After over 20 years of practicing shallow rotary tillage combined with straw direct return in the middle and lower Yangtze regions of China, the yield potential has gradually disappeared, and new alternative tillage practices are required to continuously increase rice yield. This paper investigates the yield effect and mechanism of deep tillage combined with straw return through two consecutive years of a field experiment. Three tillage depths (shallow tillage 6–7 cm, ST; medium tillage 12–14 cm, MT; and deep tillage 25–28 cm, DT) plus three straw management methods (no straw return, NR; straw direct return, SR; and straw biochar return based on the same amount of carbon input as SR, BR) were set up as experiment treatments. The aboveground and belowground growth traits of rice and soil nitrogen (N) status were determined. Compared with ST and MT, the DT enlarged rice root distribution and increased soil N content in the middle and lower soil layers (7–28 cm) and decreased the root–shoot ratio at the flowering stage, which was conducive to absorbing more soil nutrients from the subsoil and allocating more photosynthetic products to the aboveground parts and grain. The MT and DT increased spike number and rice yield compared with ST. Compared with NR, both SR and BR increased soil total and available N contents, and the remaining soil available N content at the harvest stage of BR was lower than that of SR. Straw return (SR and BR) improved rice yield by increasing spike number and kernels per spike, and the effect of BR on increasing rice yield was greater than that of SR. The DT combined with BR increased root distribution and N content in the subsoil, promoted the utilization of subsoil's nutrients, and increased rice yield. It is therefore a promising tillage practice for achieving high rice yields.

中文翻译：

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深耕结合秸秆生物炭还田，通过改善氮肥利用率和根系在底土中的分布来提高水稻产量


长江中下游地区浅耕旋耕结合秸秆还田实践20多年后，产量潜力逐渐消失，需要新的替代耕作方式不断提高水稻产量。通过连续两年的田间试验，探讨深耕结合秸秆还田的增产效果及机理。三种耕作深度（浅耕 6-7 厘米，ST；中耕 12-14 厘米，MT；深耕 25-28 厘米，DT）加三种秸秆管理方法（不秸秆还田，NR；秸秆直接还田，SR；秸秆直接还田，SR；试验处理设置与SR、BR等碳输入量的秸秆生物炭还田。测定了水稻的地上和地下生长性状以及土壤氮（N）状况。与ST、MT相比，DT扩大了水稻根系分布，提高了中下土层（7~28cm）土壤氮含量，降低了花期根冠比，有利于吸收更多的土壤养分。并将更多的光合作用产物分配给地上部分和谷物。与ST相比，MT和DT增加了穗数和水稻产量。与NR相比，SR和BR均增加了土壤全氮和速效氮含量，且BR收获期剩余土壤速效氮含量低于SR。秸秆还田（SR和BR）通过增加穗数和穗粒数来提高水稻产量，且BR对水稻增产的效果大于SR。 DT与BR结合增加了根系分布和底土氮含量，促进了底土养分的利用，提高了水稻产量。 因此，这是一种有希望实现水稻高产的耕作方法。