N. de Ridder

Some aspects of the role of organic matter in sustainable intensified arable farming systems in the West-African semi-arid-tropics (SAT.

In this paper the role of organic manure in intensified farming systems in the SAT of West-Africa is discussed. Different aspects are treated: its function as a source of plant nutrients, its effects on soil physical and on soil chemical properties. It is concluded that often the major effect is through increased nutrient supply, but that in combination with chemical fertilizer — particularly nitrogen — it serves to counteract the negative effects of these fertilizers, particularly acidification and the increased removal of nutrients other than the one applied in the fertilizer.Insufficient organic material appears to be available to realize the required production increase and prevent the negative effects of nitrogen fertilizers. However, application of chemical fertilizer alone can lead to sustainable production systems provided export and losses of all nutrient elements are sufficiently compensated and acidification is avoided by using the correct type of nitrogen fertilizer, possibly in combination with liming.

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.

Socio-ecological niche: a conceptual framework for integration of legumes in smallholder farming systems

There are numerous examples of technologies with great potential that have not been accepted by smallholder farmers. Quite often, these technologies do not fit well into smallholder systems due to the inherent high level of heterogeneity of these systems. For example, despite their great potential, the adoption of legumes by smallholder farmers in many parts of sub-Saharan Africa has remained poor. A wide range of biophysical (e.g. climate, soil fertility, etc.) and socio-economic variables (e.g. preferences, prices, production objectives etc.) influence the use of legumes in smallholder systems. While some of these variables constrain the adoption of some legumes, others offer opportunities for beneficial use of other legumes in the same system. Therefore, widespread adoption of legumes in smallholder systems can only be achieved if all of the major biophysical and socio-economic constraints are simultaneously identified and addressed. The ‘socio-ecological niche’ concept proposed in this paper provides the framework through which this might be achieved. The socio-ecological niche, in any given region of agricultural activity, is created by the convergence of agro-ecological, socio-cultural, economic and ecological factors, to describe a multidimensional environment for which compatible technologies can be predicted. The socio-ecological niche concept can be applied in many different contexts in technology development. However, this paper discusses its use with respect to the development of legume technologies. Two case studies are presented to illustrate the concept and to demonstrate its practical significance. The concept is being used in on-going research on legumes in smallholder farming systems in western Kenya.

Concepts in production ecology for analysis and design of animal and plant-animal production systems

Abstract The use of a hierarchy in growth factors (defining, limiting and reducing growth factors), as developed for plant production has shown its usefulness in the analysis and design of plant production systems. This hierarchy presents a theoretical framework for the analysis of biophysical conditions in plant production. We hypothesize that analysis and design of agricultural land use systems is facilitated by development of a similar set of production ecological concepts for animal production, as livestock is often part of such systems. In this paper we present such a hierarchy. We identify growth defining (temperature, daylength, animal genetic characteristics), limiting (water and feed quantity and quality) and reducing (diseases, pollutants and other conditions leading to sub-optimal wellbeing) factors, determining the production of an individual animal, in parallel to their definition for crop production, and aggregate this production to herd scale. We discuss how management intervenes with these factors. Application of the production ecological concepts in design of land use systems ensures that all production systems are based on the prevailing biophysical characteristics and that intrinsic system properties are taken into account. This approach also provides a valuable framework for yield-gap analysis, explaining current production levels, and identifying constraining factors, for setting the research agenda by identifying knowledge gaps and for educational purposes. We illustrate application of the concepts in the exploration and design of alternative animal and mixed plant–animal production systems with two examples. The first example relates to potential production in intensive dairy farming in a temperate climate and the second to feed-limited cattle production in the tropics.

Relationship between vegetation growth rates at the onset of the wet season and soil type in the Sahel of Burkina Faso: implications for resource utilisation at large scales

In the Sahel, poor soil quality and rainfall levels have a great influence on pasture production and hence on secondary output. In areas where rainfall is the limiting factor for primary production, recovery of primary and secondary production after the dry season depends on soil type. On sandy soils a large fraction of rainfall infiltrates and becomes available for plant growth, stimulating fast herbage growth, while on clayey and loamy soils low infiltration rates generate runoff, leading to slower herbage growth rates. The very different moisture retention characteristic of sands and clays is another possible cause for the observed differences in growth rates. In this paper we investigate the herbage growth rate from the onset of the rainy season. We hypothesise that, in areas where rainfall is the limiting factor for primary production, the vegetation growth rate on clayey soils is lower than that on sandy soils. We will test this hypothesis using long-term rainfall, soil types and satellite derived normalised difference vegetation index data. This research shows that the growth rates on sandy soil are significantly greater than that on clayey soils during the early part of the rainy season. We also show that these differences can be detected at large scales using satellite imagery. We also conclude that, at this scale, movement strategies of pastoralists would be intrinsically linked to not only rainfall patterns and distribution, but also to the underlying soil types in the region as this affects the quality and quantity of fodder available.

