In drill-seeded, delay-flooded organic rice production, reliable predictions of N supply from cover crop (CC) residues to subsequent rice are still a challenge. An incubation was conducted to determine the effects of CC types (clover, ryegrass, clover and ryegrass mixtures, and fallow), residue application rates (0, 0.6, 1.2, 1.8, and 2.4%) and incubation time on soil CO₂ evolution and N mineralization and availability. The cumulative CO₂ evolution linearly increased with increasing residue rate. Compared to the control, adding CCs residue significantly increased the cumulative CO₂ emission, which was greatest in soils with clover or mixtures of clover and ryegrass, followed by fallow, and lowest in soils with ryegrass. The modeling results indicated clover had the greatest initial C and N mineralization rates and the shortest half-lives. A temporary decrease in soil mineral N caused by immobilization occurred at the initial incubation stage in all treatments. However, the trend reversed progressively, with the clover treatment requiring the shortest time to meet the crossover point. The results suggested clover was the optimal CC type, 0.6% was the optimal residue rate, and a minimum of 27 days between CC termination and rice planting was required to maximize mineral N supply for organic rice.

中文翻译：

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覆盖作物类型和施用量对有机水稻生产中土壤氮矿化和有效性的影响

在播种播种，延迟注水的有机大米生产中，从覆盖作物残渣到后续大米的氮供应的可靠预测仍然是一个挑战。进行培养以确定CC类型（三叶草，黑麦草，三叶草和黑麦草混合物和休闲草），残留物施用率（0、0.6、1.2、1.8和2.4％）以及培养时间对土壤CO ₂释放和释放的影响。氮矿化和可用性。累积的CO ₂释放量随着残渣率的增加而线性增加。与对照组相比，添加CC残留物显着增加了累积CO ₂排放量，在三叶草或三叶草与黑麦草的混合物中最大，其次是休闲，在黑麦草的土壤中最低。模拟结果表明，三叶草的初始碳和氮矿化率最高，半衰期最短。在所有处理中，在初始孵化阶段，固定化引起的土壤矿质N暂时减少。但是，这种趋势逐渐逆转，三叶草的处理需要最短的时间才能达到交叉点。结果表明，三叶草是最佳的CC类型，最佳残留率是0.6％，从CC终止到水稻种植至少需要27天才能使有机水稻的矿质氮供应最大化。