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Soil organic carbon (C) management in agricultural fields can act improve soil health and productivity. However, reports on the C release pattern and the interactive effects of plant physiological parameters on soil C storage from subtropical regions of the world where rice is cultivated as a dominant food crop are inadequate. The interactions between plant metabolism, soil C storage, and organic-based nutrient management schemes have been little studied. Hence, a study was undertaken in rainfed winter rice to evaluate the effects of different levels of organics (crop residue (CR) and farmyard manure (FYM)) along with inorganic (NPK) inputs in an alluvial soil. The experiment was conducted in a typical humid subtropical climate in north-eastern India. The CR of the preceding rice crop (pre-monsoon) and cow dung based FYM were used as organic inputs for monsoon rice, which were applied in various combinations with inorganic fertilisers. We studied the influence of these selected nutrient management schemes on soil health attributes, C storage, and plant parameters. The highest gain in C storage (11.65%) was in soil under 80% NPK + CR (51 [ha.sup.-1]) + FYM (10 t [ha.sup.-1]) treatment. Correspondingly, significant improvement (P < 0.05) in total C, dissolved organic C, and nitrogen availability in soil was evident under this treatment leading to augmentation of soil organic matter status and the net amount of sequestered C in soil after two years of rice cultivation. Such improvements resulted in greater flag leaf photosynthesis, biomass accumulation, and grain yield than the conventionally managed crops. Overall, this research showcases that organic-dominated nutrient management not only restored soil health but was also able to compensate 20% of the recommended NPK fertilisation without penalty on crop yield. Additional keywords: carbon storage in soil, crop residue, fertiliser, photosynthesis, soil health. Received 25 October 2017, accepted 4 July 2019, published online 17 September 2019, Introduction Carbon (C) storage has a significant impact in human life and environmental sectors by reducing greenhouse gas (GHG) emissions and has attracted attention from policymakers and researchers for a [...]

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. [ABSTRACT FROM AUTHOR]

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 (28.93 mmolm-2 s-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. [ABSTRACT FROM AUTHOR]

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.

Agricultural soils are the major source of global nitrous oxide (N 2 O) emission, and more than two thirds of N 2 O emission originate from soil. Recent studies have identified that green plants contribute to transport of N 2 O to the atmosphere. We investigated the effects of foliar application of plant growth regulators (PGRs) and growth stimulating chemicals on N 2 O 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 N 2 O 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 N 2 O transport and emission. We concluded that use of ABA and kinetin can reduce N 2 O emissions without any impact on wheat grain yield.

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.