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Approaches to modeling adoption of soil conservation and soil nutrient management practices
In developing countries including Ethiopia, a lot of effort and resources have been devoted to generate and disseminate agricultural technologies to smallholder farmers.
Despite the efforts, however, adoption of improved production technologies including soil conservation and soil fertility enhancing practices remained low (Yirga et al., 1996; Demeke et al., 1997; Shiferaw and Holden, 1998; Gebre Michael, 1999; Alene et al., 2000; Gebremedhin and Swinton, 2003). Rather, smallholder farmers continued to rely on traditional production technologies, yield levels stagnated at low levels, the soil erosion problem persisted while per capita food production continued to fall as population increased. It was soon realized that soil degradation and its accompanying effect of low productivity is not simply a technical issue, rather complex including socioeconomic and behavioral factors and requires a change in approach. Consequently, the need for a systems approach became apparent in order to deal with the complex nature of low and declining agricultural productivity which necessitated biophysical and social scientists to join hands thereby make agricultural research more relevant to the situation of smallholder subsistence farmers (Mekuria, et al., 1992). The role of smallholder farmers in the technology generation and transfer process was formally recognized and took a new precedence known as participatory technology development and transfer; and the need to develop a better understanding of the conditions which encourage adoption of recommended agricultural technologies became a priority. Following a change in approach and focus, a number of technology adoption studies were initiated and implemented in developing countries including Ethiopia pertaining to production technologies (Kebede, 1990; Yirga et al., 1996; Hassan et al., 1998a; Hassan et al., 1998b; Adesina and Baidu-Forson, 1995; Baidu-Forson, 1999; Alene et al., 2000; Dadi, et al., 2001; Fufa and Hassan, 2003). The attention provided to analysing the determinants of investments in soil conservation by smallholder farmers in Ethiopia, however, remained low (Shiferaw and Holden, 1998).
Feder et al. (1985) have summarized the vast amount of empirical literature on production related adoption and indicated that the constraints to adoption of a new technology may arise from many sources, such as lack of credit, inadequate farm size, unstable supply of complementary inputs, uncertainty and risk. Factors conditioning smallholder farmers’ investment in soil conservation and soil fertility management summarized in the literature include: perception of the soil degradation problem, profitability of the proposed technology, household and farm characteristics, attributes of the technology and institutional factors such as land tenure, access to markets, information and credit (Ervin and Ervin, 1982; Norris and Batie, 1987; Pagiola, 1996; Shiferaw and Holden, 1998; Hassan et al., 1998a; Hassan et al., 1998b; Lapar and Pandey, 1999; Kazianga and Masters, 2001; Bamire et al., 2002; Gebremedhin and Swinton, 2003; Nakhumwa and Hassan, 2003; Bekele and Drake, 2003). Others have also argued that besides the above factors risk considerations also affect the rate of adoption of an innovation (Grepperud, 1997b; Shively, 2001; Fufa and Hassan, 2003).
Among the noteworthy empirical studies that investigated the factors conditioning smallholder farmers’ decision to invest in soil conservation in developing countries include that of Pagiola (1996) in Kenya, Pender and Kerr (1998) in India, Lapar and Pandy (1999) in Philippines, Kazianga and Masters (2001) in Burkina Faso, Nakhumwa and Hassan, (2003) in Malawi, Shiferaw and Holden (1998), Gebremedhin and Swinton (2003) and Bekele and Drake (2003) in Ethiopia. These studies highlighted the magnitude and direction of influence of factors hypothesized to condition adoption as largely area specific and their importance varied among countries, between agro-ecologies within countries and among sites within agro-ecologies. Attempts to generalize the relative importance of individual constraints across farm groups, regions and countries are thus unlikely to be useful.
Although important contributions have been made by previous adoption studies in identifying the factors constraining smallholder farmers benefiting from recommended technologies and suggesting ways of improving policy design, the studies, however, were not free from limitations. A fundamental problem characterizing all adoption studies is the absence of economic theory that could serve as a basis for the selection of the determinants of technology adoption decision variables. Although in principle a farmer’s investment in conservation practices could be derived from the maximization of his/her utility function, the fact that the arguments of the utility function are not known makes derivation difficult (Norris and Batie, 1987).
The nature of soil degradation problem and smallholder soil management practices in the highlands of Ethiopia
As has been pointed out earlier, the combination of soil nutrient mining through harvested crop biomass and water-induced loss of topsoil is responsible for soil quality decline in the Ethiopian highlands. Annual soil loss induced by soil erosion from arable lands is estimated to be very high in some locations reaching over 100 tons/ha (FAO, 1999). Also, loss of soil nutrients removed along with soil transported by water and in harvested biomass (grain and straw) is one of the highest in SSA (FAO, 1999). What makes this worse is the fact that the rate of nutrient replenishment is inadequate to offset nutrient losses as cash-constrained smallholder farmers lack the financial means to purchase commercial fertilizers in time and the right quantity (Makken, 1993; Yirga et al., 1996; Demeke et al., 1997; Adugna and Demeke, 2000). Furthermore, the traditional soil fertility management practices of long term fallowing, manure use and crop rotations involving legume crops, which were considered adequate to sustain soil fertility under low population densities, have considerably declined due to population pressure and land shortages in the highlands of Ethiopia (Tanner et al., 1992; Yirga and Hassena, 2001).
