Some physiological aspects of yield in cassava

Results are presented of various trials with cassava. The importance of DM production and factors affecting it, such as LAI and leaf inclination, are discussed. The relative importance of DM production and its distribution, particularly in relation to spacing, are reviewed. The author suggests a plant ideotype based on these observations. (AS)Se presentan los resultados de varios ensayos con yuca. Se discute la importancia de la produccion de MS y los factores que la afectan, tales como el IAF y la inclinacion de la hoja. Se revisa la importancia relativa de la produccion de MS y su distribucion, particularmente en relacion con la densidad de siembra. Con base en estas observaciones se sugiere un tipo de planta ideal. (RA-CIAT

Propagacion rapida de la yuca

A system for rapid propagation of cassava is described, including detailed characteristics of the installations (propagation chambers and rooting area), materials needed and process to be followed. The advantages of this system are: (1) it is the only way of rapidly propagating promissory var. in sufficient quantities; (2) var. affected by CBB (Xanthomonas manihotis) can be cleaned, and (3) it is a simple, inexpensive system. When comparing this system with the traditional one, a greater than no. of commercial-sized cuttings were obtained (100- 400 vs. 12,000-24,000 cuttings/yr). (CIAT)Se describe un sistema de propagacion rapida de la yuca, incluyendo caracteristicas detalladas de las instalaciones (camara de propagacion y area de enraizamiento), materiales requeridos y procedimiento que se debe seguir. Las ventajas de este sistema son: 1) es la unica manera de propagar var. promisorias rapidamente y en cantidades suficientes; 2) se pueden limpiar var. afectadas por CBB (Xanthomonas manihotis); y 3) es un sistema sencillo y poco costoso. Al comparar este sistema con el tradicional se obtiene un mayor no. de estacas de tamano comercial (100-400 vs. 12.000- 24.000 estacas/ano). (CIAT

The foregone risk premium: a communicative and practical method for the evaluation of risk-return profiles in agriculture

Risk considerations have become increasingly important in nowadays agriculture, due to a variety of reasons. Surprisingly, the practice of formalized risk management is not widespread despite the huge amount of scientific literature on this topic. This discrepancy between risk science and extension is described by many authors. This paper presents a communicative method, rooted in financial economics, to evaluate risk-return profiles in a way that is communicative for individual farmers. The method is derived from the modern portfolio theory, in which individual assets are implicitly compared to the risk-return trade-off of that asset with the highest Sharpe ratio. We use this idea to compare individual risk-return profiles to a particular benchmark. The method can be used for evaluating different risk-return profiles of different farms, different risk management instruments and different production systems. To illustrate the communicative nature of our method, it is applied to evaluate risk-return profiles of conventional versus organic cropping systems.Risk and Uncertainty,

Potencial futuro e investigacion necesaria para el incremento de la yuca

The possibilities of underdeveloped countries to satisfy their needs for food and to improve the standard of Eving through cassava production are analyzed. The following aspects are studied: potential cassava production (current and potential situation), general research policies and areas (var. development, pest control, agronomic practices, and multiple cropping), transfer of technology, utilization of cassava in human and animal nutrition and in the production of alcohol. Tables are included on potential yields, production costs, and price-elasticity, and income in Indonesia. (CIAT)Se analizan las posibilidades de los paises subdesarrollados para satisfacer sus necesidades de alimentacion y mejorar el nivel de vida con base en la produccion de yuca. Se contemplan los siguientes aspectos: produccion potencial de la yuca (situacion actual y potencial), politica general de la investigacion y sus areas (desarrollo var., manejo de plagas, practicas agronomicas y cultivos multiples), transferencia de tecnologia, utilizacion de la yuca en la alimentacion humana, animal y en la produccion de alcohol. Se incluyen cuadros de rendimiento potencial, costos de produccion, y de elasticidad precio e ingreso en Indonesia. (CIAT

Modelling Farm Level Economic Potential for Conversion to Organic Farming

A farm model is developed for simulating the potential income change resulting from conversion to organic farming. The model uses conventional farm data, taken from the Belgian FADN. Given the normative character of the model, and the impossibility of calibration to historical conversion behaviour, two model variants, a rigid and a flexible, are created to broaden the analysis scope. Moreover, extra attention is paid to the verification process and sensitivity analysis. Results reveal that the economic potential for conversion is rather high, if farmers are willing to change their farm management sufficiently. Furthermore, conversion potential depends on the farm type and conventional farm characteristics. The model finally proves to be an interesting tool to analyse policy impact.organic farming, conversion period, farm model, linear programming, Environmental Economics and Policy, Farm Management, C61, Q12,

La planta ideal de yuca para obtener rendimientos máximos

A series of trials were carried out using cassava. Crop growth rate increased with leaf area up to LAI 4; root growth rate increased up to LAI 3-3.5, then declined. LAI is determined by leaf size, leaf formation rate and individual leaf life. Leaf size reached a max 4 mo after planting and then decreased; the max was a varietal character. Leaf life was reduced by shading but in full daylight was determined by the var. Leaf formation rate/shoot apex showed little genetic vafiation and declined with time; large differences in leaf formation rate/plant were determined by differences in branching pattern. Top growth had preference over root growth, and root sink was not limiting when root no./plant was equal to or greater than 9. A computer program was written to implement a dynamic growth model, which suggests that high-yielding plants will branch late in life and possess large leaves and long leaf life. Potential yields of greater than 25 t/ha/yr dry roots are obtainable at 400-500 g cal (cm)-2 day radiation. (AS

La yuca: una fuente básica de energía en los trópicos

Cassava is the 4th most important source of food energy in the tropics. More than 2/3 of the total production of this crop is used as food for humans, with lesser amounts being used for animal feed and industrial purposes. The ingestion of high levels of cassava has been associated with chronic cyanide toxicity in parts of Africa, but this appears to be related to inadequate processing of the root and poor overall nutrition. Although cassava is not a complete food it is important as a cheap source of calories. The crop has a high yield potential under good conditions, and compared with other crops it excels under suboptimal conditions, thus offering the possibility of using marginal land to increase total agricultural production. Breeding programs that bring together germplasm from different regions coupled with improved agronomic practices can markedly increase yields. The future demand for fresh cassava may depend on improved storage methods. The markets for cassava as a substitute for cereal flours in bakery products and as an energy source in animal feed rations are likely to expand. The use of cassava as a source of ethanol for fuel depends on findingan efficient source of energy for distillation or an improved method of separating ethanol from water. (AS