In eastern Zambia, farmers prefer direct seeded improved fallow species like Tephrosia vogelii to other species because of the reduced labour requirement for establishment. Since relying on two locally available provenances of T. vogelii could become ecologically unsustainable, due to pest and disease outbreaks, a wider range of usable direct seeded Tephrosia provenance material is desirable. A farmer participatory evaluation of Tephrosia candida provenances for their effectiveness as improved fallows and provision of construction materials and fuel wood was conducted. Using an indigenous board game called bao, 68 farmers rated the four provenances and five control species/provenances for these benefits. The T. candida provenances were rated high for soil fertility improvement. First year T. candida post-fallow performance showed that maize yields could be obtained that were comparable with yields following Tephrosia vogelii provenances. According to farmers' ratings, T. candida provenances could provide better fuel wood and light construction materials than T. vogelii, although they were not considered to be as good as Sesbania sesban and Senna siamea. Tephrosia candida provenances have the potential to be tested by many farmers on-farm. Farmers' methods of screening trees can complement scientific predictors, and their early integration into the selection and design of agro-forestry systems can improve relevance and adoption.

Seventeen photoperiod-sensitive genotypes of cowpea (Vigna unguiculata) were grown in approximately 30 photothermal environments in Nigeria. Photoperiods ranged from 10 to 16 h d−1, mean temperatures from 19° to 30°C and times from sowing to flowering (f) from 32 to 140 d. Rate of progress towards flowering (1/f) was related to mean pre-flowering values of temperature and photoperiod using simple linear rate models comprising one, two or three planes (thermal, photothermal and insensitive). There were no significant differences (p > 0.25) among genotypes in response to temperature within the thermal plane and the common base temperature was estimated to be 7.6°C. Photoperiod-sensitivity varied by a factor of 15 among genotypes, and the critical and ceiling photoperiods varied from 12.2 to 13.4 and from 13.8 to more than 16 h d−1 at a mean temperature of 27°C, respectively. These simple models satisfactorily predicted f in an independent data set (R2 = 0.62) for plants grown in the main cowpea growing seasons at latitudes between 7° and 13°N. The utility of photothermal models and methods to screen for photothermal responses are discussed.

In two field experiments conducted over five successive sugarcane crops (including four ratoon crops), yield decline was associated with a decrease in the organic carbon content of the soil. Reduction in cane yield was minimized by the combined application of farmyard manure and urea, which resulted in an increase in soil organic carbon of 0.023% over the initial status within five years. Incorporation of farm waste materials such as cane trash, rice straw and legume husk into the soil before cane planting also increased the soil organic carbon content. Maximum benefits, however, were produced by the incorporation of legume husk with 150 kg N ha−1. A judicious mixture of chemical fertilizer and organic manures is therefore suggested as a means of sustaining the productivity of sugarcane.

To assess genotype adaptability to variable environments, we evaluated five irrigated rice genotypes, three new varieties, WAS161, a NERICA, IR32307 and ITA344, and two controls: Sahel 108, the most popular short-duration variety in the region, and IR64. In a field experiment conducted at two locations, Ndiaye and Fanaye, along the Senegal River, rice was sown on 15 consecutive dates at one month intervals starting in February 2006. Yield (0–12.2 t ha−1) and crop cycle duration (117–190 days) varied with sowing date, genotype and site. Rice yield was very sensitive to sowing date and the associated temperature regimes. Spikelet sterility due to cold stress (T < 20 °C) was observed when the crops were sown in August (Ndiaye), September (Ndiaye and Fanaye) and October (Ndiaye and Fanaye), and heat stress (T > 35 °C) resulted in spikelet sterility when sowing took place in April (Ndiaye and Fanaye) and May (Fanaye). For all experiments the source and sink balance was quantified and showed that yield was most limited by sink size when sowing between July and October. Variety WAS 161 was least affected by genotype × environment interactions, resulting in lower interactive principal component values. An increase in minimum temperature of 3 °C could decrease spikelet sterility from 100 to 45%. These changes in temperature are likely to force rice farmers in the Senegal River to adjust the cropping calendar, e.g. to delay planting or to use heat-tolerant genotypes.

