垄作稻田土壤无机氮变化及其对环境因子的响应OA

To investigate the dynamics of soil inorganic nitrogen across rice(Oryza sativa)growth stages and the responses to soil environmental factors,a two-year(2021-2022)field monitoring experiment was conducted under ridge tillage(RT)and conventional tillage(CT).It was found that:1)The ammonium nitrogen(NH₄⁺-N)peaked at the tillering jointing stage(RT:89.7 mg‧kg-1;CT:52.1 mg‧kg-1),whereas nitrate nitrogen(NO₃⁻-N)reached its maximum at maturity(RT:42.7 mg‧kg-1;CT:58.4 mg‧kg-1).NH₄⁺-N concentrations in the 0-20 cm soil layer were consistently higher under RT,while NO₃⁻-N concentrations were higher under CT.2)Whole-plant average nitrogen content and nitrogen use efficiency peaked at the tillering stage,and high nitrogen uptake during the jointing stage-heading stage coincided with a marked reduction in soil ammonium nitrogen.3)Soil temperature and electrical conductivity showed overall increasing trends during the rice growth period,whereas soil moisture fluctuated among growth stages reflecting irrigation and drainage practices.Under RT,NH ₄+-N exhibited a significant correlation with soil temperature at the jointing stage,while NO₃--N showed significant correlations during the heading and maturity stages.Under CT,NH₄⁺-N was significantly correlated with soil temperature during the tillering and heading stages,whereas NO₃--N was significantly correlated with soil moisture content at the heading stage.4)Simulation results based on nonlinear curve fitting indicated that NH₄+-N contents under both RT and CT followed a pattern of initial increase followed by a decrease.NO₃--N content under RT exhibited a similar trend,whereas NO₃--N content under CT showed a nonlinear increasing pattern.Crop uptake dominated the variations in both ammonium and nitrate nitrogen during the early growth stages(78.5％),whereas environmental factors became increasingly important during the later stages,contributing up to 61.1％of the explained variation.Compared with nitrate nitrogen,ammonium nitrogen was more sensitive to environmental factors.In conclusion,the most pronounced changes in soil inorganic nitrogen occurred during the tillering stage of paddy rice.Variations in soil inorganic nitrogen during both the tillering and maturity stages were most sensitive to changes in soil temperature.Ridge tillage increased NH₄+-N concentrations in paddy soil while reducing the accumulation of NO₃--N.These findings provide a scientific basis for optimizing nutrient management strategies in regional rice production systems.