Fourteen varieties of cowpea (Vigna unguiculata (L.) Walp.) were compared for yields of forage and seed from two sowing dates, using various agronomic parameters. Yields ranged from 1048 to 5044, 185 to 920 and 864 to 3321 kg/ha for dry matter, crude protein and seed respectively, with advantages from spreading as against semi-erect types, and early rather than late July sowing. IVu 1283-1 and IVu 1283-2 effectively combined vegetative and seed yield, and appeared most suitable for fodder and seed production. A simple forage yield index (FYI), useful in yield prediction, was evolved.

Field experiments were carried out over a period of three years to evaluate the effect of cover cropping faba bean with fibre sorghum, compared to mono-crop cultivation, on yield (dry matter), nitrogen utilization efficiency (NUE) and N fertilizer recovery fraction of sorghum. Experimental sites were located in central Greece on a fertile, clayey to loamy textured soil, and on a sandy soil of moderate fertility. A factorial combination of four nitrogen application rates (0, 50, 100, 150 kg ha−1) and three legume treatments (incorporated into the topsoil or harvested before the sowing of sorghum and mono-cropping) were tested in a split plot design in three blocks. The results showed importance of legume cover crops for both soil types as sorghum total dry biomass yield for clayey soil fluctuated from 23 to 27 t ha−1 for control plots, from 25.2 to 30.9 t ha−1 when faba bean was harvested and from 26.3 to 32.5 t ha−1 when incorporated, and for sandy soil the yield fluctuated from 18.1 to 22.1 t ha−1 for control plots, from 22 to 27 t ha−1 when faba bean was harvested and from 23.1 to 28.1 t ha−1 when incorporated. The NUE was estimated at 62 kg kg−1 and 60 kg kg−1 for clayey and sandy soils respectively. The N recovery fraction was doubled after incorporating faba bean as green manure, reaching large amounts for both soil types.

Perennial crops, guinea grass and alfalfa, and annual crops, wheat and cotton, were grown in the reclaimed Hula Valley swamp. The aim was to find ways to preserve the peat soil from aerobic oxidation, wind and water erosion; to minimize nitrate accumulation, which causes pollution of the waters draining into the Kinneret Lake (Sea of Galilee); and to select high yielding crops that both fulfilled these needs and ensured a good income for the farmers. Our results showed that high dry matter yields of guinea grass and alfalfa could be obtained. A significant decrease in peat soil erosion and nitrate accumulation was also recorded under these perennial crops, so growing them has both economic and ecological advantages.

Variety × spacing and variety × sowing date trials in south-east Tanzania showed that the long-season spreading bunch groundnut variety Red Mwitunde (A. hypogaea ssp. hypogaea var. hypogaea) was less tolerant of delayed sowing and more tolerant of wide spacing than Natal Common, a short-season upright bunch variety (ssp. fastigiata var. vulgaris). The same variety × spacing and variety × sowing date interactions were detected in groundnuts intercropped with cassava (Manihot esculenta). These observations help to explain the farmers' preference for Red Mwitunde despite the higher trial yields of Natal Common.

Some early attempts to graft black pepper are described. Good unions have formed between different clones of Piper nigrum L., and between different species of Piper grown in a glasshouse in the United Kingdom. The structure of pepper stems is considered in relation to the apparent impermanence, in the tropics, of unions that initially appear to be successful.

The importance of vegetable crops has been increasing in West Africa for the past forty years. This paper describes the evolution of intensive mixed vegetable production in the Niayes area near Dakar between 1970 and 1990. The importance of cultivation in low-lying areas with very few inputs have decreased but irrigated cropping systems have become more important due to the better adaptation of vegetative material, application of more fertilizers and better control of pests and diseases. This intensification appears to be irreversible, in spite of the negative effects of the more intensive use of land.

