Effects of Different Irrigation and Fertilizer Application Regimes on Soil En-zyme Activities and Microbial Functional Diversity in Rhizosphere of Ratoon-ing Rice

Irrigation and fertilizer application regime is one of key measures for high and stable yield of ratooning rice, especially for middle or low stubble ratooning rice by machine-harvest. Ascertaining rational management of water and fertilization is important for improving the axillary bud germination rate of lower nodes in middle or low stubble ratooning rice by machine-harvest. With Luyoumingzhan as a test material, the effects of different irrigation and fertilizer application regimes on ratooning tillers, soil enzyme activity and rhizosphere microbial functional diversity of ratooning rice were studied by setting up three treatments: (1) dry-wet alternate irrigation and nitrogen application for ratooning bud development (GN), (2) dry-wet alternate irrigation and no nitrogen application for ratooning bud development (G), (3) flooding irrigation and no nitrogen application for ratooning bud development (S). The different irrigation and fertilization treatments had a significant impact on the rhizosphere Eh potential and rhizosphere soil enzymes. On the 10th day after treatment, the rhizosphere soil Eh levels and the activities of rhizosphere soil polyphenol oxidase, peroxidase, phosphate monoester enzyme and hydrogen peroxide enzyme were significantly improved in G than in S. The activities of rhizosphere soil polyphenol oxidase, peroxidase, urease, invertase, phosphate monoester enzyme and hydrogen peroxide enzyme were significantly improved in GN than in G. The rhizosphere soil microbe differed significantly in use of single carbon sources and diversity of carbon metabolism under different treatments. On the 10th day after treatment, the uses of single carbon sources and diversity of carbon metabolism in GN and G were significantly greater than those in S. The abilities to utilize amino acids, phenolic acids, carboxylic acid in GN were higher than those in G. Compared with S, bleeding rate of GN and G was increased by 27.27% and 14.84%, ratooning rice tiller and yield were increased by 102.50%–111.11%, 42.50%–44.44% and 91.41%–108.72%, 37.93%–40.94% respectively. All these results indicated that dry-wet alternate irrigation or nitrogen application for ratooning bud development could improve rhizosphere soil enzyme activities and promote the uses of single carbon sources and diversity of carbon metabolism, which is conducive to increasing the effectiveness of nutrient, the formation of new roots and the axillary buds germination. The effects of dry-wet alternate irrigation coupling with fertilizer are the best for ratooning rice growth.