Abstract:
Field trials were conducted during the dry seasons of 2007, 2008, and 2009, at the Irrigation Research Station Farm, Kadawa (11039’N, 08027’E; altitude 500m), of the Institute for Agricultural Research to study the response of cotton varieties to irrigation methods and nitrogen fertilization. Treatments consisted of factorial combinations of four levels of nitrogen fertilizer (40, 70, 100 and 130 kg ha-1), three irrigation methods (border strip, check basin and furrow), and three cotton varieties (SAMCOT 10, SAMCOT 11 and SAMCOT 13), laid out in a split plot design replicated three times. Nitrogen and irrigation methods were factorially combined and assigned to the main plots while cotton varieties were assigned to the sub-plots. Agronomic practices where done to ensure good crop growth. In the three years the performance of the varieties was generally better in 2008 than the other two years due to better weather and nutrient status of the area. The study showed that among the varieties tested, SAMCOT 13 exhibited superior growth and yield performance in most of the characters measured than the other two varieties. SAMCOT 13 variety had significantly higher dry matter production, leaf area index, crop growth rate, net assimilation rate, number of branches per plant, number of bolls per plant, boll weight, number of seeds per boll, 100-seed weight, percentage oil content of cotton seed, fibre finess, seed cotton (600 kg ha-1) and lint yield per ha. Check basin irrigation method gave higher seed cotton yield only in 2007 while lint yield was not affected by irrigation method. Border strip significantly resulted in taller plants, earlier flowering and boll opening while furrow irrigation resulted in higher percentage of protein content of cotton seeds. Furrow irrigation resulted in higher water use efficiency and fibre finess. Increasing nitrogen fertilization significantly increased growth characters like plant height, total dry matter, leaf area index, CGR and number of branches per plant but significantly delayed days to 50% flowering and boll opening. The seed cotton yield and most of the yield components were significantly increased with application of 70 kg N ha-1 but further increase resulted in significantly lower yields. Seed cotton yield had positive and significant correlation with total dry matter, LAI, number of branches per plant, days to 50% flowering and boll opening, number of bolls plant-1 boll weight and number of seeds per boll. Path analysis indicated that the highest contribution to seed cotton yield by growth characters was through total dry weight and leaf area index while highest contribution by yield components to seed cotton yield was through boll weight and number of seeds per boll. Polynomial responses of seed cotton yield to varied nitrogen rates showed a quadratic response with 93.0 kg N ha-1 as the optimum rate for seed cotton yield during the combine mean. The partial economic analysis showed that it is more economical to apply 70 kg N ha-1 to SAMCOT 13 cotton variety under border strip irrigation method. Furrow irrigation method gave highest water use efficiency, percentage oil and protein content of cotton seed. The use of SAMCOT 13 and 93.0 kg N ha-1 using border strip irrigation method will be better adopted for maximum seed cotton yield during dry season.
RESPONSE OF COTTON (Gossypium hirsitum L.) VARIETIES TO IRRIGATION METHODS AND NITROGEN FERTILIZATION.
