In agriculture, soil health is disturbed by various anthropogenic activities, including applications of chemicals, and highly mechanized cropping methods, leading to a gradual loss in soil fertility and microbial diversity. Therefore, it is the need of the hour to shift towards eco-friendly and sustainable agri-management practices. The practice of conservation agriculture (CA) is considered a holistic approach towards sustainability due to minimum soil disturbance and permanent soil cover. The present study aimed at gaining an in-depth understanding of the impact of CA practice on dynamics of rhizospheric bacterial community in comparison to conventional agriculture (CT) and organic agriculture (OA). Field experiments were set with Cajanus cajan as a model crop under CA, CT, and OA modules, comprising of different applications of tillage, crop residue retention, crop bedding pattern, and nutrient applications for three consecutive cropping seasons (2017–2019). Soil microbial activities were evaluated using various enzymatic assays. Enhanced soil microbial activity was observed under CA- and OA-based modules compared to the CT modules. For assessment of the resident rhizospheric bacterial community 16S rRNA PCR-denaturing gradient gel electrophoresis (DGGE) was performed. Abundance of dominant bacterial taxa ( α-Proteobacteria, β-Proteobacteria, Acidobacteria, Actinobacteria, Firmicutes ) was estimated by qPCR. Definite shifts were evident in bacterial community structure under conservation regimes with relatively higher Margalef Species Richness and Shannon–Wiener indices in CA compared to CT and OA. Additionally, CA exhibited a higher abundance of dominant bacterial groups in comparison to CT. A noteworthy correlation could be drawn among agri-management practices' performance and dynamics of bacterial community structure. The study brings forth the positive impact of CA-based farming practice on soil health in terms of enhancing bacterial community abundance and diversity.

Microbes regulate soil health by negating ecological disturbances, and improve plant productivity in a sustainable manner. Indiscriminate application of pesticides creates a detrimental impact on the rhizospheric microbiota, thereby affecting soil health. Azadirachtin, earlier believed to be an environment-friendly alternative to chemical pesticides, exhibits a non-target impact on microbial communities. This study aimed to employ potent bacteria to promote the growth of mungbean plant (Vigna radiata), and mitigate the non-target impact of azadirachtin. Bacterial strains were isolated by enrichment from mungbean rhizosphere. A plant growth experiment was performed with mungbean, amended with azadirachtin to assess the impact of bacterial bioinoculants on the rhizospheric microbiota. The impact of azadirachtin on rhizospheric bacterial community was analyzed qualitatively and quantitatively by 16S rRNA PCR-DGGE and qPCR of various markers, respectively. Residual concentration of azadirachtin in the soil was estimated by HPLC. The bacterial inoculants used in combination significantly promoted plant growth and enhanced the diversity and abundance of total bacterial community in the presence of azadirachtin. Further, the abundance of specific bacterial groups (α-Proteobacteria, β-Proteobacteria, Actinobacteria, Acidobacteria, and Firmicutes) were significantly boosted. Compared to the control, the isolates significantly facilitated the reduction in residual concentration of azadirachtin in the mungbean rhizosphere. Bacterial inoculants can serve a tripartite role in reducing the stress imparted by botanical pesticides, together with promoting plant growth and enriching the rhizospheric bacterial community structure.

Soil fertility is disrupted by diverse anthropogenic activities, including intensive agricultural practices (viz., conventional agriculture (CT)), affecting environmental sustainability. Hence, for sustainability, alternative agricultural practices, such as conservation agriculture (CA) and organic agriculture (OA) that can preserve the native soil microbiome and enhance soil fertility, need to be adopted. This study aimed to assess the impacts of three farming practices on rhizospheric bacterial guilds involved in the phosphorus cycle. Extensive field experiments were performed with two crops, pigeonpea and soybean, over three consecutive cropping years (2017–2019), with nine modules under three agricultural practices (CA, OA, and CT). The modules varied in tillage, crop rotation, crop residue retention, crop establishment methods, and nutrient management. The impact of agricultural practices was assessed on rhizospheric bacterial guilds involved in P cycle by quantifying genes for P solubilization ( pqqC ) and mineralization ( phoD ), and on P uptake by plants, as P cycle holds a crucial role in maintaining soil fertility. Compared to the other two agricultural practices, CA exhibited a positive effect on the attributes (e.g. ICM7 showed 1.16–1.73 fold and 1.15–1.85 fold increment in pigeonpea and soybean, respectively, in terms of plant P uptake compared to other CT- and OA-based modules) analysed. The study offers a possible explanation for more efficient nutrient cycle in the rhizosphere under CA-based practice (comprising of zero-tillage, raised bed, crop residue retention, amendment with NPK nutrients) by enhancement of the rhizospheric bacterial guilds involved in P cycle, thereby also influencing the P uptake by plants.