Energy and protein balances in traditional livestock systems and ranching in eastern Botswana

Abstract Gross energy and crude protein balances of cattle in traditional systems and ranching in eastern Botswana have been estimated. The calculations show that ranching is more productive on a per animal basis while traditional systems are more productive on a per hectare basis. Ranching appears to be more efficient than traditional systems in terms of animal gross energy produced per unit of gross energy used for maintenance. Traditional systems, on the other hand, appear to be more efficient in terms of animal gross energy produced per unit of plant energy produced, and in terms of food chain efficiency. The same conclusions were drawn when crude protein balances were considered. The risk of pasture degradation might be greater at the higher stocking rates found in traditional systems, and feed shortages might occur more often, but lower stocking rates and ranch-type changes in product allocation in these systems would most probably lead to lower productivity per hectare. Consequently, this would lead to lower food production and less employment on a national scale. A socio-economic analysis at a national level is urgently needed to be able to weigh the advantages and disadvantages of the development of ranching at the cost of traditional systems.

Analysis of environmental and species effects on the magnitude of biomass investment in the reproductive effort of annual pasture plants

SummaryIn annual pastures utilized for grazing, the amount and quality of the standing dry matter in the dry season is of importance for the performance of the animals. Often both characteristics decline at the end of the green season. It is shown, that dispersal of the reproductive structures of the vegetation may be the main reason for this phenomenon. Determination of the reproductive effort of the annuals indicates that the proportion of their total production invested in reproductive tissue may be as high as that of cultivated species. It is shown that the harvest index (or seed ratio) of annual species is closely related to nutrient (mainly nitrogen) transfer from vegetative organs to the reproductive organs in the period between flowering and maturity, when in most cases, additional uptake of nitrogen from the soil is negligible. The effect of environmental and genetic effects on these processes is discussed.

Estimating biomass through transfer functions based on simulation model results: a case study for the Sahel

Abstract Current methods to estimate biomass as a basis for carrying capacity and secondary production include biomass measurements in the field, use of rainfall /biomass relations and simulation models. Each of the methods have their drawbacks. Collection of field data is laborious, rainfall /biomass relations lack precision and models, which simulate processes, are highly-demanding in input data, expertise and advanced equipment. An approach is presented to bridge the gap between those simulation models and the need for more accuracy in simple biomass estimates at less detailed scales. Transfer functions are developed using the results of a process-simulation model called SAHEL. The transfer functions allow estimation of the depth of wetting of the soil profile and percolation in relation to the water content at field capacity (pF 2.5). In comparison with simple rainfall-biomass relations, application of transfer functions allow more accuracy in estimating biomass production at a less detailed scale. With the transfer functions length of growing periods could be established more accurately, allowing for more precision in agro-ecological zoning methods.

Role of an explorative model for learning about sustainable agricultural development in Burkina Faso

Agricultural development is complex, highly dynamic and differs among varying contexts. Decision-making for sustainable agricultural development cannot be based on generalized science-based knowledge, but should include context-specific knowledge and values of local stakeholders. Computer models seem a useful tool to integrate scientific knowledge include local-specific data, and explore local-specific solutions. In this paper we study whether and how a multiple goal linear program (MGLP) model could enhance learning for sustainable development. According to the learning theory, multi-actor learning is only productive when it consists of first-order (experiential) learning and second-order (social) learning. We applied an action-research approach and explored the value of an MGLP model SHARES (SHAred RESources) for learning by agricultural extension staff and farmers in an integrated rural development project in Burkina Faso. Fieldwork showed the main value of SHARES in the capacity to generate farm scenarios and trigger second-order learning about tacit frames-of-reference. People rarely engage in second-order learning, but pursue different objectives and often remain trapped in confusing discussions and action. SHARES was a critical boundary-spanning object that facilitated communication between farmers and agricultural staff, enhanced mutual understanding, and the determination of area- and category-specific farm development goals.

A FLOWMETER FOR LOW DISCHARGES OF LABORATORY FLUMES

Discharge measurements over a range from 1 L/s to as low as 0.03 L/s require special instruments. A flowmeter was designed on the basis of theoretical analysis and two major design criteria: (1) the flowmeter should be accurate and flexible in monitoring the full range of indicated discharge rates, and (2) instantaneous measurements of hydrographs should be possible. Furthermore, the relationship between the observed water level in the flowmeter and the actual discharge was linearized to the maximum extent possible. This article describes the design and test results. The calibration data from four flowmeters show that the design fulfills the above criteria and is replicable.