A novel irrigation system to reduce methane emissions in paddy fields

Flood-irrigated rice uses large water volumes and is one of the major sources (similar to 30%) of methane (CH4) emissions from agriculture. Novel cultivation technologies in lowlands, such as the ridge-furrow system, enable a smaller water volume in rice cultivation than traditional flood irrigation. Moreover, it results in higher soil oxidation, which can impact the emission of CH4 and nitrous oxide (N2O). The expansion of ridge-furrow systems in southern Brazil has been occurring because it enables the cultivation of rainfed crops such as soybeans and corn in rotation with rice. The ridge-furrow system promotes adequate soil surface drainage and allows crop furrow irrigation, minimizing crop yield losses from excess or deficit water in lowlands. Thus, our objective was to evaluate the CH4 and N2O emission, partial global warming potential (pGWP), and grain yield of furrow-irrigated rice cultivated in rotation with soybeans. The trial was conducted under field conditions at the Ricetec Experimental Station in the 2020/21 and 2021/22 crop seasons in Capao do Leao, southern Brazil. The XP117 rice hybrid cultivar with a medium cycle (130 days) was used in both seasons. The treatments consisted of a slope gradient in a furrow-irrigated rice field. This slope gradient comprised up-, intermediate- and bottom-slope, representing moist, saturated, and flooded soil conditions, respectively. The furrow-irrigated rice system reduced CH4 emissions by 34% and partial global warming potential by 30%. Rice grain yield remained high (13.3 to 15.1 Mg ha(-1)) in the furrow irrigated system. In conclusion, the furrow irrigation method contributes to increasing rice production sustainability and significantly reduces CH4 emissions.