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One challenge in predictive modelling of productivity for pastures varying in topography, soils or management is to achieve the prediction over space with acceptable accuracy. As a new modelling approach, the decision tree has been shown to have high predictive accuracy; while geographical information systems (GISs), with their strong ability to deal with spatial factors, have been widely used in environmental modelling. Integration of a decision tree approach with a GIS offers a potential solution in meeting this challenge. In this study, decision tree models were developed for annual and seasonal pasture productivity (aboveground dry matter in kg/ha) using environmental and management variables and the outputs of these decision trees were integrated with a GIS to get predictions of pasture productivity in a hill-pasture grazing system. Results showed that the decision tree model for annual pasture productivity adequately predicted 91% of cases in the model validation, and the GIS-based prediction for annual pasture productivity was verified in three of four test farmlets. The decision tree models also revealed the relative importance of environmental and management variables and their interaction in influencing pasture productivity. Hill slope, soil Olsen P and annual P fertiliser input were the most significant variables influencing annual pasture productivity, while hill slope, annual P fertiliser input, autumn rainfall and soil Olsen P were the most significant variables influencing spring, summer, autumn and winter pasture productivity, respectively. The successful integration of the decision tree model with a GIS in this study provided a platform to predict pasture productivity for pastures with heterogeneous environmental variables and management features, and to present model predictions over space for further application and investigation. This modelling approach can be used as, or incorporated in, decision support systems to improve pasture management, and to investigate the interrelationship between pasture productivity and environmental and management variables. 相似文献
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《Agricultural Systems》2007,92(1-3):295-317
The worldwide loss of utilisable rangeland in (semi-) arid areas results in huge economic and social costs. Only adaptive management strategies are able to cope with these systems, which are mainly driven by unpredictable and stochastic rainfall. The aim of the study was to investigate the relevance of rest periods as part of the management scheme in these non-equilibrium rangeland systems. The starting point of the analysis is an approved management system – the Karakul sheep-breeding Gamis-Farm (Namibia). The farmer applies a flexible strategy, which combines short-term adaptation of the stocking rate to the available forage and long-term adaptation by resting a third of the paddocks in years with sufficient rainfall.We developed a simulation model that focuses on the key dynamics of this non-equilibrium system. Beginning with the strategy used by the Gamis-Farm, a set of alternative grazing strategies was defined, all adapted to the available forage but differing in whether and when resting is granted for a part of the pasture. The effectiveness of these strategies was compared according to the long-term productivity of the pasture and the farmer’s livelihood.Our results reveal ecological settings during which resting is essential for the recovery of the vegetation in a fluctuating environment, as well as those during which it is not. The growth rates of both the vegetation and of the livestock are demonstrated to be highly influential. Rests during wet years are crucial for the regeneration of the pasture. We conclude that even though a non-equilibrium rangeland system is assumed, the application of pure opportunistic strategies – destocking in times of drought and fast post-drought restocking – are not always adequate to maintain the long-term productivity of the pasture. Rest periods are indispensable when vegetation has a low regeneration potential. On an applied level, the study emphasises that improved farming conditions (supplementary feeding, unrestricted options to purchase livestock) may run the risk of ecological as well as economic damages. 相似文献
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《Agricultural Water Management》1999,40(1):51-57
Considerable effort has gone into studying the technical, social, economic and institutional constraints on improving water management in irrigated and rainfed farming systems. Although advances have been made, it can be argued that better progress could have been achieved if more water management studies had involved interdisciplinary data analysis. Such an integrated approach has been hampered primarily by the lack of a mathematical framework that facilitates interdisciplinary data capture and analysis. Belief and decision networks can provide this framework, allowing a simple, integrated methodology for the modelling of complex systems. This paper provides examples of the application of belief and decision networks to specific water management studies in Zimbabwe and Mauritius. 相似文献
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《Agricultural Systems》1999,62(1):29-49
