Criteria for evaluating different intercropping situations are suggested, and the Land Equivalent Ratio (LER) concept is considered for situations where intercropping must be compared with growing each crop sole. The need to use different standardizing sole crop yields in forming LERs is discussed, and a method of calculating an ‘effective LER’ is proposed to evaluate situations where the yield proportions achieved in intercropping are different from those that might be required by a farmer. The possible importance of effective LERs in indicating the proportions of crops likely to give biggest yield advantages is discussed.

Farming systems in west Asia and north Africa have evolved to cope with the problems of highly variable and, frequently, chronically deficient rainfall. Cereals (mainly wheat and barley) are the dominant arable crops with food legumes (chickpea, lentil and faba bean) occupying only 5 to 10% of the area planted to cereals. Livestock is closely integrated into the farming system and crop production practices often reflect the importance of animals as a major source of income, particularly on the smaller farms. Soils of the region are predominantly calcareous, frequently phosphate deficient, and their depth and texture are important in determining the maximum amount of water that can be stored which, in turn, may determine the effective length of the growing season.

Rain falls mainly during the winter months so that crops must often rely on stored soil moisture when they are growing most rapidly. Analysis of equations relating crop growth and water use shows that there are three ways in which the ‘water use efficiency’ of dry matter production can be increased. First, the amount of dry matter produced per unit of water transpired might be increased; second, if the water supply is limited, the amount of water transpired might be increased relative to evaporation from the soil surface; and third, the total amount of water used might be increased to produce extra growth provided that this results in increased transpiration rather than simply increasing evaporation from the soil surface.

These three possible routes to increased crop growth are reviewed in relation to possible improvements in water management and crop genotypes in the Mediterranean environment. Scope for improving transpiration efficiency is limited although genotypic differences exist and may be useful in the future. More immediately, changes in crop management, such as applications of fertilizer, improved tillage and better weed control, will all increase the amount of water transpired. Application of mulches will also reduce evaporation from the soil surface but crop residues are usually eaten by livestock and are, therefore, often unavailable.

The barley/livestock farming system of west Asia is used as a case study to illustrate how the Fanning Systems Programme of ICARDA has developed on-farm research programmes of direct relevance to current farming systems. Research on experimental sites directed at improving water use efficiency has been developed into on-farm trials and into collaborative trials with the Syrian Soils Directorate.

A simple competitive ratio (CR) is proposed as a measure of intercrop competition, to indicate the number of times by which one component crop is more competitive than the other. Intercropping data show that this CR term could be useful in (i) comparing the competitive ability of different crops, (ii) measuring competitive changes within a given combination, (iii) identifying which plant characters are associated with competitive ability, and (iv) determining what competitive balance between components is most likely to give maximum yield advantages.

We review the use and value of seasonal climate forecasting for agriculture in sub-Saharan Africa (SSA), with a view to understanding and exploiting opportunities to realize more of its potential benefits. Interaction between the atmosphere and underlying oceans provides the basis for probabilistic forecasts of climate conditions at a seasonal lead-time, including during cropping seasons in parts of SSA. Regional climate outlook forums (RCOF) and national meteorological services (NMS) have been at the forefront of efforts to provide forecast information for agriculture. A survey showed that African NMS often go well beyond the RCOF process to improve seasonal forecast information and disseminate it to the agricultural sector. Evidence from a combination of understanding of how climatic uncertainty impacts agriculture, model-based ex-ante analyses, subjective expressions of demand or value, and the few well-documented evaluations of actual use and resulting benefit suggests that seasonal forecasts may have considerable potential to improve agricultural management and rural livelihoods. However, constraints related to legitimacy, salience, access, understanding, capacity to respond and data scarcity have so far limited the widespread use and benefit from seasonal prediction among smallholder farmers. Those constraints that reflect inadequate information products, policies or institutional process can potentially be overcome. Additional opportunities to benefit rural communities come from expanding the use of seasonal forecast information for coordinating input and credit supply, food crisis management, trade and agricultural insurance. The surge of activity surrounding seasonal forecasting in SSA following the 1997/98 El Niño has waned in recent years, but emerging initiatives, such as the Global Framework for Climate Services and ClimDev-Africa, are poised to reinvigorate support for seasonal forecast information services for agriculture. We conclude with a discussion of institutional and policy changes that we believe will greatly enhance the benefits of seasonal forecasting to agriculture in SSA.

