Drought tolerance mechanisms of three taro landraces (Dumbe Lomfula (DL), KwaNgwanase (KW) and Umbumbulu (UM)) were evaluated under field conditions Pietermaritzburg, South Africa, over two summer seasons. Taro was slow to emerge (~ 49 days) and showed significant differences between landraces with respect to final emergence with DL never achieving a good crop stand. Growth (plant height, leaf number and LAI), VGI, SC and CCI were significantly lower under rainfed (RF) than irrigated conditions. RF conditions resulted in significantly lower biomass, HI, and final yield of taro landraces compared to irrigated conditions. The UM landrace avoided drought through increased stomatal regulation, lowering chlorophyll content, smaller canopy size and reduced growth period. It is concluded that among the three landraces, UM is suitable for production under water stress conditions, because it exhibited drought avoidance and escape mechanisms.

In dryland areas, where rains recede much earlier than the time of sowing of crops, moisture in the seed zone becomes limiting for stand establishment. Mulches are known to conserve moisture in the upper soil layers, so we studied the effect of mulching a standing maize or fallow on the yield of the maize and on following wheat. Mulching maize with green twigs of ‘basooti’ a few weeks before harvest increased its yield by 16%. Both in maize and on fallow mulching increased water storage, particularly in the upper soil layers, and increased wheat yields from 19.0 to 22.5 q/ha after maize and 29.1 to 33.3 q/ha after fallow. It also led to increased water use and water use efficiency of wheat.

A method is described for studying the distribution of absorbing roots of fruit trees using the number of light root tips per unit of soil space as a criterion for characterizing the spatial distribution of the absorbing parts of the root systems. As examples of the use of this method, some results are shown from investigations with apple trees in South-Western Germany. They demonstrate the influence of soil-type and soil management on the distribution of absorbing roots. Striking temporal variations in the number of root tips were observed in the same tree.

As part of the reform process of the Consultative Group on International Agricultural Research (CGIAR), its Technical Advisory Committee is being transformed into a Science Council. An interim Science Council has been operating since January 2002. The primary role of the Council will be to enhance and guard the relevance and quality of science in the CGIAR System. Relevance is viewed as researching the ‘right things’ to address the System's goals, and deals with the relevance of identified research priorities and strategies and the nature of the planning and consultation process. Ex-ante analyses of need and potential impact to formulate the priorities and strategies are important elements in defining relevance. Quality is viewed as researching the ‘right things well’ and deals with the efficient use of state-of-the-art knowledge, research methods and protocols. The paper outlines the interim Council's suggestions for an operational framework of the Science Council. It serves as a starting point for the development of specific criteria, procedures and guidelines for carrying out the envisioned responsibilities. The Science Council must act in a strategic advisory role, basing its advice on: (i) planning and strategy development in the context of CGIAR goals; (ii) internal self-assessments by CGIAR Centres and Programmes and independent external monitoring and evaluation; and (iii) impact assessments. The paper discusses these three complementary functions. Each depends on the other in a dynamic feedback process that is essential if the CGIAR is to remain at the frontiers of science and development, maintain its science relevance and quality, and contribute in the most effective and efficient manner to the mission and goal of the Group.

