Modelling agricultural expansion in Kenya’s Eastern Arc Mountains biodiversity hotspot

The Taita Hills are the northernmost part of the Eastern Arc Mountains of Kenya and Tanzania, which is one of the most important regions for biological conservation in the world. The indigenous cloud forests in this area have suffered substantial degradation for several centuries due to agricultural expansion. In the Taita Hills, currently only 1% of the original forested area remains preserved. In order to create effective policies to preserve the natural resources and biodiversity of the Eastern Arc Mountains it is crucial to understand the causes and interactions involved in the landscape changes in the most degraded areas. The research presented here aimed to understand the role of landscape attributes and infrastructure components as driving forces of agricultural expansion in the Taita Hills. Geospatial technology tools and a landscape dynamic simulation model were integrated to identify and evaluate the driving forces of agricultural expansion and simulate future landscape scenarios. The results indicate that, if current trends persist, agricultural areas will occupy roughly 60% of the study area by 2030. Agricultural expansion will likely take place predominantly in lowlands and foothills throughout the next 20 years, increasing the spatial dependence on distance to rivers and other water bodies. The main factors driving the spatial distribution of new croplands were the distance to markets, proximity to already established agricultural areas and distance to roads. Other driving forces of the agricultural expansion, as well as their implications for natural resources conservation, are discussed. Further studies are necessary to integrate the effects of population pressure and climate change on the sustainability and characteristics of local agricultural systems.     

基于形态学的农田景物区域检测技术

研究了形态学在农田景物区域检测中的应用，通过形态学分析对农田景物区域进行了形态特征提取，在此基础上利用先验知识对各区域进行了识别分类。试验表明，本文提出的方法可以取得良好的效果。     

Peasant emigration and land-use change at the watershed level: A GIS-based approach in Central Mexico

Demographic changes introduced by migration strongly affect economic activities and may thus trigger land-use changes. Migration has been usually overlooked in land use change modelling, even though it is recognized as a dominant demographic factor that influences land use. This paper analyzes to what extent migration patterns influence land-cover and land-use change at the watershed level. A RS-GIS and statistical approach was used to quantify and analyze both land-cover change and change in population per spatial unit. It was hypothesized that migration should exert a strong effect on land-cover change. The exercise was carried out in the Basin of Lake Cuitzeo, Michoacan, in Central Mexico, an area of high emigration to the USA, albeit showing a net increase in its total population. The expansion of scrubland areas at the expense of rain-fed agricultural land is associated with the abandonment of agricultural land with poor soils. As a consequence, vegetal succession has been promoted and subtropical scrubland increased.     

Systematic design and evaluation of crop rotations enhancing soil conservation, soil fertility and farm income: a case study for vegetable farms in South Uruguay

Rapid changes in the social and economic environment in which agriculture is developing, together with the deterioration of the natural resource base threatens sustainability of farm systems in many areas of the world. For vegetable farms in South Uruguay, survival in the long term depends upon the development of production systems able to reduce soil erosion, maintain or improve physical and biological soil fertility, and increase farmer’s income to socially acceptable levels. We propose a model-based explorative land use study to support the re-orientation of vegetable production systems in South Uruguay. In this paper we present a new method to quantitatively integrate agricultural, environmental and socio-economic aspects of agricultural land use based on explicit design objectives. We describe the method followed to design and evaluate a wide variety of land use activities for Canelón Grande (South Uruguay) and we illustrate the usefulness of this approach in an ex-ante evaluation of new farming systems using data from 25 farms in this region. Land use activities resulted from systematic combination of crops and inter-crop activities into crop rotations, different crop management techniques (i.e., mechanisation, irrigation and crop protection) and animal production. We identified and quantified all possible rotations and estimated inputs and outputs at crop rotation scale, explicitly considering interactions among crops. Relevant inputs and outputs (i.e., soil erosion, balance of soil organic matter and nutrients, environmental impact of pesticides, labour and machinery requirements, and economic performance) of each land use activity were quantified using different quantitative methods and following the target-oriented approach. By applying the methodology presented in this paper we were able to design and evaluate 336,128 land use activities suitable for the different soil types in Canelón Grande and for farms with different availability of resources, i.e., land, labour, soil quality, capital and water for irrigation. After theoretical evaluation, a large subset of these land use activities showed promise for reducing soil erosion, maintaining soil organic matter content of the soil and increasing farmer’s income, allowing improvement of current farming systems in the region and providing a widely diverse set of strategic options for farmers in the region to choose from. This method can be used as a stand-alone tool to explore options at the field and farm scale or to generate input for optimisation models to explore options at the farm or regional scale.     

