Geo-statistical mapping of some soil fertility constraints in sorghum- based cropping system of Sudano-Sahelian zone of Nigeria

This research was aimed at quantifying the extent of spatial variability of some soil fertility constraints under sorghum cropping system along a rainfall gradient to develop appropriate fertilizer recommendation. Sorghum farms were selected through multistage sampling techniques based on rainfall gradients across three States in Sudano-Sahelian Zone of Nigeria. These are Kano, Jigawa and Katsina States. Within the states, twelve communities where sorghum is predominantly grown along Kofa-Zangon Daura transect were selected. From each community, ten sorghum farms were randomly selected using 10 km x 10 km sampling grids. Five quadrants (2m x 2m) were marked diagonally from each farm to collect a composite soil sample. The soil samples were analyzed using standard laboratory procedures and subjected to descriptive statistics and geo-statistical analysis. Results obtained indicated high variability in most soil properties. Potassium presented the highest CV value of 55.3%, while moderate variability was obtained in Available Phosphorous content with a value of 15.4%. The findings also showed that Nugget to Sill ratio of Total Nitrogen, Available Phosphorus was 0% and 14% respectively indicating strong spatial dependency. The trend map also indicated that Soil Organic Carbon, Total Nitrogen, Available Phosphorus and Exchangeable Potassium increased with an increase in rainfall in the study areas. Generally, the soil was poor in major nutrients, we therefore recommend that integrated soil fertility management, and site-specific fertilizer application should be considered for adoption in the study area.