EFFECTS OF RICE PRODUCTION SYSTEMS ON PERCEIVED SOIL DEGRADATION IN EKITI STATE, NIGERIA

CHAPTER ONE

INTRODUCTION

1.1Background of the study

Ever since mankind started agriculture, soil erosion has been the single largest threat to soil productivity and has remained so till date [1]. This is so because removal of the topsoil by any means has, through research and historical evidence, been severally shown to have many deleterious effects on the productive capacity of the soil as well as on ecological wellbeing. Doran and Parkin [2] captioned the impact of soil erosion in their popular maxim that “the thin layer of soil covering the earth’s surface represents the difference between survival and extinction for most terrestrial life.” Although fertile topsoils could be lost when scraped by heavy machineries [3], the key avenues of topsoil loss include water erosion and wind erosion. Sometimes erosion can be such gradual for so long a time as to elude detection in one’s lifetime, thus making its adverse effects hard to detect.

Eswaran et al. [4] propose an annual loss of 75 billion tons of soil on a global basis which costs the world about US $400 billion per year. A review of the global agronomic impact of soil erosion identifies two severity groups of continents and reveals that Africa belongs to the more vulnerable group [5]. Soil erosion by water seems to be the greatest factor limiting soil productivity and impeding agricultural enterprise in the entire humid tropical region [6]. This is evident in many regions of Africa [7], mainly in the humid and 2 Applied and Environmental Soil Science subhumid zones of Sub-Saharan Africa (SSA) where population pressure and deforestation exacerbate the situation and the rains come as torrential downpours, with the annual soil loss put at over 50 tons ha−1 [8].

In Nigeria, the problem is not limited to water erosion as wind erosion prevails mainly in the semiarid and arid zones. For instance, soil loss to wind erosion of 58–80 tons ha−1 has recently been reported from the West African Sahel [9]. Both forms of erosion can thus aptly define land degradation in the region. Soil erosion selectively detaches the colloidal fractions of soils and carts them away in runoff [10, 11]. These soil colloidal fractions (clay and humus) are needed for soil fertility, aggregation, structural stability, and favourable pore size distribution. The concentration of humus is usually higher in topsoils while that of clay is usually higher in subsoils due to illuviation, and this is mostly true in Ultisols that are widespread in Africa. This implies that humus, which has much greater capacity to hold water and nutrient ions compared to clay, its inorganic counterpart [12], is the more easily eroded.

1.2 Problem statement

Land degradation indicates temporary or permanent long-term decline in ecosystem function and productive capacity. It may refer to the destruction or deterioration in health of terrestrial ecosystem, thus effecting the associated biodiversity, natural ecological processes and ecosystem resilience. It also considers the reduction and loss of biological / economic productivity and complexity of crop lands, pasture, woodland, forest, etc. Across the world over 20% of cultivated areas, 30% of forests and 10% of grasslands are suffering from degradation, affecting about 1.5 billion people this degradation may be the result of numerous factors or combination thereof including anthropogenic activities such as unsustainable land management practices and climatic variations (Bai et al., 2008). Land degradation occurs in the form of depletion or total loss vegetative cover, and loss of its biophysical and economic productivity through exposure of the soil surface to wind erosion and water erosion, and through salinization and water logging, leading to deterioration of the physical, chemical and biological properties of soil. The continued loss of vegetation through salinization and human activities also depletes the world’s biodiversity, and it reduces the ability of natural environment for carbon sequestration, with the consequent long-term effects of global warming and climate; overgrazing in the case of rangelands in particularly serious in arid regions. Such conditions surrounded with very complex arising problems hitting severely the human well being allow us to state plainly that we are in need to efficient programmes to be implemented in order to face the enormous challenges we are no facing to achieve our goal towards a sustainable use of the natural resources Land and Water for rice production

1.3 Purpose of the study

The purpose of this study is to examine the effects of rice production systems on perceived soil degradation in Ekiti state, Nigeria. Specifically the study:

1. assess the impact of rice production on soil nutrient

2. determine the effect of rice farming style on soil nutrient

3. assess the relationship between rice production and soil degradation

4. Significance of the study

The need to understand the dynamics of soil degradation in terms of extent and severity cannot be overemphasized. Knowledge about the dynamics of soil degradation is important in the sustainable use and management of soil resource. Soil resource is essentially non-renewable. Therefore, avoidance of soil loss by improved management and conservation of the natural resources through sustainable use of land resources is important in combating low agricultural production, food insecurity and its associated negative effects on poverty levels and population drift (Tekwa, Belel and Alhassan, 2010).

The challenge of African agriculture is not only to enhance food production to meet the growing needs of its expanding population, but also to maintain the productive capacities of soils into the future. Although land use intensification can increase food production in the ‗high potential‘ areas (Barbier, 1997) evidence also shows that the extension of agricultural activities into marginal lands have tremendous negative effects on the quality of soils (Abubakar,1995; Sherr and Yadav, 1996). Rehabilitation of degraded lands must be comprehensive and in line with the principle of sustainable development. A good way of tackling the menace of soil degradation in Africa in general and Nigeria in particular, is to provide adequate, accurate and relevant information on the forms, extent and severity of soil degradation. This can be achieved by incorporating farmers‘knowledge and perceptions of soil degradation phenomena into science based methods (quantification and analysis) of soil degradation assessment. This will provide a realistic and holistic means of assessing soil degradation while taking full advantage of the farmers‘ experience and dynamic knowledge of their environment (Vigiak, Okoba, Sterk, and Stroosnijder, 2005; Stringer and Reed, 2006).

4. Study hypothesis

The study hypothesis is:

HO: there is no significant relationship between soil degradation and rice production

H1 : there is a significant relationship between soil degradation and rice production

4. Scope and Limitations of the Study

The study scope is limited to investigating the effects of rice production systems on perceived soil degradation in Ekiti state, Nigeria. Limitation faced by the research was limited time and financial constraint

6. Organisation of study

The study is grouped into five chapters. This chapter being the first gives an introduction to the study. Chapter two gives a review of the related literature. Chapter three presents the research methodology; chapter four presents the data analysis as well as interpretation and discussion of the results. Chapter five gives a summary of findings and recommendations.

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