Rain-fed agriculture

Rain-fed farming, covering 33.2 Million ha, is the dominant agricultural system in the Nile Basin. Over 70% of the basin population depends on rain-fed agriculture (Seleshi et at., 2010). Sudan, with 14.7 million ha accounts for 45% of the total rain-fed lands, followed by Uganda, Ethiopia, Tanzania, Kenya, Rwanda and Burundi. Low rainfall does not allow rain-fed farming in Egypt, and rain-fed areas of Eritrea that fall within the Nile boundary are almost negligible. The main rain-fed crop in the Nile Basin in terms of cultivated area is sorghum, followed by sesame, maize, pulses and millet, covering 7.39, 3.68, 3.35, 2.94 and 2.86 million ha, respectively. Rain-fed agriculture in the Nile Basin is characterized by low yields with the majority of crops having an average yield of less than 1ton /ha. Different sets of reasons have been proposed for the low yields in rain-fed systems from natural causes such as poor soils and droughtprone rainfall regimes to distance from urban markets (Allan, 2009). However, the opportunity of favorable rainfall in many rain-fed areas of the basin provides a high potential for yields to increase by improved farm water management techniques such as rainwater harvesting. While the proportion of (evapotranspiration) ET from rain-fed crops remains relatively stable between years, the absolute amount varies very significantly, from 180 to 256 km3, representing a large difference in potential crop production between years and at the same time illustrating the risks associated with rain-fed agriculture in the region. The variability is in low rainfall areas: the ratio of rain-fed crop ET between the driest and the wettest years is around 0.7- 0.9 in the humid uplands, but falls to around 0.5 in the semi-arid catchments of central Sudan and the Atbara basin. In terms of food security, this annual variability is exacerbated by the occurrence of multi-year droughts.

Under these conditions, opportunistic cropping in wet years may be a viable strategy commercially, although it is difficult to reconcile it with the need for subsistent smallholders to produce crop every year to ensure food security. Much of the additional food demand in the Nile partner states is expected to be met through improvements in rain fed agriculture. The vast untapped potential of rain fed agriculture could be unlocked through knowledge-based management of land and water resources, bridging the yield gaps (a factor of two to four) between the current farmers’ yield and the researcher-managed or commercial plot yields (Rockström et al. 2007).

Small-scale agricultural water management techniques, such as rainwater harvesting and groundwater within a watershed management approach have important potential roles in securing rain-fed crops in these regions. Araya and Stroosnijder (2011) found that in northern Ethiopia, where crops failed in more than a third of years in the period 1978-2008, one month of supplementary irrigation at the end of the wet season could avoid 80 per cent of crop yield losses and 50 per cent of crop failures. Other strategies used in the area to manage erratic rainfall include supplementary irrigation to establish crops (to avoid false starts to the wet season), postponement of sowing until adequate soil moisture is available, and growing quickly maturing cash crops such as chickpea at the end of the growing period, to utilize unused soil water reserves.