Long-term trajectories of nutrient budgets and changes in soils of two
counties with contrasting land use changes: cereals vs fruit orchards
Abstract
Land use change (LUC) is a key factor affecting nutrient budgets in
agricultural soils. Comparing the long-term trajectories of nutrient
budgets and changes in soils at a regional scale with contrasting LUC is
critical to optimizing nutrient management and minimizing adverse
environmental effects. We investigated the nutrient budgets and changes
in soils in two counties in the south Loess Plateau, China, with
contrasting LUCs from 1992 to 2017. Wugong County has cereals as the
main crop, whereas Meixian County has the main cereal crops changed to
kiwi orchards. We found that nitrogen (N), phosphorus (P), and potassium
(K) inputs in two counties increased rapidly, and the nutrient outputs
by crop harvests remained relatively stable. This resulted in increasing
nutrient surpluses in the soils of two counties. Nutrient surplus in the
orchard-dominated county was higher than that of the cereal-dominated
county, and nutrient use efficiencies were contrasting. High N surplus
in the orchard-dominated county resulted in high nitrate-N accumulation
in deeper soil profiles of orchards. High P and K surpluses in the two
counties significantly increased available P and K in 0-20 cm depth.
Soil available P and K in the orchard-dominated county were
significantly higher than in the cereal-dominated county, which was also
significantly higher than the threshold values of available P and K
contents in soils. We conclude that comprehensive measures should be
taken to control nutrient surpluses, which will help to balance nutrient
inputs and outputs and minimize nutrient losses in intensive
horticultural crop systems.