The efficient use of labour,land and energy in agriculture

Fossil energy-using agricultural systems may be defined as systems transferring tradeable energy resources in tradeable agricultural products by means of untradeable labour and untradeable land. The substitution of tradeable energy and untradeable labour is considered and it is shown that the energy efficiency of agricultural production systems increases with increasing control of production and increasing yields.The main conclusion is that agriculture may contribute to a more sensible use of energy by developing in a direction where as high yields as possible per hectare are obtained from as small an area as possible.     

A commentary on systems studies in agriculture

Increasingly detailed research is continually adding to information on the components of agricultural systems. The effort is not being matched by synthesis of results into recipes that could be understood by farmers, nor by prediction of the effect of adopted measures. These omissions have drawn criticism not only from farmers and their financing institutions who are left to their own devices to assemble the bits and pieces, but also from research administrators and scientists who are disappointed at the lack of impact their work makes on agricultural practice.The tardiness to synthesise components into systems is traced to a number of factors. These are changing socio-economic circumstances; modern instrumentation; the intra-disciplinary approach; vague images of production systems; lack of a common language; limited resources for research and the limitations of the conventional concepts of the law of limiting factors and of the scientific method to steer research.In recent years, system simulation has been developing into a new skill endeavouring to meet the requirements of the changing scene. Studies of whole systems incorporating the use of abstract models and using mathematics as a common language, together with the calculating capacity of computers, are providing a framework into which to fit the fragments of data. By summarising such of the information as is relevant into models of systems, both lacunae and redundancies in the data are exposed. However, verification of models through more critical evaluation of postulates and processes is required before models can be used as predictive tools.Since approximation of what agricultural systems are like and how they function is sequential, integrative, quantitative, uses all relevant data from specialised research and conventional experimentation, leans heavily on experience, and is written in a universally understood language of symbols and mathematics, the system simulation approach is commended as a methodology worthy of consideration to complement other, ad hoc procedures in assembling information purposefully and in guiding scientists, farmers and other agricultural bodies as to where their priorities lie.     

A systematic and quantitative approach to improve water use efficiency in agriculture

As the competition for the finite water resources on earth increases due to growth in population and affluence, agriculture is faced with intensifying pressure to improve the efficiency of water used for food production. The causes for the relatively low water use efficiency in agriculture are numerous and complex, including environmental, biological, engineering, management, social, and economic facets. The complexity of the problem, with its myriads of local variations, requires a comprehensive conceptual framework of the underlying physical and biological processes as the basis to analyze the existing situation and quantify the efficiencies, and to plan and execute improvements. This paper proposes such a framework, based on the simple fact that the overall efficiency of any process consisting of a chain of sequential step is the product of the efficiency (i.e., output/input ratio) of its individual component steps. In most cases of water use, a number of process chains, both branching and merging, are involved. Means to integrate the diverging and converging chains are developed and presented as equations. Upscaling from fields to regions and beyond are discussed. This chain of efficiencies approach is general and can be applied to any process composed of chains of sequential steps. Here the framework is used to analyze the systems of irrigated and dryland crop production, and animal production on rangeland. Range of plausible efficiencies of each step is presented as tables, with values separately for the poor and for the good situation of circumstances, management and technology. Causes of the differences in efficiency of each step, going from water delivery to soil water extraction, transpiration, photosynthesis, and conversion to crop biomass and yield, and to animal product are briefly discussed. Sample calculations are made to demonstrate how modest differences in the efficiencies of the component steps are manifested as large to huge differences in the overall efficiency. Based on an equation quantifying the impact of changes in efficiency of component steps on the overall efficiency, it is concluded that generally, it is more effective to made modest improvements in several or more steps than to concentrate efforts to improve one or two steps. Hence, improvement efforts should be systematic and not overly concentrated on one or two components. The potential use of the same equation as the point of departure to optimize the allocation of economic resource among the component steps to maximize the improvement in the overall water use efficiency is elaborated on. The chain of efficiencies framework provides the means to examine the current levels of efficiency along the pathways of agricultural water use, to analyze where inefficiencies lie by comparing with the range of known efficiency values in the tables presented, to assess the potential improvements that may be achieved in various parts and their impact on the overall efficiency, and to aid in the optimal allocation of resources for improvements.

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A generic model of hierarchy for systems analysis and simulation

Problems of global change and sustainable agriculture have motivated systems analyses that span increasing numbers of hierarchical levels. The reuse of existing simulation models in these expanded analyses is appealing, though experience with crop models shows that the design of the models can limit their reuse. In order to avoid these design problems, a new framework for systems analysis was developed based on hierarchy theory. The framework formalizes a metaphor used to define hierarchy: each hierarchical object (holon) is analyzed and modeled with two faces, named up and down, through which the object can communicate data; up is a portal for data exchange with the next higher level and down provides data exchange with the object's subsystems, which are also holons. This generic model of hierarchy was coded in object-oriented computer languages and was developed into a programming framework named JanuSys. JanuSys organizes communications between modeled holons and provides an orderly sequence to their simulation. The framework permits dynamic creation of a user-defined number of hierarchical levels, containing user-defined numbers of subsystems in each holon. These capabilities, combined with the generic model of hierarchy, are required for testing basic theories of hierarchy and systems evolution. If hierarchy theories are correct, JanuSys will provide a more successful foundation for systems analysis than non-hierarchic approaches.     