Poor crop establishment was identified as a major constraint on rainfed crop production by farmers in the tribal villages of Rajasthan, Gujarat and Madhya Pradesh served by the Krishak Bharati Cooperative (KRIBHCO) Indo-British Rainfed Farming Project (KRIBP). On-farm seed priming with water was chosen as a low cost, low risk intervention appropriate to the farmers' needs. In vitro screening of the effects of priming on the germination of seeds of local and improved varieties of maize, upland rice and chickpea provided ‘safe limits’ – the maximum length of time for which farmers should prime seeds and which, if exceeded, could lead to seed or seedling damage. Recommended safe limits were 24 h for maize and rice and 10 h for chickpea, with only minor varietal differences. These recommendations were then tested in on-station trials in Dahod, Gujarat. Farmer-managed trials were conducted for chickpea in three villages in the rabi (post-monsoon) season in 1995–96; for maize and upland rice in eight villages in the kharif (monsoon) season in 1996; and for maize and chickpea in 15 villages in the 1996--97 rabi season. Farmers modified these recommendations to ‘overnight’ for all three crops. Evaluation of the technology by farmers involved focus group discussions, matrix ranking exercises and two workshops.

Direct benefits in all three crops included faster emergence, better stands and a lower incidence of re-sowing, more vigorous plants, better drought tolerance, earlier flowering, earlier harvest and higher grain yield. Indirect benefits reported were earlier sowing of rabi crops because of the shorter duration of the preceding kharif crop, earlier harvesting of rabi crops that allowed earlier migration from the area, with better chance of obtaining off-season work, and increased willingness to use fertilizers because of reduced risk of crop failure. In matrix ranking exercises in four villages in the kharif 1996, 95% of farmers indicated that, even after only one exposure to the technology, they would prime seed in the following season. Similar exercises in four villages in rabi 1996–97 revealed that 100% of collaborating farmers intended to continue seed priming. From 21 villages, 246 farmers attended two workshops to share their experiences of seed priming and resolved to continue with the technology.

Root growth of two drought tolerant and two drought sensitive bean (Phaseolus vulgaris L.) lines was compared at two locations in Colombia differing primarily in soil conditions. At Palmira, roots of drought tolerant lines reached a depth of 1.3 m, while drought sensitive lines only reached 0.8 m. These differences were associated with differences in seed yield, crop growth, canopy temperature and soil moisture extraction. Under acid soil conditions at Quili-chao, seed yields of supposedly drought tolerant genotypes were similar to those of the drought sensitive lines, and root growth of all four lines was restricted to less than 0.8 m. Drought avoidance through greater root growth and extraction of soil moisture appears to be an important drought tolerance mechanism in common beans, but its usefulness is limited where soil conditions restrict root growth.

Data from 94 experiments on sorghum/pigeonpea intercropping were examined for evidence that the stability of yield is greater with intercropping than sole cropping. Stability of the major component (sorghum) was examined by calculating the distribution of yields; stability of the overall intercropping system was examined by calculating coefficients of variation, by computing regressions of yield against an environmental index, and by estimating the probability of monetary returns falling below given ‘disaster’ levels. All these approaches have some merit; taking the last as an example, it was found that for a particular ‘disaster’ level quoted, sole pigeonpea would fail one year in five, sole sorghum one year in eight, but intercropping only one year in thirty-six. Intercropping gave yield advantages under a wide range of environmental conditions and there was no significant evidence that advantages were greater under stress. This is discussed in relation to possible mechanisms contributing to greater yield stability.

