The basic soil problems and possible solutions in agriculture

THE BASIC SOIL PROBLEMS AND POSIBLE SOLUTIONS IN AGRICULTURE

S. Usman1

1 Natural Resource Institute, Plant Health and Environmental Group, University of Greenwich, Chatham Maritime, Central Avenue Kent UK ME4 4TB

Abstract

It is widely recognised that environmental problems such as soil degradation (erosion and desertification) affects many agricultural lands globally. These problems have caused soil quality decline, crop yield reduction, economic crisis, poverty, unemployment, and rural urban migration. Soil management practices are considered as the most vital and sustainable possible solution to control soil erosion and desertification. This management include use of organic manure, crop rotation, use of cover crop, intercropping, planting shelter belt and afforestation, provision of water ways, good surface drainage system, restoration of rangeland, regeneration and secondary forest, and political changes.

1.0 INTRODUCTION

The vast importance of soil in the development of various systems of agriculture and types of civilizations has long been recognized (Jenny, 1994). Soil is the basis of production in agriculture and forestry, an important component of the human environment (Zachar, 1982), and is a significant component of arid ecosystems (Russell and Greacen, 1977). Soil provides habitats for organisms (the soil fauna and micro-organisms) (Wild, 1993) and moisture and nutrients for the basic requirements of plant growth (Okigbo, 1991). Therefore, the science of soil has played, and continues to play, an important role in global studies of food production and Earth’s natural resources (Hartemink, 2003). This work is on progress with the effort of many researchers and organizations through the provision of relevant information on global soil resources e.g. the development of the FAO-UNESCO soil map of the world. However, there is a need to improve the existing information on management and sustainability of soils in areas of poor research development such as Africa (e.g. Tor, 2001). This is to help improve the fertility and quality of soils of the region using management practices such as organic matter application, composting, proper irrigation systems, intercropping, and others. These activities may help increase food availability by improving soil quality, sustain soil fertility and maintain yield production (Blum, 1994; Zhao, 1995; Lal, 1997; World Bank, 2001; Mortimore and Adams, 2001; Osbahr and Allen, 2002; Pretty et al., 2003).

To achieve the effective soil management activities, much more attention from farmers, and general concern from government, should be given to the sustainability of soil (using available and affordable management resources by farmers) and creation of good environmental policies (by government). This is because for many years soils in most part of the world, have been affected with problems related to soil quality depletion due to land degradation factors such as erosion (wind and water) (Lal, 1998), desertification as a result of poor vegetation cover, and human-induced activities of destroying forests (deforestation) (Gad and Abdel, 2000; ICLDD, 2001).

These types of problems might lead to serious damage to farmers’ lands, which may include loss of organic matter and the deterioration of soil structural quality (Bradley and Thompson, 1998; UNEP, 2003) and subsequently lead to decreases in crop yields annually if not manage (e.g. Gachimbi et al., 2002; GSST, 2006). These problems have been mentioned by researchers studying the soil and land degradations as principal causes of nutrient losses from soil (e.g. Stoorvogel and Smaling, 1990; Mango, 1996), as well as being the major constraint to sustainability in agricultural production (Okigbo, 1991; Gomes et al., 2003; Su et al., 2003). This decline in soil fertility, and increasing population pressure, has been met with by calls from some international scientists for a soil recapitalisation programme of sustainable and economic development (DFID, 2002). This programme could lead to: enhances and sustains food production, reversal of degradative trends and improvements in soil quality and soil resilience, manages water quality, and enhancement of environmental quality through sequestration of carbon and organic matter into the soil and biomass (Lal, 1995a; FAO, 2001; Lal, 2004; Lal et al., 2004; Tieszen et al., 2004; Farage et al., 2007).