BACKGROUND Modern agricultural management approaches are often dependent on the application of chemicals, resulting in adverse impacts on human and environmental health. Therefore, for sustainable agriculture, there is a need to implement integrated agriculture practices that can maintain natural soil microbiome and enhance crop production. Various agricultural approaches influence crop production by impacting the functional bacterial community entailed in biogeochemical cycles, e.g., nitrogen (N) cycle. This study aimed to assess the rhizospheric N cycling community of soybean under three agricultural practices, viz. conservation agriculture (CA), conventional treatment (CT), and organic agriculture (OA) for two consecutive years (2017 and 2018). RESULTS A field experiment was designed under soybean-wheat cropping system employing CA, CT, and OA modules that included different practices of tillage, crop bedding pattern, crop residue retention, and nutrient application. Assessment of bacterial communities contributing to nitrogen transformation was performed with qPCR of important markers (nifH, amoA, narG, and nirK). CONCLUSION Results concluded that the practice of conservation agriculture comprising of raised bed, zero-tillage, crop residue retention, and application of NPK nutrients favorably affected the plant attributes and the abundance of N cycling bacterial community over the two consecutive years. The outcome revealed the mechanistic principle behind enhanced plant growth under conservation agriculture, and opened up the possibility of regulating the nitrogen cycling bacterial community to develop sustainable and productive agro-ecosystems. This article is protected by copyright. All rights reserved.

Soil microbiome plays a primary role in soil ecosystem functioning by being involved in necessary biochemical processes. Any changes to soil microbiome lead to differences in physiochemical properties of soil such as salinity, pH, and organic content, which eventually leads to soil infertility. Indiscriminate use of pesticides to meet global food requirements has taken a toll over soil microbiome, and thereby soil fertility. Pesticides and their metabolites accumulate in the soil over the generations of farming, and bestow several non-target effects on soil microbial communities. Soil microbial communities are considered to be sensitive bio-indicators of soil pollution as they are the early signals for long-term physiological and physiochemical changes in soil. In this chapter, we have discussed soil microbiome as sensitive markers for soil health, upon amendment with pesticides. A comprehensive picture of how repeated and excessive use of both biological and chemical pesticides cause fluctuations in the potential microbiological and ecological functioning has been presented based on available literature.

The intensification of agriculture to meet the ever-increasing demand for food has exerted a negative impact on the ecosystem. Conservation agriculture has been highlighted as a comprehensive approach to sustainability. The present study aimed to assess the performance of conservation agriculture (CA) on plant growth, and its impact on bacterial community composition, specifically guilds involved in nitrogen (N) cycling, in comparison to conventional (CT), and organic agriculture (OA). A field experiment was set up with Cajanus cajan (pigeonpea) under the three agricultural practices with a total of nine modules. The rhizospheric bacterial community composition was examined using Illumina sequencing with the 16S rRNA gene as a marker. The bacterial community involved in nitrogen cycling was examined by analysis of key genes involved in pathways, viz. nitrogen fixation (nifH), nitrification (amoA), and denitrification (narG and nirK) by qPCR. Plant growth parameters and grain yield of C.cajan were relatively higher in CA-based modules. Enhanced abundances of genes involved in the N cycle were observed under CA compared to CT and OA. CA had the highest alpha diversity at the phylum level, while CT had the lowest. Proteobacteria (28%), Planctomycetes (15–19%), Acidobacteria (10–12%), and Bacteroidetes (10–15%) were the dominant phyla across the three agricultural practices. A significant correlation could be drawn between the performance of agricultural management practice, and bacterial community structure and function. The research adds to our understanding of the various mechanisms involved in the promotion of plant growth and soil diversity under sustainable means of agriculture. Besides it emphasizes the significance of rhizospheric bacterial communities as ecological indicators for soil health in arable land.

The significance of microbial diversity in soil has been demonstrated since decades. Assorted variety of microorganisms in soil is fundamental to support soil health, as an extensive diversity of microorganisms is associated with essential soil functions. Several abiotic and biotic factors have been reported to affect the structural and functional diversity of soil microbes. This chapter centers around information related to the application of different biological amendments, and their influential role in shaping soil microbial community diversity, and health. Specifically, it focuses on the application of different organic fertilizers, and their influence on the diversity of microbial communities in arable soil, and upon the risks associated with such amendments, since they can be a source of heavy metals, antibiotics, antibiotic-resistant bacteria, and antibiotic-resistant genes carried by mobile genetic elements.