John K. Lynam

Relationships between biomass, root-yield and single-leaf photosynthesis in field-grown cassava

Abstract Preliminary field screening with 127 cultivars of cassava ( Manihot esculenta Crantz) was conducted in 1986/1987 to determine the relationships among single-leaf photosynthesis, shoot and total biomass, and storage-root tield. Gas exchange (CO 2 uptake and H 2 O loss) of individual leaves was monitored on three different occasions at 4–6 months after planning. There were significant correlations among leaf photosynthesis, total biomass and root yield across all cultivars. When the cultivars were grouped on the basis of top weight (as a proxy for leaf area), the correlations were significant only with average and high top-weight cultivars. The same trends were observed for correlations among mesophyll conductance, total biomass and root yield. There were no significant correlations between biomass or root yield and leaf conductance. The results suggest that, when light interception is not limiting, selection for high leaf photosynthesis is likely to lead to higher yield. The results of a second-year trial (1988/1989) with 16 cultivars, selected on the basis of their yield, showed a significant correlation between leaf photosynthesis, measured only once at 4 months after planting, and final root yield. Root yield was positively correlated with mesophyll conductance, and negatively correlated with intercellular CO 2 , but not significantly correlated with leaf conductance. Furthermore, root yield in the 1988/1989 season was significantly correlated with leaf photosynthesis measured in the 1986/1987 season. It is suggested that screening for high leaf photosynthetic rate under field conditions could be used as a selection criterion for parent materials to obtain progeny with high yield.

The distribution of benefits from technical change among classes of consumers and producers: An ex anteanalysis of beans in Brazil

Abstract Because new agricultural technology in developing countries has sometimes bypassed small farmers who are an important social group in low income countries, design of technology specifically appropriate to small farmers has been advocated as a policy goal. This paper appraises the comparative returns to investment in small farm biased, scale neutral, and large farm biased technology for bean production in Brazil. A consumer surplus model is developed to estimate the distribution of benefits among producing sectors and classes of consumers. While previous studies have relied on geometrical approximations to measure economic benefits as the area under the supply shifts, here an exact analytic solution is obtained by integrating from the supply axis. Scale neutral technology leads to significant small farmer benefits while maximizing benefits to consumers. Large farm biased technology results in less benefits to small farmers and consumers and only minor gains to large farmers when compared to scale neutral technology. Small farm biased technology produces the greatest gains to small farmers, but the lowest level of benefits to consumers.

New agricultural technology and smallfarmers in Latin America

Abstract Biased income distribution in agriculture as a result of the green revolution towards better agricultural regions and larger farmers has been justified by declining prices for rice and wheat making consumers the main beneficiaries of this new technology. But, there are two arguments for focusing future agricultural technology towards small farmers and poorer resource regions. First, evidence suggests that there is little productivity or nutritional improvement from migration. Second, unless the supply of prime areas can be made more elastic, most of the small farmer food crops, even with new technology, will not be sufficiently profitable to displace the high value activities currently found in these areas in Latin America.

Evaluation of new technology on farms: Methodology and some results from two crop programmes at CIAT

Abstract The yield gap between experiment station and farm yields in the production of food crops in developing countries has been frequently noted and various quantitative attempts have been made to separate its components in irrigated rice (Gomez et al., 1979; IRRI, 1979; Flinn, 1980). In two food crops in Latin America one principal hypothesis of the authors for the continuation of this yield gap over time is that many successful technologies on the experiment station do not pass a set of reasonable farm level criteria. Farm testing is the logical extension of the research evaluation process once a technology has been identified on the experiment station and regionally tested for adaptation. Farm testing is an especially important component of the research process in developing countries, where communication links between farmers and researchers are weak and farmers often do not have the information or management experience to combine and modify various technology components adapting experiment station or regional trial observations to their owen environments and production systems. The research problems at the farm are different from those at the experiment station or in regional trials so there are important distinctions in design and analysis in the farm trials. The evaluation process developed here identified the technologies later adopted by farmers. For the unsuccessful technologies, information was provided from the farm trials to the breeders and other scientists on further design requirements. The results of the farm trials substantially modifie the recombinations for farmers, which would have been arrived at utilising the results from the experiment station and/or regional trials.

Definition of the relevant constraints for research resource allocation in crop breeding programmes

Abstract During recent years in international centres there have been substantial research efforts to describe production systems, measure farm level yield losses, identify consumer preferences and specify rainfall regimes and soil types. Geographers, economists, climatologists and soil scientists produce information for the plant designers—i.e. breeders and associated disciplines. So far the contribution to research design has been marginal. Research priorities on breeding strategy alternatives have been set subjectively within the commodity teams without much systematic data processing from the target regions. More information from the target regions should lead to more efficient research programmes. Some principal research issues facing commodity programmes are first defined. Next, the efficiency of the various data gathering exercises in resolving these issues is evaluated. Less emphasis should be put on testing for wide adaptation of new varieties and more emphasis on better quantification of potential research benefits through networking in the target area. Data collection efforts should be focused more towards the research problem of priority definition. Even subjective estimates by breeders and pathologists of the costs and expected returns of different strategies would make implicit breeding strategy decisions explicit and help identify other research and data requirements.

Commodity research programs from the demand side

Abstract Agricultural research has traditionally focused on production issues and the economic discipline supported this research by studying the production process and its conditions. The authors argue that the study of marketing and demand issues usefully complements production research. This is because, apart from the producer, the consumer is also a judge of new technology; and because constraints to improved or increased utilization might be identified, which carry a higher potential for successful research than production constraints. Demand studies for orientating agricultural research show conceptual symmetry with production studies but their inclusion allows for better judgement on the potential of alternative research ventures and for improved targeting of agricultural research objectives, such as equity, rural income and price stability. Demand analysis should be consistent with the state of maturity of the commodity research program. Demand studies can be organized around the themes of research strategies, technology design and technology transfer. This is afterwards illustrated with the approaches taken by CIATs cassava and bean program, showing that the exact subjects of study are rather commodity specific.

Ex ante analysis of new technology: A comparison of cassava for the feed and fresh markets in Colombia

Abstract This paper estimates the expected economic benefits of investment in two alternative research programmes to improve yields of cassava in Colombia. The benefits from an industrial cassava variety for the animal feed market are compared with those from a higher quality cassava suitable for the fresh food market. A linear programming least-cost feed mix model is used to calculate the cost reduction is poultry feed due to new cassava technology. The impact of this cost reduction is traced through single equation models of poultry supply and demand in order to estimate social benefits in an ex ante consumer surplus framework. Costs of the alternative research programmes are projected and internal rates of return are calculated.

Benefits to cassava consumers and producers: new market options in Colombia

Abstract The Integrated Rural Development Programme has helped farmers on the north coast of Colombia to form groups with the capacity to dry cassava and sell it in an animal feed market as an alternative to the direct sale of fresh cassava in the major urban market of Baranquilla. This has effectively provided a stable floor price for fresh roots. Farmers have responded by increasing production, and derive increased benefits from both fresh and dried markets. Consumers also benefit from reduced and stable fresh root prices. This project has thus avoided the common dilemma of agricultural programmes that increase production, reduce prices paid to the farmers and benefit mainly the urban consumer.