© 2016 Lv et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. 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).15 N-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.
Lv, J., Liu, H., Wang, X., Li, K., Tian, C., & Liu, X. (2016). Highly arid oasis yield, soil mineral n accumulation and n balance in a wheat-cotton rotation with drip irrigation and mulching film management. PLoS ONE, 11(10). https://doi.org/10.1371/journal.pone.0165404