Large yields and dry matter production rates have been recorded for tropical perennial crops, despite the fact that little research has been done on most of them. Considerable increases in productivity should still be possible, since the potential energy fixation rate for such crops is estimated to be about 1.2 TJ ha−1 a−1. The dry matter equivalent of this energy varies between species; the oil crops and rubber, in particular, have large energy contents in their respective economic products. Hot leaf temperatures appear to limit productivity in some crops, while unfavourable partitioning of assimilates limits yield at the large leaf area indices necessary to maximize dry matter production. Respiratory losses are large in these crops and selection for smaller respiration rates could lead to considerable improvements in their net productivity.

The evolution of the Mediterranean pulses, the common pea (Pisum sativum L.), the faba bean (Vicia faba L.), the grass pea (Lathyrus sativus L.), the lentil (Lens culinaris Medik.) and the chickpea (Cicer arietinum L.), is considered from the points of view of geographic origin and subsequent dissemination. All appear to have originated in the Fertile Crescent, the most significant subsequent spread being to the north of the Mediterranean basin in the case of the common pea and the faba bean and to the east of it in the case of the other three species. The wild progenitor type is known for all species except the faba bean. In the grass pea the extent of divergence between wild and cultivated populations is small, possibly due to its use predominantly for forage and less as a pulse. Considerable divergence has occurred in other species, where use as a pulse is more important.

Additivity, variance homogeneity, and normality are often regarded as prerequisites for analysis of variance. Although they are desirable, their truth is never certain; they are important to probability levels in significance tests, but not to the general informativeness of the analysis. Transformation of data may improve conformity to these desiderata at the cost of producing results on a scale ill-suited to the objectives of the experiment. In this paper the generalized power transformation and the inverse sine transformation are described, and the practical problems of choosing an optimal transformation discussed. An ideal choice can seldom be based on the evidence of one experiment, and adopting the same transformation for a series of similar experiments is usually more helpful than a search for the ‘best’. Warnings are given about inappropriate guides to the choice of transformation. In some experiments, separate analyses for two or more obviously distinct sets of treatments may be more rewarding than any attempt to find a transformation that will enable all to be handled at once. When one or two treatments (or treatment combinations in a factorial experiment) show data wildly out of line with all others, consideration of reasons should precede and possibly replace any approach through transformation. A sound general principle is that data are usually most clearly interpreted on the original scale of measurement. Therefore, transformations should be avoided unless clearly necessary; by this advice, I do not imply prohibition. Finally, attention must be given to the presentation of results; the most effective presentation does not necessarily employ a transformation or other special device adopted earlier in a statistical analysis.

The results of research on the water relations and irrigation need of banana are collated and summarised in an attempt to link fundamental studies on crop physiology to irrigation practices. Background information on the ecology of the banana and crop development processes, with emphasis on root growth and water uptake, is presented, followed by reviews of the influence of water stress on gas exchange (stomatal conductance, photosynthesis and transpiration), crop water use, and yield. Emphasis is placed on research that has international relevance and, where appropriate, three geographical areas (the tropics, subtropics and Mediterranean climates) are considered. Although roots can extend to depths of 1.0–1.5 m, the ‘effective’ depth of rooting is usually taken to be 0–0.40 m, sometimes extending to 0.60 m. Stomatal conductance is a sensitive measure of soil water availability and plant water status, whilst transpiration rates can be limited by dry air (saturation deficits >2.0 kPa). In the subtropics, there are seasonal differences in the crop coefficient (Kc) with values ranging from 0.6 in the winter months to about 1.0 Epan in the summer. It is difficult to draw generic conclusions with wide applicability from the irrigation experiments as they were reported. All the components of marketable yield can be enhanced by irrigation whilst applying insufficient water delays crop development. Annual yield responses to irrigation are variable, but water use efficiencies of 40 kg ha−1 mm−1 (fresh fruit/water applied) have been achieved in the tropics and subtropics (and elsewhere up to 80 kg ha−1 mm−1 with ‘partial’ replacement of the soil water deficit). To ensure large yields of (marketable) fruit, soil water deficits must be kept low (Ψm > −20 kPa at 0.2 m depth). In the subtropics, this means irrigation intervals should not exceed 2–3 d during the summer. The cooling effect of irrigation with micro-sprinklers on the soil and pseudostem temperatures, compared with drippers, can delay crop development and reduce annual yields by 30%. There is some (limited) evidence that the presence of the B genome contributes to drought tolerance. Yield response factors to irrigation for different growth stages have yet to be confirmed. Opportunities to improve the water productivity of the many, diverse banana cultivars need to be explored further.

