Soil moisture retention through crop rotation and organic fertilizer application as a climate adaptation mechanism in rainfed agriculture of Ethiopia

It is evident that climate change and climate variability are affecting rainfed agriculture, especially smallholder farmers in sub-Saharan Africa. On the other hand, irrigation is either unavailable or unaffordable for these farmers. In this research two agronomic options were tested for two consecutive years. One set includes three cereals and three legumes rotation under cereal-cereal, cereal-legume, legume-cereal and legume-legume categories. The other set includes management of cattle manure, poultry manure, conventional compost, vermicompost, green manure, and crop residue; with chemical fertilizer and no fertilizer application used as controls. Finally, the volumetric soil water content was measured using a Delta-T wet sensor during the second season, every two days, starting immediately after the last rainfall using teff and wheat as test crops. Though effects of different fertilizers vary among the test crops, results indicated that both crop rotation and nutrient management have a significant effect on soil moisture content. Overall comparisons showed that application of poultry manure resulted in the highest soil moisture content (29.2 m3 m-3) followed by residue management and use of vermicompost (28.2 m3 m-3). But it varies with the crop type. While conventional compost was the most effective for teff, cattle manure was found to be the best at conserving soil moisture for wheat. On the other hand, legume-cereal rotation retained more water than other rotations, with maize after soybean resulting in the highest soil water content (33.1 m3 m-3). Therefore, agronomic practices such as crop rotation and the use of organic fertilizers can be considered as the potential adaptation options to address climate change and climate variability affecting the rainfed agriculture in small-scale farming.