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.

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 results of a three-year water conservation trial in the Zambezi Valley of Zambia are reported, for an area characterized by high temperatures and low, often poorly distributed, rainfall, with low infiltration and high evapotranspiration rates. As a result of these conditions local farmers often produce grain crops yielding as little as 200–300 kg./ha., though considerable increases could be obtained by simple water conservation methods. Of four treatments, tieridges made before the start of the first rains consistently gave the heaviest yields. Mean yields of the three crops under trial (maize, sorghum and bulrush millet) were higher on tie-ridges than on conventionally prepared seedbeds by 168, 159 and 17 per cent in the 1968–69 to 1970–71 seasons respectively.

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 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.

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.

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.

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.

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.

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.

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.

Temperature effects on coleoptile development were studied in 18 genotypes of spring and semi-winter wheats, illustrating a simple experimental approach for choosing genotypes and management practices that would minimize genotype–environment interactions for stand establishment.

Accessions of four Saccharum spp. from the world collection of sugarcane germplasm maintained at the ICAR-Sugarcane Breeding Institute Research Center, Kannur, Kerala State, India, were screened against Chilo sacchariphagus indicus (Kapur) (Lepidoptera: Crambidae), commonly known as internode borer. Observations on the progression of borer attack in the most susceptible Saccharum officinarum indicated that the incidence began in the first fortnight of July, increased in the next 2 months and reached its peak in September. Thereafter, the incidence decreased in the next 2 months but reached its overall peak in December. Simple correlation coefficients between mean monthly weather parameters and borer incidence were not significant. Percent of canes attacked was significantly lower in 2011 than in 2012 for S. officinarum, Saccharum barberi and Saccharum sinense but did not differ between the years for Saccharum robustum. Amongst the four Saccharum spp., S. robustum showed the lowest borer incidence whereas S. officinarum recorded the lowest attack intensity. Whilst infestation index showed the same trend as percent canes attacked, percent deadhearts did not differ amongst the four Saccharum spp. Considering the 171 accessions evaluated, 29 (16.9%) accessions were resistant, 39 (22.8%) moderately resistant and 103 (60.2%) susceptible to internode borer. Out of the 39 accessions of S. officinarum, none occupied the resistant category whereas 17.9% were in the moderately resistant category. In S. robustum, whilst nearly half (44.5%) the accessions emerged as resistant, a considerable number occupied the moderately resistant category. In S. barberi, no accession was resistant to the borer. In S. sinense, only one accession each represented resistant and moderately resistant categories. Plant morphological characters, yield and quality parameters did not show clear-cut relationship with the three infestation parameters.

Our paper ‘Loading the dice in favour of the farmer: reducing the risk of adopting agronomic innovations’ revealed mean increases but also large variation in the impact of four agroforestry practises on maize yield, as experienced by farmers in Malawi. This prompted a response from Sileshi and Akinnifesi that was critical of the data and methods used. Their main concern was that farmers did not necessarily manage crops identically in plots with and those without trees, so the yield differences that we measured may be partly caused by these differences in crop management. We argue here that it is valid and useful to look at the actual effect on crop yield of farmers having trees intercropped with maize, rather than controlling for how the crop is managed, because this is what happens in the real world. Farmers respond to having trees in their field by treating their crop differently, so this is part of the system response to having trees in fields. Attempts to eliminate this will result in measuring an artefact rather than the real impact of trees on crop yield. By doing this, we revealed important variation in the impact of trees on crop yield amongst farmers, and we argue that it is important to explore, assess and communicate to farmers and development actors the extent and implications of this variation. Understanding the contextual factors that determine who is likely to benefit most from an innovation and for whom it is less suitable can then be incorporated in scaling up, so that targeting of innovations and the appropriateness of messages given to farmers are continuously refined.

Results from an experiment with maize (variety NEH 1151) at three plant densities indicated that normally favourable environmental conditions promoted tillering and it was difficult to maintain the desired tiller densities. The higher densities produced more vegetative dry matter but less grain than the lower densities. In a second experiment, where tillers were removed from the plants, there was no advantage because the remaining tillers grew larger to compensate for the removal. It is concluded that it is desirable to breed or select for non-tillering varieties where other management parameters can be controlled.

