Sequential sowings were carried out at Dodoma, Tanzania, to examine the effect of changing climatic parameters on the growth and yield of bambara groundnut (Vigna subterranea). Sowings took place on 4 January, 4 February and 4 March 1994; 4 and 24 January, and 13 February 1995; 4 and 21 January, and 7 February 1996. Rainfall during the crop life cycle varied from 163 to 611 mm, mean photoperiod from 11.82 to 12.09 h d−1 and mean temperature from 22.6 to 24.4 °C. In 1994, the highest pod yields were achieved at the earliest sowing date, with a maximum of 2.87 and 1.42 t ha−1 for the red- and cream-seeded landraces, representing pod harvest indices of 0.56 and 0.34 respectively. A 30-d delay in sowing caused >60% reduction in pod yield, and a further 30-d delay resulted in no pods at all. Similarly, in 1995 successive delays in sowing caused dramatic yield declines, and the maximum yield was much lower, at 0.44 t ha−1. In 1996 there was no significant difference in pod yields between the two early sowing dates for the red-seeded landrace and yields were again lower than in 1994 with a maximum of 1.02 t ha−1. Differences in dry matter production between sowings and years were attributed mainly to differences in the amount and distribution of rainfall and to declining temperatures towards the end of the season; however, partitioning to pods was remarkably consistent across sowings.

Yields of rainfed barley (Hordeum vulgare) for feed and forage in small-ruminant production systems in low-rainfall areas of North Africa and West Asia are limited by low and erratic water availability. Therefore, the testing of conservation farming techniques, effective in dryland systems elsewhere, is often suggested. Seven-year results from a typical site in northern Syria showed that zero-till (direct-drill) systems with cereal residue retention may marginally enhance soil moisture status, but the yield effect on barley, either monocropped or rotated with vetch (Vicia sativa), was small and non-significant. In the vetch–barley rotation, a small and fairly consistent benefit to vetch was observed, amounting to a 20% yield increase in vetch hay. Given smallholders' strong preference for barley and reluctance to grow vetch as an alternate crop, there is little in this result to encourage the promotion of zero-till conservation techniques in these farming systems.

Photosynthetic photon flux density (PPFD) has variable effects on cotton (Gossypium hirsutum) plant growth, development and lint yield, but little is known about the responses of yield, yield components and fibre quality to low PPFD at different developmental stages. Field studies were conducted in 1993–95 to determine the effects of an 8-d period of shade (63% reduction in PPFD) imposed at different developmental stages (pinhead square (PHS), first flower (FF), peak flower (PF) and boll development (BD)) on cotton growth, lint yield, yield components and fibre quality. Shade for 8 d at the early square stage did not affect cotton growth and yield. Shade during FF, PF and BD increased fruit abscission, and decreased specific leaf weight, dry matter accumulation, lint yield, fibre micronaire, and fibre strength compared with the unshaded control. The detrimental effect of shade on yield increased with later growth stages. Shade at the FF, PF and BD stages decreased lint yield by 18, 34 and 52% in 1993, and by 18, 21 and 29% in 1994 respectively compared with the unshaded control. Shade caused the greatest decrease in the dry weight (DW) of fruits (squares + flowers + bolls) and the smallest decrease in leaf DW among leaves, stems and fruits. Of the three yield components (boll number, boll weight and lint percentage), boll number was the most sensitive to shade. Shade during squaring and early flowering had little effect on average boll weight, and did not affect lint percentage. Decreased yield of cotton shaded during FF and PF appeared to be related to decreased boll retention. Shade during BD decreased both boll retention and average boll weight. Under shade conditions, fibre micronaire and fibre strength were decreased, while other fibre properties were unaffected. These results help explain the yield response of field-grown cotton to low PPFD stress.

A field experiment was conducted to study the influence of 8- to 9-year-old nitrogen-fixing tree species (Faidherbia albida, Acacia ferruginea, Albizia lebbeck) and fertilizer nitrogen levels on yield and nitrogen uptake of intercropped cowpea (Vigna unguiculata). Grain and dry fodder yields of cowpea were reduced by 9% to 27% and by 11% to 35% respectively compared with the sole crop. Application of fertilizer nitrogen produced significantly higher yields. Nitrogen uptakes by leaves, stems and grain of cowpea were significantly reduced under A. ferruginea and A. lebbeck, but cowpea as sole crop and under F. albida showed no differences. Nitrogen uptake in different plant parts increased with increase in fertilizer nitrogen level.

Increased use of prime agricultural land for cropping and non-agricultural uses in many tropical countries implies that crop residues become more important as a source of feed for livestock. Traditionally, much research on crop residue feeding was done by focusing on laboratory measurements of feed quality but neglect of farmers' perceptions led to disappointing results in the transfer of straw feeding technologies based upon laboratory results. Farming Systems Research (FSR) provides methodologies and concepts that bridge the gap between formal commodity research (including crop residues and by-products) and field application. This paper reports the experiences of a project in India that changed the emphasis from a commodity research approach on improved crop residue feeding to a system approach by using three types of FSR. The paper first reviews the achievements of on-station research on feeding systems for crop residues in terms of treatments (biological, chemical, physical) and in terms of breeding and managing cereal crops for more and better straw. Next, it discusses definitions and problems of FSR as encountered in the project's reorientation of livestock research and development programmes. Finally it summarizes the overall results of the three FSR approaches used in the project.

