ABSTRACT
Evaluation of crop response to phosphorus (P) fertilizers is an important part of developing an efficient fertilization program. This long-term study was conducted to determine P requirements of short-season cotton using the acid-base fertilizers urea phosphates, (UP and UUP). Response to P was compared at N rates of 20, 40 and 80 lb n ac-1. Phosphorus rates were varied at 0, 20, 40 and 80 lb P2O5 AC-1. Cotton (Gossypium hirsutum L.) was grown under dryland conditions from 1978 through 1990 on an orelia fine sandy clay loam (Typic Ochraqualf). There was a significant average yield response to 20 lb P2O5 Ac-1 for the first five years where N was supplied at 80 lb N Ac-1. Responses to higher rates (40 and 80lb P2O5 Ac-1) were generally not significant. Tissue P generally increased with applied P fertilizer when N was supplied at 40 and 80 lb N AC-1. Linear correlations between leaf P and lint yields were sparingly significant for specific N rates and seasons.
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