Arti BhatiaSANDEEP KUMAR MALYAN2018-10-062018-10-062017http://krishikosh.egranth.ac.in/handle/1/5810074885t-9740Rice (Orzya sativa L.) is a major cereal crop of India which covers more than 43 Mha and plays a crucial role in the food security of the country. Rice is the only cereal crop that is consumed almost solely by more than half of the world’s human population and more than 90% of world’s rice is cultivated in Asia under submerged condition. Submerged condition in rice soils results in anthropogenic emission of methane (CH4) to the atmosphere. In the present study an attempt has been made to identify low CH4 emitting options having no negative impact on the economic benefit of rice cultivation. A laboratory experiment was conducted to quantify the CH4 emission reduction potential of nine chemical compounds from soil under submerged conditions. Subsequently four best identified compounds were tested in field growing rice for their CH4 mitigation potential. A field experiment was carried out for two consecutive years during 2013-2015 in the farm of Indian Agricultural Research Institute, New Delhi, India to evaluate the feasibility of these identified compounds [ magnesium peroxide (MgO2), ethylene diamine tetra acetic acid (EDTA), phosphogypsum (PG) and ammonium sulfate (AS)] in reducing the CH4 emission from the soil. We conducted another field experiment for two consecutive years at the IARI farm to evaluate CH4 mitigation potential of microbial interventions in rice. We evaluated Azolla, BGA, and some methanotrophs alone and in combination for assessing their impact on emission of CH4 from rice. The treatments included control (T1), Azolla (T2), BGA (T3), Azolla + BGA (T4), Hyphomicrobium facile (T5), Burkholderia sp (T6), Methylobacterium oryzae (T7), all three methanotrophs (Hyphomicrobium facile + Burkholderia sp + Methylobacterium oryzae) (T8) and no fertilizer (T9). Under the laboratory study, the average CH4 production ranged from 166 to 247 µg CH4 kg-1 soil day-1 under the different treatments. Lowest averaged emission per day was obtained in PG which was at par with AS. In the field study, average cumulative CH4 emission of both cropping years was 32.56 kg CH4 ha-1 from the control treatment, which was reduced by 12.7%, 24.0%, 20.3%, 29.8% on the application of MgO2, AS, EDTA and PG respectively. Carbon efficiency ratio (CER) which is the indicator of carbon emitted to carbon fixed in a particular treatment was observed to be lowest in MgO2 (7.79) and highest in PG (10.53) among the different treatments. The CH4 emission ranged from 26.39 to 36.38 kg CH4 ha-1 in the different treatments in the field experiment with microbial interventions. The use of Methylobacterium oryzae methanotrophs and Azolla was found effective in reducing the CH4 emission. Azolla alone and along with BGA reduced CH4 by 9.6 and 13.3% respectively. The application of Hyphomicrobium facile, Burkholderia sp, Methylobacterium oryzae methanotrophs was effective in reducing CH4 emission by 5.0, 4.1 and 19.9% respectively. However the application of all the three methanotrophs together led to an increase in CH4 emission even over control by 10.4%. This might be due to antagonistic effect on population of each other due to combined application of different strain of methanotrophs under this treatment. Among different treatment PG, AS, T4 (Azolla + BGA) and T7 (Methylobacterium oryzae) showed lower CH4 emission with higher B:C ratio while EDTA showed lower CH4 emission but was at par with control. Result indicated that treatment PG, AS, EDTA, T4 (Azolla + BGA), and T7 (Methylobacterium oryzae) can be effective in mitigating CH4 emission without any yield penalty and should be taken for experimentation for longer duration.en-USnullThesis