Figures for maximum crop growth rates, reviewed by Gifford (1974), suggest that the productivity of C3 and C4 species is almost indistinguishable. However, close inspection of these figures at source and correspondence with several authors revealed a number of errors. When all unreliable figures were discarded, the maximum growth rate for C3 stands fell in the range 34–39 g m−2 d−1 compared with 50–54 g m−2 d−1 for C4 stands. Maximum growth rates averaged over the whole growing season showed a similar difference: 13 g m−2 d−1 for C3 and 22 g m−2 d−1 for C4. These figures correspond to photosynthetic efficiencies of approximately 1·4 and 2·0%.

Farmer participatory approaches for the identification or breeding of improved crop cultivars can be usefully categorized into participatory varietal selection (PVS) and participatory plant breeding (PPB). Various PVS and PPB methods are reviewed. PVS is a more rapid and cost-effective way of identifying farmer-preferred cultivars if a suitable choice of cultivars exists. If this is impossible, then the more resource-consuming PPB is required. PPB can use, as parents, cultivars that were identified in successful PVS programmes. Compared with conventional plant breeding, PPB is more likely to produce farmer-acceptable products, particularly for marginal environments. The impact of farmer participatory research on biodiversity is considered. The long-term effect of PVS is to increase biodiversity, but where indigenous variability is high it can also reduce it. PPB has a greater effect on increasing biodiversity although its impact may be limited to smaller areas. PPB can be a dynamic form of in situ genetic conservation.

Innovation Platforms (IPs) are seen as a promising vehicle to foster a paradigm shift in agricultural research for development (AR4D). By facilitating interaction, negotiation and collective action between farmers, researchers and other stakeholders, IPs can contribute to more integrated, systemic innovation that is essential for achieving agricultural development impacts. However, successful implementation of IPs requires institutional change within AR4D establishments. The objective of this paper is to reflect on the implementation and institutionalisation of IPs in present AR4D programmes. We use experiences from sub-Saharan Africa to demonstrate how the adoption and adaptation of IPs creates both opportunities and challenges that influence platform performance and impact. Niche-regime theory is used to understand challenges, and anticipate on how to deal with them. A key concern is whether IPs in AR4D challenge or reinforce existing technology-oriented agricultural innovation paradigms. For example, stakeholder representation, facilitation and institutional embedding determine to a large extent whether the IP can strengthen systemic capacity to innovate that can lead to real paradigm change, or are merely ‘old wine in new bottles’ and a continuation of ‘business as usual’. Institutional embedding of IPs and – more broadly – the transition from technology-oriented to system-oriented AR4D approaches requires structural changes in organisational mandates, incentives, procedures and funding, as well as investments in exchange of experiences, learning and capacity development.

Varietal selection is particularly difficult for very heterogeneous environments where farmers have a range of preferences. To address these issues in Rwanda, local bean experts, generally women, are invited to the research station to assess cultivars and to select those they prefer for their plots. Farmers use observed yield as only one of several criteria to predict varietal performance in their more stressed home environments. The varieties they choose are often higher yielding on-farm and are retained longer by farmers than those selected by the breeders. The results of early farmer involvement also compare favourably with those of the standard breeding programme in terms of enhanced genetic diversity and reduced research costs. There are few pre-conditions for developing such a client-driven breeding programme.

