Induced innovation and land degradation: Results from a bioeconomic model of a village in West Africa

This paper introduces a modeling method which simulates a village's response to population and market pressure. The method combines a recursive and dynamic linear programming model with a biophysical model of soil condition and plant growth that predicts yields and land degradation for different type of land, land use and cropping patterns. The linear programming model simulates farmers' plans aggregated at the village level under constraints of risk aversion, food consumption, land area, soil fertility, soil depth, labor and cash availability. Detailed agroecological factors determine Ihe main processes of land degradation. A large number of technological alternatives, representing different degrees of labor and/or land-saving techniques available in the study areas, are introduced, taking into account their respective constraints, costs and advantages. The method has been calibrated for a village located in the sub-humid region of Burkina Faso. Several simulations are carried out to the Year 2030. The results show that population pressure leads to intensification and investment in land conservation practices out not necessarily to better farm incomes. Increasing market opportunities can play a more positive role in boosting productivity, but for the next decades the best way to increase production per farmer is to let farmers migrate from the high-population-density areas to the low-population-density areas because, under the current economic conditions of most Sahelian countries, intensification per hectare is stil more expensive than the fallow system.     

河北省不同利用方式农田土壤氮磷环境风险分析

弄清不同利用方式农田土壤氮磷养分平衡状况,进而明确其环境风险特征,为进一步指导土壤养分管理及环境政策制定具有重要意义。研究以河北省的粮田、果园和菜地为研究对象,通过分析三种利用方式氮磷的输入、化肥和有机肥的分配比例及氮磷养分的盈余状况,并结合化肥使用环境风险指数,评价三种不同利用方式化肥氮磷的环境风险类型。结果表明,氮总输入量为菜地明显高于果园和粮田,磷总输入量为菜地和果园明显高于粮田,且粮田和菜地氮磷输入主要以化肥为主。三种不同利用方式农田氮磷均呈盈余状态,其中氮盈余率为果园(532.6%)明显高于菜地(61.5%)和粮田(31.6%),磷盈余率为菜地(700.4%)和果园(615.7%)明显高于粮田(66.6%)。化肥氮磷的环境风险指数均为菜地(0.83)明显高于粮田(0.59-0.62),三种不同利用方式下化肥氮磷的环境风险类型均达低度风险及以上,特别是菜地达严重风险。为了农业的可持续发展,河北省粮田应控制氮磷肥的投入,果园和菜地应加大减少氮磷肥化肥投入,以减少对环境的潜在危害。同时为了更好地培肥地力,在控制施肥总量的前提下应加大粮田和菜地有机肥的投入比例。     

Forests to fields. Restoring tropical lands to agriculture

In discussing land use in tropical forest regions, there is an emphasis on the following topics: the need for the expansion of cropping areas, the precedent for use of the tropical forest for cropping based on past use patterns, the pressure from conservationists against cropping, debunking the mythology that forests are "natural" and refuting the claims that forest clearance is not reversible, the archeological evidence of past forest use for agricultural purposes, abandonment of tropical land to forest, and rotation of forest and field. The assumption is that the way to stop food importation is to increase crop production in the tropics. Crop production can be increased through 1) land intensification or clearing new land, 2) output per unit of land increases, or 3) reallocation to agriculture land previously cleared and overgrown with tropical forest. "Temporary" reuse of land, which reverted back to tropical forest, is recommended. This reuse would ease population pressure, and benefit bioconservation, while populations stabilize and further progress is made in international plant breeding. The land would eventually be returned to a forest state. Conservation of tropical forest areas should be accomplished, after an assessment has been made of its former uses. Primary forests need to identified and conversion to farming ceased. Research needs to be directed to understanding the process of past forest regeneration, and to devising cropping systems with longterm viability. The green revolution is unsuitable for traditional cropping systems, is contrary to demands of international funding agencies for sustainability, and is not affordable by most poor farmers. Only .48 million sq. km of closed forest loss was in tropical rainforests; 6.53 million sq. km was lost from temperate forests cleared for intensive small-scale peasant farming. The use of tropical forest land for farming has some benefits; crops in the wetter tropics are perennial, which would "reduce seasonal soil tillage, increase nutrient cycling, and remove a lower proportion of biomass." Water availability would not be a problem. Low soil nutrient levels could be increased with cutting and burning or fertilizer. The key is proper and careful management, particularly under intensive cropping systems such as rice production or extensive long fallow shifting cultivation.     

