Evaluation of land cover and crop type change: building evidence on the effect of cropping systems and orga nic inputs on sorghum yield and enhancing farmers climate change adaptive capacity
The Arid and Semi Arid Lands (ASALs), which in Kenya constitutes 80% of its landmass, are the most affected by climate change. Crop production is most affected as a result of climate variability with farmers being the most affected in terms of reduced crop yields, poverty and food insecurity. A study was carried out in Yatta sub – County, Kenya to assess farmers‟ perceptions, coping and adaptation strategies, crop type change within the past two decades in relation to climate change. Additionally, climate change effects on the growth and yield of sorghum under different cropping systems and organic inputs was modelled. A semi structured questionnaire administered to 60 farmers in the two study divisions of Yatta sub - County (Katangi and Ikombe) was used to collect the said information and ground truthing to estafblish the crop type change. Geographical Information Systems using Landsat imageries from the years 1986, 2000 and 2012 were used to assess the change in crop type over the past two decades. Field experiments were carried out in two seasons (short rains from October – December 2010; long rains from May – July 2011;) to determine the effects of cropping systems (monocropping, intercropping and rotation) and organic inputs (farm yard manure and compost) on sorghum performance. A randomized complete block design (RCBD) with a split plot design replicated three times was used. The main plots were the cropping systems while the subplots comprised of the organic inputs. The Agricultural Production Systems sIMulator (APSIM) was employed to model the effects of climate change on the growth and yield of sorghum under the different cropping systems and organic inputs. Correlation coefficient, root mean square error (RSME), normalized root mean square (NMRSE) and range ratio (RR) were used to test the model efficiency. Climate change scenarios were used to simulate future climatic effects on sorghum production under different cropping systems and organic inputs. The farmers in the region were aware of climate change and the major aspects of climate change mentioned were erratic rainfall (62%), low rainfall (43%), prolonged droughts (39%), increased temperatures (35%) and flooding (10%). The major causes of climate change were deforestation (63%), industrial pollution/chemicals (22%) and human activities (8%). Farmers in both divisions observed that reduced crop yield (52%) and crop failure (41%) were significant effects felt as a result of climate change. Introduction of drought tolerant crops (45%), reduced yields (43%) and change in planting time (38%) were the three main impacts of climate change on crop production in Yatta sub – County. The farmers identified early land preparation/planting on time (52%), use of organic and inorganic fertilizers (37%), planting early maturing crop varieties (28%) and water - soil conservation (18%) as the top adaptation strategies to climate change. Significant changes in crop types were also observed with maize and beans covering 72% while traditional crops, shrub land, bare land and riverine forest covered 14, 6, 3 and 5% of the land in 2012 respectively. There was a significant (P=0.000) decline in the area under traditional crops (28.4 and 45.33%), and a significant (P=0.000) increase in maize (41.14 and 140.93%) and beans (363.56 and 8.57%) between the years 1986 – 2000 and 2000 – 2012 respectively. Sorghum yields under rotation cropping system with applied farm yard manure had the highest significant yields (1.380 t/ha) compared to the other treatments. There were no significant differences between the observed and simulated yields with R2 = 0.96 for the short rains and R2 = 0.8 for the long rains and RMSE values of 0.87 t/ha and 0.72 t/ha for the short and long rains respectively with the mean differences between the observed and simulated values averaging to 821 kg/ha for the short rains and 708 kg/ha for the long rains. These results indicated good model performance. The Normalized Root Mean Square Error (NRMSE) was 2.4% for the short rains and 1.48% for the long rains which was low as well as the RR values which were 35.62% and 36% for the long and short rains respectively on the grain yield, both values being low further emphasizing on the good model performance. Climate change in terms of increased temperatures [To+1.60C (Tmax), To+1.80C (Tmin)] and reduced rainfall (R0-10%) had a negative effect on sorghum yields resulting in a mean average biomass yield change of 5% (190.9 kg/ha) in increased temperature as compared to 1.2% (48.04 kg/ha) for reduced rainfall while grain yield reduced by 3.7% (72.5 kg/ha) and 2.4% (44.3 kg/ha) respectively. Increase in rainfall (R0+10%), and a combination of increase in both temperature and rainfall predicted an increase in grain yields across both seasons at 3.6 (66.4 kg/ha) and 4.7% (89.9 kg/ha) respectively. Therefore this study will act as a benchmark to facilitate achievement of food security through increased crop yields as a result of using organic amendments and cropping systems. To further cushion farmers against the adverse effects of climate change, this study will facilitate capacity building on the effects, adaptation and coping strategies against climate variability as well as encourage the reintroduction of traditional crops such as sorghum through developing management options that will ensure maximum crop productivity using Decision Support tools (DSTs).