A conceptual approach to the modelling of herbage intake by hill sheep

A modelling approach is examined as a method of investigating alternative management strategies for improved systems of hill sheep production. In order to take account of the wide range in the quality of hill herbage and the ability of the hill sheep to select preferred components, herbage has been conceptually classified in terms of its digestibility; the digestibility classes are then grazed selectively by sheep. The model deals with herbage growth and deterioration, diet selection and the maintenance and liveweight change of wether sheep. Results produced by the model, in which wethers grazed Agrostis-Festuca at two stocking rates, are discussed.     

Multi-scale analysis of agricultural development: A modelling approach for Ilocos Norte,Philippines

Decisions and policies that have implications on allocation of resources are made at different levels. Goals at different scales may be conflicting and decisions at one scale have consequences for those at other scales. Performing analyses at more than one scale is, therefore necessary in analysing future options for resource use. This paper illustrates the use of a multi-scale method enabling assessment of multi-purpose natural resource management options. Three examples of analyses that it allows are presented for Ilocos Norte province in the Philippines, at the farm household, municipal (Batac municipality) and provincial levels. Results show that: (1) Differences in resource endowments of farm households strongly affect the potential adoption rates of five well-defined alternative technologies. (2) Limited markets, inadequate infrastructure and resource endowments of farm households have large effects on resource use and goal achievement in the municipality. Not including these factors in a resource use analysis results in a so-called aggregation bias. As these are significant, ignoring them may result in misleading simulation results and policy conclusions. The aggregation bias resulting from assuming spatially fixed input and output prices is significant for Batac, which has poor farm-to-market roads. This suggests large potential benefits from improving infrastructure. The factors investigated suggest that aggregate income in the municipality is most strongly affected by the size of the market for some vegetables. (3) The differences in resource allocations resulting from prioritizing objectives at different levels reveal potential conflicts. The municipal income was highest with crops which pose more risk to farmers; our farm household analysis shows that farmers tend not to select too much of these crops. Similarly, the provincial income is highest when resources in the province are allocated such that more of the staple crop rice and less of the highly profitable cash crops are cultivated in Batac, resulting in lower income for the municipality.     

A European irrigation map for spatially distributed agricultural modelling

We present a pan-European irrigation map based on regional European statistics, a European land use map and a global irrigation map. The map provides spatial information on the distribution of irrigated areas per crop type which allows determining irrigated areas at the level of spatial modelling units. The map is a requirement for a European scale assessment of the impacts of irrigated agriculture on water resources based on spatially distributed modelling of crop growth and water balance. The irrigation map was compiled in a two step procedure. First, irrigated areas were distributed to potentially irrigated crops at a regional level (European statistical regions NUTS3), combining Farm Structure Survey (FSS) data on irrigated area, crop-specific irrigated area for crops whenever available, and total crop area. Second, crop-specific irrigated area was distributed within each statistical region based on the crop distribution given in our land use map. A global map of irrigated areas with a 5′ resolution was used to further constrain the distribution within each NUTS3 based on the density of irrigated areas. The constrained distribution of irrigated areas as taken from statistics to a high resolution dataset enables us to estimate irrigated areas for various spatial entities, including administrative, natural and artificial units, providing a reasonable input scenario for large-scale distributed modelling applications. The dataset bridges a gap between global datasets and detailed regional data on the distribution of irrigated areas and provides information for various assessments and modelling applications.     

A conceptual framework for guiding the participatory development of agricultural decision support systems

Scientists develop decision support systems (DSSs) to make agricultural science more accessible for farmers and extension officers. Despite the growing use of participatory approaches in agricultural DSS development, reflection on this endeavour has largely focused on the ‘doing’ of participation or the ‘problem of implementation’ when DSSs have not been adopted by stakeholders. There has been little reference to relevant theoretical approaches to the social processes involved in ‘participation’ or ‘implementation’. However, if DSS use is to reach its full potential, a more conceptually informed understanding of how stakeholders collaborate in the participatory development of DSSs is required. To contribute to this conceptualisation, we developed a framework based on three concepts drawn from the field of science and technology studies: technological frames, interpretative flexibility and boundary objects. The framework highlights the importance and value of social learning for participatory DSS development, which relies upon exploring the participating parties’ different perspectives on the agricultural system represented in the DSS. Our framework provides a broad definition of success for participatory DSS development, placing greater weight on learning during the participatory process compared with subsequent use of the DSS by farmers and/or advisors. Two case studies of stakeholder collaboration to develop an irrigation scheduling DSS for sugarcane production were used to explore the relevance of the framework. The concepts in the framework were clearly displayed during the case studies. At the conclusion of the studies there were contrasting outcomes for the DSS. One group of farmers was keen to apply it in their ongoing irrigation management, while another saw little relative advantage in use of the DSS. In both instances co-learning occurred amongst case study participants, so the participatory process was clearly a success.     

