Unreliable and erratic rainfall combined with inherent low soil fertility in crust prone soils affect crop growth in the Sahel. Past efforts of agricultural water management have primarily focused on maximising rainfall infiltration through soil and water conservation. The challenge of how to cope with dry-spells, short periods of water stress during crop growth, remains largely unsolved. Small-scale water harvesting (WH) for supplemental irrigation may be a tool for small-holder farmers to stabilise crop water supply and thereby increase yields and create incentives for increased investments in fertilisation. Results are presented on the effects on Sorghum (Sorghum Bicolor (L.)) yields under supplemental irrigation and soil nutrient application in an on-farm experiment in northern Burkina Faso. Focus is on dry-spell bridging and water and nutrient interactions on biomass productivity. The water harvesting system consisted of a low-cost manually dug farm pond with a storage volume of 150 m3, collecting surface runoff as rill and small gully flow from a 1.8 ha catchment area.