Crop production surveys, which integrate the collection of data on both agronomic and economic variables, are increasingly common in on-farm research. A conceptual framework for designing and analysing such surveys is provided. Methodological issues in conducting crop production surveys are reviewed with respect to type of information collected, level of field observation, degree of quantification, frequency of observation, sampling, measurement of yields and yield components, and analysis of yield limiting factors. It is concluded that, while better integration of agronomic and economic perspectives in diagnosis may increase costs, the information and analysis obtained have considerable potential to improve the efficiency of experimentation.

Many national research systems have launched major on-farm research efforts aimed at generating relevant technologies for resource-poor farmers, but institutional and policy factors have often hindered the effectiveness of these efforts. Experience has shown that on-farm research, linking farmers, researchers, and technology transfer agents, poses special organizational and managerial challenges. Institutional innovations and strong policy commitment are needed if on-farm research is to succeed in meeting the needs of resource-poor farmers. Sound research methods alone are not sufficient.

This paper reviews key policy, organizational and managerial considerations for integrating on-farm client-oriented research as an effective and stable component of national agricultural research systems. It summarizes the findings of a major study sponsored by the International Service for National Agricultural Research on institutional factors affecting the performance and sustainability of such research systems. The conclusions are based on the systematic analysis of over 25 discrete on-farm research efforts in nine developing countries. The objective is to provide research managers, on-farm researchers and on-farm research advisors with concrete and practical insights for strengthening on-farm research and its contribution to the generation and transfer of relevant technologies.

Integración de la investigación de granja con los sistemas nacionales

Using a farming systems approach, a multidisciplinary team in southern Senegal examined three strategies for weed control in rainfed lowland rice: use of herbicide; replacement of broadcast seeding by row seeding with mechanical seeders; and transplanting compared with direct seeding of rice. Thorough evaluation of the agronomic and economic benefits of these strategies for farmers was facilitated by supplementing the standard analysis of on-farm trials with multivariate analysis incorporating agronomic survey data to explain treatment effects better, and by considering technical and economic effects throughout the farming system. The agro-economic analysis led the team to conclude that: where soils are productive, herbicide use is a profitable investment; when converting to direct seeding, farmers should facilitate weeding by seeding in rows with a mechanical seeder; and transplanting should not be discouraged in areas where it is still feasible, since it is less time-consuming, fits in better with other farm activities and requires less fertilizer.

Research institutes in Africa have had limited success in producing new technologies appropriate to the needs of small farmers because of an inadequate understanding of small farmers' goals and resource limitations and over-reliance on the transfer of technologies from other regions. Farming systems research (FSR) is an effective way of improving the focus of scientists on the problems farmers face. Vertically segmented thematic research programmes make institutionalization of FSR difficult within multi-commodity research centres, particularly the International Agricultural Research Centres. The Farming Systems Research Group has proved effective at overcoming such difficulties at the International Institute of Tropical Agriculture. Its organization, operation and effects on the performance of the research programmes are described.

Farming Systems Adaptive Research (FSAR) has contributed much to the understanding of maize production constraints on smallholder farms in southern Africa in the last six to eight years. But its production impact has been constrained by the often inappropriate technology available to FSAR from component research and the ineffective use of its results by extension staff. However, FSAR has demonstrated the utility of a problem (client) orientated approach to technology development, which is now being taken up by some maize commodity research and extension programmes, though effective linkages have not usually been developed. Nevertheless, experience in southern Africa suggests that the FSAR approach can provide a framework for developing more effective integration between key groups involved in technology generation, dissemination and support.

A farm survey conducted in Ethiopia in 1986 identified seasonal food shortage as an important problem facing farmers. The researchers proposed the development of an early maturing maize variety to alleviate the problem and by 1988, on-farm trials of a selected variety were initiated. About two-thirds of the farmers retained part of the harvested crop as seed for planting, indicating their strong interest in the variety. Farmer-designed trials were found to be especially effective for obtaining farmers' assessment of the new variety and for monitoring how they incorporated it into the farming system.

