5 Conclusions
Our study indicates that both the rapidly increasing application of synthetic fertilizers and LUC from cereal to intensively horticultural crops since the early 1990s in China contributed to the high nutrient surpluses in soils, resulting in low NUE of N, P, and K. Compared to the cereal-dominated county, nutrient surpluses in soils in the orchard-dominated county are very high, which reduced the NUE. The high N surplus in the orchard-dominated county increased high nitrate accumulation in deeper soil profiles of orchards; and nitrate accumulation in soil profiles increased with the stand ages of orchards. Unlike N, high P and K surpluses in the two counties from 1992 to 2017 significantly increased available P and K in 0-20 cm soil. The soil available P and K in the orchard-dominated county is significantly higher than the cereal-dominated county. This highlights that comprehensive measures should be taken to reduce nutrient surpluses to minimize nutrient loss and environmental pollution in China, especially in the intensive horticultural crop systems.