Twelve seedling cocoa families were evaluated as rootstocks in Sabah, Malaysia using three commercial cocoa clones as scions. The average yield was about 3 t dry cocoa beans ha−1. Yields on pure Scavina rootstock were about 10% above average and those on pure West African Amelonado about 10% below average. However, the effects of rootstock on yield were correlated with those on vigour and there was no effect on the ratio of yield to continuing vegetative growth. Rootstock did not influence bean weight or number of beans per pod or the uniformity of the trees. There was no indication of an interaction between rootstock and scion for any of the traits that were studied. The rootstock effect is considered large enough to warrant its control in critical work, especially field experiments with budded cocoa, but development of high performance scions is a higher priority in cocoa than intensive work with rootstocks.

Intercropped corn and soyabean were grown in a randomized block design (RBD) and a systematic design (SD) in 1981 and 1982 to evaluate total yield, yield complementarity, crop competition and land-use efficiency as affected by corn and soyabean densities. In the RBD, three corn density treatments were applied to corn–corn–soyabean–soyabean, corn–corn–soyabean, and corn–soyabean intercrop row patterns and to monocultures. In the SD, 9 or 10 corn densities were factorially combined with up to 13 soyabean densities in a corn–soyabean row pattern (91 cm spacing). In the RBD, total intercrop yields were similar to corn monoculture yields (60.8 to 62.7 t ha−1 in 1981) in the corn–corn–soyabean and corn–soyabean patterns at high corn densities but were less at low density. The corn–corn–soyabean–soyabean pattern yielded 87% of the corn monoculture at high density in 1982. These results were confirmed in the SD, where total intercrop yields were highly responsive to corn density and poorly responsive to soyabean densities. Both experiments indicated that high corn row densities are needed to maintain yields in corn–soyabean intercrops, possibly higher than the levels studied. Land equivalent ratios were above 1.0 for all but the low density corn–corn–soyabean–soyabean pattern in the RBD. The ability of an intercrop with as many as half the corn rows replaced by soyabean to produce yields similar to corn monoculture indicates a biological complementarity for dry matter production in the mixtures.

Fusarium and Lasiodiplodia species invade feeding lesions caused by mirid bugs (Distantiella theobroma [Dist.] and Sahlbergella singularis Hagl.) and inflict serious damage and yield loss to susceptible cacao (Theobroma cacao L.) varieties in West Africa. As it is the fungal invasion rather than the physical feeding injury by mirids that cause dieback and tree death in cacao, a dieback resistance strategy in cacao crop must take into account resistance to these causal agents. Twenty-nine and 15 cacao genotypes were screened in the laboratory and the greenhouse, respectively, for resistance to isolates of Fusarium decemcellulare and Lasiodiplodia theobromae at Imperial College London's Biological Sciences Campus, UK. Resistance was assessed as the size of necrotic lesions, distance of fungal colonisation in the stem and the proportion of seedlings with dieback symptoms. Genotypic differences were found in both laboratory and greenhouse tests among various cacao genotypes, and the clones showed a wide range of disease reactions from highly resistant to very susceptible. The pathogenicity of F. decemcellulare and L. theobromae were similar in this study, which suggests that a breeding programme for controlling one of the pathogens can have benefit against the other. Direct significant correlations (r = 0.7) were obtained between visual dieback assessment scores and the percentage cross-sectional area of stem necrosis. Moreover, the response of inoculated stem segments corresponded to the reaction of intact plants despite the variation in the used methodology. Three cacao genotypes (CATIE 1000, T85/799 and MXC 67) were resistant or moderately resistant to F. decemcellulare and L. theobromae. These genotypes could be useful sources of resistance to both pathogens and other wilt causing pathogens in cacao.