The paper provides an overview of institutions, scientists, and practitioners involved over the years in the various ways in which participatory plant breeding (PPB) is implemented, with indication of the crops involved and the countries in which it took place, or is still taking place. This might help creating a better awareness of the scope (both geographical and crop wise) of the different methodologies as well as of their advantages, disadvantages, applicability, and limitations. Through a literature survey, we found 254 publications showing that over a period of 36 years participatory approaches in plant breeding have been used in 69 countries (10 developed and 59 developing) with 47 crops including self-pollinated, cross-pollinated, and vegetatively propagated crops, by several Institutions including CGIAR centers, universities, and NGOs. We argue that there are no obvious scientific or technical reasons limiting the use of PPB, and we interpret the limited institutionalization as a difficulty to accept the paradigm shift that participation implies.

A two-year field trial was conducted to study the effects of prolonged water stress on cassava (Manihot esculenta) productivity, and on nutrient uptake and use efficiency. Four contrasting cultivars were supplied with adequate fertilization and watering, except when water was excluded by covering the soil with plastic sheets for different periods, depending on treatment: from two to six months, four to eight months, or from six to twelve months after planting (early, mid-season and terminal stress respectively). Sequential harvests were made at 2, 4, 6, 8 and 12 months after planting to determine leaf area index and shoot and root biomass. At final harvest, nitrogen, phosphorus, potassium, calcium and magnesium concentrations in shoots and storage roots were determined.

During both early and mid-season stress, leaf area index and shoot and root biomass were significantly smaller than those in the controls across all cultivars. After recovery from stress, leaf area index was greatly enhanced with less dry matter allocated to stems, and root yields approached those in the controls. One cultivar, CMC 40, had greater final root yield under stress treatments. Nutrient concentration in roots and shoots was less in all cultivars with early stress and resulted in higher nutrient use efficiency in all elements for root production. The same trend was observed under mid-season stress, except for nitrogen concentration, which remained unchanged.

Terminal stress did not affect leaf area index, but reduced the shoot biomass in all cultivars. Final root yields were smaller than those in the controls except for CMC 40 whose final root yield was greater under stress. Nitrogen concentration was greater in root biomass but less in shoot biomass of all cultivars, resulting in lower nitrogen–use efficiency for root production. Across cultivars, only potassium- and magnesium-use efficiencies were greater than in the controls. CMC 40 was the only cultivar with consistently greater use efficiency of nitrogen, phosphorus, potassium, calcium and magnesium for root production under terminal stress. This higher nutrient use efficiency was due, mainly, to a greater root production rather than to smaller nutrient concentration. This cultivar is suitable as a gene source for improving cassava in order to maximize root production per unit nutrient extracted under stressful environmental conditions.

Farmer participatory research (FPR) approaches are now considered mainstream and are especially applicable for developing appropriate technology options in complex, diverse and risk-prone regions, where local adaptations are crucial. Although the advantages of using farmer knowledge to guide scientific research are numerous and well documented, the challenges and potential pitfalls that befall biophysical researchers, in particular, when using FPR approaches have received much less attention, especially in sub-Saharan Africa. Our experiences show that in certain cases, the methods used to collect farmer knowledge are flawed, leading to inaccurate or incomplete information being gathered. This potentially leads to the development and promotion of unsustainable, unprofitable or socially unacceptable technologies. This paper uses a series of examples to illustrate that discrepancies between farmer and researcher observations may occur because (i) farmers and scientists may not have sufficient insight into the systems complexity, (ii) farmers and scientists use different reference frameworks, and (iii) methodological errors may lead to farmers intentionally or unintentionally providing false or ‘desired’ information to achieve (short-term) benefits. This paper concludes by providing guidelines to improve the integration of farmer and scientific knowledge in order to develop appropriate technology options that are both environmentally sound and adaptable to local conditions.

Intercropping maize or sorghum with pigeon peas, cowpeas or beans led to a reduction in leaf area indices, fresh weight yield at time of anthesis, straw yield at harvest and grain yield of the cereal crops. In sorghum, pigeon peas and cowpeas had a greater adverse effect on grain yield than beans, but with maize, beans and cowpeas had a more adverse effect on grain yield than pigeon peas. While intercropping maize with either beans or cowpeas decreased total yield of grain (cereal and legume) per hectare, intercropping sorghum with pigeon peas increased total grain yield per hectare.

