Building Resilience Against Drought and Floods: The Soil-Water Management Perspective

Many regions in the world are suffering from agricultural droughts and floods, two sides of the same coin. They result in shortage of available water for plant growth or accumulation of water on farm land that is normally not submerged, respectively. The incidence of droughts and floods is not only caused by extreme weather events, but also by an imbalanced partitioning of rainfall, with higher blue water flows at the expense of green water, i.e. soil moisture generated from infiltrating rain. This chapter suggests that poor partitioning of rainwater and an unbalanced water regime is associated with soil structural degradation, lack of physical structures or evapotranspiration controlling measures, among others. Appropriate soil-water management practices could be a first step in building resilience against agricultural droughts and floods. Such practices refer to the management of soil (in whatever way) with the purpose of enhancing the quantity and flow of soil water. They range from improving physical soil quality, i.e., increasing rainwater infiltration capacity and plant-available water capacity through the use of soil amendments, conservation agricultural practices and other field water conservation practices, over farming practices such as use of mulches and cover crops, to soil conservation practices, and runoff and flood water harvesting techniques. In this chapter, two examples from semi-arid zones in Kenya and Ethiopia are given that demonstrate that soil-water management practices lead to more water being conserved and thus reduce drought and flood risk, resulting in at least 40% higher maize and wheat yields when rainfall was lower than normal. On a Vertic Phaeozems in Kenya, best results were obtained when applying three conservation agriculture practices (minimal disturbance, soil cover, diversified cropping). On a Vertisol in Ethiopia, conservation agriculture-based soil-water management practices with narrow raised beds and furrows outperformed other tested practices. Though not demonstrated with data, this chapter also suggests that soil-water management practices can affect the incidence of hydrological and meteorological droughts and floods as well.