Effects of sugarcane and maize intercropping on sugarcane rhizosphere microbe metabolic function diversity

Sugarcane-maize intercropping is an important planting pattern in sugarcane production area, which is in favor of sugarcane production benefit and land use efficiency increases, and pesticide control of sugarcane. However, the effects of sugarcane and maize intercropping on sugarcane rhizosphere microbe community have less been reported. In this study, a plot experiment was carried out in sugarcane fields in Yuanjiang and Longchuan Counties of Yunnan Province to investigate the microbe activities, metabolic function diversity and carbon sources utilization by using Biolog techniques. The results showed that compared with monocultured sugarcane at Longchuan County experimental site, Shannon index, Simpson index, McIntosh index and evenness index of Shannon and McIntosh of microbial communities in rhizosphere soils of intercropped sugarcane increased by 7.08%, 11.25%, 63.16%, 1.31% and 2.26%, respectively. Then, compared with sugarcane monoculture in Yuanjiang County, the above diversity indices increased by 10.58%, 48.40%, 43.42%, 0.20%, and 1.65%, respectively, in intercropped sugarcane treatment. This suggested that intercropping increased the metabolic function diversity of rhizosphere soil microbes. Although the utilization of carbon resources increased in intercropping systems, it was lower at Yuanjiang experimental site than that at Longchuan experimental site. Compared with monoculture, the utilization of carbohydrate, amino acids, polymeric substances, amines, carboxylic acids and phenolic acids increased by 141.71%, 50.53%, 62.38%, 92.82%, 43.21% and 6.30%, respectively, at Yuanjiang experimental site. Correspondingly, the variables increased, respectively by 42.90%, 51.50%, 33.30%, 42.64%, 16.72% and 24.47% at Longchuan experimental site. Moreover, the utilization of D-cellobiose, D,L-α-glycerol phosphate, D-galactonic acid-γ-lactone, L-serine, Glycyl-L-Glutamine and 2-Hydroxy benzoic acid increased by over 100% at both of Yuanjiang and Longchuan experimental sites. The results of principal component analysis (PCA) suggested that intercropping changed rhizosphere soil microbial community composition and metabolic function. Three carbon resources (including carbohydrate, carboxylic acids and amino acids) were the most sensitive carbon resources utilized by soil microorganisms in sugarcane rhizosphere soils. The carbon resources with high effect on microbial community composition and metabolic function at Longchuan experimental site were 2 kinds of polymeric substances, 6 kinds of carbohydrates, 2 kinds of carboxylic acids, 4 kinds of amino acids and 1 kind of phenolic acid. There were 15 kinds of carbon resources (including 1 kind of polymeric substances, 5 kinds of carbohydrates, 3 kinds of carboxylic acids, 4 kinds of amino acids and 2 kinds of amines) at Yuanjiang experimental site. These carbon resources had significant effect on microbial community composition and metabolic function. In conclusion, intercropping of maize and sugarcane increased microbial community diversity, activation and metabolic function of rhizosphere soil.