浙江省土地退化及防治对策

浙江省属湿润季风亚热带气候区,地形以丘陵山地为主,土地退化严重,主要方式有水土流失,土地污染及土地养分贫瘠化,本文根据土地退化现状,提出了基本的防治对策。     

On-Farm Nutrient Balance Studies in the Dry Zone of Myanmar

On-farm experiments to study soil fertility depletion—one of the biophysical factors limiting crop production—were conducted in six villages of central Myanmar during 1997 to 1999. Systematic socioeconomic surveys and analysis of socioeconomic and crop production factors aided the selection of farmers.

Topsoil mineral nitrogen content at the start of the cropping season was high (10–25 mg N kg^?1). Available phosphorous was around the threshold level for most crops, but exchangeable potassium was low. The predominant continuous cropping system of sole groundnut was on average positive for P (0.24 kg ha^?1 y^?1) and K (7.05 kg ha^?1 y^?1) and negative for N (?32.4 kg ha^?1 y^?1). A negative balance for N in the groundnut/pigeonpea (?58 kg ha^?1 y^?1) and mung bean/pigeonpea (?56 kg ha^?1 y^?1) intercropping systems was noted. The nutrient balances were positive in early sesame—late sesame (29 kg N ha^?1 y^?1, 8 kg P ha^?1 y^?1, 33 kg K ha^?1 y^?1) and early sesame/pigeonpea (8 kg N ha^?1 y^?1, 15 kg P h^?1 y^?1, 44 kg K ha^?1 y^?1) production systems while sole sorghum system resulted in positive balance for N (23.8 kg ha^?1 y^?1) and negative balance for K (?3.8 kg ha^?1 y^?1).     

Deprived land-use intensification in shifting cultivation: the population pressure hypothesis revisited

This article provides a theoretical framework, based on optimal control theory, to analyze farm households' land‐use intensification decisions in forest‐based shifting cultivation (slash‐and‐burn) agroecosystems. The main results from the analysis generally coincide with the “Population Pressure Hypothesis” (PPH) as an important driver of soil degradation due to the so‐called “fallow crisis” or “deprived land‐use intensification” in shifting cultivation. However, the model also shows, from a supply perspective, that such a vicious circle of lower yields and greater forest land clearing may be avoided when the production elasticity of on‐farm labor outweighs the elasticity of substitution between farm labor and soil fertility. Furthermore, using data from shifting cultivating households from Yucatán, Mexico, we calibrate the effect of changes in population density. The numerical analysis suggests that by contrast to better‐off households, when population density increases, poorer shifting cultivating households' optimal labor allocation strategy is to further extensify land use by clearing more forest in the village common property land, or ejido land.     

Dynamics of agricultural land use change in Kerala: a policy and social-ecological perspective

Land-use change is a phenomenon highlighting significant shifts in human interaction with the natural environment. Different patterns of agriculture and a trend towards non-agricultural land use challenge the sustainability of farming systems. This study aims to identify the causes of changes in land use and cropping patterns, with a special focus on paddy, the staple crop in Asia. In the case of Wayanad, a district in Kerala, South India, we argue for an interdisciplinary analysis of rapid land-use change to unpack the multiple dimensions of sustainability: economic, ecological and social factors, aggregating up to 70% reduction in the area under paddy by 2010. The results rest on empirical field research, participatory rural appraisals and stakeholder workshops conducted during the 4-year period from 2010 to 2013, along with state- and district-level data covering the 1983–2011 period. Reduced economic viability, labour shortages and population pressure on land are the major drivers for the transformation of paddy fields to other land uses. Changes in land use and agrarian structure reflect not only the livelihood strategies adopted by farmers in response to these drivers, but also the impacts of unintended policy idiosyncrasies. At a more fundamental level, they are the consequences of policy conflicts and inadequate sectoral integration of policies and implementation strategies.     

