Exploring Climate Change Adaptation Practices and Agricultural Livelihoods among Rice Farmers of the Brahmaputra Valley in Northeast India.

Global climate change has seriously threatened agriculture and connected sectors, especially in developing countries like India. The Brahmaputra Valley in Assam, Northeast India, is vulnerable to climate change due to its agrarian economy, fragile geo-ecological setting, recurrent floods and droughts, and poor socioeconomic conditions of the farmers. The climate-induced hindrances faced by the rice farming community of this region and the local adaptation practices they employ have not been adequately studied. Therefore, we carried out a survey among 635 rice farmers across four agro-climatic zones of Assam, namely the Upper Brahmaputra Valley Zone, North Bank Plain Zone, Central Brahmaputra Valley Zone, and Lower Brahmaputra Valley Zone, to understand how they perceive and respond to climatic changes. The survey revealed that all the respondents have perceived an increase in ambient temperature, and 65% of the respondents have perceived a slight change in rainfall characteristics over the years. Most farmers reported adjusting the existing farming practices and livelihood choices to adapt to the changing climate. Farming adjustments were made mainly in terms of field preparation and management of water, rice variety, nutrients, and pests. Environmental variables like rainfall, flood, drought, and pest level, and socioeconomic variables like family size, education, farming experience, training, digital media exposure, and land area were found to influence farmers' adaptation choices. The findings imply that policies to strengthen flood, drought, pest management, education, land-use planning, agricultural training, and digital media applications in agriculture are needed for effective climate change adaptation in this region.

Greenhouse gas emission from rice fields: a review from Indian context.

Agricultural soil acts as a source and sink of important greenhouse gases (GHGs) like methane (CH4), nitrous oxide (N2O), and carbon dioxide (CO2). Rice paddies have been a major concern to scientific community, because they produce the threatening and long-lasting GHGs mainly CH4 and N2O. Around 30% and 11% of global agricultural CH4 and N2O, respectively, emitted from rice fields. Thus, it is urgent to concurrently quantify the fluxes of CH4 and N2O to improve understanding of both the gases from rice fields and to develop mitigation strategies for upcoming climate change reduction. An effort is being made in this review to discuss exclusively the emission of CH4 and N2O under normal and controlled conditions in different locations of India and also addresses the current synthesis of available data on how field and crop management activities influence CH4 and N2O emissions in rice fields. Making changes to conventional crop management regimes could have a significant impact on reducing GHG emissions from rice field. Environmental and agricultural factors related to soil could be easily altered by management practices. So, knowing the mechanism of CH4 and N2O production and release in the rice field and factors controlling the emissions is fundamental to develop well-organized strategies to reduce emissions from rice cultivated soil. This will help the regulatory bodies or policy makers to formulate adequate policies for agricultural farmers to refine the GHG emissions as well as minimize the global climate change.

Fertilizer management through coated urea to mitigate greenhouse gas (N2O) emission and improve soil quality in agroclimatic zone of Northeast India.

Agricultural soils are an important source of greenhouse gas nitrous oxide (N2O) emission. The comprehensive effects of nitrogen fertilizer management on N2O emission from paddy fields of India have not been evaluated under field conditions. A 2-year field study was conducted to evaluate the effect of different nitrogen fertilizers, namely, conventional fertilizer (NPK), starch-coated urea (SCU), neem-coated urea (NCU), and normal urea alone (NUA) on soil quality, grain yield, and N2O emission from rice field. Gas samples were collected from the field at weekly intervals by static chamber technique and analyzed in a gas chromatograph. During the crop-growing season, the application of NPK resulted in the highest cumulative N2O emission (2.49 kg N2O-N ha-1) followed by NUA (2.34 kg N2O-N ha-1), NCU (2.20 kg N2O-N ha-1), and SCU (1.97 kg N2O-N ha-1). As against the application of conventional fertilizer (NPK), the application of SCU and NCU reduced the total N2O emission by 21% and 12%, respectively (p < 0.05), during the rice-growing period. The results indicate a good correlation of N2O emissions with soil organic carbon, soil mineral nitrogen, and urease activity (p < 0.05) at different stages of crop growth. Application of SCU significantly increased the rice grain productivity by 12%, 10%, and 3% over NPK (control), NCU, and NUA respectively without affecting the soil quality and nutrient status. The use of SCU improved the nitrogen use efficiency (NUE) and was the effective substitute for conventional fertilizer in terms of reducing N2O emissions from tropical rice paddy.

Estimation of methane and nitrous oxide emission from wetland rice paddies with reference to global warming potential.

