Effects of returning organic waste on soil enzymes and microbial quantity in dryland farming

The application of animal manure combined with straw is an important strategy for sustainable agricultural production. The objective of this study was to investigate the effects of animal manure combined with straw on soil enzymes and microbial quantity. The two-year experiment involved four treatments: maize straw only, maize straw plus ox manure, maize straw plus chicken manure, and maize straw plus pig manure. In 2018 and 2019, treatments with animal manure combined with straw led to increased levels of soil microbial quantity, soil enzyme activity, and yields. Compared to other treatments, higher catalase activities were achieved in both years for the maize straw plus ox manure and maize straw plus pig manure treatments whereas the cellulase activities were higher for the maize straw plus ox manure and maize straw plus chicken manure treatments. The maize straw plus ox manure treatment had the highest number of soil bacteria, and the quantity of actinomycetes was higher after the applications of maize straw plus ox manure and maize straw plus chicken manure as compared to the other treatments. Moreover, compared to the application of maize straw only, treatment maize straw plus pig manure had the most significant effect on the soil urease activity, invertase activity, fungal quantity, and maize yield with 43.9, 35.9, 52.0, and 31.7% increases, respectively. In conclusion, our findings suggested that animal manure combined with straw, especially the application of maize straw plus pig manure was the most effective treatment for enhancing soil enzymes and microbial quantity and also promoting maize yield.