Micronutrients are essential for good crop performance. There is little or no quantitative data on the content and distribution of micronutrients in soils of Edo State, particularly those derived from coastal plain sand parent material. A study was therefore undertaken to: (1) characterize the soil (2) provide information on the total and available forms of copper (Cu), manganese (Mn), Iron (Fe) and Zinc (Zn) and Nickel (Ni) in soils developed on coastal plain sand parent material in Edo State (3) show the relationship if any, between micronutrients and soil’s physico-chemical properties.
Soil samples were collected at two depths, 0-15 cm and 15-30 cm at each of the study sites (NIFOR, UNIBEN Gmelina plantation and RRIN). The soils were characterized, total and available micronutrients were determined and simple correlation was run to show the relationship, if any between micronutrients and soil physico-chemical properties.
The soils, which decreased with depth, were generally sandy with sand accounting for up to 90 % of the particle size distribution. Clay content increased with depth with the possibility of an argillic horizon. pH ranged from medium acidic to neutral, organic matter, total nitrogen an available phosphorus were low. Exchangeable cations were also low with calcium dominating the cation exchange complex.
Total Fe ranged from 1.53-8.09 mg/kg, available Fe ranged from 0.49-2.59 mg/kg. Total Mn ranged from 1.06-3.62 mg/kg, available Mn ranged from 0.68-2.32 mg/kg. Total Zn ranged from 1.26-3.87 mg/kg, available Zn ranged from0.40-2.48 mg/kg. Total Cu ranged from 0.33-1.28 mg/kg, available Cu ranged from 0.21-0.82 mg/kg. Total Ni ranged from 0.33-3.83 mg/kg, available Ni ranged from 0.02-2.46 mg/kg in all locations. There were varied significant correlations between micronutrients with the exception of Ni with sand, clay and calcium, while varied significant correlations between Mn, Zn and Cu and organic carbon, magnesium and hydrogen.
Soil is an important natural resource for agricultural and industrial development of a nation. It has numerous functions some of which are provision of anchorage to growing plants, provision or supply of nutrients and water to crops. Optimum utilization of the soil for agricultural production is possible as long as the soil is stable and well supplied with nutrients, air and water. (Osuji and Onojake, 2006).
An essential nutrient is the nutrient without which the plant cannot complete its life cycle; its functions are primarily, that of transforming photo-energy into chemical energy (FAO, 1983) and of synthesizing a whole variety of substance which make living vegetable matter. Micronutrients are part of these essential nutrients. Although they are needed in trace quantities, it does not affect their significance in plant nutrition.
Eight of the eighteen elements that are essential for plant growth are micronutrients. They are Boron (B), Chlorine (Cl), Copper (Cu), Iron (Fe), Manganese (Mn), Molybdenum (Mo), Zinc (Zn) and Nickel (Ni) plus others that are considered to be beneficial (Cobalt (Co), Sodium (Na), Silicon (Si) and Vanadium (V)). (Penney, 2014). Research attention on micronutrients is recent in areas where intensive agriculture practices bring up the deficiencies. In soils with micronutrient deficiencies, the application of small quantities of these nutrients enhance crop production (Welch 1995, Mortvedt, 2003) while large quantities added to the soil may be harmful (toxic) to the plants and animal consuming the forage. This is unlike countries where shifting cultivation is a dominant practice and micronutrient deficiency problems have not been given much attention. This is probably because nutrient recycling through leaf litter decomposition maintains the required level of the micronutrients. Therefore, it is important to know the original concentration of micronutrients in the soils and add only as much of the micronutrients as is beneficial to plants and foraging animals.
The replenishment of micronutrients through fertilizer is still in its infancy in Nigeria. Fertilizer applications in Nigeria involves only the macronutrients even though cropping (and harvesting), erosion and leaching deplete soil of micronutrients which should be replenished by the return of organic materials such as crop residues, farm yard manure and compost.
Deficiencies of Copper and Zinc are more common than those of Fe and Mn in many coarse textured, acid soils in Africa, particularly in Nigeria, (Kparmwang et al, 1995). There are therefore, more reports of studies conducted on these two commonly deficient micronutrients in the forest, southern Guinea, Northern Guinea, Sudan and Sahel Savannah agro ecological zones of Nigeria (Osiname et al, 1973a, Lombin 1983). Therefore, studies have covered the major geological formations and soil-forming rock types including the basement complex, coastal plain and sedimentary rocks.
1.1 OBJECTIVE OF THE STUDY
The objective of the study therefore was to provide a systematic assessment of some selected micronutrients derived from coastal plain sand parent material and how some of the soil physico-chemical properties influence their abundance in the soil