Rangelands are complex systems with many interacting components. Modelling such systems presents two particular and interrelated problems. Firstly, the processes involved operate on greatly differing time scales: long-term changes in rangelands typically depend on much shorter-term processes such as rainfall, vegetation growth and livestock growth. Secondly, while complex mechanistic models of single animals or small herds have been developed (also involving differing time scales, from minutes to months), extending such models to an entire multi-species rangeland is generally an intractable problem. Recently, a new modelling paradigm has been introduced which facilitates the building of ‘economical’ systems models by using the concept of a frame. Frames are chosen to represent distinct states of the system (e.g. grassland with scattered mature trees, as opposed to dense bush cover). Independent models are constructed for each frame; these models simulate the key processes identified within that frame (and may themselves be simplifications of more complex models). Rules are established for switching frames. In this paper we describe a frame-based model of a typical Southern African rangeland supporting cattle and goats. Simple quantitative models for each frame are developed from the output of a complex mechanistic model, depending on rainfall, stocking density and animal condition. Results from the overall frames model show how long-term responses of the system (in terms of production and vegetation state) to various management strategies (such as livestock sales) may be predicted, and in this way allows comparison of different management strategies. 相似文献
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A simulation model which estimates the net primary production of the ground-storey component of the extensively grazed Acacia aneaura rangelands of semi-arid Queensland, Australia, was applied to the assessment of grazing capacity. The method described represents an alternative approach to the traditional method used by land administrators. Historic climatic records for a continuous period of 25 years were analyzed for one centre. Annual live herbage biomass production fluctuated widely in relation to both climate and grund-storey condition class. Herbage biomass carryover from year to year decreased significantly as the level of herbage utilization through animal consumption increased. At a conservative level of use, herbage biomass carryover provided an important reserve to supplement the smaller amount of live biomass produced in low rainfall years. Consequently, grazing capacity was related to the total herbage biomass available to the grazing animal at the end of each summer growing period. There were only small changes in the mean value of end-of-summer peak herbage biomass crop and sheep carrying capacity over the excellent to good ground-storey condition classes. However, there was a pronounced decline in these values as condition class decreased from moderate to poor.The implications of this method assessing grazing capacity for semi-arid rangeland management and administration are discussed. 相似文献
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Thomas Nesme Nadine Brisson Franoise Lescourret Stphane Bellon Xavier Crt Daniel Plnet Robert Habib 《Agricultural Systems》2006,90(1-3):202-225
Epistics is a model combining a biophysical and a decisional model designed to generate irrigation and N fertilisation schedules in apple orchards. These techniques were chosen since they are key elements in the management of fruit tree cropping systems. The biophysical model representing water and N dynamics in orchards was based on the water and N dynamics of Stics and was completed using a crop water and N requirement estimation method adapted to orchards. It was linked to an agronomic decision rule in a combined model able to generate N fertilisation and irrigation schedules. The Epistics evaluation process dealt with numerical evaluation of state variables (water and N soil content) and qualitative evaluation of model-generated schedules. The numerical evaluation, which concerned the biophysical model of Epistics, was performed on the basis of (i) soil nitrate and water content at the end of winters 2002 and 2003, and on (ii) nitrate and water dynamics during spring and summer 2003. The mean Root Mean Squared Error (RMSE) between observed and simulated values at the end of winter was 3.3% water per horizon and 56 kg N/ha, which is relatively good owing to the high spatial and temporal variability of soil water and nitrate content. The qualitative evaluation of generated schedules was performed during interviews with farmers. Farmers were asked to evaluate the model with reference to their own practices. A sharp difference between farmers and the model concerned the beginning of the irrigation period. This suggested that the model should take into account the constraints imposed by scab and codling moth control practices and irrigation rounds. The difference between model-generated and farmers’ fertilisation practices suggested that the model may take plot vigour into account in the fertilisation decision rule. Such a study is a first step towards the design of models linking sound agronomic decision rules to crop modelling and representing interactions between practices. 相似文献
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《Agricultural Systems》2002,73(3):233-260