Methane (CH4) and nitrous oxide (N2O) are two important greenhouse gases (GHG) and contribute largely to global warming and climate change. The impact of physiological characteristics of rice genotypes on global warming potential (GWP) and greenhouse gas intensity (GHGI) is not well documented. A 2-year field experiment was conducted with eight summer rice varieties: Dinanath, Joymoti, Kanaklata, Swarnabh, IR 64, Tapaswami (modern varieties), Number 9, and Jagilee Boro (indigenous varieties) for two successive seasons (December-June, 2015-2016 and December-June, 2016-2017) to estimate their GWP and GHGI. The GWP of the rice varieties ranged from 841.52 to 1288.67 kg CO2-equiv. ha-1 and GHGI from 0.184 to 0.854 kg CO2-equiv. kg-1 grain yield. Significant differences (p < 0.05) in seasonal GHG emission, GWP, GHGI, CEE (carbon equivalent emission), photosynthetic efficiency, stomatal conductance, transpiration rate, and grain productivity among the rice varieties were observed during the investigation. A good correlation of GWP (p < 0.01) was recorded with rate of stomatal conductance and transpiration rate of the varieties. The present study reveals a strong relationship between plant biomass (p < 0.01) with GWP and CEE of the rice varieties. The variety IR 64 and Number 9 are identified as the most suitable variety with lowest GWP (909.85 and 876.68 kg CO2-equiv. ha-1 respectively) and GHGI (0.192 and 0.227 kg CO2-equiv. kg-1 grain yield respectively) accompanied by higher grain productivity (4839 and 3867 kg ha-1 respectively). Observations from the study suggest that agricultural productivity and GHG mitigation can be simultaneously achieved by proper selection of rice genotypes.

Impacts of integrated nutrient management on methane emission, global warming potential and carbon storage capacity in rice grown in a northeast India soil.

Rice soil is a source of emission of two major greenhouse gases (methane (CH4) and nitrous oxide (N2O)) and a sink of carbon dioxide (CO2). The effect of inorganic fertilizers in combination with various organics (cow dung, green manure (Sesbania aculeata) Azolla compost, rice husk) on CH4 emission, global warming potential, and soil carbon storage along with crop productivity were studied at university farm under field conditions. The experiment was conducted in a randomized block design for 2 years in a monsoon rice (cv. Ranjit) ecosystem (June-November, 2014 and 2015). Combined application of inorganic (NPK) with Sesbania aculeata resulted in high global warming potential (GWP) of 887.4 kg CO2 ha-1 and low GWP of 540.6 kg CO2 ha-1 was recorded from inorganic fertilizer applied field. Irrespective of the type of organic amendments, flag leaf photosynthesis of the rice crop increased over NPK application (control). There was an increase in CH4 emission from the organic amended fields compared to NPK alone. The combined application of NPK and Azolla compost was effective in the buildup of soil carbon (16.93 g kg-1) and capacity of soil carbon storage (28.1 Mg C ha-1) with high carbon efficiency ratio (16.9). Azolla compost application along with NPK recorded 15.66% higher CH4 emission with 27.43% yield increment over control. Azolla compost application significantly enhanced carbon storage of soil and improved the yielding ability of grain (6.55 Mg ha-1) over other treatments.

Effect of foliar application of plant growth regulators on nitrous oxide (N2O) emission and grain yield in wheat.

Agricultural soils are the major source of global nitrous oxide (N2O) emission, and more than two thirds of N2O emission originate from soil. Recent studies have identified that green plants contribute to transport of N2O to the atmosphere. We investigated the effects of foliar application of plant growth regulators (PGRs) and growth stimulating chemicals on N2O emission and wheat grain yield for 2 years. The PGRs' abscisic acid (ABA) and cytozyme (20 mg L-1), kinetin (10 and 20 mg L-1) and wet tea extract (1:20 w/w) along with distilled water as control were sprayed on wheat canopy at the tillering and panicle initiation stages. Our results showed that cytozyme and tea extract enhanced the plant dry biomass over control. Kinetin (10 and 20 mg L-1) and cytozyme increased the plant photosynthetic rate and photosynthate partitioning towards the developing grain. ABA (20 mg L-1) and kinetin (10 and 20 mg L-1) reduced the N2O emission over control primarily through regulation of leaf growth, stomatal density and xylem vessel size. Leaf area, stomatal density and xylem vessel size were found to be associated with N2O transport and emission. We concluded that use of ABA and kinetin can reduce N2O emissions without any impact on wheat grain yield.

Genotypic variation in carbon fixation, δ13C fractionation and grain yield in seven wheat cultivars grown under well-watered conditions.

