Yield and potassium use efficiency of cotton with wheat straw incorporation and potassium fertilization on soils with various conditions in the wheat–cotton rotation system.

Potassium (K) deficiencies have occurred increasingly in cotton due to increased use of nitrogen (N) and phosphate (P) fertilizers and high yielding varieties in China. Crop residue retention can improve soil K concentration, however, the replacement effects of K fertilizer by various wheat straw incorporation rates in different soil textures were seldom reported. As a result, the effects of wheat straw incorporation and K fertilization rates on cotton yield and K use efficiency in the wheat–cotton rotation system were studied for 3 years at two sites (Nanjing and Dafeng) in the down reaches of Yangtze River in China. Compared with control, the lint yields after applying wheat straw and K fertilizer were improved by 102.4–143.5% and 44.2–144.3% at Nanjing in 2012 and 2013, respectively, and by 33.7–42.3% at Dafeng in 2013. There was no significant difference between treatments in lint yield at Dafeng in 2012. Potassium source (from wheat straw or inorganic K fertilizer) had no significant effect on lint yield and yield components. Soil available K concentration and K uptake by cotton were significantly affected by K input (wheat straw or K fertilizer). Potassium use efficiencies were typically higher in fields with wheat straw incorporation than with K fertilization. Potassium replacement amounts by wheat straw (9000 kg ha −1 ) were above 150 kg K 2 O ha −1 of inorganic K fertilizer when the soil available K concentration before cotton transplantation was above 125 mg kg −1 and about 115 kg K 2 O ha −1 when soil available K concentration was below 125 mg kg −1 at Nanjing. Moreover, K replacement effect by wheat straw was non-significant at Dafeng because of high soil available K concentration. In conclusion, K release from wheat straw can at least partly, even totally, replace chemical potash according to soil available K concentration in actual cotton production. [ABSTRACT FROM AUTHOR]