The production of perennial crops involves planting, removal, yield, and time dimensions not similarly encountered in annual crops. A model is developed to provide a structural base for estimating response relationships that encompass these dimensions. The model rests on assumptions of rational producer behavior which takes account of possible actions of other producers and of the aggregate effect of these actions on total production and profits. Because important data series often are not available, modifications of the basic model are suggested to facilitate estimation within a more restricted empirical framework. The model is illustrated by an application to asparagus, a perennial vegetable crop. I N VIEW OF the rather extensive volume of literature pertaining to agricultural supply response, the special problems associated with formulating supply models for perennial crops have until very recently received surprisingly little attention.' Prior to 1960 there were almost no attempts to estimate such supply functions.> Some new ground was broken in a 1962 study by French and Bressler [14] which developed supply response for lemons in terms of new planting and removal relationships. This type of model developmen t, with modifications or simplifications, was later applied by other researchers to United States apples [8], cherries [11], pears [24], and tung nuts [18], with varying success. Much of the recent research on perennial crop supply response has related to commodities typically produced in less developed areas-mainly coffee, cocoa, and rubber. Studies by Arak [2, 3], Bateman [4,5], and Behrman [6] in particular have made significant advances in formulating perennial crop supply models, with special reference to these tropical or warm area commodities.
services-actually operate. Incorporation of modifications in the conventional theory then provides a more workable base for studies of cost and efficiency.
Technical assistance is provided to country governments as part of international development programmes to support policymaking or strengthen state capability. This article presents the conceptual evolution of ‘technical assistance’ linked to capacity development, starting with programmes aiming exclusively to enhance individual capacity in the 1950s to 1970s and progressing to complex systems approaches in the past ten years. It also presents some of the frequent challenges in designing and implementing technical assistance, drawing from the existing literature and the authors’ experience in international development. The article summarises the latest thinking about delivering more effective development, including the adaptive management practices and the initiatives to strengthen evidence about what works. Finally, we complement this article with a follow-up open letter reflecting on the current policy options and opportunities for change.
The biogeochemical behavior of Pt and Pd in coastal sediments has been examined in a series of microcosms, both in the presence and absence of the deposit-feeding invertebrate, Arenicola marina. When metals were introduced to the overlying water column as solutes from acidified standards, A. marina dramatically enhanced their sorption to sediment throughout the core depth (14 cm) compared with an unfaunated control by exposing a greater surface area of particles to more rapidly ventilating contaminated water. After a 10 day incubation period, the assimilation efficiency (AE) by A. marina was about 10% for Pt and 1% for Pd. Calculations based on either partition constants or operational measures of metal bioaccessibility in sediment (using the protein, BSA) suggested that both aqueous and dietary sources of metal were important When Pt and Pd were introduced to the sediment-water interface as components of ground catalytic converter particles, significant subduction was effected by A. marina, and metals were solubilized to a greater extent than in an unfaunated control. AE in these experiments was < 0.1% for Pt and about 1% for Pd, and the most important vector for assimilation appeared to be from the aqueous phase via partial solubilization of metal from catalytic material. The findings of this study improve our understanding of the availability, cycling, and fate of Pt and Pd in contaminated estuaries and coastal waters.
Supply response for a perennial crop is influenced by the age composition of existing plant stocks which, in turn, is determined by historical patterns of plantings and removals. This paper develops estimates offunctions that relate the planting and removal of cling peach trees to measures of past profitability, potential future production from existing acreage, and structural changes associated with market intervention programs. The analysis also provides indications of useful forms for these functions, patterns of yield variation by age oftree, and the nonlinear relation of removal response to age of tree.
Technical assistance has been at the heart of development assistance provided to country governments by donor agencies over the past several decades. The current debates on reimagining technical assistance focus on the existing challenges of the different types of technical assistance, and the (re)construction of an ideal model for delivering this type of support, with little discussion about the dilemmas involved in making day-to-day decisions and trade-offs in implementation. This article presents technical assistance as a policy option for governments and details the existing models of delivering technical assistance, as well as their limitations and the required enabling conditions. The models presented focus on the type of role for the technical advisers- as doers (performing government functions), partners (working with the government to perform a specific role) and facilitators (enabling and facilitating change programmes to address wicked problems). As part of the programmes, the team of technical advisers can play one or more roles. The authors also discuss how problem-solving or solution implementation can be the focus of a technical assistance programme or how large programmes combine these two approaches. The paper provides a practical account of the implications of the programme design that would ideally help governments and donors to design more effective technical assistance programmes.
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