In Mozambique the sweet potato (Ipomoea batatas) is grown as both a leafy vegetable, the terminal shoots or vines being progressively harvested during the season, and as a root crop. This paper reports the development of crop yield/water-use production functions using data from two irrigation experiments designed to evaluate the effects of water availability and vine harvesting practices on the productivity and water use (ETc) of sweet potato (cv. TIS 2534) during two contrasting seasons in the south of the country. As the frequency of vine harvesting increased, the water-use efficiency (WUE-ETc) for vine production (dry mass) increased from 1–2 to 4–5 kg ha−1 mm−1 during the rainy season, and from 1 to 9 kg ha−1 mm−1 during the dry season. By contrast, there was a corresponding reduction in the WUE-ETc for storage root production from 14 to 8–9 kg ha−1 mm−1 during the rainy season, and from 23 to 15–17 kg ha−1 mm−1 during the dry season. For the total yields (vines plus storage roots) the WUE-ETc during both seasons were independent of the vine harvesting treatment. Separate lines represented each season, the slopes of which were 13 kg ha−1 mm−1 in the rains, and 24 kg ha−1 mm−1 in the dry season. When, however, crop water-use was normalised using either the seasonal mean daily total of incoming solar radiation, or reference crop evapotranspiration (ETo), but not the saturation deficit of the air, a single common, linear relationship with yield resulted. Possible explanations for this are considered. Plotting relative yields against relative rates of water-use, also gave consistent results that could have general application for predicting the effects of water availability on productivity. Vine yields, when harvested frequently, were less sensitive to drought (yield response factor, Ky=0.7–0.9) than storage roots (Ky=1.2). For total production (vines plus roots), the sensitivity to water stress (Ky) increased, from 0.9–1.0 to 1.2, as the interval between vine harvests increased. Farmers in southern Mozambique trying to maximize total yield during the season, under conditions of water uncertainty, should harvest vines at intervals of not more than 14 days.

Two studies were conducted in Kenya during 1993 and 1994 to determine the yield responses of kale (Brassica oleracea var. acephala D.C.) intercropped with beans (Phaseolus vulgaris L.) under different redroot pigweed (Amaranthus retroflexus L.) densities. Redroot pigweed significantly reduced both kale and bean yields, the reduction being greater in 1993 than in 1994, and being greater for beans than for kale. Redroot pigweed growth was suppressed more by beans than by kale. Food output per unit area, measured by Land Equivalent Ratios, was increased by 22–115% by intercropping kale with beans and the increase was greater under weedy conditions (38–115%) than under weed-free conditions (22–74%). The presence of beans did not affect the leaf yield of kale. The presence of kale did not affect the seed yield of beans in 1994, but consistently reduced it by about 50% in 1993, though the difference was not significant.

The development of mechanised large-scale farming has led to changes in rice production systems. Increases in time of farming operations often occur under large-scale farming conditions, which can lead to delayed transplanting (DTP). In this study, field experiments were conducted in the late rice-growing season in 2016 and 2017 to compare the growth stages, growing-season temperature and yield attributes between normal transplanting with 15- to 20-day-old seedlings and DTP with 30-day-old seedlings of two rice cultivars. DTP resulted in 6- and 12-day delays in heading stage for both cultivars in 2016 and 2017, respectively. As a consequence, low temperature stress occurred at anthesis under DTP in both years, which led to significantly reduced spikelet filling and grain yield under DTP for both cultivars. These results confirm that DTP can reduce spikelet filling and grain yield due to low temperature stress at anthesis in machine-transplanted late-season rice. This finding highlights that greater efforts should be made to develop high-yielding short-duration rice cultivars to meet the development of mechanised large-scale rice farming.

Crop-livestock systems in sub-Saharan Africa (SSA) are mostly rainfall-dependent and based on fragmented marginal lands that are vulnerable to soil erosion, drought and variable weather conditions. The threat of water scarcity in these systems is real, due to expanding demand for food and feed, climate variability and inappropriate land use (Amede et al., 2009). According to recent estimates, farming, industrial and urban needs in developing countries will increase water demand by 40% by 2030 (FAO, 2009). Water shortage is expected to be severe in areas where the amount of rainfall will decrease due to climate change. The lack of capacity of communities living in drought-prone regions to respond to market opportunities, climatic variability and associated water scarcity also results from very low water storage facilities, poverty and limited institutional capacities to efficiently manage the available water resources at local, national and basin scales. The spiral of watershed degradation causes decline in water budgets (Awlachew and Ayana, 2011), decreases soil fertility and reduces farm incomes in SSA (Amede and Taboge, 2007) and reduces crop and livestock water productivity (Descheemaeker et al., 2011). In areas where irrigated agriculture is feasible, there is an increasing demand for water and competition among different users and uses.

