On climate change and climate-smart agriculture

Agriculture in its simplest terms refers to growing of crops and rearing of animals for human use. Climatic conditions like rainfall, temperature, sunshine and so on all have profound effects on agriculture. However, human activities affect the climate negatively. Climate change affects agriculture negatively and leads to the risk of food insecurity for the ever growing population of Nigeria.

This raises the question: shall we abandon agriculture since the activities lead to climate change? The answer obviously is no. Rather, the idea is to practise climate-smart agriculture. Global warming and climate change occur because of the melting of the ozone layer. The ozone layer is the stratospheric layer of the atmosphere that shields the earth from harmful radiation from the sun. There are certain gases that have the capacity to alter the integrity of the ozone layer and hence speed up climate change. These gases are called Green House Gases and the effect they produce is called the Green House Effect. According to Wikipedia, without Green House Gases, the average temperature of the earth would be -18oC (0oF) rather than the present average of 15oC(59OF). The most potent Green House Gases include carbon dioxide, methane, and nitrous oxide. Others are ozone, water vapour and fluorinated gases.

Synthetic fertilizers have always been used and are still being used to improve the growth of crops. This increased fertilizer use is responsible for the dramatic rise in atmospheric nitrous oxide which is a major contributor to climate change. This is because nitrogen-based fertilizers stimulate microorganisms in the soil to convert nitrogen to nitrous oxide at a faster rate than normal. Excessive use of synthetic fertilizers depletes soil quality and alters the fertility of soil over time by increasing the acid levels in the soil. Nitrous oxide is also generated as a by-product during the production of nitric acid which is used to make synthetic fertilizers.

Climate change facilitated by nitrous oxide can be mitigated through the following ways: animal dietary manipulation to increase efficiency; avoiding excess nitrogen in the diet of animals and or making dietary nitrogen more absorbable and reducing nitrogen excretion. Manure management techniques: anaerobic digestion indirectly reduces nitrous oxide emissions when slurry is applied to land by decreasing the available nitrogen content. Grazing management methods: reduced stocking and minimised grazing periods are likely to result in lower emissions. Also, animal housing system and management options for mitigating emissions include more frequent removal of manure from animal housing floors and changing animal housing systems. Animal housing and manure stores of straw-based systems result in higher nitrous oxide emissions than anaerobic slurry based systems.

The meat from ruminants (cattle, sheep, goat) has a higher carbon than other meat or vegetarian sources of protein. The largest source of Green House Gas emission within the agricultural sector is enteric fermentation. Here, methane is produced by livestock during digestion and released via belches. This is a non-anthropogenic cause of climate change. Another source of methane emission is from rice fields. Here, anaerobic decomposition of organic materials in flooded rice fields produces methane which escapes to the atmosphere primarily through diffusive transport through the rice plants during the growing season.

The period between flooding of rice field and onset of production of methane (methanogenesis) can be different for the various soils. The addition of sulphateto the soil can reduce methane production in rice fields. Climate change facilitated by methane emission can be mitigated through dietary measures. This includes saltering and improving diet for higher animal productivity: feeding increased levels of starch, feeding supplementary dietary fat and reducing the production of fibre in the diet.

These are examples of methane reduction strategies. Others include forage selection and management; increasing forage quality combined with the management of stocking rates and rotational grazing strategies. These have been demonstrated to reduce enteric methane emissions. Further, the use of feed additives: can manipulate microorganisms in the stomach of farm animals to induce stable and modified fermentation with lower emissions. Legumes containing condensed tannins are able to lower methane by 12% to 15%. Biological additives such as cultures of Saccharomycescerevisiae to animal feeds also reduce methane production by animals.

Management systems designed for high milk output per cow will result in lower emissions per unit of milk produced. In contrast, more extensive systems require more animals to produce a given quantity of milk – resulting in higher methane output per litre. In manure management and treatment, helpful manure management techniques include frequent and complete removal of manure from indoor storage, deep cooling of manure and management of bedding and manure heaps to avoid anaerobic conditions.

Processes that release carbon dioxide into the environment include bush burning, emissions from energy use in agriculture generated from traditional fuel sources including electricity and fossil fuels burned to power agricultural machinery, irrigation pumps, etc. Consequently, there may be the need to develop the production of ethanol as a substitute to fossil fuels.

Climate change facilitated by emission of carbon dioxide within the agricultural sector can be mitigated through restoring soil carbon by improving soil management techniques, adopting conservation tillage, surface residue management and mulch farming. Cultivating crops with deep root system, developing and cultivating plants with high lignin content especially in residues and roots and increasing crop biomass production can lead to carbon reduction. Also, enhancing biological nitrogen fixation, applying animal manure and non-toxic anthropogenic bio-soil (top soil rich in decaying organic matter) can contribute to the reduction of carbon emissions. Others include improved grassland management; changing from highly intensive, short duration pastures to more permanent grasslands as well as reduced tillage can also increase carbon sequestration. Energy efficiency can be improved in milking parlours and milk processing plants whilst digestion of manure to produce heat and electricity will also contribute to lower fossil fuel energy use and carbon dioxide emission

Individual mitigation measures must, however, be evaluated with regards to emission reduction potential, environmental trade-offs within and outside the agricultural system.

Eke is the programme officer at Centre for Social Justice