Abstract
Few systematic studies have been carried out on integrated N balance in extremely arid oasis agricultural areas. A two-year field experiment was conducted to evaluate the N input and output balances under long-term fertilization conditions. Five treatments were chosen, namely CK (no fertilizer), NPK, NPKS (10% straw return N and 90% chemical N), NPKM (one third urea-N, two thirds sheep manure) and NPKM+ (1.5 times NPKM). The results show an abundance of dry and wet N deposition (33 kg N ha-1 yr-1) in this area. All treatments (excluding CK) showed no significant difference in wheat production (P>0.05). NPKM gave higher cotton yields (P<0.05). In both crops, NPKM and NPKS treatments had a relatively higher N harvest index (NHI). 15N-labeled results reveal that the fertilizer N in all N treatments leached to<1 m depth and a high proportion of fertilizer-N remained in the top 60 cm of the soil profile. The NPKM+ treatment had the highest residual soil mineral N (Nmin, 558 kg Nd ha-1), and NPKM and NPKS treatments had relatively low soil Nmin values (275 and 293 kg N ha-1, respectively). Most of the treatments exhibited very high apparent N losses, especially the NPKM+ treatment (369kg N ha-1). Our arid research area had a strikingly high N loss compared to less arid agricultural areas. Nitrogen inputs therefore need careful reconsideration, especially the initial soil Nmin, fertilizer N inputs, dry and wet deposition, and appropriate organic and straw inputs which are all factors that must be taken into account under very arid conditions.
Highlights
Most nitrogen (N) pollution results from human activities [1] and especially those linked to the use of N fertilizers in intensive agriculture [2,3,4]
Most of the treatments that we examined in the field experiment had large amounts of mineral N in the soil profile
In the present study the N inputs from atmospheric dry and wet deposition accounted for 31– 35 kg N ha-1yr-1 and those from irrigation water accounted for 8–17kg N ha-1 yr-1, indicating that abundant environmental N enters the cropping system in this region
Summary
Most nitrogen (N) pollution results from human activities [1] and especially those linked to the use of N fertilizers in intensive agriculture [2,3,4]. The N Balance under Drip Irrigation and Mulching-Film Condition in Arid Oasis Areas
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