Recent work on decision processes on French farms and irrigated systems in Africa has shown that farmers plan their cyclical (recurrent) technical operations, and that one can model this planning process. Taking the case of cotton crop management in North Cameroon, we show that with certain adjustments, modelling of this kind can also be done for rainfed crop farming in Africa. The adjustments are needed to take account of the differences in social status between different fields on one farm and the implications of the fact that farm work is primarily manual. This produces decision models with a similar structure to that described for technical management of an annual crop break in a temperate climate using mechanised implements. Not only do these models give us a detailed understanding of the variability of farming practices, we can also classify them into categories according to weather scenarios yield level as a function of weather scenario. We show that one can attribute farms to these types of model using simple indicators concerning work organisation. By analysing North Cameroon farmers' decision processes for managing cotton crops we can thus produce an effective tool for organising technical supervision of farmers at the regional level: advisers can work with these decision model types by measuring some simple indicators at farm level to predict which types of model are applicable, without the onerous work of constructing individual decision models. 相似文献
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Advances in farming systems analysis and intervention 总被引：1，自引：0，他引：1
In this paper, we recognize two key components of farming systems, namely the bio-physical ‘Production System’ of crops, pastures, animals, soil and climate, together with certain physical inputs and outputs, and the ‘Management System’, made up of people, values, goals, knowledge, resources, monitoring opportunities, and decision making. Utilising upon these constructs, we review six types of farming systems analysis and intervention that have evolved over the last 40 years, namely: (1) economic decision analysis based on production functions, (2) dynamic simulation of production processes, (3) economic decision analysis linked to biophysical simulation, (4) decision support systems, (5) expert systems, and (6) simulation-aided discussions about management in an action research paradigm. Biophysical simulation modelling features prominently in this list of approaches and considerable progress has been made in both the scope and predictive power of the modelling tools. We illustrate some more recent advances in increasing model comprehensiveness in simulating farm production systems via reference to our own group's work with the Agricultural Production Systems Simulator (APSIM). Two case studies are discussed, one with broad-scale commercial agriculture in north-eastern Australia and the other with resource poor smallholder farmers in Africa. We conclude by considering future directions for systems analysis efforts directed at farming systems. We see the major challenges and opportunities lying at the interface of ‘hard’, scientific approaches to the analysis of biophysical systems and ‘soft’, approaches to intervention in social management systems. 相似文献
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A forage model and a cattle production model were interfaced and adapted for tropical production conditions in East Africa. The objectives of the modelling were to structure and conceptualise a complex system for better comprehension, thereby determining constraints on a traditional African grazing system. The model was designed to simulate the physical linkages between the scarce resource of forage and the outputs of cattle, meat and milk. The effects of improved management practices were examined for a traditional village livestock grazing system. Verification and validation for the baseline village herd were carried out using several different sources of data. A combination of a restricted breeding season, supplemental feeding during the dry season and a seasonal sales policy resulted in a 40% increase in net revenue to village producers above the baseline for a ten-year period. 相似文献
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Water and land resource competition and environmental degradation pose difficult questions for resource managers. In particular, the ensuing trade-offs between economic, environmental, and social factors and their spatiotemporal variability must be considered when implementing management policies. This paper describes an integrated modelling toolbox that has been developed for highland catchments – specifically the Mae Chaem catchment in Northern Thailand. This toolbox contains models of crop growth, erosion and rainfall-runoff, as well as household decision and socioeconomic impact models. The approach described advances and complements previous approaches by: considering more complex interactions between land-use decisions and the hydrological cycle; modelling household decisions based on uncertain expectations; and assessing impacts of changes not only on flows and household income, but also on subsistence production and erosion. An example of the types of trade-offs and scenarios that can be assessed using the integrated modelling toolbox is also presented. This demonstrates that for the scenarios presented, the magnitude and direction of impacts simulated by the model is not dependent on climate. Further testing of the model is demonstrated in a companion paper. Overall, the plausibility of the model is shown. 相似文献
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内蒙古自治区草地资源丰富,养羊业为自治区的主要畜牧业,通过对放牧羊只牧食行为的识别并结合GPS监测其牧食路径,可为估测放牧区域采食量分布、放牧规划和草畜平衡的研究提供理论依据。本文采用三轴加速度传感器,设计了放牧羊只牧食行为数据无线采集系统,自动采集羊只牧食的三轴加速度数据,并建立羊只牧食行为识别的BP神经网络模型、全连接深度神经网络模型和卷积神经网络模型,实现对羊只采食、咀嚼、反刍3种牧食行为的分类识别。在内蒙古自治区四子王旗白音朝克图镇半荒漠化草场的试验结果表明,BP神经网络模型、全连接深度神经网络模型和卷积神经网络模型对羊只牧食行为的平均识别率分别为83.1%、89.4%和93.8%,其中卷积神经网络模型的识别精度最高,能够满足羊只牧食行为分类识别的要求。 相似文献
