Groundnut cultivation in semi-arid peninsular India for yield scaled nitrous oxide emission reduction

Studies reporting agricultural greenhouse gas (GHG) emission data from tropical upland crops or the climate adaptation and mitigation potential of farming practices that involve nutrient management and/or organic farming are very limited in number. We developed alternate groundnut (Arachis hypogaea L.) farming practices for rainfed kharif (South-west monsoon) and irrigated rabi (winter) cropping seasons for agro-ecological region 3.0 in semi-arid peninsular India; and compared their yields, farm income as well as nitrous oxide (N₂O) emissions with current baseline practices among regional small scale farm-holders. At the study farm, alternate practices including application of locally prepared fermented manures along with a 40–60 % reduction in application of total N increased pod yield by 50 and 35 % and net profit by ~120 and ~70 % in a drought-hit kharif and an irrigated rabi, respectively. High resolution field measurements of N₂O flux indicate that the seasonal emission factors for groundnut cultivation using baseline and alternate practices were 1.7–2.0 % of applied N. Thus, the average IPCC and Indian national emissions factors of 1 and 0.58 %, respectively, underestimate GHG emissions during groundnut cultivation. Crucially, alternate practices led to (1) a reduction of 0.13 ± 0.07 and 0.24 ± 0.1 tCO₂e ha⁻¹ season⁻¹ through decreases in direct N₂O emissions along with a 50 % reduction in GHG emission intensity (per unit yield) in both seasons; (2) a concomitant average reduction of ~0.1 and 0.24 tCO₂e ha⁻¹ season⁻¹ through decreased demand for manufactured fertilizers in kharif and rabi seasons, respectively. The positive implications for climate resilience, mitigation and ecosystem services are discussed.