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

This long-term field experiment (conducted since 1993) with irrigated spring wheat northeastern Xining City of Qinghai Province has six treatments including: NP, NPK, NP with 50% straw return (NP+50% ST), NP with 100% straw return (NP+100% ST), NPK with 50% straw return (NPK+50% ST), and NPK with 100% straw return (NPK+100% ST).

Results from the last 20 years of data indicated that the yield of spring wheat increased with the application of N, P and K fertilizers combined with straw. Along with N and P application, straw return and/or fertilizer K application improved the protein content of wheat grain and had no negative effects on grain quality. Compared with the control treatment without K and straw addition, fertilizer K application and/or straw return decreased soil bulk densities by 1.2 to 7%, increased the amount of soil water-stable aggregates (>0.25mm), and improved the stability of soil aggregate. The light fraction of soil organic matter, total organic matter, and soil N, P and K contents were also all increased with fertilizer K application and/or straw return. The soil available K content was 280 mg/kg in the NPK+100% ST treatment, which was about 2.6 times the available K content in the control treatment. Thus, appropriate amounts of fertilizer K application and/or straw return in addition to N and P fertilization can improve wheat yield/quality and soil fertility. A 50% straw return rate can replace fertilizer K application in the local agricultural practice. Qinghai-2010