Abstract
The demand for biomass energy production in the Philippines has led to substantial rice husk ash (RHA) generation. We combined alternate wetting and drying (AWD) and varying RHA rates (10, 20, and 30 t ha–1) to evaluate the yield, water productivity (WP), and greenhouse gas (GHG) emissions in paddy rice for four cropping seasons (CS). We compared these treatments with continuous flooding (CF) and no RHA as controls. The RHA decreased N2O emissions by 8–22%, in the order of RHA30 > RHA20 > RHA10 relative to the control. The AWD had a marginal effect (P < 0.10) on CH4 emissions, with a 10% reduction relative to CF. While yields did not differ among treatments, AWD saved 39% water, and WP increased by 0.56 kg m–3 relative to CF. A significant interaction (P < 0.05) among water, RHA, and CS on N2O emissions was associated with rice stubble management in the first CS just after the harvest of the previous crop (dry incorporation), while the other seasons incorporated stubbles during wetland preparation. Although the highest RHA rate was likely to increase N2O emissions under AWD conditions, the global warming potential (GWP) was still significantly lower (P < 0.05) in the first CS in either water management by up to 15 times lower compared to other CS at all RHA rates. Our results indicated that the primary RHA effects mitigated N2O emissions, while AWD had only marginal effects on CH4 emissions but maintained grain yield under our experimental conditions. The low total GWP in the first CS suggests that the additional mitigation measures of RHA application and water management need to be associated with the proper management of rice stubbles first.
Abstract
The demand for biomass energy production in the Philippines has led to substantial rice husk ash (RHA) generation. We combined alternate wetting and drying (AWD) and varying RHA rates (10, 20, and 30 t ha–1) to evaluate the yield, water productivity (WP), and greenhouse gas (GHG) emissions in paddy rice for four cropping seasons (CS). We compared these treatments with continuous flooding (CF) and no RHA as controls. The RHA decreased N2O emissions by 8–22%, in the order of RHA30 > RHA20 > RHA10 relative to the control. The AWD had a marginal effect (P < 0.10) on CH4 emissions, with a 10% reduction relative to CF. While yields did not differ among treatments, AWD saved 39% water, and WP increased by 0.56 kg m–3 relative to CF. A significant interaction (P < 0.05) among water, RHA, and CS on N2O emissions was associated with rice stubble management in the first CS just after the harvest of the previous crop (dry incorporation), while the other seasons incorporated stubbles during wetland preparation. Although the highest RHA rate was likely to increase N2O emissions under AWD conditions, the global warming potential (GWP) was still significantly lower (P < 0.05) in the first CS in either water management by up to 15 times lower compared to other CS at all RHA rates. Our results indicated that the primary RHA effects mitigated N2O emissions, while AWD had only marginal effects on CH4 emissions but maintained grain yield under our experimental conditions. The low total GWP in the first CS suggests that the additional mitigation measures of RHA application and water management need to be associated with the proper management of rice stubbles first. Read More
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