A laboratory study was conducted to study the effects of liming and different biochar amendments on N₂O and CO₂ emissions from acidic tea field soil. The first experiment was done with three different rates of N treatment; N 300 (300 kg N ha^-1), N 600 (600 kg N ha^-1) and N 900 (900 kg N ha^-1) and four different rates of bamboo biochar amendment; 0%, 0.5%, 1% and 2% biochar. The second experiment was done with three different biochars at a rate of 2% (rice husk, sawdust, and bamboo) and a control and lime treatment (dolomite) and control at two moisture levels (50% and 90% water filled pore space (WFPS)). The results showed that dolomite and biochar amendment significantly increased soil pH. However, only biochar amendment showed a significant increase in total carbon (C), C/N (the ratio of total carbon and total nitrogen), and C/IN ratio (the ratio of total carbon and inorganic nitrogen) at the end of incubation. Reduction in soil NO₃^--N concentration was observed under different biochar amendments. Bamboo biochar with the rates of 0.5, 1 and 2% reduced cumulative N₂O emission by 38%, 48% and 61%, respectively, compare to the control soil in experiment 1. Dolomite and biochar, either alone or combined significantly reduced cumulative N₂O emission by 4.6% to 32.7% in experiment 2. Reduction in N₂O production under biochar amendment was due to increases in soil pH and decreases in the magnitude of mineral-N in soil. Although, both dolomite and biochar increased cumulative CO₂ emission, only biochar amendment had a significant effect. The present study suggests that application of dolomite and biochar to acidic tea field soil can mitigate N₂O emissions.

Water-intensive systems of rice cultivation are facing major challenges to increase rice grain yield under conditions of water scarcity while also reducing greenhouse gas (GHG) emissions. The adoption of effective irrigation strategies in the paddy rice system is one of the most promising options for mitigating GHG emissions while maintaining high crop yields. To evaluate the effect of different alternate wetting and drying (AWD) irrigation strategies on GHG emissions from paddy rice in dry and wet seasons, a field experiment was conducted at the Tamil Nadu Rice Research Institute (TRRI), Aduthurai, Tamil Nadu, India. Four irrigation treatments were included: One-AWD (one early drying period), Two-AWD (two early drying periods), Full-AWD (wetting and drying cycles throughout the rice season), and CF (continuous flooding). Different rice varieties were also tested in the experiment. In this study, we emphasized one factor (irrigation effect) that affects the dependent variable. The results show that early AWD treatments reduced methane (CH₄) emissions by 35.7 to 51.5% in dry season and 18.5 to 20.1% in wet season, while full-AWD practice reduced CH₄ emissions by 52.8 to 61.4% compared with CF. Full-AWD in dry season not only significantly reduced CH₄ emission during that season, it also resulted in the decline of the early season emission in the succeeding wet season. Global warming potential (GWP) and yield-scaled GWP were reduced by early or full season AWD in both rice seasons. The GWP value from nitrous oxide (N₂O) was relatively low compared to that from CH₄ in both rice seasons. Rice yield was not affected by irrigation treatments although varietal differences in grain and straw yields were observed in both rice seasons. This study demonstrated that early season water managements are also effective in reducing CH₄ and total GHG emissions without affecting rice yield.

The aims of this study were to boost growth attributes, yield, and nutrient uptake of rice in paddy fields using a combination of Bacillus pumilus strain TUAT-1 biofertilizer and different nitrogen (N) application rates in nursery boxes. Bacillus pumilus strain TUAT-1 was applied as an inoculant biofertilizer in conjunction with different rates of N fertilizer to rice seedlings in a nursery. Plant growth and yield parameters were evaluated at two stages: in 21-day-old nursery seedlings and in mature rice plants growing in a paddy field. Inoculation with TUAT-1 significantly increased the seedling growth and root morphology of 21-day-old nursery seedlings. There was a marked increase in chlorophyll content, plant height, number of tillers, and tiller biomass of rice plants with the use of TUAT-1 and N fertilizers alone, and their combinations, at the maximum tillering stage in the field. The combination of TUAT-1 and 100% N (farmer recommended rate of N) resulted in the greatest tiller number and biomass at the maximum tillering stage, and positively affected other growth attributes and yield. The growth and yield were similar in the TUAT-1 + 50% N and 100% N (uninoculated) treatments, because TUAT-1 promoted root development, which increased nutrient uptake from the soil. These results suggest that the B. pumilus strain TUAT-1 has a potential to enhance the nutritional uptake of rice by promoting the growth and development of roots.

An assessment of within field spatial variations in grain yield and methane (CH₄) emission was conducted in lowland rice fields of Myanmar. Two successive rice fields (1^st field and 2^nd field) were divided into fertilized and non-fertilized parts and CH₄ measurements were conducted at the inlet, middle and outlet positions of each field. The results showed that CH₄ emissions at non-fertilized parts were higher than those at fertilized part in both rice fields. The average CH₄ emissions ranged from 8.7 to 26.6 mg m^-2 h^-1 in all positions in both rice fields. The spatial variation in CH₄ emission among the positions was high in both rice fields with the highest emissions in the outlet of the 1^st field and the inlet of the 2^nd field. The CH₄ emissions at these two positions showed 2 - 2.5 times higher than those at other positions in both rice fields. Stepwise regression analysis indicates that soil total carbon content is the primary factor for CH₄ emission. The average CH₄ emissions during rice growing season were 13.5 mg m^-2 h^-1 for the 1^st field and 15.7 mg m^-2 h^-1 for the 2^nd field. Spearman rank order correlation analysis showed that CH₄ emission was significantly and positively correlated with soil temperature, surface water depth and negatively correlated with soil redox potential. The result indicated that high within field spatial variation in CH₄ emissions required different site specific management practices to mitigate CH₄ emissions in lowland paddy rice soil.