Low-temperature stress in eggplant during the cool season causes gradual loss of pollen fertility and leads to the development of seedless fruit, but female fertility is not similarly affected. The temperature-induced male sterility is transient, and full pollen fertility is regained with normal seed development, as temperature conditions improve.

The development of the first group of short-statured, late-maturing sorghum lines and hybrids and their initial testing for the Northern Guinea and sub-Sudan Savanna zones in Nigeria is described. The necessity of developing such types of sorghum is discussed, together with some of the problems encountered when breeding the new types.

N and P fertilizers applied to maize had considerable effects over a five-year period, especially when both were given. Initial applications of 47 lb/acre/P2O5 with annual dressings of 58 lb N, produced a mean yield increase of 55 per cent above the control. K gave little response in the first three years, but thereafter became more important. 1120 lb ammonium sulphate nitrate caused striking reductions in soil pH, Ca, Mg, K, total and organic P but increases in exch. Mn and soluble P. 112 lb double superphosphate increased the total and organic P and 65 lb K2O reduced organic P. Organic carbon suffered a mean loss of 33 per cent over five years. Recommendations are made regarding P2O5, N and K on this soil.

Single-leaf net photosynthesis versus light response curves of four Hevea brasiliensis clonal seedlings showed that it was possible to divide photosynthetic rates into high and low classes.

Aflatoxin was found in forty-one out of seventy-four samples of various pulses, whereas Aspergillus flavus occurred in all samples, and there was an apparent correlation between the occurrence of the fungus and the level of the toxin in haricot beans. There was evidence that the toxin was produced in haricot beans after harvest, and drying the pods immediately after harvest is therefore suggested as a method of controlling mould growth and the formation of aflatoxin.

Land use and land cover changes are driven by human actions and, in turn, drive changes that alter the availability of products and services for people and livestock. For proper planning, these cause-and-effect interrelations need to be understood. This is especially important for Ethiopia where the resource base is declining and should be improved in order to feed the growing population. To better understand these interrelations, we studied trends in the natural resource base over a 35-year period for two contrasting sites in the Ethiopian Highlands: semi-arid and water-short Lenche Dima, and sub-humid and moisture-sufficient Kuhar Michael. Information was obtained using time-series satellite images, geographical positioning system, a socio-economic survey and a document review. Results showed that for sub-arid Lenche Dima there were minimal changes in land use and land cover patterns, while in water-sufficient Kuhar Michael cropland greatly increased at the expense of the grazing land and bare soil. At the same time land holding size and cattle numbers decreased in Lenche Dima while they remained the same in Kuhar Michael, although overall land holdings remained larger in Lenche Dima than in Kuhar Michael. This study thus found large differences in development of agriculture since the 1970s: intensification of agriculture is possible in the water-sufficient sub-humid climate by displacing animal husbandry with high value crops that need irrigation during the dry monsoon season. This is not possible for the semi-arid area where water is the limiting factor in production even if a market is close by. Agriculture in the semi-arid areas also requires larger land holdings because of the risk of droughts and low yields during some years. This comparative analysis suggests that without sufficient water, the shift from subsistent to commercial market-driven agriculture cannot be easily accomplished.

