SOIL CHARACTERIZATION AND LAND SUITABILITY EVALUATION

ABSTRACT

The land at Anuka, Nsukka Local Government Area of Enugu State in Southeastern Nigeria, under the sub-humid tropical climate was evaluated for maize (Zea mays), cassava (Manihot esculenta), yam (Dioscorea spp.) and oil palm (Elaeis guineensis) cultivation. Data were obtained by field study and laboratory analyses. Six pedons were dug and described: two pedons each for maize and oil palm fields, and one each for yam and cassava fields. These pedons were dug to represent sampling units. Auger samples were also purposefully collected from the sampling units at depths 0 - 20cm and 20 - 40cm. This was to investigate the nutrient spread in the area. Soil samples from the pedogenetic horizons of the pedons were collected after profile description, processed and analyzed. The pedons were designated P01 = cassava field, P02 and P03 = maize fields, P04 = yam field, and P05 and P06 = oil palm fields. The textural classes of the soils included sandy clay loam, sandy loam, sandy clay, loam, clay loam and clay, but the dominant textural class is sandy clay loam. The overall results showed that the soils are acidic; the phosphorus content is generally low; organic matter ranged from 0.42 - 4.31 %, decreasing down the profile depth and is medium (>2.0 %) for epipedons. Exchangeable bases are generally low: low exchangeable Ca (<3.2 cmol kg^-1), low to medium exchangeable Mg (0.2 - 3.2 cmol kg^-1), very low exchangeable Na (<0.70 cmol kg^-1) and deficient exchangeable K (<2.0 cmol kg^-1). Total nitrogen content is moderately low to very low (0.042 % < N < 0.196 %). The soils met the criteria for classification as Typic Dystrustults (P01, P03, P04, P05 and P06) and Aquic Argiustults (P02) (Soil Taxonomy), correlated to Acrisols (FAO/UNESCO). The results showed that although climate and topography are optimum or near optimum, there was no current highly suitable (S1) soil unit for maize, cassava and yam cultivation by both parametric and non-parametric methods of suitability evaluation. However, soil units P01 and P02 showed actual and potential S1 for oil palm production in the study area. None of the sampling units showed high suitability for its current utilization type. The severe constraints to crop cultivation in the area are generally low fertility for all soil units; wetness for soil unit P02 and adverse soil physical characteristic for soil unit P04. Application of organic manure, use of balanced fertilizer and drainage management practices are necessary for maximum productivity of Anuka soils for the evaluated crops.

CHAPTER ONE

INTRODUCTION

Background of the study

It is important that the land that will be used for agricultural production should be used according to its capacity for optimization and sustainability of soil productivity (Adeboye, 1994). This becomes very vital at this time when precision farming is gaining wider acceptance and the relevance is particularly more now in the developing world where the use to which a land is put is very often not related to its capacity (Senjobi, 2001).

Land evaluation using a scientific procedure is essential to assess the potentials and constraints of a given land parcel for agricultural purposes (Rossiter, 1996). The knowledge of soil limitations arising from land evaluation reports aims at ameliorating such limitations before, or during cropping period (Lin et al., 2005). Therefore, soil as a main medium for cultivation needs to be assessed (surveyed / characterized) scientifically. The performance assessment is based on matching qualities of different land units in specific area with the requirements of actual or potential land utilization types. This assessment results in classification of lands as to their suitability to produce specific crops or combination of crops (Ezeaku, 2011).

Ozcan (2006) observed that all lands can be used for utmost purpose if sufficient inputs are supplied. In the tropics, many different soil types occur as a result of combination of pedogenic factors such as climate, topography, parent materials and soil forming processes. Every land use has specific biophysical requirements with respect to land conditions, and in the matching process of land evaluation, these biophysical requirements are compared with the relevant combination of soil characteristics (measureable attributes like slope percentage, drainage, soil texture, base saturation, etc) of a land resource; which are related to the agricultural use of the soil and more specifically to specific crop requirements and tolerance (Fischer et al., 2008).

Statement of the problem

A major problem of agricultural development in Nigeria is poor knowledge and appraisal of suitability of parcels of land for agricultural production. The result is poor farm management practices, low yield and an unnecessary high cost of production (Aderonke and Gbadegesin, 2013). The soils have been under intensive cropping by inhabitants of the Anuka community. Despite the high agricultural development potential of the soils, the soils have not been classified taxonomically to make for easy transfer of knowledge carried out on similar soils elsewhere. Due to lack of guidance, many farmers cultivate crops on soils that may not be suitable for their cultivation. Against this backdrop, this study examined the soil characterization and land use suitability evaluation of Anuka Farmland in Nsukka Local Government Area of Enugu state.

Objectives of the study

Thus, the main objective of this study was to evaluate the suitability of the soils of Anuka farmland, for both arable and plantation crops. The specific objectives included to:

a) characterize the soils of the farm land, and classify them according to USDA Soil Taxonomy and FAO/UNESCO;

b) determine the crop nutrient spread in the farm; and

c) evaluate the sampling units according to their suitability for maize, yams, cassava and oil palm production.

Research questions

a) What is the characterization of the soils of the farm land according to USDA Soil Taxonomy and FAO/UNESCO?

b) What is the crop nutrient spread in the farm?

c) What is the sampling units according to their suitability for maize, yams, cassava and oil palm production?

Scope of the study

This study on the soil characterization and land suitability evaluation was carried out in Anuka Farmland in Nsukka LGA, Enugu state. Anuka is an agrarian community. Its dwellers are mainly commercial farmers of both small scale and large scale production of several staple crops such as cassava, yam, maize and tree crops like oil palm among others.

Significance of the study

Soil suitability evaluation involves characterizing the soils in a given area for specific land use type. The suitability of a given piece of land is its natural ability to support a specified land use such as rain-fed agriculture, livestock production, forestry, etc. The main objective of land evaluation is to predict the inherent capability of a land unit to support a specific land use for a long period of time without deterioration.

This study will help add valuable knowledge to existing literature on soil characterization and land suitability evaluation. It will also serve as a study guide for researchers, students, scholars and academicians that are carrying out research on related topics.