Effects of Cash Crop Production on Food Crop Productivity in Zimbabwe: Synergies or Trade-offs?

This paper studies the dynamics between cash cropping and food crop productivity in Gokwe North District in Zimbabwe, a major cotton producing area. The main research issues were: (1) to identify the determinants of commercialized crop production at the household level; and (2) to determine the effect of increasing crop commercialization on household food productivity. The paper derives a household crop commercialization index, defined as the ratio of crop sales to total crop production. Econometric models were developed for identifying the determinants of household-level commercialization and for measuring its effects on food crop productivity.food security, food policy, cash crop production, food crop productivity, Zimbabwe, Crop Production/Industries, Productivity Analysis, Downloads June 2008 - July 2009: 62, Q18,

Paintings and their implicit presuppositions : a preliminary report

In a series of earlier papers (Social Science Working Papers 350, 355. 357) we have studied the ways in which differences in "implicit presupposi tions" (i. e •• differences in world views) cause scientists and historians to reach differing conclusions from a consideration of the same evidence. In this paper we show that paintings are characterized by implicit presuppositions similar to those that characterize the written materials -- essays, letters, scientific papers -- we have already studied

Paintings and their implicit presuppositions: High Renaissance and Mannerism

All art historians who are interested in questions of "styles" or "schools" agree in identifying a High Renaissance school of Italian painting. There is, however, a disagreement, which has seemed nonterminating, regarding Mannerism: Is it another distinct school or is it merely a late development of the Renaissance school? We believe that this disagreement can be terminated by distinguishing questions of fact about paintings from questions about the definitions of schools. To this end we have had two representative subsets of paintings--one earlier, one later--rated on four of the dimensions of implicit presuppositions that we have introduced in other Working Papers. When the paintings are scaled in this way a very distinct profile emerges for the earlier, or Renaissance, paintings. In contrast, the later, or Mannerist, paintings are so heterogeneous that we conclude that they are best described as deviations from the Renaissance profile, rather than a separate school. These results are not unimportant--at least for art historians. But they are more important methodologically inasmuch as the procedures applied here can be used in classifying and distinguishing from one another all kind of cultural products

Input Subsidy Programs and Commercial Market Development: Modeling Fertilizer Use Decisions in a Two-Channel Marketing System

Replaced with revised version of paper 07/18/06.crowding out effect, input marketing channels, fertilizer, sub-Saharan Africa, survey data, Marketing,

Annona muricata (graviola): toxic or therapeutic

This paper examines annona muricata (graviola): toxic or therapeutic

Staple food prices in Zambia

Prepared for the COMESA policy seminar on “Variation in staple food prices: Causes, consequence, and policy options”, Maputo, Mozambique, 25-26 January 2010 under the Comesa-MSU-IFPRI African Agricultural Marketing Project (AAMP)Zambia, food security, food prices, Agricultural and Food Policy, Demand and Price Analysis, Food Security and Poverty, International Development, International Relations/Trade, q11, q13, q18,

Maize Yield Response to Fertilizer and Profitability of Fertilizer Use Among Small-Scale Maize Producers in Zambia

Multi-year nationwide survey data is used to estimate maize yield response functions and determine profitability of fertilizer use by small-scale farmers in Zambia. There has been a dearth of empirical studies on economics of fertilization in the context of Sub-Saharan Africa. In this paper we identify major methodological issues arising from using survey data and estimate maize yield response functions for small-scale rural households that have various management practices and soil conditions in two major agro-climatic zones. Profitability of fertilizer use is determined for each group of households. Our findings provide the following key messages. First, households that obtained fertilizer on time and used animal draught power or mechanical power for land preparation are more likely to find fertilizer use profitable than other households with similar agro-ecological and market access conditions. Second, farmers' proximity to the provincial centers has a significant impact on the profitability of fertilizer use. Greater distances and transport costs from provincial centers erode the profitability of fertilizer use. Third, high interest rates also reduce the profitability of fertilizer use. Small farmers may find fertilizer use unprofitable until efforts are made to reduce transportation costs and interest rates as well as to ensure more timely delivery of fertilizer.Maize, Yield, Fertilizer, Profitability, Survey data, Crop Production/Industries,

Controlled Environmental Effects on Creep Test Data of Woven Fabric Webbings for Inflatable Space Modules

eveloping technologies for proposed lunar and Mars space exploration missions. Enhanced habitation sy g studied as potential habitats due to their inherent low mass and small launch volume. One goal of inflatable module research is quantification of the safe-life and end-of-life creep-strain spectrum. Full-scale pressurized inflatable modules are large, costly, and difficult to experimentally study. Therefore, material subcomponents are often studied as an alternative. An experimental thermally controlled long-term creep study of VectranTM webbings for application to inflatable modules is presented. Vectran fibers have high strength and low creep properties. High strength webbing materials are desirable for the load bearing restraint layer of inflatable modules because they are strong, flexible, and lightweight. Characterization of the creep behavior, safe-life, and end-of- life of webbing specimens will help quantify comparable life properties for inflatable modules. Several experimental multiple-year creep studies of webbing specimens in uncontrolled thermal environments have been conducted at NASA Langley Research Center. Experimental data obtained exhibits the classic creep-strain curve due to load, coupled with unique sinusoidal variation due to variation in temperature and humidity over daily and annual time periods. Results also have indicated that specimens fail within a year if the applied load is greater than 50 percent of the rated load. The primary goal of this study is to eliminate thermal effects from the creep data for a group of webbing specimens, and to allow uncontrolled thermal effects to influence the creep data of a second group of webbing specimens. Comparison of both sets of data will define how temperature influences creep data. A unique creep test facility was fabricated to facilitate the generation and comparison of the two sets of data. The facility consists of five creep test stands with an integrated heating and cooling system, and four creep test stands exposed to external environmental or ambient conditions. The facility contains displacement, temperature, humidity, and load sensors. Test specimens consist of one- inch wide, 48-inch long Vectran webbings rated at 12,500 pounds-per-inch. Experimental thermally controlled creep-strain data has been generated for two groups of webbing specimens. Applied load for all test stands was above 9000 lbs and greater than 50 percent of the rated load. Temperatures varied between 58F and 83F for the four test stands exposed to ambient conditions. Associated creep data exhibited the classic creep- strain profiles. The temperature was set to 72F for the five test stands in the controlled temperature environment. Creep data for tests with temperature control also exhibited the classic strain profiles. Data indicated that if the load is greater n thermal effects do not manifest. Therefore, creep tests with loads less than 50 percent of the rated load are planned for in the near future