Interactions between upland rice and three phenologically distinct pigeonpea cultivars were examined on a medium deep Vertisol. The productivity of each intercrop component and its respective sole crop was determined in terms of a crop performance ratio (CPR). The extra-early pigeonpea cultivar recorded the largest partial CPR of grain followed by early and medium genotypes. Spreading genotypes had a larger partial CPR than semi-compact genotypes. However, the CPR of intercropped rice was less (0.65–0.69) with spreading pigeonpeas but exceeded unity with compact types. The canopy structure of pigeonpea appeared to be more important than differences in phenology. A large range of light transmission coefficients (K) existed in pigeonpea (from 0.45 to 0.78) but it is argued that a further reduction in K may not be necessary since intercropped rice yield was unaffected even with a K of 0.64. The relative height of intercropped pigeonpea and upland rice may also determine competitive ability since rice is very sensitive to low light and shading, particularly during the reproductive phase.

The phenological development of crops from emergence to flowering time is largely controlled by temperature and photoperiod. Flowering time is a critical phenological stage for subsequent reproductive phase. Lotus tenuis management in grasslands, pastures and seed production systems is through defoliation and sowing date; however, yet little is known about their effects on flowering time. The data presented in this study were obtained from experiments conducted with L. tenuis during the years 1989 to 2016 under field conditions. Our objectives were to determine if flowering time (a) is affected by sowing date; (b) can be predicted through equations using temperature and photoperiod and (c) is affected by defoliation applied at vegetative stage. Two defoliation intensities were applied, low (LDI) crop height reduced by 54% compared to pre-defoliation crop height and high (HDI), crop height reduced by 75%. The rate of progress from seedling emergence to flowering time (inverse of time from emergence to first flowering, 1/f) was modulated by temperature, photoperiod and photothermal functions. When L. tenuis sowing was delayed from autumn to spring, time from seedling emergence to first flowering decreased from 260 to 100 days. 1/f was linearly related to average temperature (R²=0.75) and photoperiod (R²=0.85) and both variables (R²=0.92). Defoliation retarded flowering time. Flower and pod growth periods were shorter under defoliation than in control one. Defoliation did not cause abortion of flowers and pods. Flower production was fitted to quadratic function of photoperiod. Flowering peak was approximately within 15.2 h. The prediction of flowering time using thermal, photoperiod and photothermal models can provide information about crop management decisions, such as optimal environmental regimes for crop growth through sowing date.

In connection with the processing of potatoes grown at Tarland, Aberdeenshire, certain field data were obtained over a period of eight years. It was found that the yield per acre was inversely correlated with rainfall and positively correlated with sunshine for the period May to September; the indications were that the period May to July was more important in this respect, high rainfall and low sunshine during this period depressing the crop more than high rainfall in the August to September period. It has been possible, statistically, to separate the effect of rainfall from that of sunshine (and temperature), and an analysis shows that sunshine (or temperature) is die dominant factor. The number of tubers produced was greatest in those years when sunshine was high and rainfall low. The dry matter content of die tubers was also highest when the sunshine was high and the rainfall low, the closest inverse correlation being with the rainfall for the month of August. The combination of high yield of potatoes and high dry matter content meant that the actual food produced was highest in the drier, more sunny, years.

The competition for fertilizer nitrogen between sugarcane and a companion crop (maize or potato) grown between the sugarcane rows was studied using nitrogen-15 labelled nitrogen in three field experiments in Mauritius. The effect of the timing of nitrogen application on nitrogen recovery by sugarcane was also investigated. Not more than 15 kg ha−1 of the 120 kg ha−1 nitrogen applied to the sugarcane was taken up by the companion crop but this was compensated for by the uptake of 8 kg ha−1 nitrogen applied to maize or potato. The present recommendations for nitrogen fertilization of pure stand sugarcane were found to be applicable to sugarcane intercropped with non-leguminous food crops. Though fertilizer nitrogen uptake by sugarcane was increased by delaying nitrogen application until after the harvest of the maize and potato, this was not accompanied by an increase in sugarcane yields.

