Effects of urea-N levels on yield of irrigated upland cotton, cv. Cnpa precoce 1

Abstract

A field experiment was carried out on an alluvial soil of the São Gonçalo Project, PB, Brazil, to evaluate the effect of urea-N, on yield cotton. The treatments consisted of levels 0, 40, 80, 120 and 160 kg/ha of N, applied all N in furrow of planting; 1/2 of N in planting + 1/2 of N 30 days after emergence of the plants; 1/3 of N in planting + 1/3 of N 30 days + 1/3 of N 50 days after emergence of the plant. The treatments were arranged in a randomized block design, in a factorial scheme with four replications. There was significant effect only to the N levels where 80, 120 and 160 kg/ha of N promoted the highest results, averaging 76,4, 76,6 and 78,2 cm for plant height and 3,445, 3,816 and 3,785 kg/ha for cotton yield, respectively. The yield results fitted the square function Y = 2,064.75 + 20.509x - 0.687x², with r² = 0.99**.