M.K. van Ittersum

On approaches and applications of the Wageningen crop models

Abstract Since the pioneering work of C.T. de Wit in the 1960s, the Wageningen group has built a tradition in developing and applying crop models. Rather than focusing on a few models, diversity is its trademark. Here we present an overview of the Wageningen crop and crop-soil modelling approaches along three criteria. The first criterion relates to the production situations the models are dealing with (i.e. potential, water and/or nutrient-limited, and actual production situations including pests, diseases and weeds). Second, models differ as a result of the objectives of model development, and hence required scale and degree of detail and comprehensiveness. Third, models have at least three potential application domains, i.e. research, education and support of learning and decision making processes. We describe both summary and more comprehensive modelling approaches for the major production situations. An overview of most of the Wageningen models is presented together with a more detailed description of LINTUL, SUCROS, ORYZA, WOFOST and INTERCOM. Illustrations for each of the three application domains are presented, i.e. plant type design, guiding experimental research, education, yield gap analysis, evaluation of manure policies, crop growth monitoring system and analysis and design of farming and regional land use systems. We discuss common issues of model verification, model validation, model validity and data requirements, and present information on software implementation, model and software documentation and distribution policy. Finally, we reflect upon the Wageningen modelling approaches and identify a number of key issues for future research. Major achievements of Wageningen modelling efforts include (1) a broad variety of approaches for modelling of systems at different scales and with different purposes; (2) their contribution to quantitative systems thinking in general, also for applications at higher hierarchical levels; (3) a strong linkage between crop modelling and higher education, both at undergraduate, graduate and post-doctoral level. To continually increase our understanding of crops and production systems a diversified approach must be cherished. At the same time we conclude that focus is required on a limited number of modules in a more integrated modelling framework for the benefit of analysing, evaluating and designing cropping systems. This review may be instrumental in the development of such an integrated framework.

Concepts in production ecology for analysis and quantification of agricultural input-output combinations.

Definitions and concepts of production ecology are presented as a basis for development of alternative production technologies characterized by their input-output combinations. With these concepts the relative importance of several growth factors and inputs is investigated to explain actual yield levels and resource-use efficiencies. Differences between potential and actual levels are analyzed to open ways for improved production technologies. The basis of the analysis is knowledge of basic physical, chemical, physiological and ecological processes at soil, field and crop level. New production technologies and their input-output combinations can be used in studies aimed at the exploration of options for sustainable agricultural production systems and land use. The concepts allow a systematic analysis and quantification of input-output combinations and clearly discriminate between bio-physical possibilities and socio-economic constraints and objectives. They help in defining objectives and means for agricultural production and land use, and may be valuable as aids to communication between various disciplines involved in studying the possibility and feasibility of future production technologies and land use options. The concepts production level, physical environment, target-oriented approach, production technique, production activity, and production orientation are applied to identify new technologies and production systems at various levels of scale, each requiring different types of information. In this paper some examples of applications are given at field, farm and at regional level.

Exploring multifunctional agriculture. A review of conceptual approaches and prospects for an integrative transitional framework

In the last decade the multifunctional agriculture (MFA) concept has emerged as a key notion in scientific and policy debates on the future of agriculture and rural development. Broadly speaking, MFA refers to the fact that agricultural activity beyond its role of producing food and fibre may also have several other functions such as renewable natural resources management, landscape and biodiversity conservation and contribution to the socio-economic viability of rural areas. The use of the concept can be traced to a number of wider societal and political transformation processes, which have influenced scientific and policy approaches in different ways amongst countries and disciplines. This paper critically discusses various existing research approaches to MFA, both from natural and social sciences. To this aim different strands of literature are classified according to their focus on specific governance mechanisms and levels of analysis into four main categories of research approaches (market regulation, land-use approaches, actor-oriented and public regulation approaches). For each category an overview of the state-of-the-art of research is given and an assessment is made of its strengths and weaknesses. The review demonstrates that the multifunctionality concept has attracted a wealth of scientific contributions, which have considerably improved our understanding of key aspects of MFA. At the same time approaches in the four categories have remained fragmented and each has limitations to understand MFA in all its complexity due to inherent constraints of applied conceptualizations and associated disciplinary backgrounds. To go beyond these limitations, we contend, new meta-level frameworks of analysis are to be developed that enable a more integrated approach. The paper concludes by presenting the main lines of an integrative, transitional framework for the study of MFA, which analyses multifunctional agriculture against the background of wider societal change processes towards sustainability and identifies a number of key elements and research challenges for this.

