Effect of long-term application of potash and straw return on wheat yield and soil K balance in Qinghai province

This fixed-site, irrigated spring wheat experiment has been conducted on a loamy, Chestnut soil site in northeastern Xining City of Qinghai Province since 1993. The study is evaluating the long-term agronomic effects of NP and NPK treatments used in combination with complete, 50%, and zero straw recycling.

In 2010, after 18 years of study, wheat yield with NP was 7.3% lower than with NPK. Use of NP plus 50% straw recycling were as productive as the NPK treatment. Complete straw recycling, with or without fertilizer K, failed to generate more yield than the NP treatment due to the poor residue decomposition and its negative effects on seed germination. The K input and output balance in 2010 showed that K input in the NPK treatment did not compensate for crop K removal, only the NPK plus straw return could maintain a positive soil K balance and soil K surplus. Either practice of partial or complete straw recycling without fertilizer K application generated a soil K deficit. Qinghai-2010