Effects of raised-bed planting for enhanced summer maize yield on rhizosphere soil microbial functional groups and enzyme activity in Henan Province, China

Abstract

Although raised-bed planting systems can enhance productivity of summer maize (Zea mays) relative to other systems employed in China, mechanisms for this remain unclear. Because of their potential to enhance maize yield, we examined effects of raise-bed planting on rhizosphere microbial functional groups and associated enzyme activities in 2006 and 2007 crop seasons. Results confirmed that raised-bed planting significantly and substantially increased maize growth. Microbial functional groups and enzyme activities varied during the maize growing season, with patterns often correlated with plant growth. For raised-bed planting, mean numbers of bacteria, fungi, and actinomycetes across all three sampling times in 2006 were 7.3×106, 1.6×104, 1.9×105CFUsg−1drysoil, respectively, 82, 44, and 43% higher than those in flat planting, respectively. In 2007, relative differences were 108, 40, and 34% higher than those in flat planting, respectively. Raised-bed planting yielded mean saccharase, urease, protease and phosphatase activities across sampling times in 2006 of 2.3mgglucoseg−1h−1, 0.8mgNH3-Ng−1h−1, 10.5mgglycinekg−1h−1, and 0.4mgnitrophenolg−1h−1, 6, 18, 34, and 31% higher than those in flat planting, respectively. In 2007, relative differences were 10, 16, 35, and 27% higher than those in flat planting, respectively. Rhizosphere enzyme activities were significantly correlated with maize yields. These results suggest that raised-bed planting (1) may enhance maize productivity in part by increasing availability of essential crop nutrients by stimulating microbial activity, and (2) is potentially important in sustainable increasing China's supply of maize.