Climate change, climate variability and adaptation options in smallholder cropping systems of the Sudano - Sahel region in West Africa

Key words: crop production, maize, millet, sorghum, cotton, fertilizer, rainfall, temperature, APSIM, Mali, In the Sudano-Sahelian zone of West Africa (SSWA) agricultural production remains the main source of livelihood for rural communities, providing employment to more than 60 percent of the population and contributing to about 30% of gross domestic product. Smallholder agricultural production is dominated by rain-fed production of millet, sorghum and maize for food consumption and of cotton for the market. Farmers experience low and variable yields resulting in increasing uncertainty about the ability to produce the food needed for their families. Major factors contributing to such uncertainty and low productivity are climate variability, climate change and poor agricultural management. The objective of this thesis was to evaluate through experimentation, modelling and participatory approaches the real and perceived characteristics of climate variability and change and their effects on crop production in order to identify opportunities for enhancing the adaptive capacity of farmers in the Sudano - Sahelian zone. The general approach was based on, first, understanding the past trend of climate and its effect on the yield of main crops cultivated in southern Mali; second, evaluating together with farmers different adaptation options in the field; third, evaluating climate adaptation options through experimentation on station; and fourth, evaluating the consequences of different adaptation options under different long term scenarios of climate change. Minimum daily air temperature increased on average by 0.05oC per year during the period from 1965 to 2005 while maximum daily air temperature remained constant. Seasonal rainfall showed large inter-annual variability with no significant change over the 1965 – 2005 period. However, the total number of dry days within the growing season increased significantly indicating a change in rainfall distribution. There was a negative effect of maximum temperature, number of dry days and total seasonal rainfall on cotton yield. Farmers perceived an increase in annual rainfall variability, an increase in the occurrence of dry spells during the rainy season, and an increase in temperature. Drought tolerant, short maturing crop varieties and appropriate planting dates were the commonly preferred adaptation strategies to deal with climate variability. Use of chemical fertilizer enhances the yield and profitability of maize while the cost of fertilizer prohibits making profit with fertilizer use on millet. Training of farmers on important aspects of weather and its variability, and especially on the onset of the rains, is critical to enhancing adaptive capacity to climate change. A field experiment (from 2009 to 2011) indicated that for fertilized cereal crops, maize out yielded millet and sorghum by respectively 57% and 45% across the three seasons. Analysis of 40 years of weather data indicated that this finding holds for longer time periods than the length of this trial. Late planting resulted in significant yield decreases for maize, sorghum and cotton, but not for millet. However, a short duration variety of millet was better adapted for late planting. When the rainy season starts late, sorghum planting can be delayed from the beginning of June to early July without substantial reductions in grain yield. Cotton yield at early planting was 28% larger than yield at medium planting and late planting gave the lowest yield with all three varieties. For all four crops the largest stover yields were obtained with early planting and the longer planting was delayed, the less stover was produced. Analysis of predicted future climate change on cereal production indicated that the temperature will increase over time. Generally stronger increases occur in the rcp8.5 scenario compared to the rcp4.5 scenario. The total annual rainfall is unlikely to change. By mid-century predicted maize grain yield losses were 45% and 47% with farmer’s practice in the rcp4.5 and rcp8.5 scenarios respectively. The recommended fertilizer application did not offset the climate change impact but reduced the yield losses to 38% of the baseline yield with farmer’s practice. For millet median yield loss was 16% and 14% with farmer’s practice in the rcp4.5 and rcp8.5 scenario. If the recommended fertilizer rates are applied to millet, the predicted yield losses with farmer’s practice due to climate change are reversed in both climate scenarios. Under future climate change, food availability will be reduced for the all farm types, but that large farm will still achieve food self – sufficiency in terms of energy requirement. The medium and small farm types see a further decrease in food self-sufficiency. Addressing smallholder food self-sufficiency depends upon the capacity of each farm type to appropriately choose the planting date while taking into account the acceptable planting date window for each individual crop.