Yield and income risk-efficiency analysis of alternative systems for rice production in the Guinea Savannah of Northern Ghana

Risk efficiency of rice grain yield and returns to farm operators' household resources generated from an improved short‐duration cover crop fallow system were compared with (traditional) natural bush fallow, and continuous rice‐cropping systems. The improved fallow system involved maintaining Calopogonium mucunoides, seeded into a natural bush fallow for 2 years before planting to rice. With no chemical fertilizer application, which reflects farmers' practice in the area, average grain yield for continuous rice (1,185 kg/ha) and the cropping sequence incorporating a natural bush fallow (1,175 kg/ha) did not differ, but were higher for the improved fallow system (1,304 kg/ha). This suggests that nutrient contribution from the leguminous cover crop made up for critical crop N requirements in the improved fallow. Stochastic dominance of grain yield distributions from the improved fallow system, relative to the other two cropping systems, was more dramatic with no N fertilizer application compared to treatments with 30 kg/ha N. Average returns were highest for the improved fallow system, followed by the natural bush fallow‐cropping system, and then continuous rice, under the no N fertilizer treatment regime. With 30 kg/ha N fertilizer, income risk efficiency was less clear (compared to treatments with no N fertilizer), especially between continuous rice and the improved fallow treatment, because of faster N mineralization effects on continuous rice. In contrast, the improved cover crop fallow system completely dominated the natural bush fallow treatment under both fertilizer regimes. Rice production systems that incorporated the leguminous cover crop fallow were superior to the natural bush fallow system, based on both grain yield and average farm income risk‐efficiency considerations.     

Quantifying the socio-economic determinants of sustainable crop production: an application to wheat cultivation in the Tarai of Nepal

This study specifies a procedure to quantify the determinants of sustainable crop production, and applies the method to wheat cultivation in the Tarai of Nepal. Three aspects of sustainability were considered. First, the fertility of the land was found to have deteriorated owing to long-term practices incompatible with soil and drainage conditions. Three-quarters of the farmers had reduced land fertility and for one-third of them the wheat yield was at least 20% lower than for farmers who applied farmyard manure to every crop and adopted a rotation consistent with soil and drainage conditions. Secondly, the study found that it was possible to improve resource-use efficiency in wheat production to give 25% higher production at current levels, type, and quality of farm resources. Resource-use efficiency was significantly related to farm management practices such as crop stand, variety, disease, and land preparation quality, and socio-economic factors such as off-farm job opportunities, poor plot accessibility, and migration. Thirdly, the increasing population pressure on land, decreasing livestock number per cropped area, and diminishing fuel wood sources, significantly reduced farm-based nutrient cycling because farmyard manure had to be used for fuel. This had implications for the higher use of the fossil-based inputs in crop production.     

Land use dynamics in the central highlands of Vietnam: a spatial model combining village survey data with satellite imagery interpretation

The paper investigates geo‐physical, agro‐ecological, and socio‐economic determinants of past land use change in two districts of Dak Lak province in the Central Highlands of Vietnam and assesses the influence of rural development policies on land cover change. Landsat satellite images from the years 1975, 1992 and 2000 are interpreted to detect land cover in two time periods. A survey in randomly selected villages provides primary recall data on socio‐economic and policy variables hypothesised to influence land use change. Secondary data on rainfall, soil suitability, and topography was obtained from meteorological stations and from a digital soil map and digital elevation model. All data were spatially referenced using geographic information systems (GIS) software. A reduced‐form, multinomial logit model is used to estimate the influence of hypothesised determinants on land use and the probabilities that a certain pixel has one of five land classes during either of the two periods. Results suggest that the first period from 1975 to 1992 was characterised by land‐intensive agricultural expansion and the conversion of forest into grass and agricultural land. During the second period, since 1992, the rapid, more labour‐ and capital‐intensive growth in the agricultural sector was enabled by the introduction of fertiliser, improved access to rural roads and markets, and expansion of the irrigated area. These policies, combined with the introduction of protected forest areas and policies discouraging shifting cultivation during the second period reduced the pressure on forests while at the same time increasing agricultural productivity and incomes for a growing population. Forest cover during the second period mainly increased due to the regeneration of areas formerly used for shifting cultivation.     

