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.

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.

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.

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.

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.

The residual effects of subsoil compaction (below 0.15 m depth) on soil properties, growth, yields and nutrient uptake by irrigated wheat (Triticum aestivum) and cotton (Gossipium hirsutum) are reported. The study was initiated during 1997 on a sandy clay loam soil in a semiarid region of Pakistan. Results showed that the adverse effects of subsoil compaction on bulk density, penetration resistance, total porosity and air-filled porosity of soil persisted for at least four years. In the third and fourth years after the imposition of treatments, compaction decreased yields of wheat by 12–18% and by 7% for cotton. The corresponding reductions in nutrient uptake by wheat were 11–16% for N, 11–15% for P and 5–10% for K. For cotton, the values were 9% for N, 3% for P and 7% for K. Subsoil compaction decreased nutrient use efficiency by 16% in wheat and 5% in cotton. The reductions in water use efficiency were estimated to be 11% in wheat and 7% in cotton. Wheat root length density was also decreased in the subsoil.

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.

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 efficiency of many intercropping research programmes could be improved if research workers made fuller use of modern statistical knowledge about experimental design. Important statistical considerations for experimental design and plot sampling are reviewed and their relevance to intercropping research assessed. The general philosophy of factorial structure and blocking, and specific ideas on the use of systematic designs and monocrop plots, are discussed.

Groundnuts given a mixture of S35-labelled ground rock phosphate and sulphur at planting were radioactive 14 days later, when go per cent of the seedlings had emerged. Forty days after planting one-third of the total plant-S was from the fertilizer, and the mean recovery of fertilizer-S was 18 per cent by harvest. In field experiments the mixture outyielded ground rock phosphate and was as good as single superphosphate, though drought diminished yields generally. At three sites which were harvested the percentages of applied-S recovered were 12, 20 and 27 per cent. Significantly more P was taken up by the crop receiving the mixture than was recovered from the ground rock phosphate alone.

The yield responses of clonal tea (Clone 6/8) to irrigation and fertilizer were studied in a field experiment (based on the line-source technique) at a high altitude site (1840 m) in the Southern Highlands of Tanzania over a three-year period. In this area (latitude 8°33′S) the annual dry season can last up to six months with potential soil water deficits reaching 600 to 700 mm. In the third year of the experiments yields for the fully irrigated, well fertilized (375 kg N ha−1) treatments had reached 4.9 t ha−1 of made tea. These were reduced by about 2.9 kg ha−1 for each mm increase in the potential soil water deficit. For tea with little or no fertilizer applied the loss of yield was about 1.4 kg ha−1 mm−1. These figures provide a basis for assessing the potential benefits from irrigation where other factors, such as large saturation deficits of the air, do not restrict shoot extension and yield. Yield responses to nitrogen (applied as N:P:K 20:10:10) were essentially linear up to a maximum of about 375 kg N ha−1 in the fully irrigated plots, and 300 kg N ha−1 for the unirrigated plots. Irrigation increased the proportion of crop harvested during the dry season, up to 45% in the fully irrigated treatments. The commercial implications of these results for ‘high’ and ‘low’ input producers are discussed.

Bambara groundnut (Vigna subterranea) is one of the most promising food legumes in Africa, due to its agronomic and nutritional potential. To take advantage of these attributes, several research programmes gathering agronomic and genetic data are being implemented throughout Africa. In this context, the response of yield and yield components to sowing density and seedbed type were tested in a three-year (2005, 2006 and 2007) field experiment using a bambara groundnut landrace with a semi-bunch growth habit. Three plant population densities: 13 900 plants ha−1, 62 500 plants ha−1 and 250 000 plants ha−1 were coupled with two seedbed types – raised and flat. A factorial trial using a split-plot design with three replicates was set up to analyse seed yield and plant biomass, as well as nine yield components. Sowing density influenced significantly (p < 0.05) seed yield (direct relationship) and most of the yield components (inverse relationship). The highest seed yields were observed on high-density plots (4.11 ± 1.05 ha−1). In contrast, seedbed type and year of experiment did not influence significantly the marketable yield and plant biomass (p > 0.05). This result has been attributed to the suitability of the amount and distribution of rainfall and temperature for the production of bambara groundnut at the target site. Based on the trend of yield response, cultivation of landraces of bambara groundnut characterized by a semi-bunch growth habit at high density on flat seedbeds was suggested in woodland savannas of Côte d'Ivoire to enhance seeds yield and reduce labour.

The extent to which coffee agroforestry systems provide ecosystem services depends on local context and management practices. There is a paucity of information about how and why farmers manage their coffee farms in the way that they do and the local knowledge that underpins this. The present research documents local agro-ecological knowledge from a coffee growing region within the vicinity of the Aberdare Forest Reserve in Central Kenya. Knowledge was acquired from over 60 coffee farmers in a purposive sample, using a knowledge-based systems approach, and tested with a stratified random sample of 125 farmers using an attribute ranking survey. Farmers had varying degrees of explanatory knowledge about how trees affected provisioning and regulating ecosystem services. Trees were described as suitable or unsuitable for growing with coffee according to tree attributes such as crown density and spread, root depth and spread, growth rate and their economic benefit. Farmers were concerned that too high a level of shade and competition for water and nutrients would decrease coffee yields, but they were also interested in diversifying production from their coffee farms to include fruits, timber, firewood and other tree products as a response to fluctuating coffee prices. A range of trees were maintained in coffee plots and along their boundaries but most were at very low abundances. Promoting tree diversity rather than focussing on one or two high value exotic species represents a change of approach for extension systems, the coffee industry and farmers alike, but is important if the coffee dominated landscapes of the region are to retain their tree species richness and the resilience this confers.