Exploring global irrigation patterns: A multilevel modelling approach

Globally, areas that are equipped for irrigation have almost doubled in size over the past 50 years and further expansions are expected for the future, to meet a growing food demand. For developing countries, the Food and Agriculture Organization of the United Nations (FAO) expects these areas to be expanded by 40 million ha, by 2030. Knowledge about the constraints to irrigation and spatially explicit information about the potential for irrigation expansion, however, are lacking on a global scale. The objective of our study was to explain the global pattern of irrigated croplands and to identify cropping regions where irrigation is likely to be expanded. We accounted for biophysical determinants, such as humidity and slope, mainly at grid-cell level. Socio-economic and governance determinants, for example, Gross Domestic Product (GDP) and control of corruption, were primarily considered on a country level, given the limitations in availability of sub-national data and the role of national level governance in irrigation decisions. To identify the variability of the determinants within these two spatial levels, we conducted a multilevel analysis. This is a method employing regression models that explicitly account for hierarchically structured data. Results show significant variability in terms of irrigation. While 56% of the global variance in irrigation occurs between countries, 44% occurs within countries. Our results suggest that it is necessary to consider biophysical, socio-economic and governance information for identifying cropland areas that are likely to be under irrigation. Under current conditions, conversion from rainfed to irrigated cropland is most likely in eastern China, northern Africa, and parts of the Mediterranean region.     

An entropy approach to spatial disaggregation of agricultural production

While agricultural production statistics are reported on a geopolitical – often national – basis we often need to know the status of production or productivity within specific sub-regions, watersheds, or agroecological zones. Such re-aggregations are typically made using expert judgments or simple area-weighting rules. We describe a new, entropy-based approach to making spatially disaggregated assessments of the distribution of crop production. Using this approach, tabular crop production statistics are blended judiciously with an array of other secondary data to assess the production of specific crops within individual ‘pixels’ – typically 25–100 square kilometers in size. The information utilized includes crop production statistics, farming system characteristics, satellite-derived land cover data, biophysical crop suitability assessments, and population density. An application is presented in which Brazilian state level production statistics are used to generate pixel level crop production data for eight crops. To validate the spatial allocation we aggregated the pixel estimates to obtain synthetic estimates of municipality level production in Brazil, and compared those estimates with actual municipality statistics. The approach produced extremely promising results. We then examined the robustness of these results compared to short-cut approaches to allocating crop production statistics and showed that, while computationally intensive, the cross-entropy method does provide more reliable estimates of crop production patterns.     

A simple approach for regulating saline groundwater inflows to natural streams in irrigated agricultural areas

Stream salinity management is of prime importance for ensuring environmental sustainability of rivers, streams, lakes and other water bodies. Saline groundwater inflows are the main cause of deteriorating quality of stream flows; especially during periods of low flows. The Murray-Darling Basin is a good example for reducing groundwater recharge from irrigated agricultural areas with successful implementation of land and water management plans (LWMPs). In most cases, these plans help minimize the influence of saline groundwater flows on the stream salinity, as a preventive measure. As a remedial measure, this paper introduces a simple but an innovative approach for regulating saline groundwater inflows to natural streams in irrigated agricultural areas. The approach uses the flap gate with an automatic lowering and raising mechanism. During low stream flow, this gate is kept in a raised position. Depending upon the upstream inflows, the ponding situation will develop hydraulic gradient away from the stream; groundwater inflows to the creek will become minimal. During high stream flows, the gate is kept in a lower position to let the diluted water flows through the stream uninterrupted. To install, operate and manage such gates on multiple sites along the stream(s), the individual control panels can be joined into a central control station via telemetric link up. This approach, which holds a key for successfully regulating groundwater induced salinity to natural streams, should be considered in conjunction with other LWMPs to improve stream salinity in an irrigated agricultural area.     

