Field experiments during the winter seasons of 1986–7 and 1987–8 studied the effect of three sub-surface drain spacings and three levels of phosphorus on the yield, chemical composition and uptake of nutrients by Indian mustard (Brassica juncea). The number of siliquae m-2 and seed yield decreased with increasing drain spacing. Application of phosphorus increased seed yield and yield attributes. The concentrations of nitrogen, phosphorus and potassium in the seed and stalks decreased and those of sodium, calcium and magnesium increased with increasing drain spacing, but application of phosphorus increased the concentration of these nutrients in the seed and stalks. Absence of phosphorus in the drain water effluent and the level of available phosphorus in the soil profile after crop harvest indicated very slow movement of phosphorus, most of which was retained in the top 30 cm of soil.

On-farm trials were conducted for seven years in north-west Syria to investigate the use of land left fallow after a barley crop to grow feed legumes for small ruminants. Common vetch (Vicia sativa), forage peas (Pisum sativum) and common chickling (Lathyrus sativus), with and without applied phosphate fertilizer, were grown in rotation with barley and a barley-fallow rotation was used as a control.

Vetch was preferable for grazing whereas chickling yielded more grain and straw and had a higher harvest index. Both species showed substantial responses to phosphate fertilizer. Yields of subsequent barley crops were slightly lower after unfertilized feed legumes than after fallow but after fertilized feed legumes, barley yields were higher than after fallow. The milk production of ewes and liveweight gains of lambs grazing vetch, chickling and common land were similar.

The project showed how results from on-farm research can modify on-station research objectives and identify questions for further on-station research.

On-farm diagnostic experiments were used to study constraints to nitrogen fertilizer use, define recommendation domains, and test fertilizer management techniques for two sorghum cropping systems in semi-arid tropical India. In the post-rainy season sorghum cropping system, nitrogen fertilizer use remains negligible because crop response is poor when sorghum is planted after the end of the monsoon, as is traditional. An earlier planting date would introduce high risks. In the dependable rainfall region, nitrogen fertilizer use on hybrid sorghum could be enhanced by tailoring recommendations to broad farmer-designated soil groups, and by educational programmes on the use of complex fertilizers. Additional research on fertilizer efficiencies on shallow Vertisols is needed. Diagnostic experiments proved a useful, relatively rapid and low cost method of research when complemented by farm management and on-station research data.

Yield stability in cassava requires genotypes that produce well under the variable moisture conditions encountered during the growth cycle. Plant characteristics related to yield stability were studied in two cassava clones subjected to 105 days of water stress in a field drainage lysimeter. Stress conditions commenced 117 days after planting, and the plants were allowed to recover at the end of the stress period for the rest of the growth cycle. Water stress restricted the growth of leaves and stems, but root yields were increased or remained unaffected. Leaf water potential varied little with stress, but gas exchange rates were about 75% those of the control throughout the stress period in both cultivars. Under stress, the plants partially closed their stomata and extracted deep soil moisture slowly. A high yield in both wet and stressed environments was associated with high mean LAI, better leaf retention, and greater partitioning of shoot biomass into leaf formation.

Thirty on-farm trials were conducted in northwest Syria over a period of four seasons to examine the main effects and interaction of sowing date, sowing method, Rhizobium inoculation, phosphate application and weed control on chickpea (Cicer arietinum). Advancing the sowing date from spring or late winter to early winter resulted in substantial yield increases. The effects of Rhizobium inoculation were small and inconsistent. Chemical weed control significantly increased grain yield compared with the unweeded control treatment in winter-sown crops but was less effective than hand weeding. Phosphate application significantly increased yield in the first three seasons, the overall increase being 10%. Drilling chickpea seed gave an overall 10% increase in yield compared with the broadcast sowing commonly practised by farmers. There is no economic or environmental risk to the farmer in adopting the proposed practices either singly or in combination. However, the greatest gains in yield and net revenue are derived from a combination of early winter sowing, drilling, weeding and, where appropriate, phosphate application.

The production of lentil (Lens culinaris) was examined in 24 on-farm trials conducted over three seasons (1985/86 to 1987/88) in northwest Syria to examine the main effects and interaction of sowing date, weed control, Sitona weevil control, and fertilizer application (phosphorus and nitrogen). Advancing the date of sowing from late winter (mid January) to early winter (mid-November) resulted in an increased yield of grain and straw in all years across locations. Responses to phosphorus application were also significant in all years. Controlling Sitona weevil increased grain yield by 20% in early sown crops and by 14% in those that were sown late. Weed control by the pre-emergence application of cyanazine and pronamide increased grain yield by 59% in early sowings and by 20% in late sowings. Economic analysis of the improved production practices showed that early sowing combined with the control of Sitona and weeds, and phosphorus application, gave the highest probability of an increase in net revenue with virtually no risk of economic loss to the farmer.

The leaf mulch of the tree legumes Acacia cunninghamii, A. fimbriata, Calliandra calothyrsus, Gliricidia sepium, Leucaena leucocephala and Sesbania sesban was evaluated as a source of nitrogen for maize growth in glasshouse pot experiments. The mulch of Sesbania sesban resulted in the largest yields of maize stover but yields were less than those that resulted from application of equivalent rates of fertilizer nitrogen. The mulches of Gliricidia and Leucaena also produced a yield response in maize but those of Calliandra and the two Acacia species were ineffective as sources of nitrogen in the short term. Sesbania mulch at the equivalent of 5 t dry matter ha-1 produced a maize yield similar to that obtained with 75 kg N ha-1. The poor response to Calliandra and Acacia mulch may be associated with the high polyphenol and/or lignin content of the leaf of these species.

On-farm research in remote areas demands methods that keep down costs and reduce the need for subsequent research and extension inputs and yet that still produce useful and sustainable recommendations. An important part of the process is to identify existing resource user groups and use them, rather than individual farmers, as a starting point for on-farm research. This approach is discussed in the context of farming systems research in the eastern hills of Nepal.

The diversity of cropping patterns on smallholder farms in southern Malawi was analysed using a framework that explicitly incorporates the extent of intercropping in each field. Diversity is defined as the relative abundance of each crop in the overall cropping pattern. Six indices of diversity were constructed for 208 farms and used in a model of a welfare-maximizing farm household to examine the reasons for diversity in cropping patterns; multiple regression techniques were used to determine the effect of different household characteristics on diversity. The results suggest that an increase in labour availability over the production period is associated with a more diverse cropping pattern. Landholding size also influences diversity, which rises to a maximum and then falls as the area cultivated per capita increases. Farmers who grow a non-food cash crop (tobacco) have more diverse cropping patterns than those who do not. As diversity increases, farmers use intercrop patterns that are more substitutive than additive.

The poor quality of the natural vegetation in the dry season affects both animal productivity and the lives of the pastoral community in the Adamawa Plateau of Cameroon but may be improved by introduction of the forage legume Stylosanthes guianensis. When used in a ‘fodder bank’ system, Stylosanthes grew to an average plant height of 1.41 m, had a dry matter productivity of 5.5 t ha−1 and comprised 93.4% of the pasture's botanical composition at the end of the growing season, indicating that fodder banks have considerable potential to enhance animal and crop production in Cameroon. Complementary studies conducted in Nigeria on the yield benefits of cropping leguminous pastures support the feasibility of using fodder banks as a means of improving the livelihoods of small scale farmers.