Soil and agriculture

Soil as one of the main resources of the biosphere (Holy, 1980) and important factor in the production of agricultural crops, forestry and horticulture (Okigbo, 1991), has been defined by many scholars with different views. According to USDA (2005) Soil is a natural substance comprised of solid minerals and organic matter, liquids and gasses that occur on the surface, occupies space, and is characterised by one or both of the following: horizons, or layers, that are distinguishable from the initial materials as a result of additions, losses, transfers and transformations of energy and matter or the ability to support plants in a natural environment. However, GSST (2006) define soil as unconsolidated mineral or organic materials on the immediate surface of the Earth that has been subjected to, and shows effects of, genetic and environmental factors of: climate (including water and temperature effects) and micro-organisms, conditioned by relief, acting on parent materials over a period of time. It can also refer to as a limited and irreplaceable resource and the growing degradation and loss of soil means that the expanding population in many part of the world is pressing this resource to its limits and its absence the biospheric environment of man will collapse with devastating results for humanity (Holy, 1980).

Fertile and productive soils in agriculture

Fertile soil may be defined as one which has a good supply of available plant nutrients to be drawn upon by plants throughout their growth (Govinda and Gopala, 1971). This definition describes the quality and ability of soil to provide the essential elements in adequate amounts and in proper balance for the growth of specified crop or plant in agriculture (DFID, 2002; GSST, 2006). However, Miller (1963) have the opinion that a fertile soil must have these nutrients not only in a reasonable amount or in suitable balance, but also in a way plants can take them from mineral and organic soil fractions and must be located in a climatic zone which provides moisture, light and heat sufficient for the need of plant under consideration.

This idea of fertile soil was opposed to the idea of sterile stone. Rocks differ in their fertility, where some of them are densely overgrown with lichens and micro-organisms, others are sparsely covered and others are more properly parts of one of same rock, which are not overgrown with lichens, but contain only certain microbial forms (bacteria, actinomycetes and fungi) (Glazovskaya, 1950; Krasil‘nikov, 1961). Therefore, continuous and rapid rock and soil decompositions (by micro-organisms), provide a constant supply of minerals for plant growth (Hartemink, 2003), and, hence, the principal factor of soil fertility is determined by biological factors, mainly by micro-organisms (Krsli‘nikov, 1961). Thus, a fertile soil is greatly depends on the amount of organic matter and the number of micro-organisms and their biodiversity in soil dynamic productivity.

Soil sustainability: meaning and importance in agriculture

Sustainability in agriculture has been defined by Conway (1985) as the ability of a system to maintain productivity in spite of larger disturbances such as repeated stress or a major perturbation (for example, the building of soil salinity or a sudden outbreak of new pests or diseases). This is largely dependent on the recycling efficiency of output per unit of resources input (Power et al., 1997). On the other hand, sustainable soil management is vital for enhancing and sustaining the productivity of soil, food, livestock, water quality and other related land resources such as forestry (World Bank, 2001). It will help to minimise environmental impact such as desertification and soil erosion (Syers and Rimmer, 1994). Sustainable soil management can also maintain and increase agricultural output, reduce the risk of output falling and minimise the irreversible damage to the environment and land degradation (Wild, 2003). This management involves maintaining ground cover in the form of cover crops, mulching of crop residues, intercropping, listing (i.e. method of providing ridges on the surface of soil with firmer subsoil on top), using a minimum tillage system for as much of the annual season as possible, to achieve the goal of sustaining soil resources. Though the system of sustainability will vary from continent to continent and country to country (see Syers and Rimmer, 1994), four main components are noted (World Bank, 2001) (a) policy and sector work, (b) research and technology development, (c) knowledge sharing and extension, and (d) providing incentive, expenditure priorities and mode of financing. These components depend on the available and affordable resources to be use for people in every continent. For this reason, the aim of this paper was to discuss the basic soil problems and their possible solutions for future sustainable management under agricultural soil environments.

2.0 GENERAL DISCUSSION

2.1 Soil problems: soil degradation and consequences

Soil degradation is widely recognised as a serious problem and its environmental consequences will remain an important issue during the 21st century (Lal et al., 2003) as well as the issues of global concern over the last few decades (Eswaran et al., 2001). This has been given special prominence since the United Nations Conference on Environment and Development in 1993 (ICLDD, 2001). It is simply defined as the decline in soil quality caused through its misuse by humans, while natural factors may cause or even intensify a process that results explicitly from human action (Lal et al., 2003).

