The yield increments with biochar amendments following AWDI could be due to the maximum productive tillers/hill and higher nutrients availability to rice grain compared to other treatments. Sanjit et al. reported that rice grain yield was a bit higher in conventional irrigation compared to the AWDI treated field plot yield during the dry boro season in Bangladesh.Ali et al. also reported that the AWDI treatment showed superiority for the rice yield performance and seasonal CH4 emission reduction, water savings, and maximum water productivity index under the dry seasonal conditions in Bangladesh. It was also reported that moderate wetting and drying increased rice yield, decreased water use and CH4 emissions . In this study, biochar applications 20 – 30 t/ha under alternate wetting and drying irrigation resulted least cumulative CH4 emissions and GWPs, while highest water productivity and moderate yield performance were found in the rainfed wet season and dry boro season.
The lower CH4 emission under AWDI treated field plots may be due to increased aeration, stabilization of soil organic carbon, improved soil redox potential status and accumulation of free iron oxides, sulfate ions which acted as electron acceptors, thereby,reduced methanogens’activity. On the contrary, Ali et al. reported that biochar amendments in paddy soils increased cumulative CH4 emissions. This contrasting result may be due to the variation in the composition of biochar as well as different agro-ecological zones. Zhang et al. reported that the soil amendment with biochar was found effective for mitigating CH4 emission, which also increased rice yield by 25% – 26% compared to inorganic fertilizers. Ali et al. also reported that intermittent irrigations significantly reduced total seasonal CH4 emissions by 27% compared to conventional irrigated rice paddy field. In this study, biochar amendments improved the soil redox status and soil porosity, mostly observed under the AWDI treated field plots.Consequently, total seasonal CH4 emission significantly decreased in AWDI plot compared to the conventional irrigated rice field. Hiya et al. found that total GWP of CH4 significantly decreased with AWDI treatments as compared to continuous flooded plots.
This result also showed that AWD irrigation system is better than conventional irrigation in terms of water productivity index and water savings. Higher productivity index was found in biochar amended field plots under the AWDI method compared to conventional irrigation. Singh et al. reported that combined application of rice husk biochar and FYM with reduced chemical fertilizer under less water inputs was effective to sustain wheat crop yield in the highly vulnerable dry tropical agro-ecosystem of India. Hossainet al. reported that water productivity increased from 0.35 kg·m−3 to 0.65kg·m−3 following better research management over the farmers’ practice, environment friendly technology for reducing groundwater use in the irrigated ecosystem.Xiao et al. reported that rice straw biochar amendments at 20 t/ha and 40 t/ha significantly decreased CH4 emissions by 29.7% and 15.6%, respectively,while rice yield was increased by 24% and 33% and irrigation water productivity was increased by 36% and 42%, respectively, over the control. In this study, biochar amendments 20 – 30 t/ha showed the maximum free iron oxide contents under both AWDI and conventional irrigated field soils, which was supported by Ali et al. .
This study showed that there were negative correlations between total seasonal CH4 fluxes with grain yield, water productivity index, soil pH, soil Eh, soil porosity, soil organic carbon, total N, available P and S , while positive correlations were recorded with plant productive tillers and above ground biomass.Hiya et al. stated that total seasonal CH4 flux was negatively correlated with grain yield, water productivity index, soil Eh, organic matter, total N,available P and S, soil porosity and soil pH under continuous irrigated treatment.The increased water productivity of rice and water saving aspects will make farmers and other stakeholders to adopt AWDI technique. Therefore, biochar applications @ 15 – 20 t/ha with half of the recommended chemical fertilizers and adopting alternate wetting drying irrigations may be a feasible technique for reducing yield scaled CH4 emission as well as GWPs and sustaining rice productivity through improving soil properties and rice rhizosphere environmental conditions. The alteration or modification in an organism’s genome using modern DNA technology is called genetic engineering or genetic modification. Since it involves the introduction of foreign DNA or synthetic genes into the organism of interest the resulting artifact is often referred as transgenic and or genetically modified . The ability to introduce alien genes from distant species or life forms into plants has made available an entirely new and novel gene resource pool to breeders in their pursuit to improve crops for survival, productivity, and products.