Nutrient cycling practices and changes in soil properties in the crop-livestock farming systems of western Niger Republic of West Africa

Pearl millet [Pennisetum glaucum R. (Br.) L.] is grown in West Africa on sandy, acid soils deficient in plant nutrients. In the mixed farming systems of western Niger, livestock graze millet stover by day and deposit dung and urine directly on cropland during overnight kraaling. Kraaling of livestock is perhaps the most important pathway to recycle nutrients and sustain soil fertility. Three tillage practices (immediate tillage, late tillage and no till) four amendment types (dung-plus-urine, dung alone, millet stover and millet stover ashes), and three fertilizer N rates (0, 15 and 30 kg N ha(-1)) were factorially combined and arranged in a split plot design. Average millet grain yield in immediate till plots was 30% higher than in no-till plots and was 13% greater in plots amended with dung-plus-urine than in plots that received manure alone. The highest pH (5.8) and lowest bulk density 1.46 g/cm(3) of surface soil were measured in plots amended with dung-plus-urine. Under the less nomadic livestock management system, where animals are mostly stall-fed, technology is needed to capture and transfer nutrients in animal urine to farmers' fields for cropping.