The production of high cotton yield is highly dependent on adequate growth rate and nutrient uptake about which relatively little information is available under semiarid conditions.
Growth rate and N, P, K uptake of two cotton (Gossypium hirsutum L.) cultivars, ‘Acala 1517-C’ and ‘Acala 4-42,’ which differ in their response to K fertilizer, were investigated in an irrigated field (soil type - Typic Rhodoxeralf) under favorable conditions conducive to high yields.
The rate of dry matter production was slow until flowering and after the first bob opened. Up to 72 days from emergence, 15% of the total dry matter was produced; from 112 days until picking, 10%; and during the 40-day period from 72 to 112 days, 75%. Throughout this period the growth rate was nearly linear, 250 kg/ ha/day.
Total dry matter was 12,200 to 13,480 kg/ha. Its distribution in mature plants was 26% in the leaves, 24% in stems, 16% in burs, 21% in seeds, and 13% in lint. The lint yield was 1,700 kg/ha. Total uptake of N, P, and K was 230, 45, and 174 kg/ha.
The total uptake of N and P followed that of dry matter production, whereas K was absorbed more rapidly, reaching a maximum at 112 days from emergence and then decreasing. The removal of nutrients from the field by seed and lint was 98 to 109 kg N/ha, 19 to 21 kg P/ha, and 43 to 47 kg K/ha.
Toward the end of growing season Acala 1517-C suffered more than Acala 4-42 from K deficiency in soils with a low supply of available K. The factors which may be responsible for this in Acala 1517-C are earlier development, greater uptake of K during early growth, the larger uptake of K by relatively more developed reproductive parts, and the relatively smaller root system.
The rates of growth and uptake in the present experiment were greater than those reported in the literature. Also, Acala 1517-C and Acala 4-42 differed in their nutrient uptake, especially of potassium.