Indeed, soil fertility decline has been a matter of concern ever since sedentary agriculture commenced some 10,000 years ago (Hartemink, 2003). This is because many agricultural lands in the world have been affected by soil degradation that leads to loss of soil, loss of micro/macro elements (e.g. N, P, K and Ca, Fe,), and decreases in crop yield (Jones, 1971; Holy, 1980; Okigbo, 1991; Lal, 1995b; Scherr, 1999; Eswaran et al., 1999). Soil degradation affects many functions of soil (Blum, 1994) and has been considered as anthropogenic process that reduces the present and future capability of soil to support life on Earth (Oldeman et al., 1991). It is also considered as a major threat to agricultural sustainability because it decreases actual and potential soil productivity (Lal, 1998).

However, Lal (1997) noted that, soil degradation occurs when soil cannot meet one of the following functions:

a) sustain biomass production and biodiversity including preservation and enhancement of gene pool (i.e. an artificial life simulation where populations of physical-based organisms evolve over time);
b) regulate water and air quality by filtering, buffering, detoxification, and regulating geochemical cycle (i.e. developmental path followed by individual elements or groups of elements in the crustal and sub-crustal zones of the Earth and on its surface)
c) preserve archaeological (scientific study of past culture), geological and astronomical records, and
d) support socio-economic structure, cultural and aesthetic values and provide engineering foundation.

After describing the functions of soil, Lal (1997) defined soil degradation as “the loss of actual or potential productivity and utility, and implies a decline in the soil’s inherent capacity to produce economic goods and perform environmental regulatory function”. This concept of soil degradation was differentiated from that of land degradation (Hartemink, 2003) which always embraces the degradation of the overall capacity of the land to produce economic goods and to perform environmental regulating functions (Hartemink, 2003). Although there are many definitions of land degradation (e.g. FAO/UNEP, 1983; Oldeman et al., 1991), they all emphasized that the degradation of soil quality is the key factor of consideration when it came to sustainable management for agricultural production.

Types of soil degradation process

There are three types of soil degradative processes namely: physical, chemical, and biological, which through their interactive effects may lead to decline in soil quality over time (Lal, 1994; Lal et al., 2003). However, important among physical process are a decline in soil structure leading to crusting, compaction, erosion, desertification, anaerobism, environmental pollution, and unsustainable use of natural resources (Eswarran et al., 2001). Significant chemical processes include acidification, salinization, and fertility depletion, while biological processes include reduction in biomass carbon and decline in land biodiversity (Eswarran et al., 2001). Classifications of these processes are based on the basic premise that a reduction in land agricultural productivity must occur (Blaikie and Brookfield, 1987). The development of rapid appraisal indication of these processes has been stressed by various organizations, including UNEP, DFID, FAO, and World Bank (see Conacher, 2001) as well as individual research (e.g. Lal, 1997; Eswarran et al., 2001; Lal, et al., 2003; Hartemink, 2003; Zhang et al., 2006; Shi et al., 2007). However, physical process is the most serious among the others because of it direct and indirect relationship with chemical and biological degradation processes. Example, soil erosion may change the entire soil structural and textural body. This effect could hinder soil microbial activities, change structural quality, and moved away with important chemical functions of soils.

Classes of land and soil degradation severity

As indicated earlier, land/soil degradation is one of the consequences of mismanagement of land and results frequently from a mismatch between land quality and land use (Beinroth et al., 1994). Although research shows that soil/land degradation, can be clearly human-induced (e.g. Oldeman et al., 1991; Eswaran et al., 2001; Reich et al., 2001; Lal et al., 2003). However, it will not be concluded that there are no other factors that may cause soil/land degradation, because natural process also affect the land, for example, erosion by rain splash. However, human activities will remain the main contributing factor in increasing land degradation today. An assessment made on land resource stresses in Africa indicated that about 25 stress classes were defined according to the severity of their constraints (Table 2.1).

Table 1: Estimated vulnerability classes of land degradation in Africa (Reich et al., 2001).

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