As per the fifth IPCC report, agriculture (including animal husbandry, fisheries, forestry, and land use) is responsible for 14 per cent of global greenhouse gas (GHG) emissions. But, the sixth report has revised the emission to 22 per cent. The rest comes from sectors like energy, industry, transport, etc. Agricultural production has to be increased to meet the increasing food demand of the global population. For this, farmers have to grow input-dependent crop varieties. The use of agrochemicals has increased significantly in the last few decades. In addition to that, deforestation was in progress in many countries to extend the farmland to grow more food. The use of water and agrochemicals is beyond the optimum level.

So, there is a huge waste in polluting the environment. Farmers are forced to shift from an eco-friendly cropping pattern to an intensive way of crop production. If irrigation is available, they turn their upland field, good for growing vegetables or upland rice into lowland rice fields in many countries like Bangladesh. Somewhere, the paddy land is being made into a wetland to cultivate fish.  The livestock and poultry industry is based on high-yielding breeds which eat more to emit more GHG. The poorly managed cow dung and poultry litter is a good source of GHG in developing countries. As a result, GHG is on the rise in every sub-sector of agriculture.

According to the FAO in 2015, GHG emissions from all forms of livestock management (farming, land use, transport, food industry, etc.) amounted to approximately 6.2 billion metric tonnes of CO2eq (Carbon dioxide equivalent) per year. It accounts for 12% of greenhouse gas emissions from the total anthropogenic activities. If no action is taken, this amount will rise to 9 billion metric tonnes by 2050. Ruminant (two-stomached) cattle emit more greenhouse gases than any other animal. Livestock food shares 35 per cent of agricultural products. Accordingly, the production of methane, nitrous oxide, and carbon dioxide due to livestock and the relevant field is significant. Methane emissions from beef and dairy account for 30-39% of the total greenhouse gas emissions from the livestock sub-sector.

About 80% of Nitrous oxide emissions come from agriculture production due to weak management of applied nitrogenous fertiliser. Half of the greenhouse gas emissions of the agricultural sector come from organic matter applied to the crop field. A lot of fuel is burnt for off-farm and on-farm activities are the direct source of GHG. Also, stubbles and crop residues left in the field are burnt in many Asian countries. Carbon dioxide is the main GHG emitted from burning crop-residues. The GHG emissions from such open-field rice straw burning in India, Thailand, and the Philippines are 0.75%, 0.18%, and 0.56% of the total GHG emissions from agriculture respectively.

So, how can this pollution be controlled? First of all, one of the ways is to increase the efficiency in nitrogenous fertilisers use. There are several methods already available to scientists. For example, how much nitrogen fertiliser should be applied to a crop and when? The best method of using nitrogen fertiliser is to test the soil and determine the exact amount of fertiliser needed. Nitrogen fertiliser should be applied deep into the soil. The fertiliser must be in a balanced dose with other fertilisers applied to the crop. The second is to follow diversified cropping pattern. That is, after rice, any other crop should be followed in a rice-based cropping pattern. In this case, it is better to cultivate a pulse crop.

Because the pulse crop itself can fix a sufficient amount of nitrogen from the air, that nitrogen comes into use for the next crop. Apart from this, it is better to grow rain-fed crops in between two irrigated crops. In this case, upland aerobic rice or maize can be cultivated. However, the problem is that we still do not have a good variety of high-yielding direct-seeded upland or aerobic rice varieties. Apart from this, in recent times, AWD (Alternate Wetting and Drying) technology has been in our hands but has not yet been popularised.

Recently, zero tillage or minimum tillage has been a matter of discussion among the scientific community. Zero tillage, or minimum tillage, is supposed to use less fossil fuel. Less stirring of the soil increases the chances of carbon being preserved in the soil, provided organic fertilisers can be used to some extent. The integrated agronomic management will help to reduce the carbon footprint. In brief, to control GHG emissions, it is necessary to take care of appropriate mechanisation, waste management, appropriate soil and water management, practising minimum tillage, selecting appropriate cropping patterns, using appropriate crop varieties, integrating nutrient management, and managing crop residue etc. which is nothing but a kind of smart farming. Is it possible for a developing country farmer who is not yet educated enough to accept all these technologies right now? So, the technology must be farmer-friendly. And that's the right away. We are on the verge of the IPCC's deadline to keep global warming within 1.5 degrees C.

Acknowledgement: Avijit Ghosh et al., (2020) Environmental Science and Pollution Research https://doi.org/10.1007/s11356-020-07949.
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The writer is Director General (Former), Bangladesh Rice Research Institute, Krishi Gobeshona Foundation