Nitrate accumulation in semiarid apple orchard on the Loess Plateau of China

Understanding of nitrate accumulation in soil profiles of semiarid regions is helpful to assess the environmental risks associated with nitrate. In the 5-year, 10-year and 20-year apple orchard, the nitrate accumulation were 169, 1683 and 1976 kg N ha−1 . A large amount of nitrate was found accumulated in the soil profile with 20-year apple orchard, and high nitrate level appears through the whole soil profile and nitrate peak appears in the top 100 cm and 300–400 cm in the soil profile. Clearly, the amount of nitrate accumulated in the soil profiles, and its tendency of downward movement, appears to potentially be an environmental risk as it may reach groundwater.

Apple trees started to plant across the Loess plateau since 1980, a large area of cropland converted into apple orchard. Overuse of chenical fertilizer is the major driver to increase soil productivity in the apple orchard. However, previous studies focused on the impact of fertilizer use on apple yield; few studies have considered the environmental implications of fertilizer use and specifically the impact of fertilizer use on nitrate risk.