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.