A two-year study was conducted at two locations in Niger to compare the response of five cowpea cultivars to two planting patterns and two sowing dates relative to the sowing date of pearl millet. All the cowpea cultivars took less time to mature when planted three weeks after millet than when sown one week after. Early-maturing cowpea cultivars had the smallest yield, whereas the yield of the local indeterminate cultivar was nearly double that of the other cultivars at both dates of sowing. Early planting of cowpea significantly depressed millet yield, but when cowpea was planted late millet yields approached those of the sole crop. The local cultivar depressed millet yields more than the other cowpea cultivars. Planting pattern had no significant effect on the yield of either cowpea or millet. Cowpea yield was reduced by more than 50% by two weeks delay in sowing, confirming that the sowing date of cowpea relative to millet is a critical factor in the Sahelian pearl millet/cowpea intercropping system. There were marked differences in the effect of cowpea cultivar on millet yield but these differences were consistent over sowing dates.

Variation in the percentage of nitrogen, phosphorus and potassium content of a variety of white yam, grown without fertilizer, and the nutrients removed per acre by various portions of the plant, were determined. The time to apply fertilizers, and the most suitable portion of the plant for foliar analysis, were deduced from the changes in nutrients with age. The effect of nitrogen fertilizer on yield, and the nutrient content of the harvested tuber, were studied. The influence of a yam crop in a rotation is discussed.

To evaluate the impact of trash management on sugarcane production and N fertiliser requirements in environmental conditions of Brazilian coastal tablelands, a simulation was conducted with APSIM-Sugar cropping systems model. The model was parameterised for, and validated against results from a long term (over 23 years) experiment comparing the system-burnt trash and green cane trash blanketing (GCTB), in Linhares-ES. Simulations were conducted over two crop cycles (14 years) with different management (100%, 75%, 50%, 25% GCTB and burnt trash), and N fertiliser rates from 0 to 240 kg ha−1 (in 40 kg ha−1 increments) on the ratoon crops, and 75% of these rates on the plant crops. Measured cane yields and soil carbon were simulated well by the model. The RMSE (root mean square error) of predictions in burnt and GCTB treatments were 14.02 Mg ha−1 and 13.45 Mg ha−1 for yield, and 0.09 and 0.13% for soil carbon. In the simulation, the cane yield responded positively to the GCTB systems. Optimum N rates were higher in the 100%, 75% and 50% GCTB than with burnt trash and 25% GCTB reflecting the greater yields under GCTB systems. The response to trash retention was dependent on N fertiliser, and it was smaller or even negative at lower N rates. With adequate N, the positive responses were predicted to occur in all crops after the imposition of GCTB system. The removal of any proportion of the trash reduced the potential sugarcane yield. The simulations showed that average environmental losses of N are likely to be greater from trash-retained systems at all N fertiliser rates.

In the oil palm plantations of Ecuador, two factorial trials (namely CP06 and CP08) were used to assess the effects of N, P and K fertilization on the soil chemical characteristics after 10 years of fertilizer application. The use of ammonia-based fertilizers has resulted in a drop in soil pH, which has reached 1.2 units in one of the two trials. A drop in cation exchange capacity (CEC) was also found, and a loss of exchangeable cations that probably reflected leaching of excess N as nitrates. The use of KCl enriched the soil in K, which contributed to impoverishment in Ca and Mg. In both trials, the highest N and K application rates had no significant effect on yield in comparison with an intermediate fertilization rate; however, their effects on the fertilized soil significantly increased the risk of N and cation leaching towards the deep soil layers. We also compared the effects of the N, P and K factors on soil properties outside the fertilizer application zone. In both trials, the mineral reserves played a major role in meeting the needs of the control palms, which had not been fertilized for 10 years, as no significant yield drop has been observed except in trial CP06 when no KCl was applied. However, uptake of nutrient in the control plots did not lead to significant impoverishment of the soil.

Perennial grain crops have been proposed as a transformative approach to agriculture. Replacing annual staple crops with perennialized growth types of the same crops could provide environmental services, improve labour efficiency and weather resilience, reduce seed costs and produce livestock fodder or fuelwood production. Yet, the technologies and science for agricultural development in Africa have focused almost exclusively on annuals. In this paper, we review the literature to explore what has been potentially overlooked, including missed opportunities as well as the disadvantages associated with perennial grains. The case studies of pigeon pea and sorghum are considered, as an analogue for perennial grain crops in Africa. We find that a substantial number of farmers persist in ‘perennializing’ pigeon pea systems through ratoon management, and that sorghum ratoons are widely practiced in some regions. In contrast, many crop scientists are not interested in perennial traits or ratoon management, citing the potential of perennials to harbour disease, and modest yield potential. Indeed, an overriding prioritization of high grain yield response to fertilizer, and not including accessory products such as fodder or soil fertility, has led to multipurpose, perennial life forms being overlooked. Agronomists are encouraged to consider a wide range of indicators of performance for a sustainable approach to agriculture, one that includes management for diversity in crop growth habits.

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.

Measurements of the stomatal apertures of young clonal tea plants (Camellia sinensis) showed that stomata of plants irrigated during the dry seasons only were wider open than those not irrigated during both wet and dry seasons. Similarly, xylem water potential values (ψx) were always higher (less negative) in irrigated than non-irrigated plants, during both wet and dry seasons. The results suggest that more drought-susceptible clones have a greater demand for water than those less susceptible to drought.

Experiments were carried out in which injuries caused by Diopsis macrophthalma larvae were simulated. The results show that these larvae can have negative or positive effects on rice (number of stems, height, maturation time, number of ears and yield), depending on time and level of attack, growing conditions and variety. The results suggest that under normal conditions the effect on number of stems, height, number of ears and yield is positive, and only becomes negative if poor growing conditions are combined with a late, heavy attack. An experiment with Diopsids was carried out to evaluate the simulation experiments.

Mixed cropping of teff (Eragrostis tef) with faba bean (Vicia faba) was compared with sole cropping in the 2002 and 2003 growing seasons at Holetta Research Centre, in the central highlands of Ethiopia. The treatments were sole teff (25 kg seed ha−1), sole faba bean (200 kg seed ha−1) and 12.5, 25, 37.5, 50 and 62.5 % of the sole seed rate of faba bean mixed with a full teff seed rate. A randomized complete block design replicated four times was used. Treatment effects were significant for seed and biomass yields of each crop species. Increasing the seed rate of faba bean in teff/faba bean mixture increased faba bean seed yield but decreased teff grain yield. Nonetheless, mixed cropping of faba bean with teff increased land use efficiency and gave higher total yields compared to growing either species in sole culture. Teff yield equivalent, land equivalent ratios (LERs) and system productivity index (SPI) of the mixtures exceeded those of sole crops especially when the seed rate of faba bean in the mixture was increased to 50 kg ha−1 (25 %) or more. The relatively high crowding coefficient values indicated yield advantages from mixed cropping of the two species. The highest values of teff yield equivalent, LER and SPI were obtained when faba bean was mixed at a rate of 62.5 % with the full seed rate of teff. We suggest that, at the current prices of the respective crops, up to 62.5 % of faba bean can be mixed in normal teff to get better total yield and income than sole culture of either species.

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.

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 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.

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.

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.

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.

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.

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.