Nutrient Management Options For Improving Growth, Yield And Quality Of Snap Bean (Phaseolus Vulgaris L.) In Embu County

Abstract

Low soil fertility, especially deficiencies in nitrogen and phosphorous, is one of the key constraints to snap bean production in Kenya. An on farm trial was carried out in Karungua village in Kawanjara Sub-location, Runyenjes division, Embu East District. The first season trial was planted on 26th July 2014 and the second trial on 15th August 2014, respectively. The objectives of the study were: (1) to determine the effect of combining inorganic and organic fertilizers on growth, yield and quality of snap bean; and (2) to determine the cost effectiveness of various nutrient management options for snap bean production. The treatments comprised the following: (i) control (no fertilizers applied); (ii) farmyard manure (5 t/ha) and di-ammonium phosphate (50 kg N/ha) at planting and top dressing with calcium ammonium nitrate (50 kg N/ha) at 21 days after planting; (iii) di-ammonium phosphate (50 kg N/ha) at planting and top dressing with calcium ammonium nitrate (50 kg N/ha) at 21 days after planting; (iv) NPK (23:23:0) (50 kg N/ha) fertilizer at planting and top dressing with calcium ammonium nitrate (50 kg N/ha) at 21 days after planting (main farmer practice); (v) di-ammonium phosphate (50 kg N/ha) at planting, calcium ammonium nitrate (50 kg N/ha) at 21 days after planting and foliar feed spraying at pre- flowering stage; (vi) farmyard manure (5 t/ha), NPK (23:23:0) (50 kg N/ha) fertilizer at planting and top dressing with NPK (17:17:0) (50 kg N/ha) fertilizer at 21 days after planting; (vii) farmyard manure (5 t/ha) at planting and foliar feed spraying at pre- flowering stage; (viii) farmyard manure (5 t/ha) at planting; (ix) farmyard manure (5 t/ha), di-ammonium phosphate (50 kg N/ha), NPK (23:23:0) (50 kg N/ha) fertilizer at planting, top dressing with calcium ammonium nitrate (50 kg N/ha) at 21 days after planting and top dressing with NPK (17:17:0) (50 kg N/ha) fertilizer at 35 days after planting; (x) farmyard manure (5 t/ha) and calcium ammonium nitrate (50 kg N/ha) at planting and top dressing with calcium ammonium nitrate (60 kg N/ha) at 21 days after planting; (xi) farmyard manure (5 t/ha) at planting and top dressing with calcium ammonium nitrate (50 kg N/ha) at 21 days after planting. The trial was laid out in a xi randomized complete block design and replicated three times. The agronomic data collected included: 50% emergence, plant stand, days to 50% flowering, days to 50% podding, number of nodules per plant, shoot dry weight, pod yield and yield components, pest and disease infestation. Data for estimating cost effectiveness included the costs of inputs and revenue from the operations during the planting trial. Data were subjected to analysis of variance and mean separation was done using the least significant difference test at p=0.05. The results of the study showed that nutrient management options did not significantly affect the number of days to 50% emergence and plant stand of snap bean. Application of farmyard manure (5 t/ha) alone and application of farmyard manure (5 t/ha) at planting plus foliar feed spraying at pre- flowering stage significantly took the shortest time to attain 50% flowering. Fertilizer application significantly depressed nodule number. Treatments with inorganic fertilizers alone had significantly fewer nodules than treatments with farmyard manure. Nutrient management options had no effect on 50% podding, extra-fine pod length, pest and disease infestation. Significantly higher extra-fine, fine and marketable pod yields were recorded in di-ammonium phosphate (50 kg N/ha) plus calcium ammonium nitrate (50 kg N/ha) treated plots than in plots with other nutrient management options. Economic analysis showed that application of di-ammonium phosphate (50 kg N/ha) at planting plus top dressing with calcium ammonium nitrate (50 kg N/ha) at 21 days after planting had the highest net benefit and marginal rate of return in both plantings compared to other nutrient management options. The control plots (no-fertilizer) had a higher net befit first planting compared to the fertilized treatments. The study has demonstrated that application of di-ammonium phosphate (50 kg N/ha) at planting plus top dressing with calcium ammonium nitrate (50 kg N/ha) at 21 days after planting can enhance yield and profitability of snap bean in Embu County.