Comparisons between an Upland and a Pima cotton cultivar: II. Nutrient uptake and partitioning

Uptake and partitioning of N, P, and K by Upland cotton (Gossypium hirsutum L.) have been studied, but no such work has included American Pima cotton (G. barbadense L.). Our objective was to describe the N, P, and K uptake and partitioning into various plant parts for two representative Upland and Pima cotton cultivars. Upland 'Deltapine 90' (DPL 90) and Pima 'S- 6' were grown at two south-central Arizona locations for 3 yr. Beginning 14 to 20 d after emergence, the aboveground portions of cotton plants were harvested and separated into stems, leaves (including petioles), burs (carpel walls), lint, and seeds. The bur fraction also included squares, flowers, immature bolls, and burs from mature bolls. Total N, P, and K analyses were conducted on each fraction (except lint). Nutrient concentration, uptake, and partitioning by cotton was modeled on a heat unit accumulation basis (HUAP). Up to about 1500 HUAP, leaves were major N sinks, leaves and the bur fraction were major P sinks, and leaves and stems were major K sinks for both cultivars. After 1500 HUAP, the bur fraction and seeds were major N and P sinks and the bur fraction was the major K sink. For DPL 90, the total N, P, and K uptake was 201, 31, and 254 kg ha^-1 and for Pima S-6, it was 201, 32, and 226 kg ha^-1, respectively. Nutrient requirements for producing 100 kg lint ha^-1 were 15-2.3-19 kg ha^-1 N-P-K for Upland cotton and 21-3.3-23 kg ha^-1 for Pima cotton.