Understanding the influence of farmer motivations on changes to soil erosion risk on sites of former serious erosion in the South Downs National Park,UK

Serious soil erosion occurred in the South Downs National Park, southern England in the years 1982–2006 and details of around 400 sites are contained in a database. In 2010 we revisited 85 of the most serious sites where erosion of >10 m³ ha⁻¹ y⁻¹ had been recorded in order to assess land use change and any conservation measures undertaken. At 79% of the sites land use change had resulted in a reduction in the risk of erosion, most notably at 28 sites with a shift to permanent grass from winter cereals. At only 21% of sites was the risk of erosion unchanged. Twenty two farmers responsible for 66 of the sites were interviewed. Land management practices had changed on all of the fields of interest to this study since the time of the serious erosion events, to those which have the potential to lower soil erosion risk. Sixteen interviewees claimed that erosion was a motivating reason for changing their practices, due to either experiencing on or on- and off-farm impacts firsthand (12), having knowledge or suspicion of serious erosion having occurred on their land prior to their management (three), or having no knowledge of any serious erosion on their land but just wanting to reduce overall erosion risk (one). Amongst the main changes reported are changes of land use from winter cereals to grass or to overwinter stubble which have undoubtedly reduced the risk of erosion. However, some changed practices claimed by farmers, such as along-the-contour-working, earlier sowing and the use of rollers may be of little value. Furthermore, deeper analysis of farmers’ motivations regarding changes in land management practices suggests a complex picture in which a range of socio-economic influences come into play over time including financial incentives offered by agri-environmental schemes which were found to be an important driver of change. Future changes in farming economics may therefore undermine the reduction in erosion risk in the longer term.     

Primary causes of total hamlet abandonment for different types of hamlets in remote mountain areas of China: A case study of Shouning County,Fujian Province

Total hamlet abandonment in remote mountains throughout the last several decades as a result of severe rural depopulation constitutes many serious socioeconomic problems now occurring in China and many other developing countries. To get a more profound insight into the primary causes of hamlet abandonment, this study builds on a conceptual framework through conducting an in-depth qualitative analysis based on a case-study of Shouning County, Southeast China. The primary causes of total hamlet abandonment have been illustrated by classifying these abandoned hamlets into three types: disaster-affected hamlets, township hamlets, and remote hamlets. Results have shown that the primary causes of abandonment were tremendously different for each type of the hamlets in question. Natural disasters and subsequently immediate government-sponsored resettlement were the primary causes of disaster-driven hamlet abandonment. Sudden onset events and ex situ resettlement have produced quick hamlet abandonment. Our results also show that in situ urbanization and government-sponsored resettlement were the dominating causes of hamlet abandonment for adjacent hamlets of townships. For remote hamlets (which were the dominating type of abandoned hamlets), severe lack of public services (especially education) was the first and foremost cause of hamlet abandonment, while in situ urbanization and the government-sponsored Poverty Alleviation Resettlement Project (PARP) were secondary causes. Adverse natural conditions, however, were relatively minor factors in remote hamlet abandonment. Lastly, external factors were significant ‘pull’ forces in comparison, leading to hamlet abandonment for all types of abandoned hamlets within the study. The heterogeneity of hamlet abandonment and multi-scale causes have been highlighted in our case study. These findings therein have important policy implications for rural sustainability in developing countries, particularly China.     

南方冬作区马铃薯发展趋势、区域格局与增产潜力

发展南方冬作区马铃薯对保障我国粮食安全和增加农民收入意义重大。2000～2008年,南方冬作区马铃薯播种面积和产量均稳定增长,但8省份趋势有所不同,广西发展尤为迅速。南方冬作区马铃薯进一步增产存在三方面有利因素:(1)冬闲田面积达733.3万hm2,广东、广西、云南、湖南四省闲田面积均超过133.3万hm2;(2)最为重要的3个技术瓶颈都与脱毒种薯培育和检测相关,相关科研正在加强;(3)马铃薯的种植收益远高于油菜,部分油菜耕地将改为种植马铃薯。     

Assessment through socioecological abstraction: The case of nutrient management models in Sudano-Sahelian West Africa

