Mandera County executive member for agriculture, Johora Mohamed and other staff in a fodder farm in the county. Feed production systems produce nitrous oxide through fertiliser application and this can be minimised by intercropping fodder with nitrogen-fixing crops such lucerne and desmondium that will reduce the amount of nitrogenous fertilisers used. PHOTO | MANASE OTSIALO

A 2007 report by the Intergovernmental Panel on Climate Change (IPCC) projected that by 2020, between 75 and 250 million people in Africa will be exposed to increased water stress.

At the same time, some countries’ yields from rain-fed agriculture would be reduced by up to 50 per cent. Marine life and the fishing industry will also be severely affected in some places.

Unfortunately, Agriculture, Forestry and Other Land Use (Afolu) sector is among the world’s largest emitter of greenhouse gasses.

Greenhouse gasses are produced through man’s activities and are responsible for global warming and climate change.

The consolation in climate change is that agriculture has the potential to mitigate (reduce, delay or avoid) its impact.

Climate change

It is the projected rise in earth’s temperatures and unpredictable rainfall patterns as a result of air pollution. The 2010 global emission by sectors was; electricity/heat (25 per cent), Afolu (24), buildings (6.4), transport (14), industry (21) and others (9.6).

There are six greenhouse gases but the ones that are directly from agriculture are carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O).

CO2 is produced through burning of fossil fuel such as coal, while cutting down of trees also raises its levels. CH4 is produced when animal or plant materials (organic matter) decompose in the absence of oxygen. N2O is a major constituent of nitrogenous fertilisers such as CAN.

In the natural environment, these gasses are released in manageable levels. For example, decomposing organic matter releases CO2 that the trees breathe in during photosynthesis while nitrogenous materials such as leguminous plants release nitrogen which is taken up by soil to assist in developing the leafy materials.

Under normal circumstances, the sun rays (ultraviolet) heat the ground, the earth absorbs some heat and the excess is discarded up into the stratosphere and beyond.

The absolved heat warms the earth making it habitable. However, when the reflected rays which are weaker than the incoming ones (infrared) find the gas cover at the stratosphere, some of rays are able to escape but most of it is not able to penetrate the blanket and is reflected back to the earth thus warming it more than necessary and this is what is referred to as global warming.

This warming affects weather and rainfall pattern and hence climate change. Rice production and livestock keeping are the agricultural activities that produce significant levels of two greenhouse gases namely CH4 and N2O.

Rice production

Rice production contributes 10 per cent of the agricultural greenhouse gas emissions. Methane is produced through paddy/flood rice production and N2O from fertiliser application.

To reduce methane production, drip irrigation is better during the water critical periods and completely draining it mid-season when the requirement is at its lowest.

Another emission reduction method is planting highland rice, which is a dry land variety that can grow in any part of the country all-year round and takes 105 days to mature.

The common practice is that after rice harvesting, the straw is left/burned then methane is produced. An integrated farming system where the straw is fed to cattle and the cow dung is put in a digester to produce biogas (methane) and slurry fertiliser can greatly reduce methane.

This further reduces the need for the inorganic fertilisers that are responsible for N2O emission.

Livestock production

Around 40 per cent of agricultural emissions come from methane production by livestock and another 25 from their manure.

Livestock production emits greenhouse gases through enteric fermentation, manure, and feed and fodder production/utilisation practices.

Methane is produced in multi-stomach (ruminant) animals such as cattle, sheep and goats. Methane production in an animal is dependent on; a) Age: Rumen in calves is not well-developed, they do not produce methane. b) Size: The bigger the animal, the more it emits. c) Production: An animal that is producing milk and is in-calf emits more than one that is not.

Issues of feed that contribute significantly to methane production include; a) Digestibility: Feeds take time to go through the digestive system.

The longer it takes, the more methane it emits. b) Type and combinations of feeds fed to an animal matter. For example, feeding napier alone produces more methane than mapier/vetch. c) Breed of the animal: Some are able to digest feed faster than others. d) Additives in the feed reduces methane production.

To reduce methane emission from livestock farming, it is recommended that you feed an animal with high quality pasture, fodder and concentrates.

Include additives such as oils if high percentage of feeds are inform of concentrates (canola oil has been used successfully); breed animals that have high conversion rates thus using less food to produce more and use a mixture of feeds as opposed to one type only.

Feed production systems produce nitrous oxide through fertiliser application (NO2). This can be minimised by intercropping fodder with nitrogen-fixing crops such lucerne and desmondium that will reduce the amount of nitrogenous fertilisers used.

Further, the carbon sink of the soil can be enhanced through use of conservation agriculture that advocates for minimum or no tillage, crop rotation and maximum ground cover.

As for the consumer, reducing consumption of animal proteins, and replacing them with plant proteins such as pulses helps.

Using animal proteins from single stomach (mono-gastric) animals such as poultry, fish and pigs contributes towards high CH4 and NO2 production.

Reach Dr Mwirigi on

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