The effects were evaluated of six methods and six durations of seed treatment on the germination of wild sunflower (Tithonia diversifolia) seeds. The treatments were as follows: (1) hot water at 80 °C, (2) hot water at 100 °C, (3) oven-drying at 80 °C, (4) oven-drying at 100 °C, (5) immersion in concentrated sulphuric acid and (6) immersion in 10% hydrogen peroxide. The durations were 0, 2.5, 5, 10, 15 and 20 min. Treatment with hot water at 80 or 100 °C for 11–14 min, and oven-drying at 100 °C for 20 min all resulted in more than 65% germination 10 d after treatment. Oven-drying at 80 °C, immersion in concentrated sulphuric acid and in 10% hydrogen peroxide resulted in less than 50% germination. Based on the higher cumulative germination, lower cost, and environmental concerns, hot water treatment at 80 or 100 °C for 11–15 min is recommended.

Weeds are major constraints to wider adoption of wet seeded rice. Two split-plot experiments on water management during crop establishment of wet seeded rice were conducted in the dry and wet seasons of 1994 to quantify crop stand establishment and weed suppression by herbicides and rice genotypes. The latter consisted of five previously identified hypoxic-tolerant lines and three standard cultivars, sown at approximately 300 seeds m−2. The tested hypoxic-tolerant genotypes had superior seedling growth, but not higher crop stand establishment than the standard ones. Genotypes that had superior crop stand establishment or faster seedling growth did not necessarily give better weed suppression. Genotypes with high tillering ability were more competitive against weeds. Echinochloa glabrescens dominated the weed flora, especially in farmers' practice and anaerobic seeding (seeding into soft mud), followed by flooding at 7 d after seeding (DAS). The relative proportion of Monochoria vaginalis increased in anaerobic seeding with flooding 3 DAS and seeding into standing water. Pretilachlor + fenclorim effectively controlled weeds in farmers' practice and anaerobic seedings, and 2,4-D in water seeding. Without herbicide, water seeding and anaerobic seeding flooded 3 DAS reduced dry weed weight by 73–88% compared with farmers' practice. Anaerobic seeding with flooding 7 DAS controlled weeds effectively when the weed pressure was low (dry season, about 136 g m−2 of weed biomass in plots without herbicide) but not when weed pressure was high (wet season, 513 g m−2). Water seeding could not sustain high rice yields due to low crop stand population caused by flotation of seedlings. Anaerobic seeding with flooding 3 DAS allowed genotypes to sustain high yield and increased water productivity (rice production per unit volume of water used in the field) without having to use herbicide or with only half of the recommended herbicide rate. The correct water management during the crop establishment stage may effectively lower the economic and possible runoff costs of herbicides without reduction in yield or water productivity.

Seven maize cultivars and seven soyabean cultivars were grown in monocultures, and in all possible 49 mixtures of maize and soyabean, at two locations to assess the intercropping advantages of mixtures. On average, intercrops produced 6% more dry matter and 17.5% more protein than the monocultures of maize, the most productive component. Both the dry matter and protein yields of intercrops were closely correlated with the yield of the maize component, but not with that of the soyabean component, indicating that there was no need for a specific breeding programme for maize to be used in intercropping systems. Although the average intercropping advantage, the monoculture yields of maize cultivars and, to a lesser extent, the monoculture yields of soyabean cultivars differed between locations, there was no evidence that the yield of various intercrop combinations differed between locations.

Land resources are scarce in Mauritius and to fulfil the export quota sugarcane (Saccharum hybrids) has to be grown in marginal areas which are not conducive to optimal growth. In order to increase overall productivity there is a need to breed and select sugarcane varieties specifically adapted to the extremely dry and extremely wet areas. In this study, 154 genotypes representing four families were planted in a randomized complete block design at two sites. The genotypes were replicated at the two sites and evaluated in the plant cane and first ratoon crops. Family × environment and genotype × environment interactions were determined using the mixed model analysis of variance. Significant differences between families, genotypes and environments were found in stalk height, stalk diameter, industrial recoverable sucrose % cane (IRSC) and cane yield per hectare in tonnes (TCH). The genotype × environment interaction was significant for stalk height, stalk number, stalk diameter, sucrose content, TCH, tonnes sugar per hectare (TSH) and kilobrix (parameter used for selection in the preliminary phase of the selection programme at the Mauritius Sugar Industry Research Institute) in both plant cane and first ratoon crops indicating that the relative performance of the genotypes is not consistent across the environments for these characters. The family × environment interaction was found to be significant for cane and sugar yields whereas it was not significant for field Brix in either the plant cane or the ratoon crops. This showed that, for the parameter Brix, the relative performance of the families is similar in both environments and there is no need to replicate in more than one environment. The environmental sensitivities measured with respect to sugar yield showed that families and genotypes with nearly equal means over all environments displayed inconsistent performances. Differences in the sensitivities of the different families and genotypes were observed and some of the family × environment and genotype × environment interactions could be ascribed to them. The results also suggest that mass selection could be more effective than family selection and selection for each specific environment is advisable.

Long-term field experiments were conducted at six different sites (representing dryland and irrigated environments) with wheat (Triticum aestivum) on sandy loam soils to generate a database relating available water supply and fertilizer nitrogen (N) rate to grain yield. Step-wise multiple regression analysis showed that water supply and fertilizer N at more than 53 cm a−1 and 103 kg ha−1 a−1 were unproductive. A method, based on the principle of equi-marginal productivity of water in different periods of crop growth, has been used to estimate the optimum allocation of the variable amounts of water supply over the growing season. The optimized quantities of water in different periods of crop growth were then employed to compute fertilizer N requirement to achieve a given yield target. For medium grain yield targets (4–5 t ha−1), the range of substitution between fertilizer N and water for efficient resource use was quite wide.