Soil liming effects on CH₄, N₂O emission and Cd, Pb accumulation in upland and paddy rice

Keeping in view the expanding environmental pollution and irrigation water deficit, a pot experiment was performed for the upland (Huyou2, Hanyou737) and paddy rice cultivars (Taigeng8; Yixiang2292), to study soil liming effects on methane (CH₄) and nitrous oxide (N₂O) emission, bioavailability and accumulation of Cd, Pb in upland and paddy rice. Upland rice reduced 90% of soil CH₄ emission as compared to paddy conditions. Soil CH₄ emission decreased by 45% and 39% with dolomite, and it reduced by 35% and 33% with lime treatment both in upland and paddy conditions, respectively. Soil N₂O emission decreased by 44% and 52% with dolomite, and with the lime application, it was reduced by 37% and 44% for both upland and paddy conditions respectively. Reduction in soil DTPA-extractable Cd was between 37-53% and 43-80% with dolomite and 16-37% and 24-72% Cd decreased with lime application in upland and paddy conditions respectively. Soil DTPA-extractable Pb reduced by 27-44% and 25-53% with dolomite and 16-40% and 11-42% with soil-applied lime in upland and paddy conditions, respectively. Cd accumulation in rice grain was decreased by 47-88% and 62-79% with dolomite and 31-86% and 45-52% reduction by lime application in upland and paddy rice respectively. Rice grain Pb reduced by 58-91% and 66-78% with dolomite application and 32-71% and 44-71% with lime in upland and paddy rice, respectively. Our results showed that soil liming significantly reduced soil N₂O and CH₄ emission and Cd, Pb accumulation in rice grain, but dolomite was more effective as compared to lime. Altogether, results of this study suggest that upland rice can be cultivated in CdPb polluted soils with least soil CH₄ emission. Cd and Pb toxicity, accumulation, and N₂O emission in upland rice can be minimized by soil liming of 3 g kg^-1 and optimizing the nutrients composition of the soil.