A wide variety of training activites has been carried out related to farming systems research (FSR). The majority have had one or more of the following objectives: to introduce the farming systems perspective, to teach new research methods, and to promote the institutionalization of FSR. Many of these objectives are important, but FSR training is not usefully seen as a separate field of endeavour. The goals of FSR training will be better served by reconsidering the roles of universities, national research institutions, and international institutions.

Yields of maize were increased when they followed successfully established pasture legumes in two rotation experiments. The largest increases were obtained after silverleaf and were equivalent in one experiment to the effects of about 30 kg N ha−1 a−1 over four years and in the other experiment to those of 40 kg N ha−1 a−1 over three years. The largest beneficial effect of some of the legumes was on the first crop of maize but in others did not occur until the third or fourth crop. The possible reasons for the different patterns of residual effect are discussed in relation to the nature of the legume residues, the quality of the seedbed following the legumes, and rainfall

Late planting of a 136-day variety of maize led to reduced yields only when planting was later than about four weeks after the start of the main rains. The reductions were caused by drought at the end of the season and by high rainfall in the first 35 days after planting. Drought beginning 80–100 days after planting (DAP) reduced weight per seed but drought beginning earlier than 80 DAP reduced seed number per cob and increased the number of barren plants. Late showers alleviated the reduction in weight per seed but not the other symptoms of drought. High rainfall after planting was associated with reduced plant size at flowering and reduced seed number per cob at harvest.

The potential for using sorghum and millet crop residues as fodder was studied in southeastern Botswana. This region is characterized by low, unevenly distributed rainfall and shallow sandy soils. There were significant differences among cultivars for grain and stover yield, digestibility, crude protein, and mineral content, but no species advantage. Stover from all entries was adequate for cattle maintenance in in vitro dry matter digestibility (IVDMD) and most of the minerals tested, but crude protein and phosphorus levels did not always meet the minimum requirement. The deficient phosphorus levels were compounded by high calcium levels. This mineral imbalance could lead to bone abnormalities and reduced fertility in livestock.

The relation between soil mechanical impedance as a result of soil drying, and root system growth (mass and length density) of rice was investigated in greenhouse and field studies. In a greenhouse experiment, soil drying for 16 days increased mechanical impedance in the 0–20 cm soil layer from near 0 to 2.5 MPa, and decreased root growth by 47% compared to the continuously flooded control. Root length density decreased with decreasing soil moisture and increasing soil mechanical impedance. In a lowland field experiment using a sprinkler irrigation gradient treatment for 19 days during the vegetative growth stage, soil mechanical impedance as low as 0.01 MPa inhibited root growth while values greater than 0.3–0.5 MPa decreased root growth and extension by 75%. The relative loss of potential root growth was continued after reflooding. Root length density, measured at flowering, was linearly related to yield.

Uniform descriptions of developmental stages in crops improve communication among producers, researchers and others. This paper gives a uniform system for the description of the developmental stages of lentil that we believe is not only universally applicable to all growing environments (field or greenhouse) and to divergent cultivars, but also useful for single plants or communities of plants. Vegetative and reproductive development are described separately. Vegetative growth stages are described by counting nodes on the main stem and continuing the count up the basal primary branch to include the highest fully developed leaf. Reproductive stages Rl and R2 are based on flowering, R3 to R6 on pod and seed development, and R7 and R8 on maturation.

Field experiments at 26 sites, selected on the basis of their varying degrees of zinc deficiency, showed that the critical deficiency levels of zinc for wheat were 0.60 mg kg−1 in the soil and 19 μg g−1 dry matter in 45-day-old plants. Further field trials at nine locations with varying levels of zinc deficiency showed successive increases in the grain yield of wheat with increases in zinc application, emphasizing the need for zinc fertilization when wheat is grown on zinc-deficient soils.

Time to flowering of mung bean crops varies appreciably depending on the genotype, and the daylengths and temperatures prevailing during the period after sowing. Relatively little is known about the precise nature and inheritance of flowering responses to photoperiod and temperature. The combined effects of variations in these two factors on time to flowering were therefore evaluated in controlled environment studies on six genotypes and four F1 hybrids. The responses were examined for conformity with hypothesized linear models from which inferences might be made of the genetic control of flowering. The analyses suggest that all the genotypes and F1s tested were quantitative short day plants, with the possible exception of one line which may be day neutral. The analyses further suggest that time to flowering was influenced by four genotype-specific attributes: minimum time to flowering, critical photoperiod (Pc), responsiveness to photoperiod longer than Pc, and responsiveness to temperature. Among the genotypes tested, different values were observed for each attribute. In most instances, the values for the F1s were closer to one or other parent, indicating dominance rather than additive genetic effects. We conclude that, with several levels each, the four attributes provide the potential for a diversity of flowering response types within mung bean. Further, it should prove possible to manipulate the mung bean germplasm to obtain novel combinations of attributes, and thus to breed genotypes adapted to photothermal regimes not previously considered suitable for the crop.

Field experiments during the rainy seasons (July–October) of 1984 and 1985 at Hisar, India showed that removing weeds in pearl millet from 10 to 60 days after sowing led to fewer weeds at harvest, and significantly higher grain yields were obtained when weeds were removed 20 days after the crop was sown. All the weed control methods tried (hand hoeing, hand wheel hoeing, or application of terbutryne or atrazine) were successful and significantly increased crop growth and grain yield. The maximum grain yield was obtained with atrazine at 0.5 kg ha−1 and the minimum in the unweeded control.

In recent studies of cassava at CIAT, net CO2 uptake rates of 20 to 35 μmol CO2 m−2 s−1 were commonly observed. Cassava photosynthesis has a high optimum temperature (35°C) and a wide plateau (25 to 35°C) corresponding to the temperature range under which cassava is cultivated. Leaf photosynthesis requires high saturation irradiance (1500 μmol m−2 s−1) and the rates are greatly reduced by leaf-air vapour pressure differences above 1.5 kPa; this reduction is associated with stomatal closure. Cassava leaves have low photorespiration, low CO2 compensation point, high percentage of carbon fixation in C4 acids and a high PEP-carboxylase activity (15–35% of that in maize), but cassava does not have the typical ‘C4-Kranz’ anatomy. Field measurements of single leaf photosynthesis among a wide range of cultivars grown under rain-fed conditions showed that when light interception was not limiting, there were significant correlations between leaf photosynthesis, total biomass and root yield. This suggests that the use of parental materials with high photosynthetic capacity, in combination with other yield determinants, could be a successful strategy for developing high yielding cultivars. This might be done by exploiting any genetical variations in leaf anatomy and biochemistry that could enhance photosynthesis efficiency and hence productivity.

Plant breeders cannot respond to every quirk of farmers' circumstances but the relevance of breeding research in poor nations can be improved. Recent innovations in germplasm screening programmes for developing nations highlight important differences in selection criteria between farmers and scientists, and among farmers themselves. Drawing on the authors' African experience with International Agricultural Research Centres working on maize and potatoes, the paper explores how breeding programmes benefit from an understanding of farmers' own detailed knowledge about the crop varieties they already cultivate. Issues considered include farmers' use of cultivar diversity, the trade-off between yield and maturity class as selection criteria, defining appropriate experimental conditions, and innovative techniques to increase farmer participation in germplasm screening.