Evaluation of the water use efficiency of alternative farm practices at a range of spatial and temporal scales: A conceptual framework and a modelling approach

Water is the principal limiting resource in Australian broadacre farming, and the efficiency with which farmers use water to produce various products is a major determinant both of farm profit and of a range of natural resource management (NRM) outcomes. We propose a conceptual framework based on multiple water use efficiencies (WUEs) that can be used to gain insight into high-level comparisons of the productivity and sustainability of alternative farming practices across temporal and spatial scales. The framework is intended as a data aggregation and presentation device. It treats flows of water, biomass and money in a mixed farming system; economic inefficiencies in these flows are tracked as they are associated with a range of NRM indicators.We illustrate the use of the framework, and its place in a larger research programme, by employing it to synthesise the results from a set of modelling analyses of the effect of land use choices on long-term productivity and a range of NRM indicators (frequency of low ground cover, deep drainage, N leaching rates and rate of change in surface soil organic carbon). The analyses span scales from single paddocks and years to whole farms and have been carried out with the APSIM and GRAZPLAN biophysical simulation models and the MIDAS whole-farm economic model.In single wheat crops in one study, different land uses in preceding years affect grain yield primarily by affecting the harvest index. When the scale changes to cropping rotations, the critical factor affecting overall water use efficiency is found to be the proportion of stored soil water that is transpired by crops. When ordinated in terms of their water use efficiencies, a set of 45 modelled rotation sequences at another location are differentiated mainly by the proportion of pasture in the rotation; when rotations are ordinated using key NRM indicators, the proportion of lucerne pasture is the main distinguishing factor. Finally, we show that for whole crop-livestock farms at three different locations across southern Australia, the pattern of water use efficiencies in the most profitable farming systems changes in similar ways as cropping proportion is altered. At this scale, land use choices affect multiple water use efficiency indices simultaneously and commodity prices determine the balance of the resulting economic tradeoffs.Limitations to the use of the WUE framework arising from its relative simplicity are discussed, as are other areas of farming systems research and development to which it can be applied.     

A linear programming formulation of the Markovian decision process approach to modelling the dairy replacement problem

In modelling the replacement decision in dairy herd management, the most common approach taken is to use dynamic programming to determine the optimal policy by comparing the future expected profitability of an animal to that of it's potential replacement. It does not, however, take into account the performance of the entire herd or that of all potential replacements, which is particularly important if replacements originate from the same herd. This paper demonstrates how to overcome this inadequacy by formulating the problem as a multi-component Markovian decision process and then solving it as an associated linear programming model. The proposed methodology is illustrated by using a simple, but realistic, example for determining the optimal replacement strategy for a dairy herd over a 10-year planning horizon. The results show that replacements should be bred from heifer cows in order to increase the genetic turnover; however, no more animals than is necessary should be culled to increase this turnover. It is also shown how to include considerations such as problems of milk quota management, and other similar resource allocation decisions into the model. Additional improvements to the model could involve considering culling of animals suffering from disease.     

Using a whole-farm modelling approach to assess prospective technologies under uncertainty

New technologies may be adopted by farmers if they fit farmers’ resource endowments, objectives and goals, and attitudes towards risk. In this paper, the role of whole-farm modelling in technology evaluation is discussed. An assessment of prospective technology options for wheat and sugar beet in a study region in Iran is presented. Data on new technologies were collected from farmers of Fars province, staff of the Shiraz Branch of the Agricultural Research Centre, the Regional Branch of the Extension Organization, and from the Shiraz University’s Research Centre. An extension of utility efficient programming to non-linear discrete stochastic programming, was adopted to evaluate prospective technology options. Results of the study demonstrated the merits of the technique, and it was found that farmers’ total net revenue would increase considerably if adoption was to occur.     

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.     

