Effect of nitrogen, phosphorus and organic manure on growth and development of cotton ( gossypium hirsutw, L.) at Tebere, Kenya.
Ikitoo, E C
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Effect of Farmyard manure, nitrogen and phosphorus on growth and yield of two upland cotton varieties (UKA 59/240 and BPA 75) was investigated at Tebere during the October, 1982 and March, 1983 cropping seasons. Varying levels of farmyard manure, nitrogen and phosphorus were tested in factorial combination. Mean seedcotton yields in the two seasons, i.e. October, 1982 to August, 1983 and March, 1983 to December, 1983 were 1806 and 1164 kg ha , respectively. The yields were lower than the expected mean yields of 2,000 kg ha for Tebere. During the October 1982 crop season trial, BPA 75 attained a height 3.0 em taller, 0.4 fruiting bodies per plant more and 55 kg ha more seedeotton than UKA 59/240 in the first flowering season. In the second flowering season however, the reverse was true and UKA 59/240 performed better than BPA 75 by attaining 4.7 em, 4.1, 1.6 and 199 kg had in plant height, fruiting bodies per plant, bolls per plant and seed-cotton yields respectiycly over nPA 75. The reversal in performance of the bvo varieties could be attributed to varietal characteristics and moisture stress. BPA 75 is earlier 'maturing, more determinate in gr-owt-h and more sensitice to moisture stress than UKA 59/240. In the first flowering season BPA 75 therefore performed better than UKA 59/240 by virtue of its plant characteristics. However, in. the second flowering season following severe midseason moisture stress, it could not regenerate vegetative growth as fast as UKA 59/240, therefore its performance was worse , Farmyard manure increased plant height by 5.9 cm and bottom crop seedcotton yield by 90 kg had over the control (115.7 cm and 795 kg ha -I) respectively in the season. Nitrogen increased plant height, fruiting bodies per plant, bolls per plant, bottom crop, and total seedcotton yield, respectively by 1405 cm, 3.5, 1.8, 143 kg ha and 254 kg had.Apart from increasing plant height by 3.5 cm at the end of the mid-season drought, phosphorus has no effect on the crop in the October 1982 crop season. During the March 1983 crop season trial, no significant (P=O.OS) differences were observed among treatments for most part of the growing season, due most probably to very 10\'1rainfall. At flowering in September and in October, treatment effects became significant (P=O.05) as rainfall increased. Over this period up to harvesting in December, UKA 59/240 performed better in plant height (3.9 cm) and fruiting (1.8 fruiting bodies per plant) than BPA 75 which attained 109.5 cm in plant height and produced an average of 12.0 bolls per plant. Farmyard manure and nitrogen had no effect on fruiting and boll production, but increased plant height (5.3 and 5.4 cm respectively) and seedcotton yield (125 and 127 kg ha respectively) in the season. There was an interaction between variety and manure so that response to manure was higher in BPA 75 than in UKA 59/240. Seedcotton yield was negatively affected by PXN interaction. Correlations of soil nitrogen and phosphorus with foliar nitrogen and phosphorus respectively and correlations of foliar nitrogen and phosphorus, boll size and branches per plant ,with seedcotton yield were not significant, However, plant height and bolls per plant were significantly correlated with seedcotton yield.