Good management of natural resources is the key to good agriculture. This is true everywhere – and particularly in the semi-arid tropics, where over-exploitation of fragile or inherently vulnerable agro-ecosystems is leading to land and soil degradation, productivity decline, and increasing hunger and poverty. Modern crop varieties offer high yields, but the larger share of this potential yield can only be realized with good crop management. The International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), working over a vast and diverse mandate area, has learned one key lesson: that technologies and interventions must be matched not only to the crop or livestock enterprise and the biophysical environment, but also with the market and investment environment, including input supply systems and policy. Various Natural Resource Management (NRM) technologies have been developed over the years, but widespread adoption has been limited for various reasons: technical, socio-economic and institutional. To change this, ICRISAT hypothesizes that ‘A research approach, founded on the need to integrate a broad consideration of technical, socio-economic and institutional issues into the generation of agricultural innovations will result in a higher level of adoption and more sustainable and diverse impacts in the rainfed systems of the semi-arid tropics.’ Traditionally, crop improvement and NRM were seen as distinct but complementary disciplines. ICRISAT is deliberately blurring these boundaries to create the new paradigm of IGNRM or Integrated Genetic and Natural Resource Management. Improved varieties and improved resource management are two sides of the same coin. Most farming problems require integrated solutions, with genetic, management-related and socio-economic components. In essence, plant breeders and NRM scientists must integrate their work with that of private and public sector change agents to develop flexible cropping systems that can respond to rapid changes in market opportunities and climatic conditions. The systems approach looks at various components of the rural economy – traditional food grains, new potential cash crops, livestock and fodder production, as well as socio-economic factors such as alternative sources of employment and income. Crucially the IGNRM approach is participatory, with farmers closely involved in technology development, testing and dissemination. ICRISAT has begun to use the IGNRM approach to catalyse technology uptake and substantially improve food security and incomes in smallholder farm communities at several locations in India, Mali, Niger, Vietnam, China, Thailand and Zimbabwe.

The effects of pre-flowering drought on millet were studied in two experiments, an on-station, dry-season trial under irrigation and an on-farm trial where drought was induced by natural rainfall regimes (one wet, two dry years). The on-station experimental conditions were adjusted to those of Sahel farms, particularly through low plant density, low soil fertility and an irrigation regime that simulated the natural rainfall pattern. The replanting (5–10%) of missing hills in the on-farm trial increased stand variance significantly, whereas small quantities of applied N reduced it. Grain yield and grain number were equally seriously affected by drought in both experiments; yields were 700–800 kg ha−1 in the control years compared with 200–300 kg ha−1 in drought years. Both experiments showed sub-populations of early-, intermediate- and late-flowering millet plants. Fertile tillers were concentrated in the group of early-flowering plants. Only this group when subjected to moisture stress could secure part of the grain production by delaying, to a maximum of 18 d, the development of fertile tillers beyond the period of stress. Later-flowering plants, mostly uniculm, would be either sterile or unaffected by drought, depending on the exact coincidence of panicle development and drought. Drought did not alter the number of fertile hills per stand, because earlier- or later-flowering plants in the same hill compensated for sterile plants. The period of flowering in a stand was stretched over 40–45 d independently of drought, and this occurred both in the on-station experiment comprising 19 plants per treatment and in the on-farm experiment comprising about 700 hills. Although stand variance was reduced by better crop management and resulted in more fertile hills, more panicles per hill, and taller hills of more uniform height, the spread in flowering period of the millet population tended to be unaffected. Stand variability therefore appeared to be of paramount importance in accounting for drought avoidance.

The nutrient composition of leaves and petioles of three yam species were studied at fortnightly intervals, and in the tubers when harvested at maturity. Highest concentrations of plant nutrients were recorded in D. alata, while D. cayenensis had the lowest. The lamina was more appropriate for determination of N and P contents, while the petiole was more satisfactory for K. Peak nutrient concentration occurred between late June and early July, suggesting that that was the period of maximum demand for nutrients. The dependence of yields on nutrients was demonstrated.

Canopy characteristics (leaf area index, fractional light interception, extinction coefficient) of mature trees of ten clonally propagated cacao cultivars were measured over a period of 14 months at an experiment site in Bahia, Brazil. Differences in leaf area index between clones became more pronounced over time. When an approximately constant leaf area index was reached (after about nine months), the leaf area index varied between clones from 2.8 to 4.5. Clonal differences in the relationship between leaf area index and fractional light interception implied differences in canopy architecture, as reflected by the range of extinction coefficients (mean values ranged from 0.63 for the clone TSH-565 to 0.82 for CC-10). The results demonstrate the potential for breeding more photosynthetically efficient cacao canopies.

