Straw return increases crop grain yields and K-use efficiency under a maize-rice cropping system
Yuling Han, Wei Ma, Baoyuan Zhou, Akram Salah, Mingjian Geng, Cougui Cao, Ming Zhan, Ming Zhao
Abstract
Straw return is an effective way to improve crop grain yield and potassium (K) use efficiency by increasing soil K content. However, the effects of straw return on soil K supplying capacity, replacement of K fertilizer, and K-use efficiency under maize (Zea mays L.)–rice (Oryza sativa L.) cropping systems are little studied. A two-year field experiment was conducted to determine the physiological determinants of K-use efficiency under straw return with four K fertilization rates. Sr33 (straw returned plus 33% of K fertilizer applied) and Sr67 (straw returned plus 67% of K fertilizer applied) increased annual crop yields by 1.5% and 3.2% and increased agronomic K-use efficiency by respectively 2.9 and 1.3-fold on average in the two years, compared with the conventional practice S0K100 (no straw returned plus normal amounts of K fertilizer applied). The Sr33 and Sr67 treatments resulted in significantly greater equilibrium K concentration ratios (CR0K) and specifically exchangeable K (KX) values according to quantity/intensity (Q/I) relationship analyses, indicating improvement of the potential soil K supply capacity. However, the Sr67 better maintained the soil exchangeable K level and K balance. The results suggested that K released from maize and rice straw can replace about half of chemical K fertilizer, depending on the available K content in maize–rice cropping system production.