Biotic carbon (C) sequestration is currently being considered as a viable option for mitigating atmospheric carbon dioxide (CO2) emission, in which photosynthesis plays a significant role. A field experiment was conducted between 2013 and 2015 to investigate the efficiency of seven modern wheat varieties for CO2 fixation, C partitioning, δ13C fractionation in the leaves, and grain yield. A strong correlation between flag leaf photosynthesis and stomatal density (r=0.891) was detected. Photosynthetic efficiency was highest in the variety WH-1021 (28.93µmolm-2s-1). Grain yield was influenced by biomass accumulation in the heads and these were significantly correlated (r=0.530). Our results show that upregulated biomass partitioning to the developing kernels of wheat was inversely proportional to biomass accumulation in the roots, and led to a higher grain yield. These results led us to conclude that identification of a wheat genotype like WH-1021 followed by WH-1080 and WH-711, with higher isotopic discrimination in the flag leaves, stomatal densities, water use and photosynthetic efficiencies along with higher grain yield, can contribute to sustainable agriculture in future climate change situation in India. A yield increment of 9-48% was recorded in WH-1021 over other six tested wheat varieties.

Nitrous oxide emission and mitigation from wheat agriculture: association of physiological and anatomical characteristics of wheat genotypes.

Agriculture is an important source of emission of the greenhouse gas nitrous oxide (N2O). The observed differences in N2O emission among different varieties of agricultural crops can be a key factor for developing N2O emission reduction strategies. N2O emissions were estimated from three varieties of wheat viz. Sonalika, DBW 39, and K 0307 during 2010-2011 in an attempt to identify plant physiological and anatomical factors contributing to differences in gas emissions within the varieties. Sonalika was identified as a low N2O emitting variety and DBW 39 as high emitting when grown in a uniform field condition. The experiment was repeated in 2011-2012 selecting low emitting Sonalika and high emitting variety DBW 39 for further confirmation of the results obtained during the first year of experimentation. Important plant factors namely rate of photosynthesis and transpiration in flag leaf, stomatal frequency of adaxial flag leaf surface, and size of the xylem vessels (mean vessel size of node, stem, and root) were studied, and their relationship with N2O flux was worked out. A good correlation between transpiration and N2O flux was observed in this study. Scanning electron microscopic investigation revealed strong association of flag leaf stomatal frequency and xylem size with N2O emission. Sonalika, identified as low N2O emitting variety during both the years of study, also recorded higher grain yield due to its higher efficiency of photosynthate allocation toward the developing grains. The observed differences in N2O emission are considered to be due largely to genetic differences in the wheat genotypes.

Response of leaf water status, stomatal characteristics, photosynthesis and yield in black gram and green gram genotypes to soil water deficit.

Drought is one of the most important abiotic stresses constraining crop productivity worldwide. The objective of the present study was to investigate the differences in drought tolerance at leaf and stomatal level of black gram (genotypes: T9, KU 301, PU 19, USJD 113) and green gram (genotypes: Pratap, SG 21-5, SGC 16, TMB 37). Drought was applied for fifteen consecutive days at flowering stage (35 days after sowing). Mid-day leaf water potential (ΨL), leaf area, photosynthesis rate (PN), leaf chlorophyll, stomatal conductance (gs) and seed yield of drought- treated plants were calculated relative to those of well watered plants. Stomatal characteristics were observed in terms of stomatal frequency (SF) and stomatal aperture size (SA). Among the studied genotypes, T9 (black gram) and Pratap (green gram) proved their better tolerance capacity to drought by maintaining higher leaf area, ΨL, PN, leaf chlorophyll, gs and SA which contributed to better seed yield. Between the two crops, green gram appeared to be affected to a greater extent, as it experienced higher reduction in yield than black gram. A highly significant positive correlation (level 0.01) of seed yield was obtained with leaf area, ΨL, PN, leaf chlorophyll, gs and SA, whereas SF was found to be poorly correlated with seed yield.

Methane emission associated with anatomical and morphophysiological characteristics of rice (Oryza sativa) plant.

Plant-mediated transport is the primary route of methane (CH(4)) emission from the reduced paddy field to the aboveground atmosphere. Experiments were conducted at North Bank Plain Agro-climatic Zone of Assam, India, during monsoon rice-growing season (July to December 2006) to elucidate the influences of anatomical and morphophysiological characteristics of rice (Oryza sativa L.) cultivars on methane emission from submerged agroecosystem. Ten rice cultivars were grown in light-textured loamy soil under rainfed uniform field condition. Among the 10 cultivars, 5 were traditional rice genotypes commonly grown in the agroclimatic zone and the other 5 were improved high-yielding varieties. Wide variation in CH(4) flux was recorded among the rice cultivars, which may be regulated by the difference in anatomical and morphophysiological characteristics of rice plant. Microscopic analysis of stem portion showed that high- and medium-CH(4)-emitting cultivars recorded higher size of the medullary cavity. Leaf area and transpirational rates were also found to be higher in high-CH(4)-emitting varieties. Scanning electron microscopic analysis revealed higher stomatal frequencies in high-methane-emitting cultivars. Data presented in this study suggest that variation in anatomical and morphophysiological characteristics among different rice genotypes may influence CH(4) emission from paddy fields.