Relationships among rates of n, p, and k, soil test values, leaf analysis and yield of cotton at 6 locations

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Abstract
Long‐term rates of N, P, and K experiments at 6 locations were made residual studies for P and K after 16 years of continuous applications. Cotton leaf samples for 2 years and soil samples after one year were analyzed and results correlated with yield. Highly significant yield response to N was found at all locations with the best rate varying from 34 to 135 kg/ha. Leaf N from treatments producing best yields varied from 3.1 to 4.9%. Significant correlations were found among N applied, leaf N, and yield at all locations. Only two soils showed response to P. Leaf P data indicate that 0.3% P was adequate. Leaf P was correlated with soil P and yield where response was found. Five locations showed response to K with significant correlations among K applied, soil test.K, leaf K, and yield in most cases. Leaf K from plots producing best yields varied from 0.90 to 1.57%. Average leaf content of N, P, K, Ca,Mg, Mn,Fe, B, Zn, and Al from 384 samples are reported.