In sub-Saharan Africa, the bollworm complex, including Helicoverpa armigera, Diparopsis watersi and Earias spp., threatens the continued success of cotton production. Pyrethroid resistance in H. armigera led to serious crop losses while endosulfan, a suitable alternative to pyrethroids, was banned for cotton pest management. Five candidates with no cross-resistance to pyrethroids were evaluated in both on-station and on-farm trials from 2002 to 2006. Two applications were made at the early peak of H. armigera infestation in September, the period when pyrethroid use should be restricted for resistance management purposes. Results showed that, as expected, bollworm infestation consistently peaked from mid-September to mid-October. Spinosad, thiodicarb and emamectin-benzoate were the most suitable alternatives to reduce damage, regardless of the cotton bollworm species. Indoxacarb and lufenuron were less effective in controlling D. watersi. On-farm experiments confirmed the suitability of spinosad for control of pyrethroid-resistant H. armigera, particularly on late sown fields. These new chemistries offer control of bollworms which justify their relevance for pyrethroid resistance management in Cameroon and sub-Saharan Africa.

Long-term data (20 years) on wheat (Triticum aestivum) grain yield under various fertilizer-nitrogen (N) and water conditions in rainfed and irrigated environments of sub-tropical north India were used to assess the magnitude and economics of N response in relation to amount and timing of irrigation. Treatments comprised combinations of fertilizer N rates (ranging from 0 to 150 kg ha−1) and irrigation regimes (rainfed, supplemental, limited, and adequately irrigated). Regression analysis of wheat yield against available water supply and fertilizer N showed a strong interaction between the two variables for grain yield and input use efficiency. The effect, on grain yield and returns, of increasing the N rate for a given water supply was influenced by the irrigation regimes. Economic optimization of water and N, based on constrained profit maximization technique, showed that optimum amounts of available water (or irrigation) and fertilizer N are related directly to the capital investment. Increased input prices lowered their optimum levels for a given investment. The analysis suggests an approach for resource allocation that relates to capital investment and input prices.

The effects of temperature and photoperiod on times from sowing to flowering (f) were investigated in medium-and late-maturing pigeonpea (Cajanus cajan). Twelve genotypes were sown in two seasons at seven sites in Kenya, covering latitudes 0–4°S and a wide range of altitudes (50–2000 m), as well as under polythene enclosures constructed at six sites to create warmer temperature regimes (a total of 26 environments). The same genotypes were also sown at monthly intervals and in an artificially extended photoperiod (in the open as well as under polythene) created by incandescent lamps suspended above the plots at Katumani (1°30′S).

Times from sowing to flowering varied from 70 to more than 300 days and were associated with variations in mean pre-flowering values of temperature and photoperiod which ranged from 15.2° to 32.7°C and from 12.6 to 15.0 h d−1. Genotypic variation in f in the most inductive regimes (a mean pre-flowering temperature of 24.3°C for the medium- and 20.8°C for the late-maturing genotypes, combined with a mean pre-flowering photoperiod of 12.6 and 12.8 h d−1) ranged from 70 and 76 days and from 85 to 112 days, respectively. There were no photoperiodic effects on f over the range from 12.6 to 13.1 h d−1, but the artificially extended day delayed flowering, especially in the late-maturing genotypes.

The relation between l/f and the mean pre-flowering temperature was linear below and above an optimum temperature, To. The genotype-specific parameters derived from these thermal linear rate models based on flowering responses in 26 environments closely predicted l/f and therefore f in an independent sequence of monthly sowings. It was thus responses to temperature below and above To and not responses to daylength which modulated flowering throughout the wide range of natural environments tested within this vast country, even in the late-maturing and most photoperiod-sensitive genotypes.

Field experiments were done during the rainy seasons of 1980 and 1981 at Hissar, India; they studied the effects of time of weed removal on the yield of mung beans. Removing weeds at 10, 20 or 30 days after sowing led to significantly larger yields than that of the weedy check. Maximum seed yields in booth years were obtained when weeds were removed 20 days after sowing

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.