Geostatistical mapping of soil fertility constraints for yam based cropping systems of North-central and Southeast Nigeria

• Selected soil fertility properties determined in main yam growing areas of Nigeria
• Spatial modeling used to map selected soil fertility properties
• Moderate spatial dependence observed for N and K, and weak spatial dependence for P
• Designed soil fertility intervention for yam proposed in the investigated areas

An extensive survey covering the area of 92,764 km2 was conducted in the fields of over 385 yam grower farmers under yam based cropping system of the North-central and Southeast Nigeria. Using geo-statistical mapping tools, we aimed to quantify the degree of spatial variability of selected soil fertility parameters under yam based copping system and to pave the way to develop an appropriate recommendation for a profitable fertilizers management for the small farmer of the region. Spatial analysis of the data showed that the best fit semi-variogram models for nutrients N and K were rational quadratic and hole effect for available P. Relative nugget effect (RNE) and nugget-to-sill ratio (Co/Co + C) of the total N concentration in soil were 70% and 45%, respectively for exchangeable K. The available P in soil (Bray-P) showed a weak spatial dependence with RNE of 83% and a range of 1.8 km. The moderate spatial dependence observed for N and exchange K recommends for developing a strategy for site-specific management of N and K nutrients taking into account the structural and random factors dominant in the study areas. The management of P nutrient to improve yam production in north–south and southeast of Nigeria is generalized at regional scale, given the weak spatial dependence observed for this nutrient.