تجزیه و تحلیل زیستی اقتصادی از فن آوری های حفاظت خاک در منطقه میانه تپه نپال

Soil degradation is a major threat to agricultural sustainability in Nepal. Increased anthropogenic activities in the inherently fragile ecosystem of unstable geology, steep slopes and intense monsoon rains have accelerated the loss of soil and its fertility in the Nepalese hills. This paper assesses soil conservation technologies from biophysical and economic perspectives using the integrated bio-economic analysis. The study applied a biophysical model, Soil Change Under Agroforestry (SCUAF), to project effects of the conservation technologies on soil erosion control as well as on crop yields over a thirty-year period. The technologies considered are hedgerow intercropping and minimum tillage. The outcome of the biophysical model was integrated into a cost-benefit analysis to examine the economic viability of the technologies. The results showed that these technologies are effective in reducing a substantial rate of soil erosion prevailing in the conventional system of maize cultivation. They have a variable impact on yield maintenance and the farmers’ economic return over time. The hedgerow intercropping sustained crop yields in the long-term although yield was reduced in the short-term. Likewise, high costs for establishing and maintaining the hedgerow intercropping significantly reduced farmers’ economic returns in the short-term. Minimum tillage technology, while better than the conventional farming system, was not able to sustain crop yield in the long-term. Yet, it provided positive returns for a longer period than the conventional system. The study concludes that though the evaluated technological options are effective in reducing the high rate of erosion resulting from the conventional maize cropping system, economically they are not viable for farmers in the short-term. Therefore, to expedite the wider adoption of these technologies and to halt and reverse soil degradation, it is suggested that farmers initially be supported with economic incentives to compensate their short-term economic loss.

Soil erosion is a serious threat to agricultural sustainability in the Himalayan region of south Asia. The annual economic loss due to soil erosion and soil fertility depletion in the south Asian countries is estimated to be US $600 million and US $1200 million, respectively (UNEP, 1994). The consequences of soil erosion in terms of fertility degradation, sedimentation and changes in hydrological regime in downstream areas of the Himalayas in general, and in Nepal in particular, have been national and global concerns. The discussion on environmental degradation in the Nepalese hills and mountains have primarily cited forest degradation and unsuitable land-use practices, caused by rapidly growing human population, as the main causes of accelerated soil erosion and its consequent impact on ecology and economy (Eckholm, 1975, Eckholm, 1976 and Ives and Messerli, 1989). Agricultural activities have been expanded and intensified on fragile and slopy areas through double and multiple cropping due to increasing population pressure and limited off-farm employment opportunities (Brown and Shrestha, 2000). According to Thapa (1996), agriculture land on slopy ridges suffers an unsustainable rate of soil erosion and nutrient loss due to frequent hoeing and ploughing. Apart from anthropogenic factors, many inherent natural factors such as active geology, steepness, fragility and high intensity rainfall are also equally responsible for soil degradation across the Nepalese hills and mountains (Ives and Messerli, 1989 and Ives, 2004). Given the complex features of the mountain terrain, the nature and extent of soil erosion varies across the topographical situation of the country. The annual soil loss from the agricultural plots ranges from 0.1 tons ha−1 to 105 tons ha−1 depending on the region, type of plot, and the methodology used for estimation (Chalise and Khanal, 1997). In the rainfed upland sloping terraces of the mid-hill region, the annual soil loss may increase up to 25 tons ha−1 (ICIMOD, 2007). The loss of soil at the rate of 20 tons ha−1 is equivalent to the loss of 300 kg ha−1 organic matter, 15 kg ha−1 nitrogen, 20 kg ha−1 of phosphorus and 40 kg ha−1 of potassium (Carson, 1992). Since cultivable land is scarce, protecting the soil resource base and maintaining the soil fertility is crucial to improving and sustaining yields in order to meet the region's present and future food demand. With the goal of reducing soil degradation and ameliorating subsequent problems, several research efforts have been focused on developing sustainable soil management technologies, which protect the soil resource base while enhancing food production. To this end, the technologies such as minimum tillage and hedgerow intercropping have proven to be promising for protecting the soil and nutrients in several studies in Nepal (Bajracharya, 2001, Maskey, 2003, ICIMOD, 2004 and Atreya et al., 2008). However, none of the studies have considered the cost effectiveness of these technologies as well as their short-term and long-term impacts. Any conservation practice to be sustainable must take into account the financial obligations of the farmers. Recommending a new technology without considering the broader socio-economic needs of farmers invariably brings a failure to adoption (Ya, 2003). Therefore, the demand to evaluate soil conservation technologies using a more holistic approach, which integrates a biophysical as well as an economic assessment, is currently emerging in the mid-hills of Nepal. The objective of this study was to assess the effects of minimum tillage and hedgerow intercropping on long-term soil erosion control, crop yields and farmers’ economic returns, using the techniques of integrated bio-economic analysis. This study differs from other biophysical studies on erosion assessment conducted in the mid-hills because of its integrated approach and long-term perspective. Furthermore, integrating economic analysis provides a better understanding of evaluating soil conservation technologies from the farmers’ point of view and therefore, impacting viability and the widespread adoption of these technologies.

Using the integrated bio-economic analysis, this study assesses the minimum tillage and hedgerow intercropping from a biophysical and economic perspective. A biophysical model, Soil Change Under Agroforestry (SCUAF), was used to project the effects of the conservation technologies on soil erosion control and on crop yields over a 30-year period. The outcome of the biophysical model was integrated into a cost–benefit analysis to examine the economic viability of the technologies. The results of the analysis conclude: (1) minimum tillage and hedgerow intercropping significantly reduces the high rate of erosion prevailing in the maize-based conventional cropping system. (2) The hedgerow intercropping is able to sustain crop yields in the long-term but it substantially reduces farmers’ economic returns in the short-term. (3) The minimum tillage technology, in its present form, is not effective to sustain crop yield in the long-term. Yet, it maintains positive economic returns comparatively longer than the conventional system. The results have the following implications for future research: (1) Though applicability of the SCUAF model has been fairly confirmed in the cropping system of the study area, an elaborate calibration of the model needs to be done with detailed input parameters to improve the model outcome representing the field conditions to a greater extent. (2) Reducing the amount of tillage alone may not sustain the crop yield and the farmers’ income in the long-term. Associated factors, such as improvement of soil acidity and application of sufficient organic matter, become indispensible to make minimum tillage more effective. Thus, impacts of such factors on improving the efficacy of minimum tillage in the context of mid-hills need to be confirmed. (3) As the initial cost of terrace leveling and hedge establishment renders hedgerow intercropping economically unviable in the short-term, it is essential to find out economic incentives for farmers to compensate their short-term economic loss and to accelerate the wider adoption of this technology. (4) The cost–benefit analysis applied in this study has only considered on-site effects at the farm level. Thus, to assist decision makers in designing an appropriate level of support to be granted to expedite the adoption, further economic analysis considering on-site as well as off-site effects of above technologies is essential.