Abstract
Background: Rice farming faces major challenges, including water limitation, drought and climate change in the current scenario of agriculture. Among the innovative water-saving techniques, drip irrigation is a forerunner, with maximized water-saving potential, increased grain yield and methane mitigation. Methods: A field experiment was conducted comprising four different drip irrigation practices: (i) sub-surface drip irrigation (SDI) with 1.0 litre per hour (lph) discharge rate emitters (DRE) (SDI+1.0 lph DRE) (ii) SDI+0.6 lph DRE, (iii) surface drip irrigation (DI) with 1.0 lph discharge rate emitters (DI+1.0 lph DRE), (iv) DI+0.6 lph DRE and were compared with (v) a conventional flood aerobic irrigation (considered conventional). Results: The estimated grain yield of rice was found to be 23.5%, 20.3%, and 15.1% higher under SDI+1.0 lph DRE, SDI+0.6 lph DRE and DI+1.0 lph DRE practices, respectively, than the conventional method. A water saving of 23.3% was also observed for all drip practices compared with conventional practices. Seasonal methane emission flux declined 78.0% in the drip methods over the conventional irrigation: better mitigation than previously reported values (alternate wetting and drying (47.5%) and system of rice intensification (29.0%) practices). Continuous soil aeration and enhanced soil methanotrophs (P<0.05) limit the peak methane emission in rice during the flowering phase in drip irrigation, which is reflected in the methane emission flux values. Consequently, the equivalent CO 2 (CO 2-eq) emissions and yield-scaled CO 2 eq-emission were found to be significantly lower in SDI (43.8% and 49.5%, respectively), and DI (25.1% and 26.7%, respectively) methods as compared with the conventional that ensures better methane mitigation and future climate-smart rice production systems. Conclusions: Drip irrigation could reduce the cumulative methane emission in aerobically grown rice. SDI + 1.0 lph DRE practice can be applied in areas with inadequate water availability and effective in reducing the CO 2-eq emission with better yield than conventional.
Highlights
Agriculture was estimated to account for 10–20% of manmade greenhouse gas (GHG) emissions (5.1–6.1 Gt CO2-eq year-1 by 2030) worldwide (Smith et al, 2008; Tubiello et al, 2013)
The results demonstrated that drip irrigation can be adapted to maintain more oxidative aerobic soil condition in rice crop
The drip response results on methane gas emission, CO2-eq emission, soil pH, soil redox potential, soil methanotrophs population from the rice ecosystem, plant height, total dry mass, yield, water productivity of rice were compared with the conventional flood aerobic irrigation practice; this section discusses the notable results
Summary
Agriculture was estimated to account for 10–20% of manmade greenhouse gas (GHG) emissions (5.1–6.1 Gt CO2-eq year-1 by 2030) worldwide (Smith et al, 2008; Tubiello et al, 2013). The system of rice intensification (SRI) practice reduces total methane emissions by 29.0% (Rajkishore et al, 2013), the value for alternate wetting and drying method was 44.0% (Bouman et al, 2005; Bouman et al, 2007; Oo et al, 2018a; Oo et al, 2018b; Setyanto et al, 2018) and for aerobic rice practice was 51.0% (Joshi et al, 2009; Jain et al, 2014; Keppler et al, 2006; Sharma et al, 2016) compared with flooded rice cultivation. Seasonal methane emission flux declined 78.0% in the drip methods over the conventional irrigation: better mitigation than previously reported values (alternate wetting and drying (47.5%) and system of rice intensification (29.0%) practices). SDI + 1.0 lph DRE practice can be Invited Reviewers version 1
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