黄壤旱地豆科绿肥养分释放特征

在贵阳市黄壤旱地内采用尼龙网袋法，研究不同含水量的绿肥在直接还田和添加生物炭后翻压还田情况下的养分释放特征，以期为黄壤旱地绿肥科学还田及化肥合理减施提供理论依据。结果表明：不同处理的腐解速率趋势相同，均呈现先快速腐解、再缓慢腐解、并逐渐趋于平稳的趋势，总腐解速率表现为风干绿肥+生物炭 > 新鲜绿肥+生物炭 > 风干绿肥 > 新鲜绿肥。经过180 d的腐解，新鲜绿肥、风干绿肥、新鲜绿肥+生物炭、风干绿肥+生物炭腐解速率分别为74.77%、83.13%、92.69%和95.83%，添加生物炭处理绿肥腐解速率高于未添加生物炭处理，风干绿肥腐解速率高于绿肥腐解速率。与腐解速率相似，不同处理的氮和磷的累积减少率均先快速腐解，再缓慢腐解，最终腐解平稳，到达平衡，经过180 d的腐解，新鲜绿肥、风干绿肥、新鲜绿肥+生物炭、风干绿肥+生物炭的氮素释放率分别为73.55%、83.80%、92.00%和95.00%，磷素释放率分别为76.40%、87.13%、93.31%和96.27%；钾素腐解率高于氮素和磷素，不同处理的绿肥在腐解30 d后释放率均在80%以上。综上，不同含水量的绿肥腐解速率不同，风干绿肥的腐解速率高于新鲜绿肥，同时添加生物炭能提高风干和新鲜绿肥的腐解速率。绿肥还田后，可适当减少氮和钾的施用量，还田初期可不调整氮磷肥的施用量，钾肥可适当延后施用。

Nutrient release characteristics of leguminous green manures in yellow soil uplands

To provide a scientific basis for the scientific returning of leguminous green manure and reasonable reduction of chemical fertilizer application in yellow soil uplands, a nylon bag net bag embedding method was utilized for the decomposition and nutrient release of leguminous green manure with different water contents and biochar addition in the yellow soil uplands experimental base of the Guizhou Academy of Agricultural Sciences. The trend of the decomposition rate was the same between the different treatments, which showed that the decomposition rate was fast at first, then slowly decomposed, and finally the decomposition stabilized and reached equilibrium. The total decomposition rate was air dried green manure + biochar > fresh green manure + biochar > air dried green manure > fresh green manure. After 180 days of decomposition, the decomposition rates of fresh green manure, air dried green manure, fresh green manure + biochar, and air dried green manure + biochar were 74.77%, 83.13%, 92.69%, and 95.83%, respectively. The decomposition rate of green manure treated with biochar was higher than that without biochar, and the decomposition rate of air dried green manure was higher than that of green manure. Similar to the decomposition rate, the decomposition rates of N and P were fast at first, then slowly decomposed, and finally the decomposition stopped and reached equilibrium. After 180 days of decomposition, the decomposition rates of N and P for fresh green manure, air dried green manure, fresh green manure + biochar, and air dried green manure + biochar were 73.55%, 83.80%, 92.00%, 95.00%, and 76.40%, 87.13%, 93.31%, 96.27%, respectively. The decomposition rate of K was higher than that of N and P, the release rate of green manure in different treatments reached more than 80% after 30 days of decomposition. The decomposition rate of the air dried green manure was higher than that of the fresh green manure, and adding biochar improved the decomposition rate of air dried and fresh green manure. In actual operation, the decomposition rate of green manure with different water content was different; leguminous green manure can be returned to the field after air drying, and biochar and other alkaline substances are added to improve the decomposition efficiency. It was indicated that after returning green manure to the field, the application rates of N and K fertilizer should be decreased and K fertilizer could be used in crop growth at a later stage, while N and P should be maintained as a usual practice at the early crop growth stage.