Management of water consumption in agriculture A model for the economic optimisation of water use: application to a sub-humid area

This paper present a set of solutions for new irrigation transformation in a sub-humid area such as Salvatierra (Alava, Spain). The research is based on the choice of crop rotation (cultivated species and its degree of participation) being able to economically optimise the use of available water for irrigation. Hence, we will be able in helping make decisions to plan, from origin, the transformation of a dry area into an irrigated area. To do this, a model of economic use of water has been used in an area with climatic features very similar to a large part of Europe, representing an interesting scenario compared to the places where the model had not been applied. Crops taking part in this rotation to optimise use of water are mainly vegetables, with high water needs, that coexist together with crops for dryland farming even in conditions of lack of water. Crops for dryland farming allow an interesting diversification of activity as well as an average resource assignment to the farms that make possible to cultivate many farms at a time, which obviously implies socio-economic benefits for the achievements in the zone.     

A simple dated water-production function for use in irrigated agriculture

Dated water-production functions are useful in evaluating alternative irrigation strategies. The dated water-production functions commonly used in irrigation-optimization models are briefly reviewed. Based on the heuristic assumption that the Boolean principle is applicable, a simple multiplicative dated water-production function is proposed. The function was compared for a number of crops, with the Stewart-Hagan-Pruitt and Jensen models. The proposed model is shown to be applicable over a wide range of stress conditions.     

Irrigation strategies to improve the water use efficiency of wheat-maize double cropping systems in North China Plain

Water is the most important limiting factor of wheat (Triticum aestivum L.) and maize (Zea mays L.) double cropping systems in the North China Plain (NCP). A two-year experiment with four irrigation levels based on crop growth stages was used to calibrate and validate RZWQM2, a hybrid model that combines the Root Zone Water Quality Model (RZWQM) and DSSAT4.0. The calibrated model was then used to investigate various irrigation strategies for high yield and water use efficiency (WUE) using weather data from 1961 to 1999. The model simulated soil moisture, crop yield, above-ground biomass and WUE in responses to irrigation schedules well, with root mean square errors (RMSEs) of 0.029 cm³ cm⁻³, 0.59 Mg ha⁻¹, 2.05 Mg ha⁻¹, and 0.19 kg m⁻³, respectively, for wheat; and 0.027 cm³ cm⁻³, 0.71 Mg ha⁻¹, 1.51 Mg ha⁻¹ and 0.35 kg m⁻³, respectively, for maize. WUE increased with the amount of irrigation applied during the dry growing season of 2001-2002, but was less sensitive to irrigation during the wet season of 2002-2003. Long-term simulation using weather data from 1961 to 1999 showed that initial soil water at planting was adequate (at 82% of crop available water) for wheat establishment due to the high rainfall during the previous maize season. Preseason irrigation for wheat commonly practiced by local farmers should be postponed to the most sensitive growth stage (stem extension) for higher yield and WUE in the area. Preseason irrigation for maize is needed in 40% of the years. With limited irrigation available (100, 150, 200, or 250 mm per year), 80% of the water allocated to the critical wheat growth stages and 20% applied at maize planting achieved the highest WUE and the least water drainage overall for the two crops.     

Integration of forestry and agriculture—A model

This paper describes a modelling approach to the allocation of land as between forestry and agriculture in the context of hill and upland. The model can be used to examine objectively the outcome of some of the stated objectives and constraints concerned with integration. Examples in the use of the model are presented.     

Smallholder farmers and forestry development: A study of rural land use in Bendel,Nigeria

The supply of forest products has lagged behind the demand in Bendel State, Nigeria. This derives from unplanned growth of wood-based industries and low capital input in afforestation programmes. Another reason has to do with the general misconception that the supply of timber to wood-based industries is solely a government venture. In the face of these problems, forest regeneration efforts within the reserves could not keep pace with the rate of timber exploitation. It is on the basis of the foregoing deficiencies of wood supply that the land outside reserve boundaries forms an alternative source of timber production.The study described in this paper explored ways of integrating tree planting into the traditional farming system. Data were collected through a questionnaire survey. A sampled population of 300 rural farmers was randomly selected from 32 settlements in Bendel State.Available data indicate high prospects for wood production by the smallholder farmers. This form of land use is favoured by the land tenure system, willingness of farmers to plant trees and the long fallow periods of between 6 and 12 years. However, successful adoption of tree planting relies heavily on cost-sharing devices between government and rural farmers, virile extension services and the possibility of free crops to generate cash flow.     

