Soil amended with biochar has many potential environmental benefits, but its influence on the fate of nitrogen (N) under irrigated conditions is unclear. The objective of this research was to determine the effects of biochar and interactions with irrigation on N movement in soil, gas emissions, and leaching. A three-year study was conducted in an onion field with three main irrigation treatments (50, 75, and 100% of a reference that provided sufficient water for plant growth) and three biochar amendment rates (0 or control, low char - applied first year at 29 Mg ha-1, and high char - added both first and second year for a total 58 Mg ha-1) as sub-treatments in a split-plot design. Nitrogen fertilizer was applied three times during first year growing season, but weekly the second year. Ammonia (NH3) volatilization, nitrous oxide (N2O) emission, and nitrate (NO3-) in soil pore water were monitored during growing season, and annual N (total and NO3-) changes in soil profile were determined for first two years. Nitrate leaching was measured in the third year. Ammonia volatilization was affected by fertilization frequency with higher loss (5-8% of total applied) when fertilizer was applied in large doses during the first year compared to the second year (4-5%). Nitrous oxide emissions were ≤0.1% of applied N for both years and not affected by any treatments or fertilization frequency. Nitrate concentration in soil profile increased significantly as irrigation level dropped, but most of the NO3- was leached by winter rain. There was no significant biochar effect on total N gas emissions or soil NO3- accumulation, but significant irrigation effect and interaction with biochar were determined on soil NO3- accumulation. High leaching was associated with biochar amendment and higher irrigation level. Irrigation strategies are the key to improving N management and developing the best practices associated with biochar.

中文翻译：

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氮素动态受洋葱田中生物炭和灌溉水平的影响。

用生物炭改良的土壤具有许多潜在的环境效益，但对灌溉条件下其对氮素命运的影响尚不清楚。这项研究的目的是确定生物炭及其与灌溉的相互作用对土壤中氮移动，气体排放和淋溶的影响。在洋葱田进行了为期三年的研究，对洋葱进行了三种主要灌溉处理（50％，75％和100％的参考水，为植物生长提供了充足的水）和三种生物炭修正率（0或对照，低碳-首先施用一年的时间为29 Mg ha-1，高焦炭-第一年和第二年共增加了58 Mg ha-1），作为分块设计中的子处理。氮肥在第一年的生长期施用了三次，第二年每周施用一次。氨（NH3）挥发，一氧化二氮（N2O）排放，在生长期监测土壤孔隙水中的硝酸盐（NO3-）和硝酸盐（NO3-），并确定前两年土壤剖面中氮（总氮和NO3-）的年度变化。第三年测量硝酸盐的浸出量。与第二年（4-5％）相比，第一年大剂量施肥时，氨气挥发受施肥频率的影响，损失较高（占施用总量的5-8％）。两年中一氧化二氮排放量≤施氮量的0.1％，且不受任何处理或施肥频率的影响。随着灌溉水位的降低，土壤剖面中的硝酸盐浓度显着增加，但是大多数NO3-被冬季降雨淋滤掉。生物碳对总氮气体排放或土壤NO3的积累无明显影响，但对土壤NO3-的累积具有显着的灌溉效果以及与生物炭的相互作用。高浸出与生物炭改良和更高的灌溉水平有关。灌溉策略是改善氮素管理和开发与生物炭有关的最佳做法的关键。