Effects of fungal residues return on soil enzymatic activities and fertility dynamics in a paddy soil under a rice-wheat rotation in Chengdu Plain

In the Peoples Republic of China, more than 4 Mt of fungal residues needs to be treated yearly. To investigate the effect of Agaricus bisporus residues return on soil fertility, this study compared the effects of five treatments on soil nutrients, soil enzymatic activities, N use efficiency and crop yields in a paddy soil under a rice-wheat rotation. Five treatments were designed including application of chemical fertilizer only (CF), a combined application of 30% fungal residues and 70% chemical fertilizer with the ratio of total N in the fungal residues to that in CF being 0.3:1 (30%FR), a combined application of 70% fungal residues and 30% chemical fertilizer with the ratio of total N in the fungal residues to that in CF being 0.7:1 (70%FR), a full dose of fungal residues return only with the ratio of total N in fungal residues to that in CF being 1:1 (100%FR), and a full return of fungal residues only with the ratio of total N in fungal residues to that in CF being 1.5:1 (150%FR). We found that the content of soil nutrients and soil enzymatic activities in the same treatment were higher at VGS (vegetative growth stage) than at RGS (reproductive growth stage) in rice and wheat seasons. 100%FR and 150%FR treatments had higher level of soil organic matter, available N, P, K, invertase, urease, neutral-phosphatase, catalase, N use efficiency and crop yields than CF treatment. These results indicated that A. bisporus residues return could positively affect soil nutrients, soil enzymatic activities, N use efficiency and crop yields as organic manure in a paddy soil. The information obtained will be helpful to more rational utilization of fungal residues.