Effectively nodulated cowpea plants, grown in pots without applied nitrogen, were vegetatively equal to non-nodulated plants supplied with 60 ppm N throughout growth (88 days) and produced significantly greater seed yields. Supplying non-nodulated plants with 120 or 240 ppm N improved seed yields (but not significantly) compared with plants completely dependent on symbiotic fixation. Nodulation promoted branching, and improved pod set and/or retention compared with plants relying on applied N.

In a field experiment, microbiological and chemical amelioration of a highly deteriorated alkaline soil (pH 10.6, exchangeable sodium percentage 95) was undertaken during 1989–92 using two reclamation technologies: namely, growing Karnal grass (Leptochloa fusca) as a first crop in the absence of any amendment (biological reclamation) or applying gypsum as a chemical amendment for different cropping sequences. After ten months average dehydrogenase activity, used as a measure of catabolic activity of micro-organisms under anaerobic conditions, was 49.5 μg triphenylformazan (TPF) per g soil in treatments where the soil was reclaimed by growing Karnal grass, compared with 26.8 μg TPF by applying 50% of the estimated requirement of gypsum. After three years of reclamation, average dehydrogenase activity was 118.7 μg TPF per g soil with Karnal grass and 96.1 μg TPF with gypsum. After three years average microbial biomass carbon was 28% greater in the gypsum treatments (206.5 mg per kg soil) compared with Karnal grass treatments (161.7 mg). However, at this stage the ratio between average dehydrogenase activity and microbial biomass carbon was greater with Karnal grass (0.77) than in gypsum treatments (0.47). The microbiological properties changed more than the chemical properties of alkali soil as the time period advanced. After three years of reclamation, the average pH of the alkali soil dropped from 10.6 to 9.45 and the average exchangeable sodium percentage was reduced from 95 to 47.5. The increase in total organic carbon was 64% and in available nitrogen about 38% compared with the original soil. Higher microbial biomass carbon in gypsum treatments corresponded with lower exchangeable sodium percentage, higher availability of nitrogen and potassium and greater total yield of sensitive winter clovers.

Uniform descriptions of developmental stages in crops improve communication among producers, researchers and others. This paper gives a uniform system for the description of the developmental stages of lentil that we believe is not only universally applicable to all growing environments (field or greenhouse) and to divergent cultivars, but also useful for single plants or communities of plants. Vegetative and reproductive development are described separately. Vegetative growth stages are described by counting nodes on the main stem and continuing the count up the basal primary branch to include the highest fully developed leaf. Reproductive stages Rl and R2 are based on flowering, R3 to R6 on pod and seed development, and R7 and R8 on maturation.

The physiological performance of four cacao clones was examined under three artificial shade regimes over the course of a year in Ghana. Plants under light shade had significantly higher photosynthetic rates in the rainy seasons whereas in the dry season there was a trend of higher photosynthetic rates under heavy shade. The results imply that during the wet seasons light was the main limiting factor to photosynthesis whereas in the dry season vapour pressure deficit was the major factor limiting photosynthesis through stomatal regulation. Leaf area was generally lower under heavier shade but the difference between shade treatments varied between clones. Such differences in leaf area allocation appeared to underlie genotypic differences in final biomass production in response to shade. The results suggest that shade for young cacao should be provided based on the current ambient environment and genotype.

The effect of seed priming and micro-dosing (the application of small amounts of mineral fertilizers) was studied in sorghum and pearl millet in on-station and on-farm experiments for three seasons under rainfed conditions in the North Kordofan State, western Sudan. Seed priming consists of soaking the seeds for eight hours in water prior to sowing. Seed priming increased sorghum grain yield in the on-station experiments across three seasons from 482 kg ha−1 to 807 kg ha−1. Micro-dosing of 0.3 g, 0.6 g and 0.9 g NPK fertilizer (17-17-17) per pocket increased sorghum grain yield by 50.4, 68.8 and 109.7% respectively compared to the control. Seed priming did not significantly increase pearl millet yield while the micro-doses of 0.3, 0.6 and 0.9 g fertilizer increased millet yield by 31.3, 30.7 and 47% respectively. On-farm seed priming increased sorghum yields by 32.6% while seed priming plus 0.3 g fertilizer increased yields by 69.5%. For millet, the corresponding yields increased by 29.8% and 71% respectively. Fertilizer use efficiency for both crops increased remarkably with seed priming, although this effect was more apparent in sorghum than in millet. In sorghum, seed priming and the application of 0.9 g fertilizer per pocket increased the gross margin from 49.5 to 206.5 US$/ha. For millet, the gross margin increased from 44.9 in the control to 90.0 US$/ha with the combination of seed priming and 0.3 g fertilizer per pocket. These technologies are simple to apply; they offer low financial cost and low risk and are affordable for resource-poor farmers.

