Modeling potential impact of climate change on Sorghum (Sorghum bicolor) and Cowpea (Vigna inguiculatas growth and performance under different tillage and cropping systems in semi-arid areas of Eastern Kenya

Crop models can be used to assess risk associated with climate change and variability. The \noutput can be more useful to farmers if the process involves their input. This study was hinged \non a participatory concept and therefore a survey in the study area (Makueni County, in Eastern, \nKenya) was conducted to capture farmers experience, knowledge- and adaptation strategies \nemployed in response to climate change and variability. A field trial was carried at Kambi ya \nMae location in Eastern Kenya, to evaluate the effect of tillage and cropping system on \nperformance of sorghum and cowpea. The trial was done during long rains (LRS) 2010 and short \nrains (SRS) 20 10/20 11 and consisted of three tillage (Tie-ridge, sub soiling and ox plough) and \nfour cropping systems (sole sorghum and cowpea, sorghum-cowpea intercrop and rotation). The \ntreatments were arranged in split plots with tillage practices as the main plots and cropping \nsystems as the sub-plots in a Randomized Complete BIC!'CkDesign (RCBD).The APSIM model was used to assess the potential impact of~limate change on sorghum and cowpea yields under \nsemi-arid conditions with the following future climate scenarios considered, current temperature . \n(To) and rainfall (Ro) provided the baseline, To+2°C (T2), To+3°C (T3) and To+10% R \nreduction (R2) and a combined effect of T2 and T3 and R2 was examined for both crops. For \nCowpea, CO2 fertilization at 450ppm and 700ppm and their combination with T2 and T3 and R2 \nwas also examined. Rainfall unreliability and low amount was ranked top as the most important \nchallenge farmers face and on average constituted 58% of the risks in their farming system.53% \nalleging that significant change in climate will manifest in 10 -20 years. CCV as an issue was \nrated very high by 72% of the farmers who solely depended on farming as their only source of \nlivelihood compared to just 15% who had diversified; income sources. This gave an insight into and confirmed farmer's vulnerability.