Papel del agricultor en la selección de variedades para una estación inaestigación

Conservation agriculture (CA) systems are based on minimal soil disturbance, crop residue retention and crop rotation. Although the capacity of rotations to break pest and disease cycles is generally recognized, other benefits of crop rotations in CA systems are seldom acknowledged and little understood. We monitored different conventional and CA cropping systems over the period from 2005 to 2009 in a multi-seasonal trial in Monze, southern Zambia. Both monocropped maize and different maize rotations including cotton and the green manure cover crop sunnhemp (Crotalaria juncea) were compared under CA conditions, with the aim of elucidating the effects of crop rotations on soil quality, soil moisture relations and maize productivity. Infiltration, a sensitive indicator of soil quality, was significantly lower on conventionally ploughed plots in all cropping seasons compared to CA plots. Higher water infiltration rate led to greater soil moisture content in CA maize treatments seeded after cotton. Earthworm populations, total carbon and aggregate stability were also significantly higher on CA plots. Improvements in soil quality resulted in higher rainfall use efficiency and higher maize grain yield on CA plots especially those in a two- or three-year rotation. In the 2007/08 and 2008/2009 season, highest yields were obtained from direct-seeded maize after sunnhemp, which yielded 74% and 136% more than maize in the conventionally ploughed control treatment with a continuous maize crop. Even in a two-year rotation (maize-cotton), without a legume green manure cover crop, 47% and 38% higher maize yields were recorded compared to maize in the conventionally ploughed control in the two years, respectively. This suggests that there are positive effects from crop rotations even in the absence of disease and pest problems. The overall profitability of each system will, however, depend on markets and prices, which will guide the farmer's decision on which, if any, rotation to choose.

Legume species are uniquely suited to enhance soil productivity and provide nutrient-enriched grains and vegetables for limited-resource farmers. Yet substantial barriers to diversification with legumes exist, such as moderate yield potential and establishment costs, indicating the need for long-term engagement and farmer-centered research and extension. This review and in-depth analysis of a Malawian case study illustrates that farmer experimentation and adoption of legumes can be fostered among even the most resource-poor smallholders. Multi-educational activities and participatory research involving farmer research teams was carried out with 80 communities. Over five years more than 3000 farmers tested legumes and gained knowledge of legume contributions to child nutrition and soil productivity. The average area of expansion of legume systems was 862 m2 in 2005; 772 m2 for women and 956 m2 for men indicating a gender dimension to legume adoption. Farmers chose edible legume intercrops such as pigeonpea and groundnut over the mucuna green manure system, particularly women farmers. Interestingly, expansion in area of doubled-up edible legumes (854 m2 in 2005) was practiced by more farmers, but was a smaller area than that of mucuna green manure system (1429 m2). An information gap was discovered around the biological consequences of legume residue management. Education on the soil benefits of improved residue management and participatory methods of knowledge sharing were associated with enhanced labour investment; 72 % of farmers reported burying legume residues in 2005 compared to 15 % in 2000. Households reported feeding significantly more edible legumes to their children compared with control households. Participatory research that incorporated nutritional education fostered discussions within households and communities, the foundation for sustained adoption of legume-diversified systems.

This study examines farmers’ perceptions of short- and long-term variability in climate, their ability to discern trends in climate and how the perceived trends converge with actual weather observations in five districts of Eastern Province in Kenya where the climate is semi-arid with high intra- and inter-annual variability in rainfall. Field surveys to elicit farmers’ perceptions about climate variability and change were conducted in Machakos, Makueni, Kitui, Mwingi and Mutomo districts. Long-term rainfall records from five meteorological stations within a 10 km radius from the survey locations were obtained from the Kenya Meteorological Department and were analysed to compare with farmers’ observations. Farmers’ responses indicate that they are well aware of the general climate in their location, its variability, the probabilistic nature of the variability and the impacts of this variability on crop production. However, their ability to synthesize the knowledge they have gained from their observations and discern long-term trends in the probabilistic distribution of seasonal conditions is more subjective, mainly due to the compounding interactions between climate and other factors such as soil fertility, soil water and land use change that determine the climate's overall influence on crop productivity. There is a general tendency among the farmers to give greater weight to negative impacts leading to higher risk perception. In relation to long-term changes in the climate, farmer observations in our study that rainfall patterns are changing corroborated well with reported perceptions from other places across the African continent but were not supported by the observed trends in rainfall data from the five study locations. The main implication of our findings is the need to be aware of and account for the risk during the development and promotion of technologies involving significant investments by smallholder farmers and exercise caution in interpreting farmers’ perceptions about long-term climate variability and change.