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《Agricultural Systems》1999,61(3):151-164
Use of grazing is decreasing in dairy cow systems in many European countries. However, pasture has a lower production cost than most conserved forage. Furthermore, agronomic decision rules are available to provide dairy cows with sufficient quality and quantity of dry matter. The decline in use of grazing is partly due to organisational difficulties in planning the grazing period. Land use at the farm level requires that this plan must be made in September, about 6 months before the turnout date. This area planning depends on the decision rule used for the turnout date. So we propose to search for a combination of area planning and turnout decision rules that allows a dairy herd to be fed in the spring by means of grazing without any risk of an interruption in the feeding. For this we propose to use a simulation model combining a grass growth model and a model for scheduling the farmer's decisions. A test of a turnout date rule showed that it is necessary to use an area allocation decision rule that depends on the turnout date rule and not the converse. We therefore proposed another turnout date rule based on the available herbage per ha and we calculated the area to allocate on the basis of this turnout rule. 相似文献
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A systematic representation of crop rotations 总被引：1，自引：0，他引：1
M.S. Castellazzi G.A. Wood P.J. Burgess J. Morris K.F. Conrad J.N. Perry 《Agricultural Systems》2008,97(1-2):26-33
Crop rotations are allocations by growers of crop types to specific fields through time. This paper aims at presenting (i) a systematic and rigorous mathematical representation of crops rotations; and (ii) a concise mathematical framework to model crop rotations, which is useable on landscape scale modelling of agronomical practices. Rotations can be defined as temporal arrangements of crops and can be classified systematically according to their internal variability and cyclical pattern. Crop sequences in a rotation can be quantified as a transition matrix, with the Markovian property that the allocation in a given year depends on the crop allocated in the previous year. Such transition matrices can represent stochastic processes and thus facilitate modelling uncertainty in rotations, and forecasting of the long-term proportions of each crop in a rotation, such as changes in climate or economics. The matrices also permit modelling transitions between rotations due to external variables. Computer software was developed that incorporates these techniques and was used to simulate landscape scale agronomic processes over decadal periods. 相似文献
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A linear programming (LP) based optimization model and a simulation model are developed and applied in a typical diversion type irrigation system for land and water allocation during the dry season. Optimum cropping patterns for different management strategies are obtained by the LP model for different irrigation efficiencies and water availability scenarios. The simulation model yields the risk-related irrigation system performance measures (i.e. reliability, resiliency and vulnerability) for the management policies defined by the optimization model. The alternative strategies are evaluated in terms of all performance criteria (i.e. net economic benefit, equity and reliability) simultaneously through a trade-off analysis using a multi-criteria decision making method (compromise programming). For the case study of the Kankai irrigation system in Nepal, with equal preference to the objectives, a management strategy with equal share of water among the project subareas appears to be the most satisfactory alternative under water shortage conditions. The existing water allocation policy is not economically efficient. Deficit irrigation in Early paddy appears attractive under favorable hydrologic scenario, particularly if accompanied by measures to improve existing irrigation system efficiency. 相似文献
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《Agricultural Systems》1999,62(3):169-188
Appropriate selection of holistic management strategies for livestock farming systems requires: (1) understanding of the behaviour of, and interrelations between, the different parts of the system; (2) knowledge of the basic objectives of the decision maker managing such enterprise; and (3) understanding of the system as a whole in its agro-ecoregional context. A decision-support system based on simulation and mathematical programming techniques has been built to represent pastoral dairy production systems. The biological aspects (grass growth, grazing, digestion and metabolism, animal performance) are represented by simulation studies under a variety of management regimes. The outputs from the simulation runs (such as pasture utilisation, stocking rates, milk yields, fertilizer use, etc.) are used as data input to the multi-criteria decision-making models, and the latter have been used to select the management strategies which make the most efficient use of the farm's resources (i.e. land, animals, pastures). The paper discusses the effects and implications of different management scenarios and policies on the bio-economic performance of highland dairy farms in Costa Rica. Nevertheless, the model frameworks are generic and can be adapted to different farming systems or ruminant species. The effect of model formulation and sensitivity, different decision-maker objectives, and/or activity or constraint definitions on management strategy selection are also analysed. 相似文献