Energy budget and carbon footprint in a no-till and mulch based rice-mustard cropping system

The increase in emission of greenhouse gases (GHGs) due to anthropogenic perturbation in both the agricultural and natural eco-systems are degrading the environmental quality. Conventional tillage (CT) and residue burning/removal exacerbates the land degradation and GHG emission, and the impacts are much more in the upland ecosystem than valley lands. Therefore, the aim of the present study was to evaluate the energy budget, and carbon footprint (CF) of no-till (NT) and mulches under the upland rice (Oryza sativa)-mustard (Brassica campestris var. toria) cropping system over CT based system to develop a clean production technology for improving the environmental quality and conservingnatural resources. The novelty of the study is that integrated effect of NT, diverse mulches and cropping system effect has been considered together as a conservation measure for sustainable and clean agricultural practice over those of CT based technologies. The experiment comprised of two tillage systems as the main-plot and four mulch types as the sub-plot treatments under a split-plot design. Two tillage systems included: 1. CT-RI: CT with 100% residue incorporation (RI), and 2. NT-RR: NT with 100% residue retention (RR). Four mulch types included: 1. rice straw mulch (SM), 2. green manure (GM) - Gliricidia sp. (a leguminous shrub) mulch, 3. brown manuring (BM) mulch [cowpea (Vigna unguiculata) grown as an intercrop and killed with a spray of 2, 4-D, 40 days after sowing (DAS)] and 4. no mulch (NM) control. The adoption of NT-RR significantly (p = 0.05) reduced the energy use (16,727 MJ/ha) and the cost of production (INR 54,271/ha, 1 US$ = 64.46 INR) compared with those under CT-RI (27,630 MJ/ha and INR 76,903/ha, respectively). Thus, NT-RR also increased the energy use efficiency (EUE), energy productivity (EP), net returns, and reduced CF of the system compared with those under CT-RI. Use of different mulches also increased the energy use efficiency, system productivity, and net returnscompared with those under NM. The total CO2-e emission (CF) was higher under CT-RI (2307 kg CO2-e/ha) as compared to those under NT-RR (2013 kg CO2-e/ha). The savings of fossil fuel from less number of tillage operations and also low emissions associated with energy consumed in manufacture, transport, repair and use of machines contributed to the lowest GWP under NT-RR. Thus, the study supports and recommended that the NT-RR with BM is an environmentally safe and clean production technology for enhancing the energy use efficiency, reducing the CF and cost of production of direct-seeded upland rice-mustard cropping system in India and similar agro-eco-regions elsewhere in the rice based cropping system in the world.