ABSTRACT
Boron an essential plant nutrient element is one of the few with limited research work and yet is a significant prerequisite for plant growth and development. The study of this research was carried out to determine the distribution of boron in soils of selected profiles along a toposequence in the Landmark University Farm, Eleyin in Isin Local Government Area of Kwara State which is a Derived savanna agro-ecological zone. For this to be done, a reconnaissance study was conducted in which a toposequence was identified. Three profile pits were dug along the toposequence and sited at the upper (EP1), lower (EP2) and bottom (EP3) positions. Soil samples were collected from identifiable genetic horizons down the profiles and were prepared and subjected to laboratory analysis for their physico – chemical properties and boron distribution. Results show that the soils of the area are slightly acidic to moderately acidic (pH in water 4.98-6.66), while soil texture is generally light-textured to medium-textured with texture ranging from sand to loamy sand at the surface and sandy loam, sand, loamy sand to sandy clay loam at sub-surface levels. Total Nitrogen is rated very low to medium (0.02%-1.11%).
Available P and Organic matter of the soils are not generally adequate with a range of “very low” to “low” i.e. 4.93-97.23 ppm and 0.40% to 0.44% respectively.
Generally, Boron is found to be inadequate in the soils with a range of 4.00-7.03 mg/kg of soil which is rated low to medium and thus it is recommended that intergrated soil fertility management processes which would as well involve use of boron micronutrient fertilizers should be incorporated into soils of area.
CHAPTER 1
INTRODUCTION
Soil has been commonly defined as a definite layer of the earth’s crust which serves as a medium for plant growth. It also serves for effective plant, organism and environmental interaction. One major attribute of any soil that is of maximum relevance is its fertility rate. In the consideration of soil in its fertility, it is common to mention the presence of soil nutrients which are essentially classified into major or primary and minor or secondary nutrients.
Boron is one of the elements least considered even amongst the minor nutrients.
Therefore it can be thus referred to as a minor in the minors. Chemically, it comes with the symbol B, has the atomic number 5 and belongs to the group 13 (also called IIIa) in the periodic table; it is found in the same family with Aluminum and has similarity with carbon and silicon. It also has a valence of 3.
Biologically, it is not a component of enzymes unlike many essential nutrients. It plays an important role in nucleic acid metabolism, protein metabolism, photosynthesis, carbohydrate biosynthesis and in cell membrane stability (Kumar and Kumar, 2013).
BORON AND ITS USEFULNESS
Boron, although not much recognized is found in various areas of our everyday life. They can be found in plants, food, soil, water, e.t.c. Boron has been processed industrially as a bleaching agent which is added to most detergent and cleaning agents during its formulations.
BORON, AS A PLANT NUTRIENT
Boron is a very essential minor element as a plant nutrient as it is important for pollination and seed production. In plants, it helps to ensure uptake of nutrients such as calcium and to create a balance between the interactions of magnesium, calcium and a host of other plant nutrients. It also plays a very active role in plants, despite its availability in seemingly measured quantity; it contributes essentially to plant nutrition. According to (Mineral zone, 2012), the main function of boron in plants is structural. One of the ways boron functions as a plant nutrient is in relation to the cell wall, its development and strength.
As a plant nutrient, boron is not metabolically driven process (i.e. passive response) in its uptake by plants. Through mass flow, it is transported to the roots from the soil solution as it is highly mobile.
BORON’S ROLE IN PLANTS
The roles of Boron in the plant are numerous and very significant. In Cell wall structure, boron works hand in hand with calcium to ensure structural development of the cell. Just like
calcium helps in bone formation and development in humans and animals, the presence of boron helps for unrestricted movement of calcium.
It functions as a translocation for sugar and carbohydrate as well as performs the function of balancing between starch components and sugar.
Various metabolic processes occur through the support which boron renders. This implies that the activity of boron engenders continuity in chain of metabolic processes. Some metabolic processes such as sugar transport, respiration etc. in plants are also affected directly or indirectly by the presence or absence of boron. Boron helps to transfer water and nutrients in plants. Potassium is transported to cells called “guard cells” so as to ensure the control of internal water balance and the presence of boron is an important factor.
TOPOSEQUENCE
Toposequences are adjacent soils that show differing profile characteristics reflecting the influence of local topography (Jan Glinski, 2011). Most times soils in toposequence regions encounter a lot of nutrient loss or elluviation alongside illuviation and this result in poor maximization of land space in toposequence areas.
It is found associated with major soil groups e.g. oxisols, ultisols, inceptisols, etc.
BORON IN SOIL
Boron, with a mass 0.0010% of the earth’s crust is found in the soil as non-chargeable molecules in soil solution and readily available in concentrated deposits of borate minerals like borax (Na2B4O7.10H2O), inorganic borate complexes of micronutrients, and from mineralization of organic materials. It is also seen as a component of Tourmaline which is an insoluble mineral. It is also present as a non-chargeable molecule in soil solution because at soil pH below 8, non-dissociated boron species are predominant. It is relevant under extremely alkaline conditions. Complex surfaces formed with organic matter helps its retention. This retention is more stable metal hydroxides and clay minerals at pH 9 and 10.
Due to its lack of retention as ionic species, it is also easily leached in humid climates, thereby limiting its availability for plant uptake. When boron binds by soil organic matter it is stronger than by minerals due to capability of boric acid to form complexes with polyhydroxylic compounds. Slow release of boron from this organic matter in the course of microbial decomposition appears to be an important source for plant nutrition (Hooda, 2010).
BORON SOURCE MATERIALS (CAN BE USED AS FERTILIZERS)
The understanding of nutrients in the soil and their rate of availability allows a farmer to adequately manage his land, invariably his soil, so as to ensure high yield of economically feasible crops. Toposequence region soils have been a major concern towards preservation of soil nutrients.
Boron fertilizers are readily available in compounds of boron. Borate is a common form in
which boron is utilized. Widely used borates in fertilizer application include:
Borax pentahydrate borax decahydrate though Disodium octaborate tetrahydrate (Etidot-67) because it is more soluble than the former. Sodium borates are used on soil by direct application or used on plants by spraying on the plants which absorb it due to its good soluble nature. Calcium borate (Colemanite) is natural occurring fertilizer materials. They have been known to have low solubility and as such are retained in the soil much longer than sodium borates. Therefore, as such they are more useful in sandy soils (John Emsley, 2011; Spectrum Analysis, 2015).
The Landmark University soils at Eleyin, Kwara State is a newly acquired land and has not been previously studied. It is also observed to be on a toposequence and therefore before major activities commence on the soil, it is essential to explore and understand the basic characteristics of the soil. Since it is aimed at cropping activities, necessity demands that availability and distribution of nutrients are well understood as this will make for proper agronomic practices now and in future.
Therefore this research project is aimed at,
Understanding Boron and its essence in soil and cultivation of crops, Identification of the soil type present on the toposequence.
Identification of boron present in soils of the Eleyin toposequence. Understanding the rate of availability and distribution.
Identification of areas of boron abundance and boron level in soil.
Identification of forms of amendment to toposequence soil in “Eleyin” if need arises