Residual soil phosphorus as the missing piece in the global phosphorus crisis puzzle

Phosphorus (P) is a finite and dwindling resource. Debate focuses on current production and use of phosphate rock rather than on the amounts of P required in the future to feed the world. We applied a two-pool soil P model to reproduce historical continental crop P uptake as a function of P inputs from fertilizer and manure and to estimate P requirements for crop production in 2050. The key feature is the consideration of the role of residual soil P in crop production. Model simulations closely fit historical P uptake for all continents. Cumulative inputs of P fertilizer and manure for the period 1965–2007 in Europe (1,115 kg⋅ha−1 of cropland) grossly exceeded the cumulative P uptake by crops (360 kg⋅ha−1). Since the 1980s in much of Europe, P application rates have been reduced, and uptake continues to increase due to the supply of plant-available P from residual soil P pool. We estimate that between 2008 and 2050 a global cumulative P application of 700–790 kg⋅ha−1 of cropland (in total 1,070–1,200 teragrams P) is required to achieve crop production according to the various Millennium Ecosystem Assessment scenarios [Alcamo J, Van Vuuren D, Cramer W (2006) Ecosystems and Human Well-Being: Scenarios, Vol 2, pp 279–354]. We estimate that average global P fertilizer use must change from the current 17.8 to 16.8–20.8 teragrams per year in 2050, which is up to 50% less than other estimates in the literature that ignore the role of residual soil P.

Exploratory land use studies and their role in strategic policy making.

To support the different phases of a policy making process aimed at changing land use, distinct types of land use studies are required. This paper focuses on exploratory land use studies and their role in the phase of formulating strategic policy objectives. Exploratory land use studies contribute to a transparent discussion on policy objectives by showing ultimate technical possibilities and consequences of imposing different priorities to agro-technical, food security, socio-economic and environmental objectives. A methodology is presented in which science-driven technical information is confronted with value-driven objectives under given values of exogenous variables (e.g. regarding population growth and requirements for agricultural produce). Land use scenarios are generated showing consequences of different priorities for objectives by using natural resources and technical possibilities in different ways. Applications of such an approach are given for the global, regional and farm level, each addressing specific questions and target groups. The paper focuses on the type of results these studies produce and their role in the societal and political debate on strategic land use policy and planning. It is concluded that if exploratory land use studies are carried out in true interaction with target groups, they may well contribute to the debate and learning on sustainable land use options and a purposeful identification of effective policy instruments in a next phase of the policy making process.

rotat, a tool for systematically generating crop rotations

Abstract This paper reports part of a methodology for a model-based exploration of land use motivated by the lack of sustainability of small farming systems in southern Uruguay. Explorative land use studies aim to gain insight into future possibilities for agricultural development. They support strategic thinking during the design of new farming systems. The crop rotation plays a central role in a farming system and represents a logical starting point in the design process. The combination and sequence of crop species determine characteristics of farming systems such as crop yields, soil erosion, occurrence of soil-borne pests, diseases and weeds, and dynamics of nitrogen and labour. Here, we present a software tool called rotat , designed for generating crop rotations based on agronomic criteria in a transparent manner. The program combines crops from a predefined list to generate all possible rotations. The full factorial number of possible combinations of crops is limited by a number of filters controlled by the user. These filters are designed to eliminate crop successions which are agronomically unfeasible and for farm-specific reasons not practical or desirable. The filters represent expert knowledge in a quantitative and explicit way. The use of this computer program as a stand-alone tool in the process of designing crop rotations is illustrated with a published case study from an ecological pilot farm in Flevoland (The Netherlands). Using this software we were able to design 840 rotations based on the same crops and designing criteria that were used for the example farm. Many of these rotations might be interesting alternatives to the one actually implemented. Coupled with a sound procedure to evaluate the performance of such a large number of rotations ‘a priori’, rotat can reduce the risk of ignoring promising options and the arbitrariness present in previous studies dealing with design of rotations. The usefulness of rotat for designing production activities in explorative land use studies based on linear programming is discussed.

Farming options for The Netherlands explored by multi-objective modelling

Abstract Intensive agriculture in The Netherlands has a price in the form of environmental degradation and the diminution of nature and landscape values. A reorientation of farming is needed to find a new balance between economic goals and rural employment, and care for clean water and air, animal well-being, safe food, and the preservation of soil, landscape and biodiversity. The search for farm systems that meet such multiple goals requires a systematic combination of (a) agrotechnical, agroecological and agroeconomic knowledge, with (b) the stakeholders’ joint agreement on normative objectives, to arrive at conceptual new designs followed by (c) empirical work to test, adapt and refine these under real commercial farming conditions. In this paper explorative modelling at the whole farm level is presented as a method that effectively integrates component knowledge at crop or animal level, and outlines the consequences of particular choices on scientific grounds. This enables quantitative consideration of a broad spectrum of alternative farming systems, including very innovative and risky ones, before empirical work starts. It thus contributes to a transparent learning and development process needed to arrive at farm concepts acceptable to both entrepreneurs and society. Three case studies are presented to illustrate the method: dairy farming on sandy soils; highly intensified flower bulb industry in sensitive areas in the western Netherlands; and integrated arable farming. Trade-offs between economic and environmental objectives were assessed in all three cases, as well as virtual farm configurations that best satisfy specified priority settings of objectives. In two of the three cases the mutual reinforcement and true integration of modelling and on-farm empirical research appeared difficult, but for obvious reasons. Only in the flower bulb case was the explorative approach utilized to its full potential by involving a broad platform of stakeholders. The other two case studies lacked such formalised platforms and their impact remained limited. Three critical success factors for explorative modelling are identified: to cover a well-differentiated spectrum of possible production technologies; early timing of modelling work relative to empirical farm prototyping; and involvement of stakeholders throughout.