In order to get the benefit of the growing world demand for natural rubber, Hevea brasiliensis is increasingly planted in drought-prone areas, such as in the southern part of northeast Thailand. Modelling can be a useful approach in identifying key points of improvement for rubber tree cultivation in such water-limited areas. The first objective of this study was to test the possibility of using the Water Nutrients and Light Capture in Agroforestry Systems (WaNuLCAS) model as an exploratory tool to simulate water use, growth and latex production in a pure stand on a daily basis. The second was to evaluate the relative accuracy of predictions with the current model version. Finally, the third aim of this study was to identify particular parameterisations that may be adapted to improve overall prediction quality. Model outputs were compared to measurements recorded in a mature rubber tree stand of RRIM 600 clones growing in the water-limited area of northeast Thailand. The period of analysis concerned seven months of full foliation, from May to November, including a severe drought spell. Whole-tree transpiration was estimated by xylem sap flow measurement from 11 trees. The results show that the model was able to simulate daily and seasonal change of soil water content, tree transpiration, girth increment and latex production within plausible ranges. However, under detailed scrutiny, the predictions show large inaccuracies compared to the observations: soil water content (determination coefficient (R2) = 0.461, relative root mean square error (RMSErel) = 35%), tree transpiration (R2 = 0.104, RMSErel = 94%), tree girth increment (R2 = 0.916, RMSErel = 208%) and latex production (R2 = 0.423, RMSErel = 169%). As soil water content was overestimated during the driest periods, no water stress was predicted and transpiration, growth and latex production were logically overestimated during such periods. However, tree transpiration was also largely overestimated in conditions of non-limiting soil water availability with high evaporative demand. Hence, two key points of parameterisation and improvement are identified for better simulation in our conditions: the soil water balance and particularly the ratio between water infiltration and run-off, and the regulation of transpiration under high evaporative demand. In conclusion, the WaNuLCAS model is usable as an exploratory model to simulate water use, growth and production for a pure rubber tree stand. However, in our conditions of much degraded soil and high evaporative demand, the modules of soil water balance and tree transpiration require particular parameterisations and improvement.

The use of fertilizers in balanced and adequate amounts is a prerequisite for increasing crop productivity and production. Unbalanced plant nutrient management continues to be a major factor contributing to low maize (Zea mays L.) yields due to lack of information on the dose–responses to macronutrients on different soil types in Ethiopia. This study was carried out to quantify maize yield response and agronomic efficiency of varying application rates of nitrogen (N), phosphorus (P), potassium (K) and sulphur (S) under balanced application of other nutrients across two soil types in Ethiopia. Field trials were set up on 29 farmers’ fields in four districts of Oromia and Southern Nations, Nationalities and Peoples Region (SNNPR) for three consecutive cropping seasons (2014–2017). The treatments consisted of six rates of N, P and S each and eight rates of K combined with balanced application of the remaining macronutrients, zinc (Zn) and boron (B). The treatments were laid out in randomised complete blocks design with three replicates per farm. Using nutrient dose–response modelling, the agronomic optimum rates of N, P, K and S were estimated at 46, 40, 17 and 10 kg ha−1 on Nitisols, with balanced application of the other nutrients. On Andosols, the optimum rates of N, P and S were estimated at 184, 20 and 30 kg ha−1, respectively, but the optimum K rate could not be estimated. The predicted maximum yields obtained with balanced nutrient application were lower on Andosols (3397–3640 kg ha−1) than on Nitisols (4630–6094 kg ha−1). Using the Mitscherlich dose–response model, the percentage deficiencies of N, P, K and S were estimated to be 1.3–3.3 times more on Nitisols than Andosols. Consequently, agronomic efficiencies of N, P, K and S were significantly lower on Andosols than on Nitisols. It is concluded that balanced application of 46 kg N ha−1, 40 kg P ha−1, 17 kg K ha−1, 10 kg ha−1 S, 2 kg Zn ha−1 and 0.5 kg B ha−1 could be recommended for maize on Nitisols in the study area. Although this recommendation may also apply to Andosol, further research is needed as the productivity of Andosols appears to be limited by constrains other than N, P, K, S, Zn and B. We also recommend a shift from the blanket fertilizer recommendations to site-specific nutrient management based on good understanding of the variations in crop response with soil type and agroecology and appropriate soil and plant analyses.

