RESUMO
Soil microbial communities are important drivers of biogeochemical cycling of nutrients, organic matter decomposition, soil organic carbon, and Greenhouse gas emissions (GHGs: CO2, N2O, and CH4) and are influenced by crop and soil management practices. The knowledge on the impact of conservation agriculture (CA) on soil bacterial diversity, nutrient availability, and GHG emissions in semi-arid regions under rainfed conditions is vital to develop sustainable agricultural practices, but such information has not been systemically documented. Hence, studies were conducted for 10 years in rainfed pigeonpea (Cajanus cajan L.)-castor bean (Ricinus communis L.) cropping system under semi-arid conditions to assess the effects of tillage and crop residue levels on the soil bacterial diversity, enzyme activity (Dehydrogenase, urease, acid phosphatase, and alkaline phosphatase), GHG emissions, and soil available nutrients (Nitrogen, phosphorus, and potassium). Sequencing of soil DNA through Illumina HiSeq-based 16S rRNA amplicon sequencing technology has revealed that bacterial community responded to both tillage and residue levels. The relative abundance of Actinobacteria in terms of Operational Taxonomic Unit (OTUs) at phyla, class as well as genera level was higher in CA (NTR1: No Tillage + 10 cm anchored residue and NTR2 NT + 30 cm anchored residue) over CT (conventional tillage without crop residues). CA resulted in higher enzyme activities (dehydrogenase, urease, acid phosphatase, and alkaline phosphatase) and reduction in GHG emissions over CT. CA recorded 34% higher and 3% lower OC, as compared to CT, and CTR1, respectively. CA recorded 10, 34, and 26% higher available nitrogen, phosphorus, and potassium over CT and CTR1, respectively. NTR1 recorded 25 and 38% lower N2O emissions as compared to CTR1 and CTR2, respectively. Whereas only NT recorded 12% higher N2O emissions as compared to CT. Overall, the results of the study indicate that CA improves the relative abundance of soil bacterial communities, nutrient availability, and enzyme activities, and may help to contribute to the mitigation of climate change, and sustainability in rainfed areas.
RESUMO
Decreasing greenhouse gas (GHG) emissions and enhancing soil carbon (C) sequestration in cropland are necessary to achieve carbon neutrality at national scale. The major objective of this study is to quantify the GHG mitigation potential of adopted climate resilient (CR) practices in CR villages using Ex-ACT tool developed by Food and Agriculture Organization (FAO). Intensively cultivated area of Punjab and Haryana was selected for carrying out this study. In both the states, villages were selected by considering the climate for past 30 years. In the selected villages, a set of CR practices were implemented in annuals, perennials, irrigated rice, fertilizer use, land use change and livestock and quantified the GHG mitigation potential in these villages for next twenty years. The tool predicted that the CR practices adopted were successful in enhancing the overall sink (carbon balance) in all the study villages. The villages of Punjab had recorded higher mitigation potential as compared to the villages of Haryana. The overall sink potential in these villages ranged from -354 to -38309 Mg CO2-eq. The change in sink potential varied from 3.16 to 112% with lowest in Radauri and highest in Badhauchhi kalan village. The sink potential got doubled in Badhauchhi kalan village due to stopping rice straw burning and increase in area under perennials by 25%. The source potential varied from 6.33 to -7.44% across the study villages. Even with the implementation of NICRA, there was increase in source by 5.58 and 6.33% in Killi Nihal Singh Wala and Radauri due to irrigated rice, land use change and livestock. Majorly, rice straw burning was seen in most of the study villages, yet, with proper residue management and adoption of CR practices (mainly intermittent flooding) in rice cultivation resulted in emissions reduction up to 5-26% with enhanced productivity up to 15-18%, which can be considered for scaling up. Fertilizer management reduced the emissions by average of 13% across the study villages. Farm gate emission intensity per ton of milk and rice recorded highest emission intensity compared to annuals and perennials suggesting strict implementation of CR practices in rice cultivation and livestock sector. Implementation and scaling up of CR practices could potentially reduce the emissions and make the village C negative in intensive rice-wheat production system.
