Greenhouse Gases from Irrigated Rice Systems Under Alternative Water Management.

In order to meet the global food demand, agricultural intensification is steadily becoming a norm. Increases in food production also increase the demand for water. One potential environmental consequence of agricultural intensification is the increase in atmospheric greenhouse gases (GHG). Rice is a major staple crop and it is usually grown under continuously flooded conditions. Under such conditions these systems produce high methane (CH₄) emissions and thus, have more global warming potential. There are studies which have shown that rice can be grown under alternative water requirements with periodic drainage. This type of management practice is often referred as Alternate Wetting and Drying (AWD). However, this management practice has not been extensively assessed in high yield rice fields present in California, USA. So, in order to evaluate the effect of AWD on GHG, we conducted a two year study to measure CH₄ and nitrous oxide (N₂O) emissions from the irrigated rice under AWD management practice. Treatments included were continuously flooded (CF) and two AWD treatments where soils were dried to 35% (AWD 35) and 25% volumetric water content (AWD 25) during the drain periods. Results showed that CH₄ emissions were significantly higher under CF when compared with AWD 35 and AWD 25. However, N₂O emissions were low among all treatments.