Effects of traditional soil management practices on the nutrient status in Sahelian sandy soils of Niger, West Africa

In the Fakara region of the Sahel zone, Niger, West Africa, farmers have been implementing traditional soil management practices such as the application of dry farmyard manure (FYM) and household waste (HHW), livestock corralling, and fallows. Previous studies, however, have not accumulated enough data on the effects of these practices on the soil nitrogen (N) pool in the Sahelian sandy soils.The objectives of this study were to evaluate the effects of these traditional practices on each N pool and on other nutrients. As the indicator of available N, phosphate buffer extractable organic nitrogen (PEON) was employed. Total N was significantly higher in the fields adjacent to houses (H) and suburban fields where FYM had been applied for 10years (FYM10) or 5years (FYM5), compared with that in the no-treatment fields (NT) which had received no organic matter (OM) and chemical fertilizer for several decades. FYM10, H, and reserved fallows (RF) showed significantly higher levels of PEON than of NT. The amounts of total N and PEON in soils from all corralling practices, and all normal fallows were at the same level compared with NT. Similarly, the mineral N pool was higher for the soils from H, FYM10, and mixed corralling with sheep and goats.The principal component analyses (PCA) showed that all eigenvalues of soil pH, exchangeable potassium (K), available phosphorus (P), total N and carbon (C), PEON and mineral N in principal component 1 (PC1) were positive, thus relating strongly to soil management practices which can enhance the essential nutrients: the pool of N, P, and K, and C pool in soil. For PC2, the eigenvalues of mineral N, exchangeable K, and pH were positive, strongly relating to soil management practices which can enhance cations in soil. In comparison with NT the eigenvalues of PC1 of the managements with OM application were higher than in NT while those for the normal fallows without OM application were as low as those in NT. The eigenvalues of PC2 were higher for H and all corralling practices compared with the values for NT. We understood that the practices of transporting manure and corralling are important for the improvement of the fertility of Sahelian soils. Furthermore, the findings suggest that corralling is a more economical and useful practice than the others; livestock are moved around and drop manure directly on the farmland, thus the loss of OM in transportation and the labor requirement are also low.