We studied physiological traits of 12 Criollo cocoa cultivars growing in a germplasm bank in the southern region of Maracaibo Lake Basin, during the rainy (RS) and dry seasons (DS) of 2007. A further evaluation of photosynthetic responses to changes in environmental parameters was done on three cultivars: Los Caños 001 (LCA001), Sur Porcelana 010 (SP010) and Escalante 001 (ESC001) in 2009 and 2010. Leaf water potential (ΨL) of most cultivars decreased during the DS of 2007, with the exception of ESC001. Maximum photosynthetic rate (Amax), stomatal conductance and water use efficiency varied among cultivars and seasons. The CO2-saturated photosynthetic rate (ACO2sat) was higher in LCA001 and ESC001 than in SP010, with no differences in carboxylation efficiency. Light curve responses of the three cultivars were similar. In all cultivars, no evidence of chronic photoinhibition was observed, since maximum quantum yield of photosystem II was high (0.77–0.81). We conclude that ESC001 has the best physiological performance (ΨL remained unchanged, highest Amax, ACO2sat and photochemical activity), and it seems to be a promising cultivar for cocoa agroforestry systems in the southern region of Maracaibo.

Photosynthetic photon flux density (PPFD) has variable effects on cotton (Gossypium hirsutum) plant growth, development and lint yield, but little is known about the responses of yield, yield components and fibre quality to low PPFD at different developmental stages. Field studies were conducted in 1993–95 to determine the effects of an 8-d period of shade (63% reduction in PPFD) imposed at different developmental stages (pinhead square (PHS), first flower (FF), peak flower (PF) and boll development (BD)) on cotton growth, lint yield, yield components and fibre quality. Shade for 8 d at the early square stage did not affect cotton growth and yield. Shade during FF, PF and BD increased fruit abscission, and decreased specific leaf weight, dry matter accumulation, lint yield, fibre micronaire, and fibre strength compared with the unshaded control. The detrimental effect of shade on yield increased with later growth stages. Shade at the FF, PF and BD stages decreased lint yield by 18, 34 and 52% in 1993, and by 18, 21 and 29% in 1994 respectively compared with the unshaded control. Shade caused the greatest decrease in the dry weight (DW) of fruits (squares + flowers + bolls) and the smallest decrease in leaf DW among leaves, stems and fruits. Of the three yield components (boll number, boll weight and lint percentage), boll number was the most sensitive to shade. Shade during squaring and early flowering had little effect on average boll weight, and did not affect lint percentage. Decreased yield of cotton shaded during FF and PF appeared to be related to decreased boll retention. Shade during BD decreased both boll retention and average boll weight. Under shade conditions, fibre micronaire and fibre strength were decreased, while other fibre properties were unaffected. These results help explain the yield response of field-grown cotton to low PPFD stress.

When a leaf absorbs radiant energy, only a small fraction is stored chemically in photosynthesis. In sunlight, this fraction is at most one-fifth of the energy in the visible spectrum, decreasing with increasing light intensity because of the finite resistance to the diffusion of carbon dioxide through the leaf to the chloroplasts. Energy absorbed but not stored in photosynthesis is dissipated by transpiration and convection.

The potential or maximum photosynthesis of a crop canopy can be estimated from a set of six parameters describing the photosynthesis-light curve of single leaves, the arrangement of leaves in the canopy, and radiation climate. Comparing estimates of potential photosynthesis with measurements of carbon dioxide exchange over a field of sugar beet, the estimated rate of respiration was 2 gm carbohydrate per m2 leaf area per day, equivalent to 44 per cent of gross photosynthesis over the whole growing season. Over the season, the foliage lost 34 per cent of incident radiation by transmission to the soil.

The potential rate of transpiration can be found from Penman's formula assuming values of external (aerodynamic) and internal (mainly stomatal) resistance for the canopy as a whole. In south-east England, the energy for potential transpiration is almost equal to net heat H in summer and is therefore about half the energy of incoming solar radiation. For a real crop of grass subject to moisture stress, transpiration was less than the potential rate at about 0·8 H on average and 0·3 H in very dry weather.