An evaluation was conducted in eastern India over three years, 2005–2007, to compare the performance of certain System of Rice Intensification (SRI) practices: transplanting single, young (10-day-old) seedlings in a square pattern; no continuous flooding; and use of a mechanical weeder – with those currently endorsed by the Central Rice Research Institute of India, referred to here as recommended management practices (RMP). All plots received the same fertilization, a combination of organic and inorganic nutrients, and the SRI spacing used was 20% less than usually recommended. Accordingly, the results reported here are designated as a modification of SRI recommendations (SRIm). The objective of this research was to understand the benefits in terms of yield and other physiological parameters, if any, from using most if not all recommended SRI practices compared to RMP. These selected SRI practices out-yielded RMP by 42%, with the higher yield associated with various phenotypical alterations, which are reported here. Significant measurable changes were observed in physiological processes and plant characteristics, such as longer panicles, more grains panicle−1 and higher % of grain-filling. The decreased plant density with SRIm management was compensated for by increased per-plant productivity. SRIm hills with single plants were found to have deeper and better-distributed root systems, higher xylem exudation rates, more open plant architecture with more erect and larger leaves, and more tillers than did RMP hills having multiple plants. Due to the reduction in number of hills m−2 in SRIm plots compared to RMP, no significant difference was found in root dry weight or leaf number, tillers or panicle number on an area basis. Nevertheless, in spite of SRIm having fewer hills and fewer tillers per unit area, the leaf area index (LAI) with SRIm practice was greater due to larger leaves. These together with altered plant architecture, contributed to more light interception by SRIm plants. The higher leaf chlorophyll content at ripening stage reflected delayed senescence and the greater fluorescence efficiency (Fv/Fm and ФPS II) associated with SRIm practices contributed to more efficient utilization of light and a higher rate of photosynthesis, which was probably responsible for the observed increase in grain filling and heavier grains compared to RMP plants. The higher photosynthesis rate coupled with lower transpiration in SRIm plants indicated that they were using water more efficiently than did RMP plants. The latter produced 1.6 μ mol CO2 fixed per m mol water transpired, compared to 3.6 μ mol CO2 in SRIm plants.

In this paper we attempt to remove the dichotomy created by distinguishing between participatory and non-participatory breeding programmes by using the degree of client orientation as the basis for an analysis. Although all breeding programmes are implicitly client-oriented, we examine how participatory approaches explicitly increase the extent of client orientation. We briefly review the history of participatory plant breeding (PPB) and analyse the participatory techniques used at different stages of the breeding programme. In common with several other authors, we find that farmer involvement in selecting in the segregating generations may not be an essential component of PPB. However, in some circumstances such collaboration is required and is the subject of a second paper in this series. The purpose of all the techniques used in PPB programmes is to better meet the needs of clients. Thus, breeding programmes can be differentiated by their extent of client-orientation removing the dichotomy involved with the term participatory. We discuss four techniques in the suite of techniques that have been employed by PPB: identifying the target market or clients; using germplasm that can best meet the needs of target clients; matching the environments of the target clients; and product testing in the target market with target clients. Most attention is paid to the last of these four that is often referred to as participatory varietal selection (PVS) and how it is done varies with circumstances. Rice varieties from a client-oriented breeding programme in Nepal were tested in mother and baby trials in Bangladesh. The rapid acceptance of these varieties by farmers illustrates the power of the participatory trials system and the success of a highly client-oriented breeding approach.

