B. Application of 50 kg NPSB ha−1 had no advantage for ANUE compared to application of fertilizers containing only DAP. This implies the agronomic nutrient use efficiency advantage of incorporating micronutrients except for the lowest rate (50 kg NPSB ha−1).

Economic feasibility of applying balanced nutrients on food barely

The highest net return of 30829 Ethiopian birr (EB) per ha with the highest marginal rate of return (832.99%) was obtained from plots treated with 100 NPSB kg ha−1 (Table 6). This implies that shifting from treatment one to two would result in the MRR of 833% which means that investing one birr on

Table 4. Means for main effects of year and fertilizer application rate on food barley yield and yield components for 2017 and 2018 cropping seasons (n = 56).

Factor

Biomass Grain yield Straw

HI (%)

Plant height Spike length

Kernel per spike (no)(t/ha) (cm)

Year2017 16.1a 3.7a 12.4 a 29a 103a 6.4a 47.4a

2018 9.9b 2.8b 7.1 b 24b 99b 6.3a 41.1b

Fertilizer rate (kg ha−1)50 NPSB 12.8a 2.6 c 10.2a 20 c 97ab 6.5a 42.9ab

100 NPSB 14.0a 3.7a 10.2a 27a 104a 6.4a 46.7ab

150 NPSB 13.7a 3.6a 9.9a 28a 102ab 6.2a 45.4ab

200 NPSB 14.1a 3.5a 10.6a 25ab 100ab 6.6a 45.1ab

300 NPSB 14.4a 3.4a 11.0a 23bc 101ab 6.1a 41.5ab

100 NPS 14.1a 3.6a 10.5a 26a 99ab 6.6a 47.1a

150 DAP 13.6a 3.2b 10.3a 25ab 101ab 6.5a 45.9ab

Significance level ns ** ns ** ns ns nsCV (%) 20.7 15.2 25.0 15.4 5.7 8.3 9.9

Means with the same letter along the column are not significantly different. Significant at **p ≤ 0.01, ***p ≤ 0.001; ns, not significant

Table 5. Effect of blended fertilizer on PFP and ANUE of food barley grown for two cropping seasons.

Treatments Nutrient applied Grain yield (kg ha−1) PFP ANUE (kg kg−1)

50 NPSB (T1) 67.2 2626 39.1 −9.1100 NPSB (T2) 88.2 3679 41.7 5.0150 NPSB (T3) 109.3 3667 32.9 4.1200 NPSB (T4) 130.4 3489 26.8 1.9300 NPSB (T5) 172.6 3356 19.5 0.7100 NPS (T6) 88.6 3601 40.7 4.1150 DAP (T7) 104.1 3236 31.1 0.0

PFP partial factor productivity; ANUE agronomic nutrient use efficiency

COMMUNICATIONS IN SOIL SCIENCE AND PLANT ANALYSIS 7

treatment two instead of treatment one would give a net additional benefit of 8.32 Birr. The lowest rate of fertilizer application had the highest benefit to cost ratio while the highest rate of application had the lowest benefit to cost ratio.

Discussion

Soil properties of the study site and its suitability for growing food barley

The average soil pH was 4.85 (pH H2O) which is characterized as very strongly acidic according to the pH rating by Landon (1991). This is typical characteristics of Alisols which accumulated high activity clays in their subsoils having Al saturation. Soils with pH values less than 5.5 are deficient in Calcium (Ca) and/or Magnesium (Mg) and P (Marschner 2002) and thus, the soil fertility status in the study area is suboptimal for the production of food barley. This confirms the soil nutrient deficiency and fertility atlas of the region (Ethio-SIS. 2016). The soil organic carbon (OC) and total nitrogen (TN) were 3.61 and 0.34% respectively which are rated as high while the mean available P was 9.39 mg kg−1

which is rated as low (Murphy 1968; Tekalign and Haque 1991). Available sulfur (S) and B were 28.65 and 0.30 mg kg−1 respectively. Based on the ratings by Landon (1991) for tropical soils, S level is rated as high while B is low. However, the mean values largely mask the large variability between trial fields that were used as replications for the experiment (Table 2). The result is not in agreement with the EthioSIS report that classify 65% of the highland soils are deficient in S which might be due to the arbitrary selection of the critical limits of these nutrients.

Food barley response to blended fertilizer rates

Cropping season difference has brought about significant differences in yield and yield components except for spike length. The amount of seasonal rainfall received in the growing season greatly affected the response to fertilizer application in increasing productivity of food barley. In 2018, lower yield and yield components were recorded due to early insufficient amount of rainfall during the tillering and grain filling period in the months of July and September respectively (Figure 2). Studies have indicated that grain yield and nutrient uptake of barley were greater in a relatively wetter season than the drier ones (Agegnehu, Ghizaw, and Sinebo 2006). According to Jones, Olson-Rutz, and Dinkins (2011) low nutrient uptake early in a plant’s growth lowers the nutrient quantity for the seed affecting yield. Crop uptake of nutrients is affected by soil and climatic conditions. One of the constraints is low soil moisture that restricts uptake of plant nutrients. This indicates that a successful soil test fertilizer program is reliant on rainfall and soil moisture status which influences the response of crops and yield to a greater extent than fertilizer applications.

