Soil Fertility Index of paddy land in Benin: understanding of factors driving sustainable soil use and management

Increasing rice consumption is expected to continue shortly spatially in Africa, where its productivity is currently low. The increasing degradation of soil fertility is leading to ever-lower yields in rice cropping systems. This study aimed to assess the fertility of rice-growing soils in Benin, with a view to their sustainable and optimal management. We collected 700 georeferenced composite soil samples from rice-growing plots in 14 communes of Benin's three rice-growing basins. Organic carbon, total nitrogen, available phosphorus, exchangeable potassium, pH, and cation exchange capacity were determined. Soil fertility indexes were calculated following geospatial analysis. Soil fertility index ranged from 0.37 to 0.92; from 0.43 to 0.99; and from 0.24 to 0.83, respectively in the northern, north-western, and southern rice-growing basins of Benin. The rice-growing soils are classified as low to moderate fertility, with some geographical points for high fertility. Geostatistical analysis of soil fertility index shows variation in rice-growing soil fertility within and between basins. Soil fertility is low and highly dependent on available phosphorus, exchangeable potassium, organic carbon, and cation exchange capacity. Fertilizer use and rates should consider these basins' soil fertility index map.