Potassium uptake and partitioning relative to dry matter accumulation in cotton cultivars differing in maturity

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Dry matter may accumulate faster in fruit of earlier maturing cotton (Gossypium hirsutum L.) cultivars than in later cultivars, requiring more rapid K uptake and/or partitioning to developing bolls. Faster K uptake may require higher K fertility. We examined K uptake and partitioning relative to dry matter accumulation during boll filling of two cultivars contrasting in maturity, under two K fertility regimes at Jackson, TN. Plots fertilized with 56 kg K ha–1 yr–1 received the recommended rate of K, while plots receiving 112 kg K ha–1 yr–1 were overfertilized with K. ‘PM 1218 BG/RR’ (PVP 200000213) matured earlier than ‘DP 555 BG/RR’ (PVP 200200047) in 2005, and ‘FM 960BR’ PVP 200400224 matured earlier than DP 555 BG/RR in 2006, but not 2007. Higher K fertility did not increase lint yields, but it delayed maturity in two of 3 yr. During boll filling, the earlier cultivar accumulated more dry matter and K in fruit than the later cultivar, and accumulated them faster in 2 of 3 yr. Higher K fertility shifted the partitioning of dry matter and K to vegetative organs relative to fruit. The proportion of plant K in fruit exceeded the proportion of dry matter in fruit, and the difference increased during boll filling. Evidently, K translocation to fruit exceeded dry matter accumulation in fruit, indicating that boll filling was not limited by K. Neither the K-uptake ratio (total aboveground K relative to residual soil K plus fertilizer K) nor the K-utilization ratio (lint produced per unit plant K) differed between cultivars with sufficient K fertility.

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