Effect of SRI methods on water use, NPS pollution discharge, and GHG emission in Korean trials

A field experiment with a locally-bred Japonica rice cultivar was conducted in 2011 to measure the effect of paddy irrigation management in Korea on rice yield, water use, NPS pollution discharge, and greenhouse gas (GHG) emissions. Experimental treatments were conventional paddy cultivation (CT), CT with SRI water management (CS), CT with two forced mid-season drainages (CD), and SRI methods with two different transplant spacing (SRI-30, SRI-40). Each treatment was replicated. The rice yields, selected water quality indices of the irrigation and drainage water, and GHG emissions were measured and analyzed. Irrigation water was reduced by 49.4 and 47.6 % in the SRI and CS treatments, respectively, compared with the CT treatment. Reductions in non-point source (NPS) pollution load with SRI water management ranged from 16.5 to 53.9 % in the CS plots and from 27.1 to 46.0 % in the SRI plots, depending on the water quality indices measured. The GHG emissions from the CD and CS plots when converted to CO2 equivalents were reduced by 65.5 and 72.8 %, respectively, compared with emissions from the CT plots because CH4 reduction far exceeded the N2O increase from the CD and CS plots. The two highest polished rice yields were 6.47 and 6.34 ton/ha from the SRI-30 and CS plots, respectively; these represented 20 and 17 % increase over yields from the CT plots. Trial results indicate that SRI water management in Korean paddy farming could significantly decrease the paddy irrigation requirements and also discharges of NPS pollution and GHG emissions.