Environmental transport of excess nitrogen fertilizer in peach orchard: Evidence arising from 15N tracing trial

Abstract

In pursuit of high fruit yield, overwhelming amount of nitrogen (N) fertilizer was unreasonably applied in orchard, resulting in lower fertilizer N uptake and higher environmental loss. It is crucial to propose appropriate fertilization timing and optimal N management by clarifying fruit tree N uptake pattern in orchard systems. Here, a ¹⁵N isotope enrichment trial was conducted in peach orchard to assess the transport of applied synthesized fertilizer-N to the plant and environment in the Taihu Lake region. Ammonium sulfate ((NH₄)₂SO₄, 10.12 atom % ¹⁵N), as the N source, was applied with four split applications at 382.5 kg N ha⁻¹ during one plant growth cycle. Results showed N deriving from fertilizer (NDFF) accounted for 24.5% in leaves and 38.4% in fruits, respectively. During the annual growth cycle, the applied fertilizer-N uptake and utilization was higher in reproductive growth stage than vegetative growth stage. After harvest, 28.8% of applied fertilizer-N was absorbed by peach tree, 9.5% was lost to the environment through surface runoff, ammonia (NH₃) volatilization and nitrous oxide (N₂O) emission, 29.6% was retained in the 0–160 cm soil profile, the remaining 32.1% was unaccounted N including N leaching and N loss from the N removal progress. Generally, more applied fertilizer-N moved to the environment in high N input peach orchard. In order to promote optimal N management, the applied fertilizer-N rate should be reduced by 30% and emphasized on fertilization at the reproductive growth period according to tree N uptake pattern.