The results of a three-year water conservation trial in the Zambezi Valley of Zambia are reported, for an area characterized by high temperatures and low, often poorly distributed, rainfall, with low infiltration and high evapotranspiration rates. As a result of these conditions local farmers often produce grain crops yielding as little as 200–300 kg./ha., though considerable increases could be obtained by simple water conservation methods. Of four treatments, tieridges made before the start of the first rains consistently gave the heaviest yields. Mean yields of the three crops under trial (maize, sorghum and bulrush millet) were higher on tie-ridges than on conventionally prepared seedbeds by 168, 159 and 17 per cent in the 1968–69 to 1970–71 seasons respectively.