The productivity of each component of a sorghum/groundnut intercrop and its constituent sole crops is determined in terms of a ‘Crop Performance Ratio’ (CPR) defined as the productivity of an intercrop per unit area of ground compared with that expected from sole crops sown in the same proportions. The CPR allows productivity, intercepted radiation and seasonal transpiration to be compared so that conversion coefficients for radiation (e; g MJ−1) and dry matter/water ratios (q; g kg−1) can be calculated for each intercrop component and its constituent sole crops. In this experiment, CPR for total dry weight in the intercrop was 1.08 and that for reproductive yield was 1.27. These advantages in overall productivity and yield were typical of those reported elsewhere for sorghum/groundnut intercrops. The proportional increase in total dry matter in the intercrop was largely a result of its greater interception of radiation. The further advantage in reproductive yield was a consequence of an improved harvest index in the sorghum component of the intercrop (0.64) compared with that of its sole crop counterpart (0.55).

Yield efficiency of cocoa, defined as yield over a period of time divided by the increment in trunk cross-sectional area over that period, was estimated in four factorial matings in Sabah, Malaysia, evaluated at a single planting density. The parents were 18 seedlings of Upper Amazon Forastero type, broadly representative of Peruvian Amazon material, and 15 clones of Trinitario type, selected from cultivated cocoa in Ecuador, Trinidad and Papua New Guinea. Both the Upper Amazon and Trinitario parents varied in general combining ability (gca) for yield efficiency, with strong evidence of additive inheritance of the trait. Some of the Upper Amazon parents showed higher yield efficiency than many of the Trinitarios. Correlations between gcas for yield efficiency and yield were inconsistent. This is thought to be because the parents differed markedly in optimal planting density, which is higher for many of the Upper Amazons with high gca for yield efficiency than it is for some of the Trinitarios. At the current stage of cocoa breeding, selection for adaptation to planting density is a higher priority than selection for yield efficiency.

Research has proved that integrated soil fertility management (ISFM) can increase crop yields at the field and farm scales. However, its uptake by smallholder farmers in Africa is often constrained by lack of technical guidelines on effective starting points and how the different ISFM options can be combined to increase crop productivity on a sustainable basis. A 4-year study was conducted on sandy soils (<10% clay) on smallholder farms in eastern Zimbabwe to assess how sequencing of different ISFM options may lead to incremental gains in soil productivity, enhanced efficiency of resource use, and increase crop yields at field scale. The sequences were primarily based on low-quality organic resources, nitrogen-fixing green manure and grain legumes, and mineral fertilizers. To enable comparison of legume and maize grain yields among treatments, yields were converted to energy (kilocalories) and protein (kg) equivalents. In the first year, ‘Manure-start’, a cattle manure-based sequence, yielded 3.4 t ha−1 of maize grain compared with 2.5 and 0.4 t ha−1 under a woodland litter-based sequence (‘Litter-start’) and continuous unfertilized maize control, respectively. The ‘Manure-start’ produced 12 × 106 kilocalories (kcal); significantly (p < 0.05) out-yielding ‘Litter start’ and a fertilizer-based sequence (‘Fertilizer-start’) by 50%. A soyabean-based sequence, ‘Soya-start’, gave the highest protein production of 720 kg against <450 kg for the other sequencing treatments. In the second year, the sequences yielded an average of 5.7 t ha−1 of maize grain, producing over 19 × 106 kcal and 400 kg of protein. Consequently, the sequences significantly out-performed farmers’ designated poor fields by ~ fivefold. In the third year, ‘Soya-start’ gave the highest maize grain yield of 3.7 t ha−1; translating to 1.5 and 3 times more calories than under farmers’ designated rich and poor fields, respectively. In the fourth year, ‘Fertilizer-start’ produced the highest calories and protein of 14 × 106 kcal and 340 kg, respectively. Cumulatively over 4 years, ‘Manure-start’ and ‘Soya-start’ gave the highest calories and protein, out-performing farmers’ designated rich and poor fields. Sunnhemp (Crotalaria juncea L.)-based sequences, ‘Green-start’ and ‘Fertilizer-start’, recorded the highest gains in plant available soil P of ~ 4 mg kg−1 over the 4-year period. Assessment of P agronomic efficiencies showed significantly more benefits under the ISFM-based sequences than under farmers’ designated rich and poor fields. Based on costs of seed, nutrients and labour, ‘Soya-start’ gave the best net present value over the 4 years, while ‘Fertilizer-start’ was financially the least attractive. Overall, the ISFM-based sequences were more profitable than fields designated as rich and poor by farmers. We concluded that ISFM-based sequences can provide options for farm-level intensification by different categories of smallholder farmers in Southern Africa.

