Effects Of Field Return Of Fungal Residues On Soil Enzyme Activities In A Paddy Soil Under A Rice-Wheat Rotation In Chengdu Plain

Most of fungal residues disposed without recycled use in agriculture in Chengdu Plain. Base on above, this paper compared the effects of different treatments on soil enzymatic activities and crop yields in a paddy soil under a rice-wheat rotation in Chengdu Plain by the method of field surveys, field experiments and statistical analysis. This work can put a high light on the effects of fungal residues returned to the field on changes of soil enzymatic activities and soil productivity under a rice-wheat rotation.Six treatments were designed including application of chemical fertilizer only (CF), chemical fertilizer plus straw return (CF+S), 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). Treatments were arranged in a randomized block design with four replications. The plot size was 5 m×6 m. Soil samples were collected at different stages during the rice or wheat growing seasons. In rice growing season, soil samples were collected at tillering, jointing, heading and ripening stages; in wheat growing season, soil samples were collected at seeding, tillering, jointing, heading and ripening stages. Soil samples were taken with a soil auger at depths of 0-10,10-20 and 20-40 cm between rows. Soil invertase, urease, phosphatase, catalase and crop yields were studies. The main researeh results were as follow:(1) The profile distribution of soil enzymatic activities of different fertilization treatments:Soil invertase, urease, phosphatase and catalase activities increased with decreasing soil depth among rice and wheat growing stages except at the tillering and jointing stages in rice growing season. The 10-20 cm soil layer showed the highest soil catalase activity at the tillering and jointing stages in rice growing season. (2) Effect of different fertilization treatments on soil enzymatic activities:CF+S,30%FR and 70%FR treatments had no effective effects on soil invertase, urease, phosphatase and catalase activities compared with CF treatment, at least under a rice-wheat rotation; 100%FR and 150%FR treatments had more effective effects on soil invertase, urease, phosphatase and catalase activities compared with CF treatment, at least under a rice-wheat rotation.(3) Effect of different fertilization treatments on crop yields:In rice season, yield increased by 4.89% under CF+S,9.83% under 100%FR and 4.01% under 150%FR compared to that of CF, whereas yield decreased by 6.99% under 30%FR and 1.05% under 70%FR compared to that of CF. In wheat season, yield increased by 13.23% under CF+S,10.61% under 100%FR and 9.68% under 150%FR compared to that of CF, whereas yield decreased by 6.02% under 30%FR and 3.31% under 70%FR compared to that of CF.(4) The selection of optimum amout of fungal residues returned to the field:Under our experimental conditions,100%FR and 150%FR treatments had more effective effects on soil invertase, urease, phosphatase, catalase and crop yields compared with CF treatment.