A field practical approach for assessing biophysical sustainability of alternative agricultural systems

Participatory research and farmer-led extension principles are employed to conduct meaningful monitoring and evaluation while working within the constraints encountered in the field by farmers and rural agents. This assessment method is characterized as Field Practical, that is, it is (1) quick, (2) inexpensive, (3) easily applied, (4) of direct and immediate relevance, and (5) a tool for stimulating project productivity. It harmonizes external expertise with local experience for biophysical sustainability assessment of proposed production alternatives in the context of the local agricultural system. This is accomplished via a Likert rating survey based on locally defined criteria and indicators and has two outputs: (1) a Summary Measure based on weighted average ratings giving indication of overall patterns of contributions to the biophysical sustainability of the agricultural system and (2) Frequency Distribution Matrices for more detailed analyses of the data. Statistical tests for differences add discriminatory power. This assessment was applied in northern Ecuador, but could be adapted to other locations.     

抓住机遇转变方式推进农机推广——丁翔文在全国农机推广站站长会议上的讲话(摘要)

今年是我国十一五的最后一年,也是我国农业生产遭受自然灾害较多的一年.沧海横流,方显出英雄本色,在这一年中,农业机械化和农机推广工作不仅在农业生产的抗旱、抗低温抢种、三夏的抢收抢种、三秋的秋收秋种等一系列生产中发挥了机械化威力和生力军的作用,保证了农业生产形势的基本稳定;而且在抗洪排涝抢险等抗灾救灾中也发挥了积极的作用,凸显了机械化快速、高效、有力的保障作用和农机化队伍敢打硬仗的作风.     

A modelling approach for analysis of agro pastoral activity at the one-farm level

A model was developed to represent the general functioning of a low input farming system in order to dispose of a tool able to simulate the effects of changes in productive and social organisation in traditional Andean rural communities. The model analyses daily agro pastoral activities of different members of an Andean peasant family, and farm crop production, across a 1-year timeframe, according to climate and labour organisation. The modelling approach uses object-oriented language, describes the objects and their relations with a unified modelling language formalism and manages time as illustrated by a sample potato crop. To demonstrate this methodology, one-farm observed and simulated data are compared within two frameworks: the cattle-feeding system, and the labour allocation system detailed by task and by gender. Results show good reliance in the first case study and, in the second case, a satisfactory overview of the agro pastoral calendar of household member workers, regarding the priorities given by peasants according to climate, land-use constraints, social organisation and out-farm activities. Due to its modularity, the object-oriented modelling approach appears to improve understanding of the general functioning of agro pastoral households by allowing multi-purpose simulations and exploring the links between social and productive activities.     

农业技术经济动态方法的适用性

农业技术经济学研究的根本目的是为了实现农业生产资源的优化配置,提高农业生产效率,发展农业生产,提高农民生活水平,保障社会对农产品的需求。净现值法和内部收益率法是农业技术经济分析中常用的两种动态方法,它们各有其优缺点和适用范围,为此对两方案进行应用上的比较,正确理解方法特点和经济含义,具有重要的实际意义。     

A simplified modelling approach for pesticide transport in a tile-drained field: The PESTDRAIN model

The paper presents a simplified model called PESTDRAIN. It simulates pesticide transport in a subsurface tile-drained field. It computes surface runoff and tile-drainage flow rates, along with the associated pesticide concentrations, with a variable event-driven time step. PESTDRAIN consists of three coupled modules: SIDRA, SIRUP and SILASOL. SIDRA and SIRUP are the water flow simulation modules in the saturated and unsaturated zones, respectively. SIDRA follows a simplified physically based approach while SIRUP follows a conceptual capacitive approach. SILASOL is the solute transport module for both the saturated and unsaturated zones and is based on transfer functions. It includes simple representations of adsorption and degradation of pesticides.PESTDRAIN was tested on field data sets collected for three drainage seasons at the La Jaillière experimental site in north-western France, for the wheat herbicides isoproturon (IPU) and diflufenican (DFF). After model calibration, relative errors for drainage and surface runoff flows over the season were 14% and 4%, respectively, and the Nash-Sutcliffe efficiency coefficient (N_eff) value for drainage discharge was 0.58. A fair reproduction of a high temporal resolution IPU concentration data set in drainage discharge was also obtained (N_eff=0.28). For the validation data sets, PESTDRAIN was able to simulate accurately drainage discharge with Nash-Sutcliffe efficiency coefficients of 0.57 and 0.69. The global N_eff was 0.44 for all flow-weighted average weekly concentrations in drainage. Relative errors for the pesticide losses were 2.5% and 35% (IPU), and 60% (DFF). For surface runoff the results were not as accurate, but they remained correct in terms of time location and order of magnitude. Although further validation is necessary with more field data, PESTDRAIN appears as a promising tool for agricultural water management.     

