免耕条件下水稻产量及稻田无机氮供应特征

【目的】研究免耕条件下水稻产量及稻田无机氮供应特征。【方法】于2007—2010连续4年采用田间定位试验研究方法。试验设传统翻耕、免耕两个处理，4次重复。供试水稻品种为皖稻68。【结果】免耕显著提高了水稻生育前期耕层土壤NH4+-N含量，但是降低了水稻生育中、后期耕层土壤NH4+-N含量。同时免耕显著提高了0—10 cm土层NO3--N含量，降低了主要生育时期10—20 cm土层NO3--N含量，有利于减少耕层土壤NO3--N的淋失。免耕促进了土壤有机碳和全氮在表层土壤的富集。0—10 cm土层有机碳和全氮含量比翻耕处理显著增加，而10—20 cm土层上述养分含量明显低于翻耕处理。免耕提高了耕层（0—20 cm）土壤容重，增幅为3.06%—6.25%。产量结果显示，免耕使水稻减产4.11%—7.70%。【结论】免耕稻田自拔节期后期土壤NH4+-N供应量的减少使免耕水稻拔节期和抽穗期的氮素吸收量均明显低于翻耕处理，导致免耕水稻成穗率的减少，是免耕水稻产量降低的主要原因。

Effects of No-Tillage on Supply Characteristics of Soil Inorganic Nitrogen and Rice Yield

【Objective】To study the effect of no-tillage on supply characteristics of soil inorganic nitrogen and rice yield in paddy-upland rotation system.【Method】A long-term (2007-2010) experiment was conducted the field trail was designed to have two treatments with four replicates: No-tillage; conventional tillage, and the rice cultivar Wandao 68 was used as material.【Result】The results showed that NH4+-N content in arable layer soil was higher at rice early growth stage and lower at the middle and late growth stages than conventional tillage. Compared to conventional tillage, the NO3--N content in 0-10 cm soil layer was increased significantly while NO3--N content in 10-20 cm soil layer of main growth stage was decreased with no-tillage. That could help reduce the leaching loss of NO3--N in soil. The inorganic nitrogen of no-tillage was lower than that of conventional tillage in whole arable layer during rice season. No-tillage enriched soil organic matter and total nitrogen in the surface soil layer. Both the soil organic matter and total N content of no-tillage were significantly higher in 0-10 cm layer and lower in 10-20 cm layer than that of conventional tillage. The soil bulk density in 0-20 cm layer was increased by 3.06%-6.25% compared with conventional tillage. The yield results indicated that no-tillage treatment decreased rice yield notably by 4.11-7.70%. 【Conclusion】In comparison to conventional tillage, no-tillage treatment decreased NH4＋-N content since elongating and resulted in reducing absorption of nitrogen in plants at elongating and heading and the ratio of productive tillers to total tillers significantly. This was the main reason for the reduction of rice yield with no-tillage.