Abstract
A better understanding of tree‐based intercropping effects on soil physicochemical properties and bacterial community has a potential contribution to improvement of agroforestry productivity and sustainability. In this study, we investigated the effects of mulberry/alfalfa intercropping on soil physicochemical properties and soil bacterial community by MiSeq sequencing of bacterial 16S rRNA gene. The results showed a significant increase in the contents of available nitrogen, available phosphate, available potassium, and total carbon in the rhizosphere soil of the intercropped alfalfa. Sequencing results showed that intercropping improved bacterial richness and diversity of mulberry and alfalfa based on richness estimates and diversity indices. The relative abundances of Proteobacteria, Actinobacteria, and Firmicutes were significantly higher in intercropping mulberry than in monoculture mulberry; and the abundances of Proteobacteria, Bacteroidetes, and Gemmatimonadetes in the intercropping alfalfa were markedly higher than that in monoculture alfalfa. Bacterial taxa with soil nutrients cycling were enriched in the intercropping system. There were higher relative abundances of Bacillus (0.32%), Pseudomonas (0.14%), and Microbacterium (0.07%) in intercropping mulberry soil, and Bradyrhizobium (1.0%), Sphingomonas (0.56%), Pseudomonas (0.18%), Microbacterium (0.15%), Rhizobium (0.09%), Neorhizobium (0.08%), Rhodococcus (0.06%), and Burkholderia (0.04%) in intercropping alfalfa soil. Variance partition analysis showed that planting pattern contributed 26.7% of the total variation of bacterial community, and soil environmental factors explained approximately 56.5% of the total variation. This result indicated that the soil environmental factors were more important than the planting pattern in shaping the bacterial community in the field soil. Overall, mulberry/alfalfa intercropping changed soil bacterial community, which was related to changes in soil total carbon, available phosphate, and available potassium.
Highlights
Soil plays a vital role in maintaining the balance of earth’s ecosystem (Nesme, Colomb, Hinsinger, & Watson, 2014)
Twenty-eight phyla were found in all samples, among them, the dominant bacterial phyla were Proteobacteria, Acidobacteria, Actinobacteria, Gemmatimonadetes, Chloroflexi, Planctomycetes, Bacteroidetes, and Nitrospirae; they accounted for over 95% of the reads in each sample, representing 35.5%, 19.0%, 16.1%, 9.6%, 6.8%, 4.3%, 4.3%, and 1.4%, respectively (Figure 1left)
The distinctions of bacterial community structure among mulberry and alfalfa groups were supported by the redundancy analysis (RDA)
Summary
Soil plays a vital role in maintaining the balance of earth’s ecosystem (Nesme, Colomb, Hinsinger, & Watson, 2014). Agroforestry system of intercropping between mulberry and crops has become an important planting pattern to bring economic development in this region. The effects of the mulberry/alfalfa intercropping system on soil physicochemical properties and bacterial community of crop rhizosphere were analyzed. We hypothesize that soil bacterial communities differ between mulberry and alfalfa as planting pattern conversion can induce changes in availability of plant-derived nutrients. Plants have species-specific effects on soil microbial communities (Bever, Platt, & Morton, 2012), and tree-based intercropping systems support a more diverse soil microbial community compared to conventional agricultural systems (Bainard, Koch, Gordon, & Klironomos, 2013). We hypothesize that soil bacterial community composition change and its diversity increase after intercropping
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