In order to explore the regulation effects of straw return replacing the application of potassium fertilizer on dryland summer maize—winter wheat rotation system

four treatments including no fertilizer (CK)

nitrogen and phosphorus fertilizer (NP)

nitrogen

phosphorus and potassium fertilizer (NPK)

nitrogen and phosphorus fertilizer plus straw returning (NPS) were selected based on the long-term located field experiment which started in 2007 at dry farming platform (Luoyang) of Chinese Academy of Agricultural Sciences. We investigated the grain yield

water and fertilizer use efficiency of summer maize and winter wheat rotation system from 2015 to 2020

as well as the content of organic matter

total nitrogen

available phosphorus and available potassium in 0—60 cm soil layer

and soil nitrate accumulation in 0—260 cm soil layer at harvest of winter wheat in 2020. Compared with NP

NPK significantly increased the content of available potassium in the 0—60 cm soil layer

but did not change the grain yield

water and fertilizer use efficiency of summer maize and winter wheat rotation system

while NPS was beneficial to improve soil nutrient

and significantly increased the grain yield

water and fertilizer use efficiency in summer maize and whole year. Compared with NPK

NPS significantly increased the organic matter content by 10.68% in 0—20 cm soil layer

the grain yield

water use efficiency

and the agronomic efficiency of N(P) fertilizer in summer maize and whole year increased by 20.91%

33.77%

114.39% and 13.60%

13.63%

65.41%

respectively

but significantly decreased the available phosphorus content by 7.43% in 0—20 cm soil layer and the available potassium content by 14.31% in 0—60 cm soil layer. Compared with NP and NPK

the nitrate accumulation in NPS was increased by 37.14% and 25.92% in 0—100 cm soil layer

and decreased by 32.33% and 21.64% in 160—260 cm soil layer. In conclusion

straw return could be used for replacing the application of potassium fertilizer on the basis of N and P fertilizer

because it could not only increase the content of organic matter and total nitrogen in 0—20 cm soil layer and nitrate accumulation in 0—100 cm soil layer

thereby improving the grain yield

water and fertilizer use efficiency in summer maize and whole year

but also reduced the risk of soil nitrate leaching to deep layer. Therefore

NPS was a suitable measure in dryland summer maize—winter wheat rotation system

but it should be paid more attention to the problems of the decrease of available phosphorus and available potassium in soil.