Fruit Growing Research, Vol. XXX, 2014

INFLUENŢA FERTILIZĂRII CHIMICE ASUPRA PRODUCTIEI DE FRUCTE LA CĂPŞUN INFLUENCE OF CHEMICAL FERTILIZATION ON STRAWBERRY FRUIT PRODUCTION Alina Florea Research Institute for Fruit Growing Pitesti, Romania Abstract

The nutritional control of strawberry is very difficult, because a large number of factors influence the absorption and availability of nutrients through mechanisms that are not fully understood. Aim is to establish concrete measures for improving crop technology by applying optimum dose of fertilizers, leading to increased productivity and fruit quality of strawberry culture. The research was conducted during 2009-2011, in a two-way experience. It was located at the Institute of Research - Institute for Fruit Growing Pitesti. Experimental factors were: A - cultivars: a1 - Onebor, a2 – Real, a3 - Elsanta a3, a4 - Magic, a5 - Alba, a6 – Premial; a7-Queen Elisa; B – Fertilizer with 6 graduations: b1 - unfertilized, and five graduations b2 - b6 were applied mixtures of the below fertilizers, thus: b2 - 6.4 kg/ha/week, b3 - 14.3 kg/ha/week, b4 - 21.4 kg/ha/week, b5 - 28.5 kg/ha/week and b6 - 35.8 kg/ha/week. The fertilizers applied were: Polyfeed (N19: P19: K19), potassium nitrate (N12: P0: K43: Mg2) and Magnisal (N11: P0: K0: Mg15). Mixtures were applied at 2 weeks intervals, as follows: 1 April to 15 May (flowering time), 2 applications, containing macroelements N: P: K: Mg - 14:6,3:20,7:5,7 g/100 g mixed fertilizers; May 15 - June 15 (in the picking period), 2 applications of N: P: K: Mg 10,2:6,3:13,5:2,83 g/100 g blend fertilizer and August 1 to September 15 (2 applications) with N: P: K: Mg 12,2:6,3:20,7:31,6 g/100 g mixed fertilizers. Following determinations were made: number of fruit per plant, average weight of fruit (g) by weighing a sample of 250 fruits and production in tons/hectare. Experimental treatments have led to differences in fruit production. Thus, the analysis of fertilizer doses on the chemical components of the fruits of the seven studied cultivars, we concluded that V5 and V6 treatments had a positive influence on number of fruit per plant and on yielding capacity. Treatments induced also, highest average fruit weight in variety Queen Elisa (20.61 g). Cuvinte cheie: fertilizare, soiuri de căpșun, producție, greutate fruct Keywords: fertilization, strawberries cultivars, production, fruit weight 1. Introduction

Applying nutrients to soil or foliar, plant relies on the ability to take nutrients and transport them to their points of growth. Supplementing these elements is an important link in the growing technology. In the context of sustainable agriculture, seeks to use those products, besides feeding plants also improves soil structure by stimulating the activity of microorganisms. Being an intensive culture, from which we obtain high yields of fruits, strawberries require proper fertilization. The unanimous opinion of those who have dealt with strawberry technology, is that by applying the complex of measures for ensuring a high density of plants per hectare, fertilization, irrigation and application of ordinary maintenance, ensure high and stable yields.

Aim of this paper is to establish concrete measures for improving crop technology by applying optimum dose of fertilizers, leading to increased productivity of strawberry culture. 2. Material and methods

The research was conducted during 2009-2011, in a two-way experiment. The experiment was located at the Research Institute for Fruit Growing Pitesti. Experimental factors were: Factor A - cultivars: a1 - Onebor, a2 – Real, a3 - Elsanta, a4 - Magic, a5 - Alba, a6 - Premial, a7 – Queen Elisa; Factor B – fertilizer with 6 graduations: b1 - unfertilized, and five graduations B2 - B6 were applied soil fertilizer mixtures with the following doses: b2 - 6.4 kg/ha/week, b3 - 14.3 kg/ha/week b4 - 21.4 kg/ha/week, b5 - 28.5 kg/ha/week and b6 - 35.8 kg/ha/week. The administered fertilizers were: Polyfeed (N19: P19: K19), potassium nitrate (N12: P0: K43: Mg2) and Magnisal (N11: P0: K0: Mg15). Mixtures were applied at 2 weeks intervals, as follows: 1 April -15 May (flowering time), 2 applications, containing macroelements N: P: K: Mg 14:6.3:20.7:5.7 g/100 g mixed fertilizers, 15 May -15 June (in the picking time), 2 applications of N: P: K: Mg 10,2:6,3:13,5:2,83 g/100 g blend fertilizer and August 1st to September 15th (2 applications) with N: P: K: Mg 12,2:6,3:20,7:31,6 g/100 g mixed fertilizers.