Maíl con maduración temprana para Etiopía

A method is discussed for classifying small scale rice farmers from the Dominican Republic who have similar production systems and access to land, but differ widely in the yields they obtain and in the adoption of new technology. The results are used to define two recommendation domains, for farmers with ‘good’ and ‘poor’ production conditions, and to suggest appropriate technology for each. For farmers working in good production conditions the development of a technological package based on the double cropping of semi-dwarf varieties with high yield potential and production efficiency is recommended; for farmers with poor production conditions, a technological package is suggested based on varieties with a high tolerance of drought, flooding and weed development, which yield adequately at low input levels.

Despite numerous altempts, the development of generalixed models capable of accurate predictions of the times from sowing to flowering (f) of crop plants in field environments has remained elusive. Models which seek to correlate ;ʃ with various states of environmental factors such as photoperiod, P, and temperature, T, using formal statistical procedures arc often complex. Here, we describe a family of photothermal responses (involving unambiguous parameters and limits) which quantify the linear, non-interacting effects of P and T not on ʃ but on 1/ʃ, i.e. on the rate of progress towards flowering. Based on these relations we suggest that the modelling of crop phenology will be simplified, more reliable and more biologically plausible.

The objective of this study was to identify whether grain yield in four contrasting rice cultivars is limited by supply of assimilate to fill the grains or by sink capacity to accept the assimilate. Grain yield was limited mostly by sink capacity, with little variation in single grain weight among cultivars, but an old cultivar showed some ability to adjust single grain weight. Sink capacity was very sensitive to variation in assimilate supply immediately after anthesis. Reduction in assimilate supply in the anthesis to early grain filling period reduced filled grain percentage and grain yield, particularly in high yielding cultivars with a large number of grains per panicle.

Trials were conducted in 1987 and 1988 to test methods of intercropping annual Ethiopian clovers, Trifolium spp, with wheat. Several different clover varieties, sowing methods, plant spacings, planting dates and rates of phosphorus application were compared. Planting in single or double alternative rows 20 cm apart did not affect wheat grain and straw yield but broadcast sowing of Trifolium in wheat rows 20 cm apart reduced wheat yield. The Trifolium species used significantly affected legume yield. Phosphorus fertilizer increased yield significantly, especially that of the legume component. The trials indicated that the intercropping of Ethiopian clovers in wheat has potential under African highland conditions.

Siembra simultanea de trigo/ Trifolium en Etiopía

Differences in the age at which okra pods were harvested (4, 7, 10 or 13 days after pod set) had no effect on vegetative growth or pod yield, but pods harvested more than seven days after pod set were of poorer quality. The reduction in pod quality arose mainly from an increase in crude fibre and a reduction in the moisture, crude protein and ash content of older pods.

Cropping systems research to improve the productivity of an acid upland rice and maize-based farming system is described and evaluations by co-operating farmers are presented. Farmers rejected introduced patterns. The cropping choices of non-cooperating farmers are described in terms of cost–benefits and the reasons underlying their decisions. An approach that combines an understanding of farmers' systems in order to conduct focused research on the weak points of such systems, together with an evaluation of farmer technology and adaptation, may be more effective than researcher-designed, farmer-implemented cropping pattern trials.

On-farm trials were carried out in the Operation Haute Vallée project, Mali, to assess the possibility of replacing, partially or entirely, imported cotton fertilizer with natural rock phosphate from a local source, and to assess the residual effect on maize and sorghum grown after cotton. The maize/cotton sequence, although not normally used by Malian farmers, was more profitable than either pure cotton grown alone or a cotton/maize sequence when local rock phosphate was used instead of imported fertilizer.

A multidisciplinary team has attempted to find a sustainable alternative to slash and burn agriculture in deciduous forest in the Bolivian lowlands for those who do not have access to tractor power. Farm size ranges from 30 to 50 hectares and labour and capital are major constraints to development. Fertilizers are not used because of their high price. The alternative proposed is that the farm should contain an area of not more than one hectare in alley cropping producing the family's requirements in farinaceous foods and vegetables, and an area, limited by labour constraints, of perennial crops for cash income. The balance of the farm would be in a silvipastoral system producing various tree products, beef and cheese for sale and sheep for home consumption.