The sustainability of smallholder agriculture in the drylands of West Africa is a topic of long-lasting concern. This paper is focused on the scientific assessment of nutrient (mis)management affecting the long-term productivity of cropland. “Nutrient mining” is seen as a major mechanism for land degradation in the region. Two models will be the focus: that tied to the rangeland-to-cropland metric and the nutrient balance model. These tools of assessment follow a long history of environmental assessment and modeling that purposefully abstracts from the heterogeneity of the same farming practices that modeling efforts seek to assess. Abstraction is always part of modeling but the form of abstraction described here ignores any detailed understanding of farming practices and in so doing, demands very little information about farming practices. In this way, models serve as both the symptom and cause of continued ignorance of farming practices by most agronomists and soil scientists working in the region. The variables used in these models will be described and how these same variables are strongly influenced by the variation of farmers’ practices will be discussed. In addition, it will be shown that needless model abstraction results in research outcomes that provide very little insights to guide land policy formulation and agricultural extension. In short, these models point to the ultimate resource limits of the regional agricultural system but provide few insights of what could be changed to reduce rates of land degradation. The paper concludes by presenting alternative approaches that through their engagement with the diverse positionalities of farmers, provides insights useful for the development of effective land policies.     

Rice to shrimp: Land use/land cover changes and soil degradation in Southwestern Bangladesh

This paper examines the impact of shrimp farming on rice ecosystem in a village in Southwestern Bangladesh. The village Damarpota has experienced transformation of 274 ha (79%) of its prime quality rice fields into shrimp farms during the period between 1985 and 2003. Prolonged shrimp farming for 5-, 10-, and 15-year period has increased soil salinity, acidity, and depleted soil Ca, K, Mg, and organic C content of all three types of soils in the villages to a variable degree and caused soil degradation that significantly affected the rice yield. Declined yield and acreage of rice jointly reduced the total production of rice and animal fodder. Soil degradation and loss of acreage under rice have threatened the sustainability of the village rice ecosystem.     

The politics of swidden: A case study from Nghe An and Son La in Vietnam

Swidden cultivation practices have been seen as a major driver of deforestation and forest degradation in Southeast Asia. Using two case studies from Vietnam, this paper examines discourses around swidden practices at multiple levels of governance. Our findings show diverse interpretations of swidden resulting in different policy preferences and policy translations when addressing the issue. At national level, swidden is blamed as a principal driver of deforestation and forest degradation, and as such is a practice to be eliminated. As a result of this national stance, provincial level authorities see the existence of swidden as a failure by which their political performance will be judged. Conversely, swidden communities are seen at district level as an innovative solution to help resource-limited police forces ensure national security in border areas. Local commune and village leaders view swidden as a traditional practice to be respected, so as to maintain harmonious relationships amongst social groups, and avoid ethnic groups protesting against the government. Such differences in discourses and political interests have led to swidden becoming an ‘invisible’ issue, with government authorities failing to collect and report on data. Not recognizing swidden also means that swidden actors are practically ‘forgotten’ in the design and implementation of Reducing Emissions from Deforestation and Forest Degradation (REDD+) and Payments for Ecosystem Services (PES). Their omission from forest conservation and management incentive programmes could lead to further social marginalization, and potentially result in deforestation and forest degradation in the area. Our findings suggest that REDD+ policies should take into account diverging political interests on controversial land uses such as swidden cultivation.     

基于GIS的合肥市耕地地力评价

[目的]为查清合肥市耕地质量状况。[方法]利用GIS技术和县域耕地资源管理信息系统(CLRMIS)等软件,从耕地的立地条件、剖面组成、土壤理化性状、土壤管理4个方面选取14个评价因子,采用特尔斐法确定评价因子的权重和隶属函数对耕地地力进行综合性评价。[结果]合肥市耕地地力分五个等级,一,二,三,四,五等地面积分别占总耕地面积的14.85%,31.47%,35.00%,10.24%和8.43%。[结论]一,二等地主要分布在巢湖市、庐江县和肥西县,主要是水田,地貌类型以平原、平畈冲田和台地为主,少数地区存在黏磐层障碍层,灌溉排涝能力较强;三,四,五等地主要分布在肥东县和长丰县,地形部位主要是中坡地、平畈冲田、陡坡地和塝田,耕层质地主要是重壤和中壤,障碍层类型为黏磐层和砂砾层,灌溉排涝能力较低,土壤养分含量与一,二等地相比有所下降;合肥市耕地土壤有机质、有效磷和速效钾的平均含量均处于中等水平,其中巢湖市的有机质平均含量最高,肥西县有效磷和速效钾平均含量最高。     

