Spatial distribution of potassium uptake across the cotton plant affects fiber length

To enhance whole plant fiber quality of cotton, the relationship between the spatial distribution of potassium (K) absorption and fiber length was investigated. In 2007, a field experiment was conducted to assess genotypic differences among 17 cultivars for potassium absorption and fiber length. Differences in both K uptake and fiber length existed among cultivars in field conditions. The cultivars could be categorized into three classes: moderate K uptake and high fiber length; high K uptake and moderate fiber length; and both low K uptake fiber length. In 2008, single cultivars representative of each of these three classes were selected to further investigate spatial distribution patterns of K absorption and cotton fiber length, respectively. In 2009, differences among the three selected cultivars in K uptake and fiber length were further studied under three K fertilizer regimes and by foliar spraying of KCl. Higher K uptake at upper and distal positions of the plant was associated with longer fiber; however, at lower and proximal positions no such association was observed. The change of K uptake and fiber length is related to cultivar and K fertilizer application as well. For all three cultivars, without K fertilizer application, K uptake and fiber length decreased from lower to upper sections and from proximal to distal positions. With increasing K application, K uptake increased for all positions, especially upper and distal positions. For cultivar Siza3, higher fiber lengths were consistent with greater K uptake at upper and distal sections. For cultivar Xuza3, fiber length declined markedly when K application rate increased from 225 to 450 kg hm(-1) even if K absorption was enhanced. For Sumian9, fiber lengths were no longer increased when K rate increased from 225 to 450 kg hm(-1). These results suggested that rational K fertilizer management could improve whole plant fiber length of cotton cultivars that have intermediate K absorption potential with high uptake ability at upper and distal positions. (C) 2016 Elsevier B.V. All rights reserved.