The effect of one, two or three applications of monocrotophos at 1120 g ai/ha at weekly intervals was determined on cowpea var. Ife Brown. All regimes were equally effective in grain production in early 1974 but spray applications 35 and 42 days after planting gave the best result in the late crop. Grain production from two applications was not significantly different from three applications in 1975. The control plots in the late season of both years failed, due to moisture stress and lack of pest control measures. It is considered that two sprays at flowering is adequate to forestall a crop failure in this variety.

Osmotic constraints, nutrient deficiencies, especially phosphorus, and the lack of efficient strains of rhizobia in Mediterranean soils are major factors limiting symbiotic nitrogen fixation and yield in common bean (Phaseolus vulgaris). In order to improve yields, we investigated responses to rhizobial inoculation and P fertilization under glasshouse and field conditions with two bean cultivars, Coco blanc and BAT477. The nodulation test, using a hydroponic system in a glasshouse, revealed strong variability among 22 rhizobium strains of various origins, in their symbiotic efficiency, compared with Rhizobium tropici CIAT899. The introduced strains proved to be more efficient although some local rhizobia revealed high potential efficiencies. Glasshouse trials showed a significant effect of inoculation and P supply on nodulation, N content and shoot dry weight that varied with rhizobial strain. Field trials substantiated the glasshouse observations and emphasized the effects of cultivar-rhizobia interactions on symbiotic parameters and yields. It is concluded that inoculation with suitable rhizobia with supply of additional P is a technology that may improve symbiotic nitrogen fixation and yield in common bean in some soils under a Mediterranean climate.

The CGIAR System conducts research to produce international public goods (IPG) that are of wide applicability, creating a scientific base which speeds and broadens local adaptive development. Integrated natural resources management (INRM) research is sometimes seen to be very location specific and consequently does not lend itself readily to the production of IPGs. In this paper we analyse ways in which strategic approaches to INRM research can have broad international applicability and serve as useful foundations for the development of locally adapted technologies. The paper describes the evolution of the IPG concept within the CGIAR and elaborates on five major types of IPGs that have been generated from a varied set of recent INRM research efforts. CGIAR networks have both strengths and weaknesses in INRM research and application, with enormous differences in relative research and development capacities, responsibilities and data access of its partners, making programme process evolution critical to acceptance and participation. Many of the lessons learnt regarding challenges and corresponding IPG research approaches are relevant to designing and managing future multi-scale, multi-locational, co-ordinated INRM programmes involving broad-based partnerships to address complex environmental and livelihood problems for development.

Defoliation affected inflorescence production by oil palms, causing a decrease in sex ratio (ratio of female inflorescences to total) and an increase in abortion rate. Clones differed in response to defoliation. One of seven clones showed no increase in abortion rate; in one clone there was a tendency for female inflorescences to abort in greater numbers than males. The change in sex ratio occurred much sooner after defoliation in some clones than in others, and comparison of flowering records with dissections done at the time of defoliation indicated that inflorescence sex was affected at more than one stage in development. This has important consequences for attempts to predict yields.

Three varieties of rice, selected for their differences in height and tillering ability, were grown side by side in 10-row plots to determine the effect of varietal competition on plot yields. Plants in border rows performed differently from those in the centres of plots, higher-tillering or taller varieties tending to depress the performance of adjacent plants. Comparisons among varieties based on plot yields, determined with and without excluding the border rows, gave different results. Excluding two rows on each side of a plot was sufficient to eliminate the effects of varietal competition on yield data.

Manure is a key input to smallholder farming systems, especially in the semi-arid environment of West Africa where cost and availability limit the use of inorganic fertilizers. This paper considers manure management by farmers in an intensive integrated farming system in the Nigerian savanna. The paper reports farmers' indigenous knowledge concerning manure production, quality and application, chemical analysis of manure nutrient content and application rates of manure. The potential manure supply of the livestock population of the Kano close-settled zone is calculated and compared with application rates. Recommendations are made concerning methods for improving manure quality through changes in management practices.