triennial cropping

例句：

1. 1. The farmers arepracticing triennial cropping to improve soil fertility.
   农民们正在练习三熟作物种植，以提高土壤肥力。
2. 2.This method is based on the principle of triennial cropping, which helps to reduce the risk of soil contamination.
   这种方法基于三熟作物种植的原理，有助于降低土壤污染的风险。
3. 3. In this region, triennial cropping is an important agricultural practice for maintaining soil health and productivity.
   在这个地区，三熟作物种植是保持土壤健康和生产力的重要农业实践。