Effects of straw return on soil nutrients and microorganisms in late rice under different soil tillage systems
不同土壤耕作方式下秸秆还田量对晚稻土壤养分与微生物的影响

The effects of returning early rice straw to the soil on soil nutrients and microorganisms in late rice under different tillage conditions, including normal tillage (deeply plowing and harrowing), minimum tillage (rotary tillage only) and no-tillage were studied. The main results showed that (1) contents of phosphorus and potassium in soil were improved significantly by straw return, while improvement of the available nitrogen was only observed in the late stage of rice cultivation. The effects of straw return on the available nitrogen and phosphorus were best under no-tillage conditions, while the content of potassium was best under the minimum tillage condition. (2) Different return straw percentages should be adopted under different tillage systems. To improve contents of phosphorus and potassium, 100% straw return should be adopted under normal tillage and minimum tillage conditions, while two thirds straw return should be adopted under the no-tillage condition. (3) Soil fungi and anaerobic bacteria decreased, while actinomycetes and aerobic bacteria increased after straw return. Tillage led to decrease of fungi and anaerobic bacteria and increase of aerobic bacteria. (4) Soil tillage improved the microbial activity in the early and late growth stages of late rice. The amount of straw returned affected microbial activity differently under different tillage systems, and it was highest in the treatment with 2/3 return straw under normal tillage conditions, while it was highest in the treatment with 1/3 return straw under minimum and no-tillage conditions.