The irrigation water treatments in three experiments were based on a ‘water duty’ principle. One cosec of water was assumed to be available to irrigate 96, 211, 326 or 442 acres, representing minimum irrigation cycle times of 5, 11, 17 and 23 days respectively. Each experiment included a rainfed control treatment. The plots were watered as indicated by a soil moisture profit and loss account, but never more frequently than the minimum cycle time would allow. The results showed that maximum productivity could be achieved on a sand when I cosec of water was used to irrigate approximately 200 acres, but on clay maximum productivity was obtained with the largest water duty (442 ac/cusec). Net photosynthetic efficiency reached 3·9 per cent in the most heavily irrigated crops, and rainfall efficiency fell from about 85 per cent for rainfed conditions to about 50 per cent when the maximum amount of irrigation water was applied.

Input-responsive, high yielding rice varieties and associated technologies responsible for the doubling of yields on irrigated lands in Asia have not suited the area of more than 40 million hectares of Asian rainfed lowland rice. These environments are home to some of the poorest rural populations in South and Southeast Asia, and the rice crops are subject to drought, prolonged submergence from uncontrolled flooding and nutrient deficiencies. Farmers grow unimproved varieties and these, combined with abiotic stresses and low inputs, result in grain yields often less than 2 t ha−1. The International Rice Research Institute (IRRI) and National Agricultural Research Systems (NARS) have recently joined to form the Rainfed Lowland Rice Research Consortium in order to identify, prioritize and execute strategic research that addresses critical yield and productivity constraints. Principal intervention points for achieving sustainable yield increases are in developing drought- and submergence-tolerant germplasm with good yield potential, improved nutrient management under stress conditions, water use-efficient crop establishment practices, and understanding farmers' approaches to risk management. Multidisciplinary teams of IRRI and NARS scientists execute research at sites selected across the region to represent the key sets of constraints.

Four forage bassicas, kale, rape, turnips and swede, and fodder beet were evaluated for adaptation to tropical highland conditions using small-plot experiments and field observations. In a short cropping season turnips were best adapted with a mean yield of 22 t ha−1. The crop was quick to establish and gave good ground cover. Kale and swedes were better adapted to a long season and yielded more than perennial forage grasses or maize. Yield was related to the length of growing season, exceeding 100 t ha−1 by about 250 days. Kale and swedes established poorly on soils high in aluminium. Direct sunlight appeared to damage swede roots, causing secondary soft rots. Rape showed no advantage over kale. Fodder beet failed to establish satisfactorily in any of the experiments.

The effects on the potato crop of the herbicides metribuzin, linuron and metobromuron, singly and in combination with each other and with hand weeding, were investigated and compared with cropped and uncropped weedy controls. Weed competition was determined by measuring weed dry weight. When the three herbicides were applied singly metribuzin gave the lowest weed dry weight, while the combination of metribuzin, metobromuron and hand weeding gave the lowest weed dry weight per unit area of all treatments in both seasons. However, the best potato yield was obtained from the combination of metribuzin and hand weeding. Metobromuron consistently reduced yield through reduction of tuber size irrespective of its effect on weed competition. Metribuzin was the best herbicide for the control of broad leaved weeds and many grasses.

In order to intensify cassava production in southern Côte d'Ivoire, multiple farmers’ field trials were carried out in two important cassava-producing areas (Dabou and Bingerville). The effectiveness of an Integrated Soil Fertility Management (ISFM) approach as intensification pathway was evaluated for poor sandy soils. Overall, ISFM-based systems outperformed the local cultivation system. The average cassava yield was 14.5 and 6.5 t ha−1 and 12.6 and 5.7 t ha−1 for the ISFM and traditional systems, in Dabou and Bingerville, respectively. The average profitability of ISFM systems was ca. 2500 Euro ha−1, whereby 66% was generated by cowpea intercrop, which yielded on average 3.1 t ha−1. Taking into account the limited farmer's resource endowment and poor soil fertility, ISFM is a crucial component for sustainable intensification of cassava production and poverty alleviate in southern Côte d'Ivoire.