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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 (CH 4 ) emissions by 35.7 to 51.5% in dry season and 18.5 to 20.1% in wet season, while full-AWD practice reduced CH 4 emissions by 52.8 to 61.4% compared with CF. Full-AWD in dry season not only significantly reduced CH 4 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 (N 2 O) was relatively low compared to that from CH 4 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 CH 4 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.

Azolla (Azolla filiculoides) is a common aquatic fern that has been used successfully as a dual crop with lowland rice. It grows rapidly and has the ability to fix N 2 for rice paddy. However, its ecological significance especially on greenhouse gases emissions remains unclear. To investigate the effect of azolla cover on methane (CH 4 ) and nitrous oxide (N 2 O) emissions from rice paddy, a pot experiment with two treatments, control (rice plant only) and azolla cover (rice plus azolla covering on the flooding water), was carried out in Tsuruoka, Yamagata, Japan, in 2016. The results showed that the rice growth parameters, like shoot height, maximum and productive tiller numbers, and plant biomass were not significantly different between the two treatments. Dual cropping of azolla with rice significantly suppressed CH 4 emissions, likely due to an increase in dissolved oxygen concentration and redox potential at the soil-water interface between flooding water and soil surface. There were significant (P < 0.05) positive correlations between CH 4 flux and night respiration (CO 2 emissions) between the two treatments. The cumulated CH 4 emissions during the growth period until 106 days after transplanting (DAT) was significantly lower at 36.2 g C m −2 from azolla cover treatment than that from control treatment pot at 55.4 g C m −2 . A prolonged nonsignificant N 2 O emission under the azolla cover treatment after the initial highest peak at 15 DAT was recorded due to denitrification of the nitrate in initial soil. No further N 2 O emissions were recorded thereafter from both treatments. Azolla cover did not affect N 2 O emissions from both treatments. ARTICLE HISTORY

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Two incubation experiments were conducted under controlled moisture and temperature conditions to determine the effects of soil amendment treatments based on pruning waste biochar and oyster shell, on N2O and CO2 emissions from an orchard soil. In experiment 1, four treatments were tested including, control (CK), pruning waste biochar at 2% (B2%), at 10% (B10%), and oyster shell (OS), mixed with soil from two different depths, namely, from the 0–5 cm and the 0–10 cm layers. In experiment 2, only the 0–10 cm soil layer was used to study the effect of surface application of pruning waste biochar (B2% and B10%) on soil N2O and CO2 emissions. The results showed that soil pH, total C and C: N ratio increased with biochar amendment treatments. Significant reduction in soil NO3− content was observed for the B10% treatment. Although OS application increased soil pH, no effect was observed on soil mineral N content, total C or C: N ratio. The rate of N2O emissions from the 0–5 cm soil layer after B2% and B10% addition, significantly declined by 12.5% and 26.3%, respectively. However, only the B10% treatment caused significant reduction in N2O emissions from the 0–10 cm soil layer and from surface soil, by 15.1% and 13.8%, respectively. Oyster shell application had no effect on either soil N2O or CO2 emissions from either soil layer tested. Our results suggest that the addition of pruning waste biochar at a high rate has the potential to mitigate N2O emissions from orchard soils; while, oyster shell can be used for liming without altering soil N2O nor CO2 emissions.

Climate change is a vital environmental issue that significantly affects rice productivity. Rice paddy fields are one of the greatest anthropogenic sources of methane (CH 4) and nitrous oxide (N 2 O) emissions. To evaluate the combined effects of manure amendment and water management on GHG emissions, grain yield and water productivity per rice yield in a lowland rice field with a sandy clay loam soil in Myanmar, this study was conducted with a split-plot design. Two water management practices (continuous flooding [CF] and alternate wetting and drying [AWD]) and four levels of cow dung manure (0, 2.5, 5.0 and 7.5 t ha −1) were applied with three replications in the dry (February-May) and wet (July-October) seasons in 2017. In the dry season, significantly higher cumulative methane (CH 4) emissions (50.5%) were recorded in CF than in AWD, while cumulative nitrous oxide (N 2 O) emissions were 70% higher in AWD than in CF, although the difference was not significant. Manure application showed no effect on CH 4 and N 2 O emissions compared with the no-manure control, irrespective of application level. In the wet season, significantly higher cumulative CH 4 emissions (65.2%) were again recorded in CF than in AWD; however, the cumulative N 2 O emissions were similar between CF and AWD. Methane and N 2 O emissions in the wet season were 65.8 and 35.8% higher, respectively, than those in the dry season. In both seasons, higher grain yields (1.8% in dry and 7.6% in wet) and higher water productivity (130% in dry and 31% in wet) were recorded in AWD than in CF. Increased grain yields (18.9% in dry and 7.7% in wet) and water productivity (25.5% in dry and 15.8% in wet) were recorded in the manure treatments compared to those in the no-manure treatment. This study presents quantitative data on how manure amendment and water management affected GHG emissions in a paddy field in Myanmar.