ABSTRACT
Micronutrients are essential for good crop performance. There is little or no quantitative data on the content and distribution of micronutrients in soils of Imo State, particularly those derived from coastal plain sand parent material. Horizon differences in soils influence ability of crops to obtain nutrients and indeed support other uses. The study aimed at investigating the micronutrient (Cu, Mn, Fe, Zn) contents of horizons of two different pedons which lies on similar parent material (Coastal plain sand) in Imo State. Random survey technique guided by the geologic map of the area was used in siting one profile pits on each of the locations. The profile pits were described; and identification and delineation of horizon boundaries were accomplished using FAO guidelines before actual sample collection for laboratory analyses. Soil data were subjected to coefficient of variation (CV) analysis. The results of the micronutrients indicated range values of 0.02- 0.36 mg kg-1 for Mn, 36.6-108 mg kg-1 for Fe, 0.091-0.256 mg kg-1 for Cu and 0.205-0.774 mg kg-1 for Zn in pedon 1. In pedon 2, the ranges were 0.13-1.09 mg kg-1 for Mn, 19-50.6 mg kg-1for Fe, 0.143-0.613 mg kg-1 for Cu and 0.22- 0.962 mg kg-1 for Zn respectively. The values of Zn, Cu and Mn were below the critical limits recommended for arable crop production. However, Fe concentration was generally high in all the horizons and was above the critical level recommended. Hence, the soils were surplus in iron but deficient in Cu, Mn and Zn. It is therefore recommended that agronomic requirements should consider these essential edaphic attributes in the study area.
CHAPTER ONE
INTRODUCTION
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.