However, for this study, given the dependency of Ethiopian agriculture on rainfall, much emphasis has been given for enhancing production and productivity through availing inputs (seeds and fertilizer) and applying proper agronomic practices. Accordingly, the application of blanket

Table 6. Effect of applying balanced nutrients on economic feasibility of food barley.

Treatments Adjusted grain yield (kg/ha)Birr/ha

Benefit cost ratio MRR (%)GR TVC NB

50 NPSB 2294 24756 2133 22624 10.6100 NPSB 3244 33946 3118 30829UD 9.9 832.99150 NPSB 3248 33736 4063 29673D 7.3200 NPSB 2995 31502 5008 26494D 5.3300 NPSB 2988 31649 6818 24832D 3.6100 NPS 3096 32519 3178 29342D 9.2150 DAP 2718 28969 3988 24981D 6.3

ND = non-dominated; D = dominated treatments; GR = gross revenue; TVC = total variable cost; NB = net benefit; MRR = marginal rate of return;

8 E. ELIAS ET AL.

recommendation of DAP and urea fertilizers has been promoted in Ethiopia for the past four decades. The continuous application of these fertilizers is claimed for the depletion of other important nutrients and as a result has been supposed to be the cause of declining crop productivity (Abebaw and Hirpa 2018). This study confirms substantial food barley yield advantage of using blended fertilizers compared to the N and P containing fertilizer (Tables 3 and 4). This suggests the importance of applying B-blended fertilizers in Alisols of Ethiopian highlands where B is believed to be limited (Ethio-SIS. 2016). The 500 kg ha−1 grain yield advantage of applying 100 kg ha−1 NPSB than DAP not only contribute for food self-sufficiency of smallholder farmers but also for sustainable agricultural production as it does not lead to depletion of micronutrients like B.

The available boron (B) (>0.3 mg kg−1) of the study area could be rated as low (Landon 1991). These further signifies the agronomic and economic value of shifting away from DAP to NPS plus micro-nutrient blend at least for food barley production in the southern highlands. As micronutrients like B and S are required in small amount for plant growth, their incorporation is vital to reduce continuous removal of these elements. The higher nutrient use efficiency (5.1 kg kg−1) obtained by application of 100 NPSB than application of the same rate without B may be explained by the response of B when it is applied in B deficient soils of the study area (Table 5). This implies that B containing blended fertilizer application enhanced nutrient efficiency by increasing plant uptake and use via decreasing nutrient losses from the soil-plant system. This is perhaps due to the effectiveness of S and B functions in plant physiology, including protein synthesis, carbohydrates metabolism, activated enzyme carbonic anhydrase, synthesis of RNA, and ribosome functions (Shireen et al. 2018; Uchida 2000). This suggests the need of recommending niche specific blended fertilizers based on the soil fertility status and if possible, in less moisture stress areas.

Conclusion

The study found that application of 100 NPSB kg ha-1 was the most profitable rate for food barley production in the study area of the southern Ethiopian highlands. The study also found substantial yield advantage from the newly introduced compound fertilizer (NPS+B) compared to the conventionally used DAP fertilizer. Better yield and agronomic efficiency advantages of applying 100 kg ha−1 NPSB blended fertilizer than the same rate of blends without B was observed. Generally, incorporation of micronutrients, S and B has improved the agronomic nutrient use efficiency when fertilizers are applied at the rate of above 50 kg/ha. Therefore, the shift from the conventionally used DAP fertilizer to B-blended fertilizer is worthwhile in area like southern Ethiopian highlands for sustainable food barely production.

Acknowledgments

This research was a part of project called “Capacity Building for Scaling up of Evidence-based Best Practices in Agricultural Production in Ethiopia” (CASCAPE) funded by the government of The Netherlands. We thank the farmers who participated in this research. Our thanks are extended to experts from Bureau of Agriculture in Melga Woreda for their cooperation during all processes of data collection. We also wish to thank CASCAPE project, Hawassa team for their work in implementing the trial and collecting the data. We also thank Hawassa University for providing offices and cooperation in facilitating activities at all level of the research work.

Funding

This work was supported by the Capacity Building for Scaling up of Evidence-based Best Practices in Agricultural Production in Ethiopia” (CASCAPE) funded by the government of The Netherlands [pc16/CDIo296].

ORCID

Eyasu Elias http://orcid.org/0000-0003-4008-6470

COMMUNICATIONS IN SOIL SCIENCE AND PLANT ANALYSIS 9

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