Exploring the Association Between Inherent Soil Nutrient Availability and Crop Responses Following Long-term Cessation of Fertilizer Inputs in a Wheat–Maize Cropping System

Intensive agriculture relies mainly on the injudicious application of fertilizers. The importance of inherent soil fertility is often ignored owing to the complexity of the relationship between crop productivity and soil properties in the field with continuous fertilization. Here, our goal was to improve the understanding of long-term crop responses to soil nutrient availability. This study was one component of long-term nutrient management experiments conducted from 1993 to 2018. Field receiving standard fertilization before 2007 was divided into fertilized and non-fertilized plots. Fertilizer application was suspended in non-fertilized treatment since 2007 for 11 years, but control treatment continuously received standard fertilization (252–164–281 kg ha−1 year−1 of N–P–K) from 1993 to 2018. Crop biomass and N uptake decreased by 29–69% and 28–76% of standard fertilization in wheat and maize, respectively from 2008 to 2011, and then stabilized at 10–41% and 31–73% of standard fertilization in wheat and maize, respectively, from 2012 to 2018. Spatial analysis of crop growth and soil characteristics showed that grain yields of both species after cessation of fertilization were associated with total and available soil N (r = 0.62–0.79). The large within-field yield variation (42–52%) after 3 years of suspended fertilization resulted from a slight (9%) variation in soil N availability. Cessation of fertilizer affected vegetative growth of wheat and reproductive growth of maize and both species showed different determinants of the yield formation processes under low soil fertility.