Land-use changes from arable crop to kiwi-orchard increased nutrient surpluses and accumulation in soils

Abstract

The potential environmental risk associated to nutrient surpluses after changing arable crops to kiwi-orchards was assessed in the Yujiahe catchment of Shaanxi, China. This was achieved by surveying 242 kiwi-orchards and 21 croplands and determining their nutrient inputs and outputs as well as the soil nutrient status for the over 2 years. The total inputs of nitrogen (N), phosphorus (P) and potassium (K) from fertilizers, manures, deposition, and irrigation in kiwi-orchards were 1201, 268 and 615kgha−1yr−1, respectively, which were higher than the rates of 425, 59 and 109kgha−1yr−1 in wheat-maize fields. The mean annual apparent nutrient surpluses in kiwi-orchards were 1081kgNha−1yr−1, 237kg Pha−1yr−1 and 491kgKha−1yr−1. Within comparison to the croplands, the soil organic matter (SOM) and total N (TN) in the topsoil (0–20cm) increased in kiwi-orchards, and soil pH decreased. The average contents of Olsen-P, and available K in 0–20cm soils of the orchards were 86mgkg−1, and 360mgkg−1, which were higher than recommended levels. The nitrate-N accumulation in the 0–100cm and 0–200cm soil layers in kiwi-orchards were 466 and 793kgNha−1, respectively. The high proportion of nitrate-N in deeper soil profiles of kiwi-orchards poses a great risk for nitrate leaching and subsequent ground water pollution. It is concluded that changing arable crops to kiwi-orchards increased the environmental burden of the catchment due to excessive fertilizer application in kiwi-orchards.