Integration of Systems Network (SysNet) tools for regional land use scenario analysis in Asia

Abstract This paper introduces the approach of the Systems research Network (SysNet) for land use planning in tropical Asia with a focus on its main scientific–technical output: the development of the land use planning and analysis system (LUPAS) and its component models. These include crop simulation models, expert systems, GIS, and multiple goal linear programming (MGLP) models for land evaluation and optimization. LUPAS was designed as a decision support system (DSS) for strategic land use planning. Integration of LUPAS components in four case studies was performed in a network with national research teams and local stakeholders. This network allowed iterative evaluation and refinement of LUPAS for scenario analysis on technical and policy changes. Several interactive sessions with stakeholders led to more detail in scenarios (goals and constraints), model features and databases. To facilitate negotiation among stakeholders, the MGLP user interface (UI) was developed. In interactive sessions, goal restrictions are tightened to quantify trade-offs between conflicting goals. Choice and degree of tightening reflect the specific priorities for sustainable land use. The development of LUPAS is exemplified for one case study, Ilocos Norte, Philippines. Weak points of the system include inadequate spatial differentiation of socio-economic characteristics, scarce database for quantifying perennials and mixed cropping systems, and insufficient consideration of long-term effects of production technologies on resource quality. However, a promising perspective for effective policy support lies in the possible link of the regional LUPAS approach with farm household models.

Long-term global availability of food: continued abundance or new scarcity?

Abstract During the 20th century hunger has become a problem of poverty amidst plenty rather than absolute food scarcity. The question is whether this will remain so or whether the hunger of the poor will once more be exacerbated by rising food prices. In this paper we discuss biophysical conditions, social forces and non-linear interactions that may critically influence the global availability of food in the long term. Until 2050, the global demand for primary phytomass for food will more than double, while competing claims to natural resources for other purposes (including biobased non-foods] will increase. A sober assessment of the earths biophysical potential for biomass production, which recognizes competing claims and unavoidable losses, suggests that this is in itself still large enough for accommodating this rising demand. However, the exploitation of this biophysical potential proceeds through technical paradigms that set a relative maximum to food production. In addition, socio-economic mechanisms make the food economy run up against a ceiling even before this maximum is reached. As a consequence, current developments may well entail a new trend change in international markets. These developments include the depletion of land and water reserves, the stagnation of the potential yields of major crops, the rise in energy prices, and the way in which systemic socio-economic factors lead to a strong underutilization of production possibilities in the developing world. Given these conditions, the avoidance of steep rises in food prices may depend on the timely relaxation of socio-economic constraints in developing countries and on timely breakthroughs in sustainable yield increases, biorefinement and non-farm production systems. Myopic expectations make it doubtful whether spontaneous market forces will provide the necessary incentives for this, which may be reason for societal actors to consider the need for more active policies.

Model-based explorations to support development of sustainable farming systems: case studies from France and the Netherlands.

Abstract Sustainable land use requires development of agricultural production systems that, in addition to economic objectives, contribute to objectives in areas such as environment, health and well-being, rural scenery and nature. Since these objectives are at least partially conflicting, development of sustainable farming systems is characterized by negotiation about acceptable compromises among objectives. Four phases can be distinguished in the course of farming systems development: diagnosis, design, testing and improvement, and dissemination. During the last decade an approach coined ‘prototyping’ has emerged as a promising method for empirical farming systems development in Western Europe. Limitations of the approach include: (1) the limited number of systems that can be evaluated, resulting in a lack of perspective on conflicts among objectives, and (2) the expertise-based nature of rules used during systems design which unduly narrows the range of available options and obscures understanding of systems behaviour. In the paper, explorative studies based on transparent models of agronomy and management are put forward to supplement empirical prototyping and to remedy its shortcomings. To illustrate the potential of model-based explorations, two case studies are presented. The first case study deals with diagnosis and design of wheat-based rotations in the Paris Basin of France, aimed at alleviating tactical problems of poor resource-use efficiency within the constraints imposed by existing crop rotations. The second case study addresses design of sustainable bulb-based farming systems in the Netherlands with the purpose of investigating strategic options at crop rotation and farm level to resolve conflicts between economic and environmental objectives. In the discussion, methodological elements of model-based explorations and interaction with stakeholders are addressed, and opportunities for enhanced development of sustainable farming systems are identified.