Water and soil conservation for improved crop productivity, water household and soil quality in Niger

Growing population pressure and ongoing soil degradation increasingly force Nigerien farmers to rely on marginal and shallow lands for crop production. Regular crop management, however, generally fails to produce millet grains on these soils, as they suffer from a low soil nutrient content and imbalanced partitioning of water in the rootzone. Recently, major attention went to small scale water water and soil conservation (WSC) practices to secure food production, as these are believed to tackle the two major crop growth limitations on marginal lands through the combination of both water and nutrient management. To assess the impact of various small scale WH techniques on agronomical, hydrological and soil quality parameters, we installed a field experiment according to a randomized block design with five treatments and three replications. The treatments include: zaï (traditional planting pit) + manure, half moon + manure, no till with scarification + manure, control + manure and control. The paper evaluates the results of the 2011, 2012 and 2013 growing seasons. The highest grain yield is produced by the zaï-pits, which is approximately three times better than the grain yield produced by the half moon treatment that in its turn did not significantly outperform the no-till with scarification treatment. The higher soil moisture levels, as measured by a neutron probe, for the zaï and half moon treatment, rather result from the physical form of the zaï-pits and the half moons, than from improved physical soil properties related with manure application. As such, soil moisture levels are higher for the half moon and the zaï treatment because the bunds and pits respectively break runoff water and give it time to infiltrate into the basin. The application of manure does on the other hand increase biological soil quality, as nematode count of the free living species for the treatments with manure was higher than that for the control treatment. Besides the improved soil moisture conditions, the potential of WSC practices to increase the agronomic efficiency is also largely explained by their positive impact on the soil nutrient status.