Mechanism harvesting of main crops straw returning effects on ratooning fragrant rice yield and 2-acetyl-1-pyrroline and their drivers to soil microbial communities.

Straw return to the field is an important measure for increasing soil fertility to increase production. Recent studies have shown that straw return to fields can increase rice yield, but the effect of straw return to fields on ratooning rice is limited. To address this problem, this paper investigated the effect of straw return on a ratooning rice system by harvesting at different heights during the first season. A two-year field experiment was conducted by using a fragrant rice variety (Meixiangzhan 2) as the material. Three experimental treatments including i) the CK treatment: manual harvesting and straw harvested at a height of 20 cm was not returned to the field; ii) the MT1 treatment: mechanical harvesting and straw was returned to the field at a harvest height of 10 cm; iii) the MT2 treatment: mechanical harvesting and straw at a harvest height of 20 cm was returned to the field. The investigated parameters in the rice cropping system in this study were the agronomic traits, yield formation, soil properties, and root soil microorganisms. We found that compared with those in the CK treatment, the yield and 2AP content in the MT treatment significantly increased, the yields of MT1 and MT2 increased by 18.17-32.64% and 12.19-20.42%, respectively. The contents of available potassium, available phosphorus, ammonium nitrogen and active organic carbon in the soil were significantly increased by straw return to the field. The soil capacity increased, and rice production increased. In addition, the straw returned to the field produced a large amount of cellulose and anaerobic environment, which provided an explanation for the increase in some anaerobic bacteria, such as pseudxanthomonas, Rhodobacteriaceae and desulphurides in the MT treatment group. Specifically, straw return provides a large amount of organic material for rice cultivation systems and improves soil fertility under the action of microorganisms to increase production. Overall, the interaction between straw return and harvest height had different effects on yield and 2AP content, and the MT2 treatment was the most beneficial for harvesting ratooning fragrant rice.