Assessment of Micronutrient Status and Crop Response to Zinc and Boron Fertilisation in Soils of Ekiti State, South West Nigeria

This study assesses the micronutrient status of soils in Ekiti State, located in Nigeria's South West geopolitical zone, and evaluates crop responses to zinc and boron fertilisation. Micronutrient deficiencies are increasingly recognised as hidden constraints on crop productivity in Nigerian soils, yet routine soil testing and micronutrient fertilisation are almost entirely absent from smallholder farming practice in the South West zone, and published micronutrient deficiency data for Ekiti State soils are lacking. Using a soil survey and field trial design, 50 surface soil samples were collected from different land use areas across Ekiti Central, Ekiti North, and Ekiti South West senatorial districts and analysed for DTPA-extractable zinc, copper, manganese, iron, and boron by hot water extraction. Critical deficiency thresholds were applied to classify deficiency prevalence. Greenhouse pot experiments using maize and cowpea as test crops were conducted with zinc applied at 0, 2.5, 5, and 10 mg/kg and boron at 0, 0.5, 1.0, and 2.0 mg/kg on three representative soils. Findings revealed zinc deficiency (DTPA-Zn below 0.5 mg/kg) in 66 percent of sampled soils and boron deficiency (hot water-B below 0.25 mg/kg) in 72 percent. Maize dry matter yield increased significantly with zinc application in deficient soils, with maximum response at 5 mg/kg ZnSO4. Cowpea showed the most severe boron deficiency symptoms, with seed set completely absent in boron-deficient control treatments. The study recommends systematic inclusion of zinc and boron in fertiliser recommendations for Ekiti State crop production systems. Keywords: micronutrients, zinc deficiency, boron deficiency, Ekiti State, crop response.