Technical and economic criteria in agricultural production: A case for a systems approach to farm decision-making in the Pakistan Punjab

This paper defines the criteria of ‘technical’ and ‘economic’ efficiencies. The relationship between these criteria is identified, and its implications are discussed. These two sets of criteria do diverge, with ramifications both at the farm and the national levels. An illustration of their relationship at the farm level is provided by examining the nature of water allocation to crops in the Punjab of Pakistan. The divergences that exist between ‘technical’ and ‘economic’ efficiencies at both farm and national levels are highlighted by considering the process of mechanisation in the Punjab in some detail. Finally, it is pointed out how a ‘systems approach’ can accomodate both the technical and economic criteria and their interaction.     

Assessing water consumption of banana: traditional versus modelling approach

The water consumption, expressed as ‘actual evapotranspiration’ (ET_a), plays an important role in understanding the soil–water–atmosphere–plant environment. This paper highlights two different methods to assess the water consumption of banana, a traditional and modelling approach, respectively.The first method to assess ET_a was based on the water balance equation and thus included field measurements. The second method involved the simulation model soil water atmosphere plant (SWAP). The results showed that both methods led to comparative results.This study also aimed at evaluating the performance of the SWAP-model under very different circumstances as for which it has been used previously. The uncertainty about the parameters of the SWAP model remained rather high. The most important drawback of SWAP is the enormous amount of data that is required. Since these data were not always available, this resulted in a large amount of parameters to be estimated and involved in the sensitivity analyses and calibration process. The final simulation results showed several inconsistencies. It seemed that, for successful predictions, more data were needed to describe the bottom boundary condition (BBC) of the considered soil profile in greater detail, especially when there is influence of groundwater. This BBC has indeed a great impact on the simulation results. SWAP offers several ‘simplified’ approaches concerning the BBC in case no data are available. However, in all cases SWAP seemed to overestimate the moisture content.     

An integrated ecological approach to agricultural policy-making with reference to the urban fringe: The case of Hong Kong

An integrated ecological approach to agricultural production, urban planning and food policy-making is examined in respect of the agricultural zone peripheral to large urban settlements. It is asserted that intensive agriculture at the urban-rural interface can reduce reliance on food imports from other countries, provide employment opportunities, recycle valuable urban and agricultural wastes back into the human food chain and maintain environmental amenity for the human population. The ecosystem approach to urban fringe agriculture is examined in the context of Hong Kong, a city of 4·5 million people. It is hypothesised that intensive agriculture in Hong Kong, developed in the ways specified, can provide a model for ecological management of the urban-rural interface for urban settlements in general.     

Integrating agricultural research and policy analysis: analytical framework and policy applications for bio-economic modelling

Interdisciplinary approaches to identify suitable incentives for enhancing sustainable natural resource use require an analytical framework that satisfies both practical purposes of policy support and disciplinary requirements regarding the specification of underlying technical and behavioural relations. Different approaches for agricultural policy analysis are distinguished according to the nature of problems addressed and the analytical procedures applied. Major drawbacks of more disciplinary analysis can be circumvented through functional integration of these approaches. The methodological foundations of an integrated bio-economic modelling framework for the simultaneous appraisal of agro-ecological and socio- economic parameters are presented, and assumptions on farm household decision making regarding crop and technology choice, labour use, market exchange and price responsiveness are discussed. Implications of this integrated approach are analysed against the background of policy discussions on land markets, incentives for innovation, and public investment for agricultural intensification. Policy analysis for sustainable land use proves to be critically dependent on the specification of the linkages between decision-making procedures regarding resource allocation by farm households and their supply response to changes in the economic and institutional environment.