The effect of seed priming and micro-dosing in groundnut, cowpea and sesame was studied for three years in on-farm and on station experiments under rainfed agriculture in North Kordofan, Sudan. The on-station trials showed that seed priming increased groundnut pod and hay yields by 18% and 20% respectively. Micro-dosing of 0.3, 0.6 and 0.9 g fertilizer per pocket increased groundnut pod yield across the three years by 36.7, 67.6 and 50.8% respectively compared to the control. The highest yield increases were consistently obtained when micro-dosing was combined with seed priming. A combination of seed priming and micro-dosing of 0.6 g increased groundnut yield by 106%. Priming alone did not significantly affect sesame seed or hay yield, but micro-dosing of 0.6 g per pocket increased the grain yield by 38% over the control. Cowpea grain yield in the on-station experiments was not significantly affected by seed priming or micro-dosing. However, both seed priming and micro-dosing increased cowpea hay yield. In the on-farm trials, seed priming increased groundnut and cowpea yields by 18.2 and 25.5% respectively, and seed priming combined with 0.3 g fertilizer increased their yields by 42.2 and 54.5% respectively compared to the control. For sesame the yield increase after 0.3 g fertilizer per pocket was 46.3%. The economic analyses of the on-station experiments showed that the highest gross margin was obtained when combining seed priming with 0.6 g micro-dosing for all the crops. These results show that the combination of micro-dosing and seed priming has the potential to increase productivity and improve net return in the crops tested.

Our knowledge of melon (Cucumis melo L.) response to salinity stress is limited under field conditions and then the genotype × environment interaction and heritability of agro-morphological traits are poor understood. A field trial (2014/2015) was carried out to evaluate the performance of 17 melon cultivars, including 16 native and one exotic (Galia), under salinity stress. Leaf ion concentrations, agronomic, morphological and fruit quality traits were evaluated and their heritabilities were estimated. The results showed significant effects of salinity stress and genotype on the studied traits except for days to anthesis and peel thickness. Salinity stress also caused significant reductions in fruit weight and leaf K+ concentration, while increasing leaf Na+ and Ca2+ concentrations and total soluble solids. The most salt-tolerant cultivars (‘Sabouni’ and ‘Shahabadi-1’) had higher fruit yield, low leaf Na+ and high leaf K+ concentrations and enhanced K+/Na+ ratio under stress conditions. In general, the heritability estimates were higher under control than under salinity conditions, and the highest heritability was observed for total soluble solids. In addition, fruit weight, number of fruit per plant and leaf Na+ concentration were the strongest predictors of fruit yield, explaining 92% of yield variation under salt stress. These observations suggest that indirect selection based on these traits would be effective in improving fruit production under saline conditions.

Pea is a self-pollinated, diploid (2n = 14), annual crop produced worldwide for human consumption and animal feed. The exploitation of maximum genetic potential from available pea resources implies the knowledge of genetic parameters of yield components. Hence, the present study was conducted in a cross between two pea varieties, namely DDR14 and Explorer, its F2 progeny and F3 families to find out transgressive segregants and to determine the magnitude of narrow sense heritability and heterosis. The high narrow sense heritability values obtained indicated that rapid gain could be achieved through selection for the different traits; however, the presence of genotype x environment interaction could limit the correspondence of these estimated values with the observed ones. The selection of lines through their phenotypic values is influenced by environmental and error effects. Best linear unbiased prediction (BLUP) was used for the prediction of genotypic values using morphological data from different years, allowing the correction for environmental effects. These estimates were used for genetic analysis of the traits. Heterosis was observed for number of pods (27.1%) and number of seeds (23.3%), characters that have a direct effect on yield. The cross also showed high frequency of transgressive segregation for these characters in F3 generation (15.5% and 13.6%, respectively). There were 12.73% families transgressive for two or more characters, with genotypic values of 49.82–64.41 for number of pods and 153.75–189.59 for seed number. The crossing between Explorer and DDR14 provided a base for the selection of superior progeny.