In Ethiopia, smallholder subsistence farmers manage several small plots of land scattered across a topo-sequnce or agro-ecology (Shiferaw and Holden, 1998; Yirga et al., 1998; Bekele, 2003). These plots generally differ in soil types, fertility levels, degree of slope and other plot specific features. Group discussion with smallholder farmers in the study area revealed that smallholder farmers recognize three soil depth classes: shallow (less than than 30 cm), deep (31-50) and very deep (above 50 cm); three soil fertility levels (fertile, medium and poor); and three slope classes (flat, medium and high). Accordingly, farmers’ plots of land could broadly be classified into four soil quality classes depending on slope, soil depth, distance from residences and farmer perceptions:
1. Plots on flat and bottomlands. Plots under this category often referred to locally as meda (having a slope of less than 10%) are situated on flat to slightly undulating bottomlands in the mid highlands (areas between 2000 and 2800 meters) and extensive plateaus in the upper highlands (areas above 2800 meters). They are generally considered to have reasonable topsoil depth (medium to high), high to medium soil fertility and less vulnerable to water induced erosion. However, these plots suffer from nutrient mining due to continuous cropping and the disruption of traditional soil fertility management practices. In most of the upper highlands irrespective of soil type and the mid highlands where vertisols predominate the problem of declining soil fertility is further complicated by poor drainage (water logging). Consequently, smallholder farmers’ are concerned more about improving drainage and soil fertility than soil conservation. The most common soil fertility management practices used on this category of plots include crop rotations involving cereals, legumes and oil seeds and application of moderate levels of commercial fertilizers in the mid highlands whereas seasonal fallowing locally known as chiflik or wortab7 and the use of manure and soil burning (locally known as guie8) are common in the upper highlands.
CHAPTER I: INTRODUCTION
1.1 Background and motivation
1.2 Problem statement
1.3 Objectives of the study
1.4 Approaches and methods of the study
1.5 Organization of the thesis
CHAPTER II:OVER VIEW OF THE AGRICULTURAL SECTOR, SOIL RESOURCES AND SOIL DEGRADATION IN ETHIOPIA
2.1 Performance of the agricultural sector
2.2 Overview of the soil resources and soil degradation in Ethiopia
2.3 The policy environment
2.4 Summary
CHAPTER III: REVIEW OF ANALYTICAL AND EMPIRICAL APPROCHES TO STUDYING SOIL DEGRADATION AND CONSERVATION
3.1 The relationship between soil quality and soil degradation processes
3.2 Causes of divergence between private and social rates of soil depletion
3.3 Effect of soil degradation on agricultural productivity
3.4 Approaches to measuring effect of soil degradation on income and adoption decision behavior of smallholder farmers
3.5 Summary
CHAPTER IV: STUDY APPROACH TO MODELLING THE DYNAMICS OF SOIL EROSION AND SOIL NUTRIENT MINING
4.1 The analytical framework
4.2 The nature of soil degradation problem and smallholder soil management practices in the highlands of Ethiopia
4.3 Modeling agricultural output, soil erosion and nutrient mining
4.4 Input substitution
CHAPTER V: STUDY AREA, SURVEY DESIGN AND SELECTED SOCIO-ECONOMIC CHARACTERISTICS OF THE SAMPLE HOUSEHOLDS
5.1 The study area
5.2 Survey design and sampling procedures
5.3 Types of data collected
5.4 Socio-economic characteristics of the study sample
CHAPTER VI: EMPIRICAL SPECIFICATION AND RESULTS OF THE SOIL DEGRADATION OPTIMAL CONTROL MODEL
6.1 Empirical specification of the control model
6.2 The empirical control model and optimal solutions
6.3 Estimating the control model parameters
6.4 Model solutions
6.5 Concluding summary
CHAPTER VII: MODELLING ADOPTION OF SOIL FERTILITY MANAGEMENT AND CONSERVATION PRACTICES
7.1 Analytical framework
7.2 Soil fertility and soil conservation technologies in the study area
7.3 Choice of variables and hypotheses to be tested
CHAPTER VIII: FACTORS INFLUENCING ADOPTION OF SOIL FERTILITY MANAGEMENT AND SOIL CONSERVATION PRACTICES
8.1 Empirical parameter estimation procedures
8.2 Results of the empirical analyses of determinants of the use of soil fertility management practices
8.3 Results of the econometric analyses of factors determining use of soil and water conservation practices
8.4 Concluding summary
CHAPTER IX: SUMMARY, CONCLUSION AND IMPLICATIONS OF THE STUDY TO POLICY AND RESEARCH
REFERENCES
