Distribution of Available Sulfur in Some Soils of South Chad Irrigation Project Area, Lake Chad Basin, Borno State, Nigeria

Aims: A field study was carried out to evaluate the content and distribution of available sulfur in soils underlain by the Chad Formation under the South Chad Irrigation Project area, Borno State.

Study Design: Purposive sampling technique was employed based on homogeneity in general surface features especially vegetation, topography and morphology.

Place and Duration of Study: The study site includes the clay plains of the Lake Chad Basin where the South Chad Irrigation Project is located. The study was carried out in 2016.

Methodology: Seven profile pits were sunk at selected locations across the study areas and samples collected in each pedogenic horizons of the profiles. Surface and sub-surface samples were also collected for physico-chemical analyses using standard procedures. The available sulfur was determined turbidimetrically after extracting with calcium phosphate solution.

Results: Textural classes were generally clayey with islands of sandy loam. The soil reaction ranged from moderately acid to slightly alkaline. The percentage organic matter content was generally low, being higher in clay than sandy soil texture. The available sulfur content was low with a range of 2.0 to 6.9 mg/kg. The distribution of available S content decreased with depth. The results also indicated that available P in profile P6 is positively correlated (r = 0.989**) with the available sulfur content. There was little or no correlation between the available sulfur and soil pH in all the profiles, except profile P1 (r = 0.531*). Significant negative correlation between organic matter content and the available sulfur in profiles P1 (r = -0.817**), P5 (r = -0.527*) and P7 (r = -0.989**) were observed. Significant negative correlation (r = -0.562*) was also observed between available sulfur and clay content in profile P1. The significant negative correlation of available sulfur with clay and organic matter could be due to adsorptive properties of clay and organic matter fractions.

Conclusion: The soils were observed to be deficient in available sulfur. The low available sulfur status of the soils indicated that supplemental application of sulfur containing fertilizer and manure would be required for maximum cereals and vegetable crop production in the study area.