A case study in the use of soft systems methodology: Restructuring an academic organisation to facilitate the education of systems agriculturalists

A programme of reform of educational programs began at Hawkesbury Agricultural College in 1978. The new programs are based on experiential learning and systems thinking and practice and are a major departure from the previous didactic and discipline-based curricula. Problems associated with servicing the needs of the new curricula and dissatisfaction with attempts to overcome them led to a series of situation improving projects in 1983-4 that led to a radical restructuring of the School of Agriculture in 1985. The projects were guided by soft systems methodology. The projects and a subsequent evaluation of the changes are described. The way soft systems methodology and associated techniques were used to guide the process is included, and an assessment of their usefulness made by the authors.     

A simulation model of the growth of the cassava crop and its use to estimate cassava productivity in northern Australia

A simulation model of the growth of the cassava crop is described. It estimates crop establishment from temperature data, and weekly increment of total biomass and underground storage organ biomass from temperature, solar radiation, pan evaporation and rainfall data.The predictive ability of the model was tested using data from time of planting and irrigation experiments conducted in South-East Queensland, Australia. The predicted values were close to those obtained in the field experiments. The model was then used to estimate productivity at different locations in northern Australia. Two limiting factors for cassava production are low temperature in winter in the southern area and low rainfall in general.     

Salt River Project experience in conversion from agriculture to urban water use

Salt River Project (SRP) was established in 1903 to deliver water to farms on about 250,000 ac (100,000 ha) located in South-Central Arizona. While SRP continues to deliver water to the entire area, today only about 10% of that land is still in agriculture. The remainder has been urbanized. Urbanization of the vast majority of water service area has caused SRP to rethink and adjust every aspect of its business, from daily operation and maintenance to the overarching issues of liability and public involvement. Some of the issues being addressed and lessons learned are addressed in this paper.     

Local land use strategies in a globalizing world: Subsistence farming,cash crops and income diversification

This paper introduces the special issue, which deals with local rural people’s responses to external and internal pressures brought about by global change processes. The contributions are grouped in three categories: (1) Deforestation, land use change and local management systems, including papers on the spread of an alien wattle species in South Africa, large scale forest conservation and rehabilitation in China and consequences of government efforts to reverse deforestation in Indonesia; (2) Subsistence farming and cash crop interaction, addressed by two articles on swidden systems in Malaysia and Indonesia; and (3) Land use change and income diversification, which includes two contributions on changing livelihoods of farmers in Tanzania and Papua New Guinea and one paper developing a method for identifying and mapping the spatial distribution of farming systems in Vietnam. All articles were originally presented at an International Conference in Copenhagen, Denmark in 2003, under the auspices of the Danish University Consortium on Environment and Development - Sustainable Land Use and Natural Resource Management (DUCED SLUSE).     

Integration of legume trees in maize-based cropping systems improves rain use efficiency and yield stability under rain-fed agriculture

Water availability is a major constraint to crop production in sub-Saharan Africa (SSA) where agriculture is predominantly rain-fed. This study aimed to investigate the effect of the nitrogen-fixing legume tree Leucaena (Leucaena leucocephala) and inorganic fertilizer on rain use efficiency (RUE), a robust measure of productivity and land degradation, in three long-term (11-12 years) experiments conducted in Zambia and Nigeria. On the two Zambian sites, sole maize (Zea mays) grown continuously (for 11-12 years) with the recommended fertilizer achieved the highest RUE (3.9-4.6 kg ha⁻¹ mm⁻¹) followed by maize intercropped with Leucaena (2.5-3.4 kg ha⁻¹ mm⁻¹). This translated to 192-383% increase in RUE over the control (maize grown without nutrient inputs), which is the de facto resource-poor farmers’ practice. RUE was more stable in fully fertilized sole maize on the first Zambian site and not statistically different from the maize-Leucaena associations on the second site. On the Nigerian site, RUE was higher in maize planted between Leucaena hedgerows supplemented with 50% of the recommended fertilizer (3.9 kg ha⁻¹ mm⁻¹), maize grown between Leucaena hedgerows without fertilizer (3.0 kg ha⁻¹ mm⁻¹) and sole maize receiving the recommended fertilizer (2.8 kg ha⁻¹ mm⁻¹), which translated to increases in RUE of 202%, 139% and 85%, respectively, over the control. RUE was more stable in the maize grown between Leucaena hedgerows than in the fully fertilized maize. On all sites RUE was least stable in the control. Yield stability in the maize-Leucaena association was not significantly different from the fully fertilized maize on the Zambian sites. On the Nigerian site, maize yields were more stable in maize grown in Leucaena hedgerows than in fully fertilized sole maize. Supplementation of maize grown in Leucaena hedgerows with 50% of the recommended fertilizers resulted in greater yield stability. It is concluded that intercropping cereals with legume trees and supplementation with inorganic fertilizer can increase rain use efficiency and yield stability in rain-fed agriculture in SSA.     

