Extractable Micronutrients In Relation To Physico-Chemical Properties Of Soils In Four Ecological Zones Of Nigeria

Abstract

Micronutrients play an important role in crop production. Discerning their bioavailability is a necessity to diagnose deficient or toxic levels. Yet, the non-static nature of the complex reservoir of mineral nutrients (the soil) is implied in biological, physical and chemical changes that also affect the supply of micronutrients to crops. In this study, total and 0.01N HCl extractable Mn, Zn, Fe and Cu were determined in 25 soil samples collected from various locations representing the major soil types and parent materials found in the Rainforest, Derived savannah, Coastal rainforest and Northern guinea savannah ecological zones in Nigeria. The resulting analytical values were subsequently related to the physico-chemical properties of the soils. There were substantial variations in the amounts of total and extractable micronutrients. Total Mn and Zn ranged from 24.00 to 114.00 and 14.00-54.00 mg kg^-1 with means of 60.55 and 23.55mg kg^-1, respectively while the 0.1N HCl-extractable Mn, Fe, Cu and Zn values varied from 0.03-14.21, 10.00-100.00, 0.27-0.46 and 0.60-95.50 mg kg^-1, the means being 4.82, 62.32, 0.35 and 6.91mg kg^-1, respectively. Majority of the soils are not deficient in Mn and Zn while none was deficient in Fe and Cu. Extractable Mn correlated significantly with organic carbon (OC) (r=-0.413) while total Zn correlated with soil pH (-505) and OC (+0.521). Organic matter and the clay fractions had strong influence on the contents of Mn. Soil reaction (pH) and could be used to predict Zn contents whereas there was no assurance that 0.1NHCl-extractable Fe and Cu values could be predicted from the physico-chemical properties. In view of their relatively low correlation coefficients with soil properties, it appears that the 0.1N HCl test procedure proved to be a non- promising extractant for the determination of available micronutrients in the soils tested.

KEY WORDS: 0.01N HCl extractable, Bioavailability, Micronutrients, Physico-chemical properties, Relationship.

Global Journal of Pure and Applied Sciences Vol.11(2) 2005: 197-200