Foreword by Dr. H.S.Sen, President, SFE for the Newsletter #4(2)

Reducing carbon footprint is the key to environmental sustainability

Agriculture is the greatest source of living on the planet, and fertilizers are the major means to compensate mining of nutrient reserves in soil due to plant growth. According to FAO, world agriculture is currently responsible for more than half of the atmospheric increase of nitrous oxide (N₂O), two-thirds of the global ammonia (NH₃) input into the atmosphere, and 40% of global methane (CH₄) emissions. These compounds play important roles in atmospheric chemistry, ozone depletion, aerosol formation and greenhouse warming. N₂O comes from two main sources - livestock manure and chemical fertilizers. In dairy and cattle operations, large amounts of ammonia are produced when urea and livestock manure break down in water or slurry. Since fertilizer is responsible for large amounts of agricultural sector N₂O emissions, farmers can choose to implement soil management practices that lead to appropriate fertilizer application rates. In addition to nitrogen field sampling, further N₂O mitigation options include using cattle feed pads during winter months, using nitrification inhibitors with fertilizer, properly timing fertilizer applications, improving field drainage, and avoiding soil compaction which slows water drainage.

On the other hand, crop-based agriculture occupies 1.7 billion hectares, globally, with a soil C stock of approximately 170 Pg. The oxidation of soil organic matter in cultivated soils is estimated to have contributed approximately 50 Pg C to the atmosphere. Returning the lost soil carbon via increasing C storage in soils is a clear sequestration possibility, and the latter is related to the productivity of crop plants. 

The long-term strategy therefore for environmental sustainability through fertilizer use and other interventions under intensive agricultural practices should be by employing such practices that agricultural lands can both sequester carbon and reduce CO₂, CH₄, and N₂O emissions, thereby reducing their GHG footprint.  There could be seven key farming tactics that are proven to be effective in increasing grain production while lowering carbon footprint: (1) using diversified cropping systems can reduce the system’s carbon footprint by 32 to 315 % compared with conventional monoculture systems; (2) improving N fertilizer use efficiency can lower the carbon footprints of field crops as N fertilizer applied to these crops might contribute 36 to 52 % of the total emissions; (3) adopting intensified rotation with reduced fallow during summer can lower the carbon footprint by as much as 150 %, compared with a system that has high frequency of summer fallow; (4) enhancing soil carbon sequestration can reduce carbon footprint, as the emissions from crop inputs can be partly offset by carbon conversion from atmospheric CO₂ into plant biomass and ultimately sequestered into the soil; (5) using reduced tillage in combination with crop residue retention, called as conservation agriculture, can increase soil organic carbon and reduce carbon footprints; (6) integrating key cropping practices can increase crop yield by 15 to 59 %, reduce emissions by 25 to 50 %, and lower the carbon footprint of cereal crops by 25 to 34 %; and (7) including N₂-fixing pulses in rotations can reduce the use of inorganic fertilizer, and lower carbon footprints. With the adoption of these improved farming tactics, one can optimize the systems performance while reducing the carbon footprint of crop cultivation (https://link.springer.com/article/10.1007/s13593-016-0404-8).

The present issue of the newsletter deals with impact of nitrogen use on inorganic C stock in soil, activities of beneficial microorganisms to nitrogenous fertilizer application for sustained fertility status, and role of phosphorus in agriculture and environment. In a departure from the trend of use of major nutrients on soil and atmospheric environment role of micronutrients on human and animal health from industrial perspectives has been discussed. Finally, protocol for assessing mitigation potential of GHG emission in terms of C balance in soil tested through large number of village-based trials has been discussed.