Catchment management for dryland salinity control: Model analysis for the Liverpool plains in New South Wales

Human-induced soil salinisation is a major resource degradation issue in Australia. While the processes and remedial activities are generally understood, the pressing questions remain as to whether the problem can be managed and who should take what action. This paper presents an analysis for a catchment in Eastern Australia where dryland salinisation is emerging in the plains. A spatial and dynamic mathematical programming model is developed as a systems analysis tool. The model results establish that salinisation on the plains is caused by water imports from surrounding areas. Salinity imposes severe external costs on affected landholders who have to change their land use systems, both as a response to its emergence and to control groundwater tables. Taking a catchment perspective, it is investigated what contribution different areas within the catchment ought to make to control soil salinisation on the plains. The results indicate that some land use changes for groundwater table control would optimally be implemented in uphill recharge areas but most of the cost would be borne by plains farmers. The results also demonstrate that climatic variability tends to exacerbate salinisation and lower agricultural incomes.     

Groundwater recharge under alkali soils during reclamation

Reclamation of alkali soils modifies the water balance of an area. Hydrologically the soils under reclamation remain in a transient state over a long period of time because of the progressive improvement in their physio-chemical properties. The major component of the water balance that undergoes change is the groundwater recharge from crop land. A procedure to estimate the rate of change in recharge from crop land is presented and applied to typical alkali conditions in the command area of the Western Jamuna Canal.The value of groundwater recharge from this composite watershed, having normal and alkali soils in the ratio of 70 to 30, respectively, shows an increase of about 17.5% of the recharge value before reclamation for the optimal cropping patterns over a period of 20 years.     

基于混合DEA的临沂市农业土地利用效率研究

本文采用BCC模型和Malmquist指数方法,对临沂市2017-2020年的农业土地利用效率进行静态、动态分析。研究结果表明,临沂市整体农业土地利用效率水平在0.969左右,制约农业土地利用效率的关键是规模效率较低,大部分县级区域存在不同程度的规模效率和纯技术效率的提升空间,且在农业要素投入过程中存在一定程度的冗余和浪费。临沂市农业土地利用的全要素生产率呈上升趋势,并且存在明显的波动,技术进步率对于全要素生产率贡献较大,发展状态良好。临沂市各县级区域应因地制宜的调整农业政策,加大农业科技的投入,推行土地流转,优化资源投入结构。     

Use of animal density to estimate manure nutrient recycling ability of Wisconsin dairy farms

Animal density is increasingly being used as an indicator of agricultural nitrogen (N) and phosphorus (P) loss potential in Europe and the US. This study estimated animal-cropland ratios for over 800 Wisconsin dairy farms to: (1) illustrate the impact of alternative definitions of this ratio; (2) evaluate how the definition of ‘cropland’ would affect Wisconsin dairy farmers’ ability to comply to manure N and P land spreading standards and (3) investigate the potential of using an animal density standard for targeting manure management plan implementation on Wisconsin dairy farms. Animal density calculations based on total cropland area indicate that 95% of Wisconsin dairy farmers have sufficient cropland for recycling manure according to a N-based nutrient management standard. Calculating animal density based on tilled cropland area decreases this value to 79% of dairy farms. Implementation of a P-based standard increases the land requirement for manure application, and a large proportion of Wisconsin dairy farms (37% based on total cropland and 75% based on tilled cropland) would lack sufficient land area for recycling manure P. When the area of cropland on which manure is actually spread is used to calculate animal density, it is clear that the majority of farms do not currently meet either manure N- or P-based land application standards. Reasons for not utilizing the full cropland base for manure application are unclear, but regional differences suggest soil texture, land tenure, and development pressures may limit the proportion of cropland receiving manure. These results indicate the need to better understand factors influencing cropland management and manure spreading behavior on Wisconsin dairy farms.     

