Mapping of soil nutrient deficiency in oil palm plantations of Southern Benin

Abstract

Soil degradation poses a threat to sub-Saharan sustainability of agriculture namely because of chemical and physical degradation. The objective of this study was to characterise soil properties in oil palm plantation in the districts of Ouémé and Plateau and develop spatial maps for soil nutrients useful in agricultural land use as a basis for designing soil fertility management strategies. A survey carried out in oil palm (Elaeis guineensis Jacq.) plantations in the southern Benin, revealed mineral deficiency symptoms consequent to poor mineral nutrition of the plant. A total of 428 soil composite samples were collected under farmers’ adult oil palm trees, randomly selected. These oil palm plantations were located on four soil types: Acrisol, Plintics and luvisols, Hydromorphic soil and Vertisols. In total, 370 samples were collected on plantations under Acrisols, 22 samples under Plintics and luvisols, 26 samples under Hydromorphic soil and 10 samples under Vertisols. Geostatistic methods were used to determine the spatial variability; and semi-variogram methods were established using ordinary kriging. A strong spatial dependency for nitrogen, phosphorus, potassium and magnesium was observed; while spatial dependency of calcium was moderated. The map of nutrient deficiency revealed two large areas. The first, included the districts of Bonou, Adjohoun, Sakété, Adja-Ouèrè, and Pobè, where oil palm plants showed an acute nitrogen, phosphorus and potassium deficiency; and the second area of Dangbo, Missérété, Ifangni, Avrankou, Adjarra which presented nitrogen, potassium and slight phosphorus deficiency in the oil palm plantations. Most of the soils under the oil palm plantations showed nitrogen, phosphorus and potassium deficiency.