Field experiments were carried out under irrigation in Central Saudi Arabia during the winters of 1987–88 and 1988–89 to examine the productivity and quality (grain protein content) of wheat intercropped with inoculated and uninoculated alfalfa with or without additional nitrogen. Nitrogen increased wheat grain yield and protein percentage but inoculation of the alfalfa had no additional effect. Herbage yield of intercropped alfa4fa was unaffected by nitrogen application. Added nitrogen reduced the protein percentage in alfalfa but increased its protein yield. Intercropping had benefits for alfalfa, increasing its protein content and yield.

Siembra simultánea de trigoy alfalfa

Early season defoliation of maize significantly reduced plant height and leaf area index but leaf number and leaf emergence rate were not affected. Ear development was significantly affected by both early and late season defoliation although tassel development was barely influenced. Silk growth was the phase of ear development most sensitive to defoliation. Early season defoliation significantly reduced all yield components, leading to yield losses ranging from 54 to 100%. The position of the leaves which were removed had an important effect on the final grain yield. Harvest index was affected by both the intensity and timing of defoliation.

Two tropical and one temperate genotypes of maize were grown during the cool dry winter seasons in northern Nigeria. The tall tropical genotypes produced a greater leaf area index and more above-ground dry matter, and so had a higher crop growth rate, than the dwarf temperate genotype. However, the early flowering temperate genotype yielded more grain than the late flowering tropical genotypes. Although the initial low winter temperatures prolonged the preflowering growth period in the tropical genotypes, the terminal high temperatures hastened maturity and were associated with poor grain filling.

Maíz de temporada seca en Nigeria

The growing season in the semi-arid region of West Africa is drought prone and of irregular duration. Two experiments were conducted in 1986 and 1987 to test the effects of flat cultivation and tied ridge cultivation (TRC) on the yields of maize and the component crops of a maize and cowpea relay cropping system. The two research sites, with slopes of 0.05% and 3%, were near Sapu, The Gambia, on an Aridic Kandiustalf in the 700 mm rainfall zone.

Both growing seasons had above average rainfall. In both years, maize on level sites showed no response to tillage practices. On the sloped site in 1987, soil moisture 10 and 15 days after the last rain was greater with TRC than with flat cultivation and yields of sole cowpea and maize were 25% and 18% greater, respectively. On the level site, TRC had no effect on residual soil moisture or grain yield. When rainfall was well distributed, tied ridging did not appear to be a viable tillage alternative for maize-based systems on flat land in central Gambia but with modest slopes, tied ridges markedly increased soil water reserves in the 0.15 to 0.60 m depth after maize harvest.

A selection programme conducted on young clonal tea plants grown in large sleeved bags and in a field trial established criteria for selecting high yielding field clones on the basis of their growth in early years. Bush area, number of branches and shoots per bush, and foliar phosphorus content at the second crop peak were correlated with yield but the correlation between stem circumference at ground level and yield was inconsistent. It is therefore concluded that all these bush and growth characters, apart from stem circumference, may be reliably used to predict and select high yielding tea clones.

The effect of advancing the sowing date from early February to November on the growth and seed and straw yields of three large seeded and three small seeded lines of lentil (Lens culinaris) was studied under rainfed conditions in northern Syria between 1982 and 1985. The average seed and straw yields from early winter sowing were 838 and 2476 kg ha−1 compared with 679 and 1470 kg ha−1, respectively, from a late sown crop. There were seasonal differences in the advantage in seed yield from early sowing, largely because infestation by Orbanche species limited the use of early sowing. There were no overall differences between the growth and yields of large and small seeded lines, but genetic variation within groups was apparent for all characters. A high rate of dry matter accumulation, manifested as early vigour, was always related to a high final economic biomass.