Tracking environmental dynamics and agricultural intensification in southern Mali

The Office de la Haute Vallée du Fleuve Niger (OHVN) zone in southern Mali is a small but important agricultural production region. Against a background of environmental degradation including decades of declining rainfall, soil erosion, and human pressure on forest resources, numerous farming communities stand out through the use of improved soil and water management practices that have improved agricultural and environmental conditions. Field surveys conducted in 1998–2001 indicated that environmental and agricultural conditions have improved in the past decade. In an effort to better quantify environmental trends, we conducted a study using medium- and high-resolution remotely sensed images from 1965 to 2001 in order to analyze land use and land cover trends in 21 village territories. The trends show clear indications of agricultural intensification and diversification among villages that have received assistance from the OHVN agricultural development agency. Some communities have improved environmental conditions by protecting their forest resources through community management actions. Four decades of remotely sensed images played a practical role in tracking and quantifying environmental and agricultural conditions over time.     

Water harvesting and supplemental irrigation for improved water productivity of dry farming systems in West Asia and North Africa

In the dry areas, water, not land, is the most limiting resource for improved agricultural production. Maximizing water productivity, and not yield per unit of land, is therefore a better strategy for dry farming systems. Under such conditions, more efficient water management techniques must be adopted. Supplemental irrigation (SI) is a highly efficient practice with great potential for increasing agricultural production and improving livelihoods in the dry rainfed areas. In the drier environments, most of the rainwater is lost by evaporation; therefore the rainwater productivity is extremely low. Water harvesting can improve agriculture by directing and concentrating rainwater through runoff to the plants and other beneficial uses. It was found that over 50% of lost water can be recovered at a very little cost. However, socioeconomic and environmental benefits of this practice are far more important than increasing agricultural water productivity. This paper highlights the major research findings regarding improving water productivity in the dry rainfed region of West Asia and North Africa. It shows that substantial and sustainable improvements in water productivity can only be achieved through integrated farm resources management. On-farm water-productive techniques if coupled with improved irrigation management options, better crop selection and appropriate cultural practices, improved genetic make-up, and timely socioeconomic interventions will help to achieve this objective. Conventional water management guidelines should be revised to ensure maximum water productivity instead of land productivity.     

Environmental impacts from herbicide tolerant canola production in Western Canada

The commercial production of herbicide tolerant (HT) canola began in Western Canada in 1997. With more than a decade of use, the actual farm-level environmental impact of HT canola can be evaluated. This article reports on a spring 2007 survey of nearly 600 canola farmers in the three prairie provinces of Western Canada. Producers were asked about their crop production experiences for 2005 and 2006 and expected crop planting for 2007. A reduction in the total number of chemical applications over the 3-year period was reported, resulting in a decrease of herbicide active ingredient being applied to farmland in Western Canada of nearly 1.3 million kg annually. Fewer tillage passes over the survey period were reported, improving moisture conservation, decreasing soil erosion and contributing to carbon sequestration in annual cropland. An estimated 1 million tonnes of carbon is either sequestered or no longer released under land management facilitated by HT canola production, as compared to 1995. The value of this carbon off-set is estimated to be C$5 million. Comparisons with similar studies and against non-adoption of HT canola can guide future decisions about HT canola adoption.     

Using the DRAINMOD-N model to study effects of drainage system design and management on crop productivity,profitability and NO3–N losses in drainage water