This paper investigates farmers’ perceptions of climate change and variability in southwest Uganda and compares them with daily rainfall and temperature measurements from the 1960s to the present, including trends in daily rainfall and temperature, seasonality, changing probability of risk and intensity of rainfall events. Statistical analyses and modelling of rainfall and temperature were performed and contrasted with qualitative data collected through a semi-structured questionnaire. The fieldwork showed that farmers perceived regional climate to have changed in the past 20 years. In particular, farmers felt that temperature had increased and seasonality and variability had changed, with the first rainy season between March and May becoming more variable. Farmers reported detailed accounts of climate characteristics during specific years, with recent droughts in the late 1990s and late 2000s confirming local perceptions that there has been a shift in climate towards more variable conditions that are less favourable to production. There is a clear signal that temperature has been increasing in the climate data and, to a lesser extent, evidence that the reliability of rains in the first season has decreased slightly. However, rainfall measurements do not show a downward trend in rainfall amount, a significant shift in the intensity of rainfall events or in the start and end of the rainy seasons. We explore why there are some differences between farmers’ perceptions and the climate data due to different associations of risk between ideal rainfall by farmers, including the amount and distribution needed for production, meteorological definitions of normal rainfall or the long-term statistical mean and its variation, and the impact of higher temperatures. The paper reflects on the methodological approach and considers the implications for communicating information about risk to users in order to support agricultural innovation.

Soil deficiencies of zinc (Zn) and boron (B) limit crop production in Nepal. Improving the micronutrient status of plants would increase yield and increase micronutrient content of the seeds, leading to better nutrition of the progeny crop and to improved human micronutrient nutrition. The primary micronutrient problem in grain legumes is B deficiency, while in rice (Oryza sativa), Zn deficiency is more important, and wheat (Triticum aestivum) suffers from both deficiencies. A series of field experiments was carried out over two seasons to compare soil fertilization and micronutrient seed priming as methods of improving Zn and B nutrition of each crop. Micronutrient treatments were evaluated for their effect on grain yield and grain micronutrient content. Soil B fertilization increased B content of the grain of lentil (Lens culinaris), chickpea (Cicer arietinum), and wheat by a factor of two to five, while increasing the yield of chickpea only. Soil fertilization with Zn had no effect on yield of any crop, but resulted in a small increase in Zn in wheat grain. Sowing micronutrient-primed seeds had no effect on yield or micronutrient content of the progeny seeds in most cases. During the first season, the primed chickpea seeds failed to emerge at either site, causing complete yield loss, but this negative effect was not observed in the second season with similar priming treatments at nearby sites, and no effect of priming on yield was observed with any other crop in either season.

The results of research into the water relations of cocoa are reviewed in the context of drought mitigation and irrigation need. Background information on the centres of production of the cocoa tree, and the role of water in crop development and growth processes, is followed by reviews of the effects of water stress on stomatal conductance, leaf water status and gas exchange, together with drought tolerance, crop water use and water productivity. Leaf and shoot growth occur in a series of flushes, which are synchronized by the start of the rains following a dry season (or an increase in temperature), alternating with periods of ‘dormancy’. Flowering is inhibited by water stress but synchronous flowering occurs soon after the dry season ends. Roots too grow in a rhythmic pattern similar to that of leaf flushes. Roots can reach depths of 1.5–2.0 m, but with a mass of roots in the top 0.2–0.4 m, and spread laterally >5 m from the stem. Stomata open in low light intensities and remain fully open in full sunlight in well-watered plants. Partial stomatal closure begins at a leaf water potential of about −1.5 MPa. Stomatal conductance is sensitive to dry air, declining as the saturation deficit increases from about 1.0 up to 3.5 kPa. Net photosynthesis and transpiration both consequently decline over a similar range of values. Little has been published on the actual water use of cocoa in the field. Measured ETc values equate to <2 mm d−1 only, whereas computed ETc rates of 3–6 mm d−1 in the rains and <2 mm d−1 in the dry season have also been reported. Despite its sensitivity to water stress, there is too a paucity of reliable, field-based published data of practical value on the yield responses of cocoa to drought or to irrigation. With the threat of climate change leading to less, or more erratic, rainfall in the tropics, uncertainty in yield forecasting as a result of water stress will increase. Social, technical and economic issues influencing the research agenda are discussed.