Harnessing Microbial Agents to Improve Soil Health and Rice Yield Under Straw Return in Rice–Wheat Agroecosystems

We clarified the effect of wheat straw return combined with microbial agents on rice yield and soil properties. A field experiment was conducted using hybrid indica rice ‘ Chuankangyou 2115 ’ and five treatments: no wheat straw return (T 1 ), wheat straw return alone (T 2 ), T 2 + microbial agent application ( Bacillus subtilis / Trichoderma harzianum = 1:1) (T 3 ); T 2 + microbial agent application ( Bacillus subtili s/ Trichoderma harzianum = 3:1) (T 4 ); T 2 + microbial agent application ( Bacillus subtilis / Trichoderma harzianum = 1:3) (T 5 ). T 2 –T 5 significantly increased dry matter accumulation, soil total N, ammonium N, nitrate N, and organic matter, improving yield by 3.81–26.63%. T 3 exhibited the highest yield increases in two consecutive years. At the jointing and heading stages, Penicillium and Saitozyma dominated under T 3 and positively correlated with dry matter, yield, and nitrogen levels. Straw return combined with Bacillus subtilis and Trichoderma harzianum (20 g m −2 each) enhanced soil nitrogen availability and dry matter accumulation and translocation. Our findings guide efficient straw utilization, soil microbial regulation, and sustainable high-yield rice production.