The environmental impacts of agricultural drainage have become a critical issue. There is a need to design and manage drainage and related water table control systems to satisfy both crop production and water quality objectives. The model DRAINMOD-N was used to study long-term effects of drainage system design and management on crop production, profitability, and nitrogen losses in two poorly drained soils typical of eastern North Carolina (NC), USA. Simulations were conducted for a 20-yr period (1971–1990) of continuous corn production at Plymouth, NC. The design scenarios evaluated consisted of three drain depths (0.75, 1.0, and 1.25 m), ten drain spacings (10, 15, 20, 25, 30, 40, 50, 60, 80, and 100 m), and two surface conditions (0.5 and 2.5 cm depressional storage). The management treatments included conventional drainage, controlled drainage during the summer season and controlled drainage during both the summer and winter seasons. Maximum profits for both soils were predicted for a 1.25 m drain depth and poor surface drainage (2.5 cm depressional storage). The optimum spacings were 40 and 20 m for the Portsmouth and Tomotley soils, respectively. These systems however would not be optimum from the water quality perspective. If the water quality objective is of equal importance to the productivity objective, the drainage systems need to be designed and managed to reduce NO₃–N losses while still providing an acceptable profit from the crop. Simulated results showed NO₃–N losses can be substantially reduced by decreasing drain depth, improving surface drainage, and using controlled drainage. Within this context, NO₃–N losses can be reduced by providing only the minimum subsurface drainage intensity required for production, by designing drainage systems to fit soil properties, and by using controlled drainage during periods when maximum drainage is not needed for production. The simulation results have demonstrated the applicability of DRAINMOD-N for quantifying effects of drainage design and management combinations on profits from agricultural crops and on losses of NO₃–N to the environment for specific crop, soil and climatic conditions. Thus, the model can be used to guide design and management decisions for satisfying both productivity and environmental objectives and assessing the costs and benefits of alternative choices to each set of objectives.     

Assessing the impact of the Nitrate Directive on farming systems using a bio-economic modelling chain

Bio-economic models can be used to assess the impact of policy and environmental measures through economic and environmental indicators. Focusing on agricultural systems, farmers’ decisions in terms of cropping systems and the associated crop management at field scale are essential in such studies. The objective of this paper is to present a study using a bio-economic model to assess the impact of the Nitrate Directive in the Midi-Pyrenees region (France) by analyzing, at the farm scale, farm income and three environmental indicators: nitrate leaching, erosion and water consumption. Two scenarios, the 2003 CAP reform (baseline scenario) and the Nitrate Directive (policy scenario), with a 2013 time horizon, were developed and compared for three representative arable farm types in the Midi-Pyrenees region. Different types of data characterizing the biophysical context in the region (soil, climate), the current cropping systems (rotation, crop management) and farm resources (irrigated land, labor) were collected to calibrate and run the models. Results showed that the implementation of the Nitrate Directive may not affect farm income. However, significant modifications to cropping systems and crop allocation to soil types were simulated. Contrary to expectations, nitrogen leaching at the farm scale did not change. Overall water consumption increased and soil erosion decreased due mainly to a modification in cropping patterns and management by soil type. This study provides an example of unanticipated effects of policy and trade-offs between environmental issues.     

Mapping agricultural responses to water supply shocks in large irrigation systems, southern India

Irrigated agriculture experienced a water supply shock during a drought in southern India in 2002-2003. In this paper, hotspots of agricultural change were mapped and put in the context of hydrology and water management. Time series of MODIS imagery taken every eight days before (2001-2002) and during (2002-2003) the supply shock were combined with agricultural census data to document changes in cropping patterns in four large irrigation projects in the downstream sections of the Krishna and Godavari River basins (total command area 18,287 km²). The area cropped in rice in the four irrigated command areas decreased by 32% during the drought year, and rice production in the two districts that experienced the largest flow reductions fell below production levels of 1980. The irrigation project that showed the largest change in double cropped area (−90%) was upstream of the Krishna Delta. In the Krishna Delta, large areas changed from rice-rice to rice-gram double cropping. Historical water management contributed to the vulnerability of rice production to drought: the main reservoir in the system was drained to dead storage levels by the end of each growing season over 1968-2000, with little carryover storage. The land cover change maps suggested that the lower Krishna Basin has experienced a “hard landing” during basin closure, and revised management strategies that account for the new flow regime will be required to maintain agricultural production during droughts.     

