Effects of soil conditioner on soil-crop nitrogen transport and crop nitrogen utilization under different irrigation levels in China.

Purpose: The application of soil conditioner has become one of the most important strategies to reduce nitrogen (N) losses from agricultural fields. However, it is still unclear about the effect of conditioners on soil profile N accumulation and crop N utilization under different irrigation levels. Materials and methods: In this study, the effects of combination of N fertilizer (255 kg/ha) and different doses of soil conditioner (mixture of anionic polyacrylamide, polyvinyl alcohol, and manganese sulfate) (0 (N), 0.008 (P₁N), 0.016 (P₂N), and 0.024 (P₃N) g/kg) on soil - oat crop N transport and oat crop N utilization were explored under different irrigation levels (conventional irrigation volume (4.1 × 10⁶ L/ha), W₁₀₀; 80% of the conventional irrigation volume (3.28 × 10⁶ L/ha), W₈₀). Results and discussion: The combination of conditioner and N fertilizer increased soil capillary moisture capacity (CWC), field capacity (FC), total porosity (TP), and capillary porosity (CP) in the 0–40 cm (W₈₀) and 20–60 cm (W₁₀₀) soil layers, and reduced non-capillary porosity (N-CP) of the 0–40 cm soil layer (W₁₀₀). Besides, it also positively affected the total N storage (STN) and nitrate N storage (SNN) in the 0–80 cm soil layer, especially under the W₁₀₀ condition (the STN and SNN in the combination treatments of conditioner and N fertilizer (P₁N, P₂N, and P₃N) increased by 5.5%–9.2% and 14.6%–16.3%, respectively compared with those in the single N treatment). Correlation analysis of N fractions and soil physical properties showed that STN was significantly positively correlated with CP; SNN was significantly negatively correlated with CP under the W₈₀ condition, but there was no significant correlation between them under the W₁₀₀ condition. Finally, the combination of different doses of conditioner and N fertilizer increased grain N accumulation and oat yield, especially under the W₈₀ condition. Conclusions: The addition of conditioner had a higher N loss risk under the W₁₀₀ condition than under the W₈₀ condition, although it was beneficial to reducing N loss (31.8%–32.2%) and increasing inorganic N accumulation (14.5%–16.0%) during the reproductive period. We suggest that the combination of 12 kg/ha conditioner, 255 kg/ha N, and 80% of the conventional irrigation volume could be widely used to increase oat crop yield and reduce production cost and environmental pollution risk in the study area. [ABSTRACT FROM AUTHOR]