Scientists at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) suggest better use of fertilizers and water to counter negative effects of climate change. Far more than climate change, low fertiliser use and poor rain-water management among small-holder farmers in sub-Saharan Africa and Asia will continue to undermine food security, scientists at the International Crop Research Institute for Semi-Arid Tropics (ICRISAT) have found. Using climate and crop growth models to forecast the impacts of global warming on food production in the semi-arid tropics in several countries in sub-Saharan Africa and India, ICRISAT scientists found that improved use of fertiliser and harnessing rainwater would increase food production even if climate changes for the worse, notably drastic increases in temperatures with the same rainfall patterns.
In contrast with low-input farming, ICRISAT found out that enhanced fertiliser use, rainwater harvesting and mulching could almost double crop yields, even with a 3o C temperature increase with the quantum of rainfall and its distribution remaining the same. Stressing the need for resilience on the part of dry land farmers in dealing with global warming, ICRISAT Director General Dr William Dar says, “The world is now locked into the inevitable changes of climate patterns and however uncertain those changes might be, farmers must eventually adapt to them.” The latest report of the Inter-governmental Panel on Climate Change (IPCC) cites that average global temperatures are currently 0.43oC to 0.54oC higher than the yearly temperatures recorded between 1961 and 1990. All IPCC models concur that temperatures are increasing steadily within the tropics but give divergent predictions on rainfall trends.“The impact of temperature increases on farm yields from low-input agricultural systems, typical of semi-arid tropics, is likely to be minimal as other factors such as low and declining soil fertility, poor weed control and lack of water conservation practices. These will continue to provide overriding constraints to crop growth and yield in the semi-arid tropics,” says Dr Peter Cooper, a senior scientist of ICRISAT. “The adoption of existing recommendations for improved crop, soil and water management practices, even under an increase of 3o C, will result in substantially higher yields than farmers are currently obtaining,” says Dr KPC Rao, another ICRISAT senior scientist.
Increases in temperature reduce the length of growing period, which is defined as the number of days the soil has enough water stored to support crop growth to full maturity. High temperatures also speed up crop growth leading to earlier, premature flowering and, as a result, depressed yields. Most farmers in the semi-arid tropics of sub-Saharan Africa and Asia rely exclusively on highly unpredictable rainfall to produce food and generate income, and are therefore extremely vulnerable even to prevailing climatic shocks and rainfall variability. Climate change is expected to worsen matters for them. Nevertheless, farmers have evolved highly risk-averse mechanisms of coping with erratic rainfall and temperature to minimise possible losses by investing as minimally as possible, in farm inputs.
FAO statistics show that while all other regions of the world have recorded steady increase in fertilizer use over the past four decades, sub-Saharan Africa’s fertilizer use stagnates at a very low level at 5 kilos per hectare. “We find that vulnerable communities tend to over-estimate the negative effects of the current climate-induced uncertainties by trying to minimise losses, but this also means they fail to take full advantage of the better seasons, losing opportunities to recoup losses from poor seasons,” adds KPC Rao. As one example from a wider study, working with meteorological rainfall and temperature data for Makindu in eastern Kenya from 1959 to 2004, ICRISAT scientists found that farmers in the area are already experiencing and enduring extreme weather shocks expected as a result of global warming.
Makindu, like other semi-arid zones, receives bursts of intense rainfall in short spells of time most of which is lost as runoff accompanied by massive soil erosion. ICRISAT found that by using tied ridging and mulching, farmers are able to increase and retain water in soil for longer, even under warmer climate conditions, attaining more successful crop growth and better yields. “By promoting the use of commonly available methods of soil fertility management and water conservation, we find that governments can help farmers to avert crop failure and famines, as well as prepare farmers to better cope with climate change impacts,” says Cooper.
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