Composted organic manures modulated soil-microbe interactions that enhanced the growth of tobacco by improving...

Stacking, a pivotal step in the preparation of composted organic manures, plays a crucial role in organic matter decomposition, nutrient availability, and soil microbial diversity, with effects dependent on the stacking duration. However, the mechanisms through which organic manures with different stacking times influence crop growth and development via alterations in the soil environment remain poorly understood. This study employed a pot experiment with tobacco plants, applying conventional fertilizers alongside organic cottonseed meal manures subjected to various stacking times (0, 10, 20, and 30 days). The primary aim was to examine the impact of cottonseed meal organic manures on the microbial community structure, function, and chemical properties of tobacco-growing soil, as well as to assess dry matter accumulation in tobacco plants. Results revealed that, compared to conventional fertilizers alone, the addition of cottonseed meal organic manures significantly enhanced soil organic matter content, with the 20d-stacked manure showing the highest increase (68.94%). Additionally, the composition of the soil microbial community was modified, which has increased the relative abundance of carbon and nitrogen metabolic functions. Dry matter accumulation in tobacco plants increased by 13.66%, 25.83%, 31.65%, and 9.69% across the different stacking times. In conclusion, composted organic manures regulate the soil-microbe system, promoting tobacco growth by enhancing the microbial structure of rhizosphere soil and improving nutrient availability. Cottonseed meal organic manures subjected to 20d of composting exhibited the most comprehensive benefits. The enrichment of beneficial microbes like Chryseobacterium and Humicola (potential antagonists of soil pathogens) might contribute to the observed enhancement in soil organic matter and available nutrients. This improvement in soil quality led to a balanced nutrient environment, ultimately promoting dry matter accumulation in tobacco plants. These findings offer robust theoretical support for the application of composted organic manures.IMPORTANCEThis study is important because it elucidates the crucial mechanisms by which composted organic manures, specifically through the regulation of the soil-microbe system, promote crop growth. It provides key evidence that the stacking duration is a critical factor, identifying a 20-day (d) composting period for cottonseed meal manure as optimal for delivering comprehensive benefits: (i) Enhanced soil health: significantly increasing soil organic matter and improving nutrient availability. (ii) Improved microbial community: shifting the soil microbial structure to favor beneficial bacteria and suppress pathogens, thereby enhancing metabolic functions related to carbon and nitrogen cycling. (iii) Direct crop promotion: leading to a substantial increase in dry matter accumulation in tobacco plants.