基于LU-SWAT模型的土地利用/覆被变化对水文过程的影响研究——以黑河上游为例

【目的】揭示内陆河流域集水区土地利用/覆被变化对水文过程的影响及其成因。【方法】基于能够逐年调用土地利用/覆被数据的LU-SWAT模型,并结合控制变量法研究了黑河流域集水区黑河上游1990—2009年土地利用/覆被变化对地表径流、侧向流、蒸散发量、地下径流以及总产水量的影响。【结果】LU-SWAT模型对于黑河上游月、年出山径流模拟结果较好,其月径流模拟的纳什系数为0.93,相关性系数为0.94;其年径流模拟的纳什系数为0.83,相关性系数为0.86。此外,其对各个水文要素的模拟结果符合西北干旱区内陆河流域集水区的水文特征;1990—2001年黑河上游土地利用变化主要表现在林地的减少,而2002—2009年土地利用的变化除了林地和草地的增加之外,还表现在裸地的大面积减少;1990—2001年黑河上游地表径流、侧向流、蒸散发量以及总产水量都呈现增加趋势,而地下径流呈减少趋势,2002—2009年流域地表径流、侧向流、蒸散发量以及总产水量减少,而地下径流量增加。在黑河上游,干旱条件下各水文要素对于土地利用覆被变化的响应更明显。【结论】1990—2001年林地的减少可能是流域地表径流、侧向流、蒸散发量以及总产水量都呈现增加趋势而地下径流呈减少趋势的主要原因。2002—2009年裸地的大面积减少可能是流域地表径流、侧向流、蒸散发量以及总产水量减少而地下径流量增加的主要原因。     

Transformation toward agricultural sustainability in New Zealand hill country pastoral landscapes

A multi-stakeholder representative group was established to oversee a project examining the economic and environmental performance of a representative North Island hill country catchment farm at Whatawhata in the western Waikato region of New Zealand. The group included representation from landowners, government agencies and scientists. The group was facilitated through an action research approach incorporating three phases: (1) awareness; (2) forecasting; and (3) implementation. The group identified a set of goals and indicators relevant to achieving a “well managed rural hill catchment” The indicators were used to (a) assess the current state of the catchment farm in relation to the goals; (b) evaluate a range of strategies for improving system performance and (c) evaluate progress toward the goals following land use changes implemented within the catchment farm. Key issues for the group included the availability of data and the setting of appropriate performance benchmarks. From both economic and environmental points of view, the existing farm system was failing to meet the goals set by the management group. Key factors driving these outcomes included the physical and productivity limitations of the soil resource, poor livestock performance and poor water quality. A mixture of research observations, decision support models and expert stakeholder knowledge indicated scope for improving performance through forestry, riparian management, erosion control and livestock intensification options. Based on their evaluation of the forecasting results, the group developed a new land use plan, which depended on significant capital investment in land use and enterprise change. Subsequent monitoring of soils, vegetation, water quality, animal production and financial results over four years showed marked improvement in a number of key performance indicators. In particular, sediment and phosphorus loads and faecal coliform levels decreased rapidly, native forest fragments showed early signs of restoration, lamb and beef productivity increased and the per hectare financial returns of the pastoral component increased. Better matching of land use to land capability has led to short-term improvement in some aspects of the economic and environmental performance of the catchment farm. Progress toward a more sustainable agricultural system was achieved, but at a substantial cost for transformation of the biophysical system, which has implications for the wider sector.     

Regional land use analysis: the development of operational tools

Regional land use analysis plays a key role in the analysis of agricultural policies. However, few operational tools for regional land use analysis are available. Current developments in regional land use analysis are rather ad hoc. More generic methodologies are required to effectively answer questions by policy makers. The analysis may require methods to explore, project and predict agricultural land use. An all-encompassing methodology seems unrealistic. A toolbox for regional land use analysis is proposed. The tools (including, e.g. database management systems, GIS and economic models) can be linked in such a way that they can carry out the analysis required for the specific conditions of stakeholders. To facilitate linkages between the different tools, data standards need to be developed for both bio-physical as well as economic data. Discussions with stakeholders in an early phase of the analysis may set priorities and determine the selection of tools. Results of the analysis need to be presented in such a way that they are appealing to the stakeholders. Only then can they be transferred effectively. The general framework is illustrated with a methodology for regional land use analysis in terms of economic and environmental trade-offs.     

小波变换在农田图像边缘检测中的应用

为了给农业机器人田间行走提供准确导航方向线,以农田景物为研究对象,提出用紧支撑双正交小波变换检测图像中的边缘,并改进了传统的小波算法。运用此方法,在计算机上对图像做边缘提取的实验。实验结果表明,该方法能够得到连续、光滑、单像素宽边缘链图像。程序的单幅图像处理平均效率为0.12s,不仅证明了该算法能够达到实时检测、自主导航的要求,而且也表明这种边缘提取方法是有效和可行的。