Intercropping Alters the Soil Microbial Diversity and Community to Facilitate Nitrogen Assimilation: A Potential Mechanism for Increasing Proso Millet Grain Yield

Abstract

Intercropping of cereals and legumes has been used in modern agricultural systems, and the soil microorganisms associated with legumes play a vital role in organic matter decomposition and nitrogen (N) fixation. This study investigated the effect of intercropping on the rhizosphere soil microbial composition and structure and how this interaction affects N absorption and utilization by plants to improve crop productivity. Experiments were conducted to analyze the rhizosphere soil microbial diversity and the relationship between microbial composition and N assimilation by proso millet (Panicum miliaceum L.) and mung bean (Vigna radiata L.) from 2017 to 2019. Four different intercropping row arrangements were evaluated, and individual plantings of proso millet and mung bean were used as controls. Microbial diversity and community composition were determined through Illumina sequencing of 16S rRNA and internal transcribed spacer (ITS) genes. The results indicated that intercropping increased N levels in the soil–plant system and this alteration was strongly dependent on changes in the microbial (bacterial and fungal) diversities and communities. The increase in bacterial alpha diversity and changes in unique operational taxonomic unit (OTU) numbers increased the soil N availability and plant N accumulation. Certain bacterial taxa (such as Proteobacteria) and fungal taxa (such as Ascomycota) were significantly altered under intercropping and showed positive responses to increased N assimilation. The average grain yield of intercropped proso millet increased by 13.9–50.1% compared to that of monoculture proso millet. Our data clearly showed that intercropping proso millet with mung bean altered the rhizosphere soil microbial diversity and community composition; thus, this intercropping system represents a potential mechanism for promoting N assimilation and increasing grain yield.

Long-term maize-Desmodium intercropping shifts structure and composition of soil microbiome with stronger impact on fungal communities

“…Other studies have reported a similar trend where cereal-legume intercropping increases overall diversity of soil microorganisms. Such observations have been made in wheat-soybean intercropping (Bargaz et al 2017), maize/wheat-faba bean intercropping (Wang et al 2020) and millet-mung bean intercropping (Dang et al 2020). While intercropping with annual legumes may cause a temporary shift in the soil microbial profiles, the impact of perennial crops and intercrops, such as Desmodium spp., on soil microbial diversity is likely to be stronger and more resilient.…”

Influence of Peanut, Sorghum, and Soil Salinity on Microbial Community Composition in Interspecific Interaction Zone

“…Particularly, in salinized soils, monoculture farming faces a double combination of excess salinity and continuous cropping obstacles. To overcome these problems, intercropping can be considered a novel approach to increase the efficiency of resource utilization, management of soil-borne diseases, and tolerance of farmland ecosystem stress ( Li Q. et al, 2016 ; Guo et al, 2018 ; Dang et al, 2020 ).…”

Rhizosphere P-Enzyme Activity, Mineral Nutrient Concentrations, and Microbial Community Structure Are Altered by Intra-Hole Cropping of Cowpea With Cereals

“…It is also therefore likely that the Pseudomonas and Xanthomonas species found in the Proteobacteria phylum in this study were the beneficial rather than pathogenic species, given the greater abundance of mutualistic microbes such as Flavobacteriales, Sphingobacteriales, Bascillales, Phycisphaerae, Rhizobiales, and Sphingomonadales found in this same study. Dang et al (2020) found similar changes in some bacterial taxa, especially Proteobacteria, in a mung bean-millet intercropping system. Even with a tomato/potato-onion intercropping devoid of legumes, there was an alteration in soil microbial communities (Li et al, 2020), suggesting that changes in rhizosphere microflora is not unique to legume-cereal systems, but more likely an outcome of the composition of root exudates released by the intercropped partners.…”

“…Although rhizosphere microbial composition used to be studied by culturing the bacteria for single species interactions, now however, root-microbe interactions and the composition of root-associated microbial community have become easier to assess, with the development of next generation sequencing (Mendes et al, 2013;Hacquard et al, 2015). Furthermore, while several studies have been conducted on intercropping (Wahua, 1984;Li and Wu, 2018;Dang et al, 2020;Li et al, 2020), to our knowledge little is known about intra-hole cropping of legumes and cereals. We hypothesized that intra-hole cropping of cowpea-maize, and cowpea-sorghum would influence soil P-enzyme activity, mineral nutrient accumulation and microbial communities based on the partners used in the intra-hole cropping system.…”