Soil Fertility Management and Compost Use in Senegal's Peanut Basin

The Jóór (Dior) soils of Senegal's Peanut Basin are inherently low in organic matter, limiting yields of millet and other crops and threatening the food security of smallholders. Focus groups and interviews were conducted in eight villages to characterise the site-specific fertility management by farmers in the Peanut Basin. Results of the qualitative survey revealed that farmers base management decisions on a series of fertility indicators that include type, colour, and texture of soil, presence of vegetation, and productivity in previous years. In an effort to equalise fertility across the field, farmers amend areas they classify as less fertile with decomposed manure and household waste from the family sëntaare (traditional pile) orwith compost from managed piles. On-site measurements of soil in areas of fields amended with compost or sëntaare material revealed significant increases in peanut and millet growth over unamended areas, but little difference between the effects of compost and manure. Similarly, chemical analysis revealed increased effective cation exchange capacity (ECEC) and nutrient concentrations (K, Mg and Al) in soils amended with compost or manure. Similarities in the chemical characteristics of compost and sëntaare material suggest that development workers could emphasise improved pile management rather than promoting more labour-intensive composting.     

高台县耕地地力评价

[目的]根据高台县耕地地力评价结果和不同地力等级统计结果,分析耕地质量存在的问题,并为高台县耕地地力保护和耕地质量提升提出建议对策。[方法]把甘肃省张掖市高台县土壤图、土地利用现状和行政区划图叠加求交,得到3.309 3万个评价单元。利用特尔斐法选取耕层盐化、质地构型、有机质、质地、有效磷、耕层厚度、海拔、CEC(土壤阳离子交换量,下同)、速效钾和坡度作为高台县耕地地力评价指标体系并建立层次分析模型和隶属函数模型,由专家打分取平均值给出各层次权重和评价指标的隶属度。再使用GIS软件根据公式计算耕地地力综合指数IFI值。[结果]IFI值0.850 5的划为一等地,IFI值在0.850 5~0.720 0的划为二等地,IFI值在0.720 0~0.662 6的划为三等地,IFI值在0.662 6~0.630 0的划为四等地,IFI值0.630 0的划为五等地。[结论]当前耕地存在的主要问题是因化肥过量使用造成的面源污染和灌溉造成的盐渍化,建议从改良耕作制度、轮作休耕、化肥减量增效、增施有机肥、节水灌溉技术和秸秆还田等措施加以改良。     

东北典型黑土区耕地地力评价与障碍因素诊断

研究目的:从影响耕地地力的土壤管理、理化性质、土壤养分、剖面性状、立地条件和气候条件等6个方面选取13个评价指标对东北典型黑土区耕地地力进行综合评价,并在评价基础上进行障碍因素诊断,为今后定量化分析耕地地力障碍因素提供方法。研究方法:该研究运用层次分析法和模糊数学法等方法进行耕地地力评价,并引入障碍度模型对影响该区域耕地地力的障碍因素进行定量化分析。研究结果:(1)东北典型黑土区耕地地力整体呈现南高北低的趋势,其中以中等地(四、五、六、七等地)为主,占研究区总耕地面积的64.47%;其次为高等地(一、二、三等地),占研究区总耕地面积的28.31%;低等地(八、九、十等地)最少,只占研究区总耕地面积的7.22%;(2)对研究区评价指标体系中耕层厚度、有机质、有效磷、p H、灌溉能力、排涝能力6个指标进行障碍度分析,发现除有效磷和p H对耕地地力障碍作用不明显外,其他因素均有明显障碍作用,且障碍程度呈现一定的规律性。研究结论:(1)通过对研究区进行耕地地力评价,对东北典型黑土区的耕地数量和质量在空间分布特征上有了全面掌握,为今后耕地的合理利用提供了依据;(2)障碍度模型的引入为分析影响耕地地力的障碍因素提供了定量化的研究方法,为耕地地力保护和提升研究提供了方法支撑。