A model of decision-making and information flows for information-intensive agriculture

This paper describes the development of a systems based model to characterise farmers’ decision-making process in information-intensive practices, and its evaluation in the context of Precision Agriculture (PA). A participative methodology was developed in which farm managers decomposed their process of decision-making into brief decision statements along with associated information requirements. The methodology was first developed on a university research farm in Denmark and further revised during testing on a number of research and commercial farms in Indiana, USA. Twenty-one decision-analysis factors were identified to characterise a farm manager’s decision-making process. Then, a general data flow diagram (DFD) was constructed that describes the information flows “from data to decision”. Illustrative examples of the model in the form of DFDs are presented for a strategic, a tactical and an operational decision. The model was validated for a range of decisions related to operations by three university farm managers and by five commercial farmers practicing PA for cereal, corn and soybean production in Denmark and in Indiana, USA.     

Application of simulation technique to activity-based costing of agricultural systems: a case study

The aim of this paper is to analyse the operational costs of the Pu-Shin wholesale fish market in Taiwan, using both the activity-based costing (ABC) model and the simulation technique. By using simulation results in the calculated model of ABC, allocated resource costs are more accurate and arbitrary allocation is avoided. The objective of this study is to compute the processing cost per kilogram of fish. We conclude by providing relevant and accurate information about cost management of the Pu-Shin wholesale fish market, comparing ABC with traditional costing methods, and discussing key related issues which may provide opportunities for future research. We believe that the use of the ABC model in conjunction with simulation techniques can also be applied to agricultural systems in other countries.     

Quantification of land use systems using technical coefficient generators: a case study for the Northern Atlantic zone of Costa Rica

This paper describes two generic so-called technical coefficient generators, PASTOR (Pasture and Animal System Technical coefficient generatOR) and LUCTOR (Land Use Crop Technical coefficient generatOR), that quantify land use systems in terms of inputs and outputs based on the integration of systems-analytical knowledge, standard agronomic and animal husbandry data and expert knowledge. PASTOR quantifies livestock systems while LUCTOR is geared towards cropping systems. Main inputs quantified include costs, labour requirements, fertiliser use and application of crop protection agents. Outputs are production and a number of associated environmental indicators. Although both PASTOR and LUCTOR were developed to generate input data for land use models, they are also useful as stand-alone tools to explore the technical efficiency of land use systems, to perform cost-benefit analyses and to quantify the trade-off among socio-economic, agronomic and environmental indicators at the field level. PASTOR and LUCTOR are illustrated with data from the Northern Atlantic zone in Costa Rica. Tools such as PASTOR and LUCTOR integrate different types of knowledge, including non-documented knowledge from field experts and make that knowledge transparent and open to critical review and discussion by others.     

Agricultural land management strategies to reduce phosphorus loads in the Gippsland Lakes, Australia

A target to reduce phosphorus flows into the Gippsland Lakes in south-eastern Australia by 40% in order to improve water quality has previously been established by stakeholders. This target, like many others worldwide, has been set mostly on the basis of environmental concerns, with limited consideration of issues such as technical feasibility, socio-economic constraints, political factors and associated costs and benefits. An integrated analysis at the catchment scale is undertaken to assess the agricultural land management changes required to achieve this target, and to evaluate the cost-effectiveness of these changes. Based on assumptions used, it appears technically feasible to achieve a 40% reduction in P load entering the Lakes. However, the least-costly way of doing so would require around A$1 billion over 25 years, a dramatic increase in the current levels of funding provided for management. Results of a sensitivity analysis indicate that there is little or no chance of investment in a 40% reduction being cost-effective. On the other hand, a 20% P reduction could be achieved at much lower cost: around $80 million over 25 years and requiring more modest land-management changes. Reliance on voluntary adoption of ‘Current Recommended Practices’ is unlikely to deliver changes in management practices at the scale required to have sufficient environmental impacts. Enforcement of existing regulations for the dairy industry would be amongst the most cost-effective management strategies. The major implications of this work for agriculturally induced diffuse-source pollution include the need for feedback between goal setting and program costs, and consideration of factors such as the levels of landholder adoption of new practices that are required and the feasibility of achieving those adoption levels. Costs, landholder adoption of new practices and socio-political risks appear neglected in the formulation of many water quality programs. The study provides a demonstration of an approach to integrated multidisciplinary research addressing complex environmental problems with multiple decision makers, multiple stakeholders, and high uncertainty. On the evidence of experience in this study, the approach deserves consideration in other contexts.