Discussion
To understand the functional diversity, composition, structure and dynamics of rhizospheric diazotrophs communities under sugarcane-legume intercropping, we carried out this study to examine the effect of different cultivation systems on the stability of the soil properties and rhizospheric diazotrophs. Previous studies have investigated that soil microbial diversity, soil enzyme activities and crop yield could be affected by land management practices and all these soil properties were increased under intercropping systems than monoculture (Yang et al. 2013; Li et al. 2015b; Wang et al. 2014; Zou et al. 2011). Moreover, our previous study also discussed that soil biochemical and enzymes have direct effect by intercropping system …show more content…
2012). Our results also correlated with these studies. Soil enzymes are essential for nutrient cycling. Soil enzyme activity is also an important bio-indicator of soil fertility and quality. Activities of soil urease, nitrite reductase, protease, dehydrogenase and nitrogenase are important indexes for evaluating biochemical processes related to soil N transformation. In our study, the activity of urease was increased in monoculture and the activities of nitrite reductase, protease, dehydrogenase and nitrogenase were increased in intercropping. One possibility is that in monoculture for higher urease activity, N-fertilizer rate was same in monoculture and intercrops, and intercrops utilized soil urea faster than monoculture. Nitrite reductase, protease and nitrogenase play significant roles in nitrogen cycle and higher activities of these enzymes showed that vital microbial community enhanced in intercropping system. The nitrogenase enzyme catalyzes the reduction of atmospheric dinitrogen to ammonia. This process is energy expensive and is, therefore, tightly regulated (Dixon and Kahn, 2004). Low pH, low available N and increased levels of C will permit more optimal environments for free-living …show more content…
Moreover, Rhizobium sp. is well notorious to colonize roots of a broad range of nonlegume plants like sugarcane (Li et al. 2015b, Perin et al. 2006), sorghum (Coelho et al. 2009), rice (Xie and Yokota, 2006), maize (Perin et al. 2006) and switch grass (Bahulikar et al. 2014), and Burkholderia sp. has been already detected as an active N-fixing bacterium in sugarcane (Perin et al. 2006). Regardless of N-fixers, alphaproteobacteria were the most abundant, and this outcome was generally consistent with those of some researchers who demonstrated that alphaproteobacteria were the most abundant and common group in soil (Coelho et al. 2009; Yousuf et al. 2014). Based on the observed nifH OTUs richness and calculated estimates, the farming soil is the most diverse in the soil sites included in this study. The predominance of nifH OTUs related to proteobacteria and the nonappearance of nifH gene sequence related to Cyanobacteria, Firmicutes and Archaea have also been described from some previous studies (Coelho et al. 2009; Lovell et al. 2001; Jenkins et al. 2004; Tai et at. 2013; Tai et at. 2014;
To understand the functional diversity, composition, structure and dynamics of rhizospheric diazotrophs communities under sugarcane-legume intercropping, we carried out this study to examine the effect of different cultivation systems on the stability of the soil properties and rhizospheric diazotrophs. Previous studies have investigated that soil microbial diversity, soil enzyme activities and crop yield could be affected by land management practices and all these soil properties were increased under intercropping systems than monoculture (Yang et al. 2013; Li et al. 2015b; Wang et al. 2014; Zou et al. 2011). Moreover, our previous study also discussed that soil biochemical and enzymes have direct effect by intercropping system …show more content…
2012). Our results also correlated with these studies. Soil enzymes are essential for nutrient cycling. Soil enzyme activity is also an important bio-indicator of soil fertility and quality. Activities of soil urease, nitrite reductase, protease, dehydrogenase and nitrogenase are important indexes for evaluating biochemical processes related to soil N transformation. In our study, the activity of urease was increased in monoculture and the activities of nitrite reductase, protease, dehydrogenase and nitrogenase were increased in intercropping. One possibility is that in monoculture for higher urease activity, N-fertilizer rate was same in monoculture and intercrops, and intercrops utilized soil urea faster than monoculture. Nitrite reductase, protease and nitrogenase play significant roles in nitrogen cycle and higher activities of these enzymes showed that vital microbial community enhanced in intercropping system. The nitrogenase enzyme catalyzes the reduction of atmospheric dinitrogen to ammonia. This process is energy expensive and is, therefore, tightly regulated (Dixon and Kahn, 2004). Low pH, low available N and increased levels of C will permit more optimal environments for free-living …show more content…
Moreover, Rhizobium sp. is well notorious to colonize roots of a broad range of nonlegume plants like sugarcane (Li et al. 2015b, Perin et al. 2006), sorghum (Coelho et al. 2009), rice (Xie and Yokota, 2006), maize (Perin et al. 2006) and switch grass (Bahulikar et al. 2014), and Burkholderia sp. has been already detected as an active N-fixing bacterium in sugarcane (Perin et al. 2006). Regardless of N-fixers, alphaproteobacteria were the most abundant, and this outcome was generally consistent with those of some researchers who demonstrated that alphaproteobacteria were the most abundant and common group in soil (Coelho et al. 2009; Yousuf et al. 2014). Based on the observed nifH OTUs richness and calculated estimates, the farming soil is the most diverse in the soil sites included in this study. The predominance of nifH OTUs related to proteobacteria and the nonappearance of nifH gene sequence related to Cyanobacteria, Firmicutes and Archaea have also been described from some previous studies (Coelho et al. 2009; Lovell et al. 2001; Jenkins et al. 2004; Tai et at. 2013; Tai et at. 2014;