During the summer, cumulative photosynthesis increases linearly with cumulative transpiration to give a production ratio (gross photosynthesis/transpiration) of 1/100 in the Thames Valley and 1/200 in the Sacramento Valley. The production ratio is expected to change with crop type as well as with climate.

Innovation Platforms (IPs) have become a popular vehicle in agricultural research for development (AR4D). The IP promise is that integrating scientific and local knowledge results in innovations that can have impact at scale. Many studies have uncovered how IPs work in various countries, value chains and themes. The conclusion is clear: IPs generate enthusiasm and can bring together stakeholders to effectively address specific problems and achieve ‘local’ impact. However, few studies focus on ‘mature’ IPs and whether or not these achieve impact at a ‘higher’ scale: address systems trade-offs to guide decision making, focus on integration of multiple commodities, reach a large number of beneficiaries and learn from their failures. This study evaluates the impact of mature IPs in AR4D by analysing the success factors of eight case studies across three continents. Although we found pockets of IP success and impact, these were rarely achieved at scale. We therefore critically question the use of IPs as a technology dissemination and scaling mechanism in AR4D programs that aim to benefit the livelihoods of many farmers in developing countries. Nevertheless, we do find that IPs can fulfil an important role in AR4D. If the IP processes are truly demand-driven, participatory and based on collective investment and action, they have the ability to bring together committed stakeholders, and result in innovations that are technically sound, locally adapted, economically feasible for farmers, and socially, culturally and politically acceptable. Several of our cases show that if these IPs are firmly embedded in other public and private extension mechanisms and networks, they can allow the technologies or other types of innovations to scale out beyond the original IP scope, geographical focus or target audience. We see a need for more rigorous, accurate and continuous measurement of IP performance which can contribute to adaptive management of IPs, better understanding of ‘what works’ in terms of process design and facilitation, as well as to cost-benefit analysis of IPs as compared to other approaches that aim to contribute to agricultural development.

The new Brazilian Forest Code obliges farmers to restore degraded lands on conservation set-asides required on all rural properties, known as Permanent Preservation Areas and Legal Reserves. While farmers can do so through agroforestry systems (AFS) to improve their livelihoods and offset the costs of restoration, these areas must also maintain basic ecological functions. How this can be done in practice, however, stills need to be regulated at the state level, but there are few scientific studies in Brazil on the costs and benefits of restoration through AFS. These knowledge and policy gaps have left ample room for interpretation and thus discouraged technicians from recommending — and policymakers from regulating — AFS for restoration. Aiming to bridge these gaps, this study draws from a comprehensive literature review, expert knowledge, stakeholder participation and analyses of agroforestry-based restoration efforts in the field. First, we discuss the social and ecological benefits of AFS as well as key constraints to upscaling agroforestry-based restoration. Focusing on different biophysical and social contexts within the Brazilian Cerrado and Caatinga biomes, we conclude that AFS can provide win–win solutions for reconciling livelihoods needs with conservation goals and propose practical options to do so, which vary according to farmer objectives, resource constraints and opportunities. In order to guide implementation of these agroforestry options, we propose design principles and criteria as well as key species and management practices most suited to different contexts and farmer objectives.

In recent studies of cassava at CIAT, net CO2 uptake rates of 20 to 35 μmol CO2 m−2 s−1 were commonly observed. Cassava photosynthesis has a high optimum temperature (35°C) and a wide plateau (25 to 35°C) corresponding to the temperature range under which cassava is cultivated. Leaf photosynthesis requires high saturation irradiance (1500 μmol m−2 s−1) and the rates are greatly reduced by leaf-air vapour pressure differences above 1.5 kPa; this reduction is associated with stomatal closure. Cassava leaves have low photorespiration, low CO2 compensation point, high percentage of carbon fixation in C4 acids and a high PEP-carboxylase activity (15–35% of that in maize), but cassava does not have the typical ‘C4-Kranz’ anatomy. Field measurements of single leaf photosynthesis among a wide range of cultivars grown under rain-fed conditions showed that when light interception was not limiting, there were significant correlations between leaf photosynthesis, total biomass and root yield. This suggests that the use of parental materials with high photosynthetic capacity, in combination with other yield determinants, could be a successful strategy for developing high yielding cultivars. This might be done by exploiting any genetical variations in leaf anatomy and biochemistry that could enhance photosynthesis efficiency and hence productivity.

The response of tea shoots to temperature was studied in the field and in controlled environments. Shoot extension stopped below about 12.5°C. Shoots of mature tea took 491 day degrees above the base temperature of 12.8°C to grow to a harvestable size of 15 cm.