Effects of integrated nutrient management on sucrose phosphate synthase enzyme activity and grain quality traits in rice.

Cropping systems and management practices can greatly affect rice crop, finally determining their grain yield and quality. In this study, we evaluated the effects of integrated nutrient management practices on sucrose phosphate synthase enzyme (SPS) activity and grain quality traits of rice. Field experiments were conducted at North Bank Plain Agro-climatic Zone of Assam, India from 2013 to 2015 on three rice ecosystems (winter, summer, and pre-monsoon). Selected fertilizer treatments were NPK as recommended inorganic fertilizer, NPK + cow dung, NPK + whole parts of the green manure Sesbania aculeata, NPK + compost of Azolla caroliniana and NPK + rice husk dust. NPK + Azolla compost application resulted in higher SPS activity compared to control. A significant relationship between panicle biomass and SPS enzyme activity was observed in the rice plants grown in different ecosystems. Integrated nutrient fertilizers in rice soil had a significant impact on the grain quality of rice. Grain nitrogen and crude protein content were higher at NPK + green manure Sesbania aculeata applied field irrespective of the ecosystems. NPK and Azolla compost were effective in improving grain productivity and grain quality parameters viz; total carbohydrates, starch, and amylose in rice crop. Supplementary Information: The online version contains supplementary material available at 10.1007/s12298-022-01148-w.

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.

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.