Recent years have seen increasing political interest and growing public health awareness and advocacy for diversifying diets into highly nutritious traditional vegetables, fruits and other nutrition-sensitive crops as a more viable approach to mitigate the growing scourge of malnutrition due to unhealthy and imbalanced diets. These foods contribute essential micronutrients, vitamins, antioxidants, and other health-related phytochemicals to staple-based diets and their consumption is crucial for the attainment of several Millennium Development Goals. Despite their nutritional benefits and the high farm gate values per unit of land, the production and marketing of traditional vegetables from Tanzania and other countries in sub-Saharan Africa are constrained by factors such as poor quality seeds, lack of appropriate market information and support systems, and lack of consumer awareness of their nutritional importance. This paper investigates the determinants and pathways for smallholder participation in traditional African vegetable production and identifies entry points for farmers to increase traditional vegetable production by linking nutritional awareness and promotion with potential high value markets. A primary survey of 181 traditional vegetable growers from five regions of Tanzania indicates that perceptions about the nutritional value of traditional African vegetables are a main driver of household production decisions in the sector. The results of this study provide evidence that farmers tend to grow more African traditional vegetables as compared to other crops based on their increased level of perception towards nutritional value of traditional vegetables along with other factors such as their market value, timely availability of quality certified seeds, willingness to invest in labour, required training for women and better access to credits. Farm size negatively affects growing traditional vegetables, implying that on a comparative basis, smallholders tend to grow more traditional vegetables than larger-farm operators. Thus, more attention should be given to reducing production and its associated transaction costs by ensuring timely access to quality certified seeds, ensuring optimal use of inputs and increasing labour productivity, particularly for smallholders.

There is a quest for resource-conserving technologies that can save water, reduce production costs and improve production to address the slow down in productivity growth in the Indo-Gangetic Plains, the cereal bowl of South Asia. Findings from farm surveys are used to evaluate the farm household factors that affect the adoption of zero tillage (ZT) wheat in the rice-wheat systems of India's Haryana State and Pakistan's Punjab province. Three adoption classes are distinguished in each site: ZT adopters, dis-adopters and non-adopters. Bivariate analysis shows that adopters typically have the most favourable values for most of the indicators compiled and the non-adopters the least favourable, with dis-adopters often taking an intermediate position. The study highlights that ZT adoption in the initial diffusion stage is strongly linked to the wealth of the farm household. This indicates the need for closer consideration of equity implications in future research and development. The structural differences between adoption categories also easily confound the assessment of ZT impact.

Potato is an important source of food and income in the highlands of East Africa. Identification of superior genotypes for improved agronomic characteristics will enhance tuber yield. Seven promising clones from population B potato selections (quantitative resistance to late blight) obtained from the International Potato Center, two genotypes from population A (qualitative resistance) and three control cultivars were evaluated for three cropping seasons at four locations in western Uganda in order to determine performance and yield stability. The additive main effects and multiplicative interactive (AMMI) model was used for the analysis. The analysis of variance of yield data for genotypes × locations, genotypes × seasons and genotypes × locations × seasons was significant (p < 0.05) showing the variable response of genotypes and the need for stability analysis. The AMMI statistical model showed that the most stable genotypes were 392618.250 (B5) and 392127.270 (B6) (high yield) and 392618.256 (B1), 391049.255 (B2) and 392127.256 (B7) (low yield) and had negligible interactions with the environments. Across environments, the ranking of genotypes for tuber yield was not consistent. The clones 381471.18 (A2), 387121.4 (A1) and cultivar Victoria had high average yields, but these yields were below average in a few environments. Selective deployment of cultivars can improve tuber yield in the highland tropics.

Note: Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation for endorsement by the US Department of Agriculture, Makerere University or Kachwekano Agricultural Research and Development Center.

Forty different cultivars of cassava were grown in unreplicated plots at a plant population of 20,000 plants/ha in fertile soil. Harvests were taken at 4, 6, 8, 10 and 12 months after planting 18 varieties. The characteristics of the two highest yielding varieties, M Colombia 113 (66 t/ha) and M Colombia 22 (32 t/ha), were compared with the other types. M Colombia 22 is an early type (25 t/ha after 6 months) with a very high harvest index; M Colombia 113 yields little better than average 6 months after planting. High yield is associated with a balance between leaf production and root production, so that leaf area index does not decline excessively in the later growth stages. Changing canopy structure is unlikely to increase yields.

In a short-term competition experiment in large containers, growth of cotton planted 3 weeks after bermudagrass (Cynodon dactylon), johnsongrass (Sorghum halepense) or purple nutsedge (Cyperus rotundus), was severely reduced; after 10 weeks of competition, weedy cotton weighed only 15 per cent of the weed-free control. Cotton sown before weeds, or weeds planted before cotton, were only slightly affected by competition. Highly significant negative correlations were found between growth parameters of cotton and weeds. Inhibiting effects, and in some cases transitory stimulation, were produced on mustard seedlings by leachate from weed-infested soil and by extracts from subterranean weed parts, suggesting that the competitive effects of perennial weeds are due to nutrient depletion and to biologically active substances.

The line-source sprinkler irrigation system provides a continuously variable water application rate, which depends on distance from the line-source. The system is simple to set up and minimizes the amount of land required for experimental work. As the irrigation treatments are allocated systematically, the assumptions of analysis of variance are not satisfied. It is proposed that the effects of irrigation treatments be assessed using analysis of covariance, with distance from the sprinkler line as covariate, thus adjusting for a linear fertility trend. This method of analysis provides an approximate residual mean square for the fitting of response curves, but could be vulnerable to a quadratic fertility trend.