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Following determinations were made: number of fruits per plant, average weight of fruits (g) by weighing a sample of 250 fruits and production in tons/hectare. 3. Results and discussions Number of fruits/plant

Statistical analysis of data on the number of fruits per plant, using Duncan’s multiple range test (P ≤ 0.05) shows that between varieties were significant differences. The highest average number of fruits per plant, was recorded by Premial cultivar (13.43 fruits/plant), and the lowest average number of fruits was recorded by Alba cv. (8.86 fruits/plant). Besides the variety Premial, a large number of fruit per bush was recorded by the following cultivars: Queen Elisa (11.61 fruits/plant), Elsanta (12.75 fruits/bush) and Magic (11.30 fruits/bush). On average, in the six fertilization treatments, the best results were obtained by fertilization variant V6 - 35.8 kg/ha /day (11.71 fruits/plant) and the lowest by the fertilization variant V2 - 6.4 kg/ha/day (10.58 fruits/plant). In case of fertilization variant V6, when were applied in total 35.8 kg/ha/week, the highest average number of fruit was recorded by Real and Elsanta cv. In the case of applying an amount of 28.5 kg/ha/week (V5), the highest average number of fruits per plant was recorded by Onebor and Queen Elisa cultivars. Regarding Premial and Magic cultivars, the best results were obtained when we applied 21.4 kg/ha/week, respectively variant V4. For Alba cultivar, surprisingly, the best results were obtained in control variant - untreated (Fig. 1).

Analyzing the average number of fruits per bush, over the years, it was observed that the best results were obtained in 2010, respectively 11.28 fruits/plant, and the lowest number of fruits per plant was obtained in 2009 (10.91 fruits/plant). Premial cultivar obtained very good results in all three years of study. Magic, Queen Elisa and Onebor cultivars had a lower number of fruits per bush in 2009, and Real, Elsanta and Alba cultivars had poor results in 2011 (Fig. 2).

Regarding the influence of fertilization variant on the average number of fruits per bush, for every year of study, it was observed that, in the years 2010 and 2011 the best results were obtained in the case of variant V6 - 35.8 kg/ha/week and in 2009 the best results were obtained in variant V5 - 28.5 kg/ha/day (Fig. 3).

Regarding the histogram values of the average number of fruit/plant of strawberry cultivars under study, it was found that the sample mean was 11.08, ranging from 5.9 to 18.4, with amplitude of 12.5 fruits/plant and a standard deviation of 2.33 (Fig. 10).

Fruit weight

Statistical analysis of average fruit weight showed that among the seven studied cultivars there are significant differences, the largest fruit being obtained by the cultivar Queen Elisa (20.61 g) and the smallest fruit Premial (12.10 g). Regarding fertilization variant it was observed that, on average, the best results were obtained in the case of variant V3 - 14.3 kg/ha/week. Taken cultivars response individually, it was observed that there are differences between cultivars depending on the variant of fertilization. For the cultivars Onebor, Real and Alba, the best results were obtained in fertilization variant V3 - 14.3 kg/ha/week. For the cultivars Queen Elisa and Premial, the largest fruits were obtained in variant V5 - 28.5 kg/ha/week and in the case of Magic cv., the largest fruits were obtained in the untreated variant (Fig. 4).

On average for the entire period of study, the largest fruits were obtained in 2009 (18.26 g), and the lowest in 2011 (15.45g). Most studied cultivars showed the largest fruit in 2009, except Premial, in that case the largest fruits being recorded in 2010 (Fig. 5).

Regarding the influence of fertilization variant on the average fruit weight, it was observed that, in 2009 and in 2011 the best results were obtained in the case of variant V3 - 14.3 kg/ha/week and in 2010 the best results were obtained in the case of variant V1 - untreated (Fig. 5).

Regarding the histogram values of average fruit weight of strawberry cultivars under study, it was found that the sample mean was 16.27 g, ranging from 9.8 g to 28.3 g, with an amplitude of 18.5 g and a standard deviation of 2.92 (Fig. 11). Yielding capacity

Statistical analysis of the data of production per plant, using Duncan’s multiple range test (P ≤ 0.05) allowed us to group the studied cultivars in homogeneous groups of yields, between these being registered significant differences. The highest production was obtained by ‘Queen Elisa’ cultivar (18.23 t/ha). The smallest yield was obtained by ‘Alba’ cultivar (12.41 tons/hectare) (Fig. 7).

Regarding the influence of fertilization variant on the production of fruits, it was observed that the biggest yield (14.75 t/ha) was obtained when was applied a total amount of 28.5 kg/ha/week - V5, followed very close by the variant 6 - 35.8 kg/ha/week. In most cultivars the variant V5 led to the largest fruit production, except Premial cultivar, which obtained the best results in the case of variant V4 - 21.4 kg/ha/week (Fig. 7).

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Fig. 11. Histogram of fruit weight (g) Fig. 12. Histogram of fruit yield (t/ha)

Fig. 13. Correlations between the main studied characteristics

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