New initiatives in agroforestry are seeking to integrate indigenous trees, whose products have traditionally been gathered from natural forests, into tropical farming systems such as cacao farms. This is being done to provide from farms, marketable timber and non-timber forest products that will enhance rural livelihoods by generating cash for resource-poor rural and peri-urban households. There are many potential candidate species for domestication that have commercial potential in local, regional or even international markets. Little or no formal research has been carried out on many of these hitherto wild species to assess potential for genetic improvement, reproductive biology or suitability for cultivation. With the participation of subsistence farmers a number of projects to bring candidate species into cultivation are in progress, however. This paper describes some tree domestication activities being carried out in southern Cameroon, especially with Irvingia gabonensis (bush mango; dika nut) and Dacryodes edulis (African plum; safoutier). As part of this, fruits and kernels from 300 D. edulis and 150 I. gabonensis trees in six villages of Cameroon and Nigeria have been quantitatively characterized for 11 traits to determine combinations defining multi-trait ideotypes for a genetic selection programme. I. gabonensis fruits are rich in vitamin A (67 mg 100 ml−1), while the kernels are rich in fat (51.3%) and contain a polysaccharide that is a food thickener. The fruits of D. edulis are also rich in oil (31.9%) and protein (25.9%). This poverty-reducing agroforestry strategy is at the same time linked to one in which perennial, biologically diverse and complex mature-stage agroecosystems are developed as sustainable alternatives to slash-and-burn agriculture. To meet the objective of poverty reduction, however, it is crucial that market expansion and creation are possible. Hence, for example, it is important to determine which marketable traits are amenable to genetic improvement. While some traits (such as fruit and kernel mass) that benefit the farmer are relatively easy to identify, there are undoubtedly others that are important to the food, pharmaceutical or other industries which require more sophisticated chemical evaluation. There is a need, therefore, for better linkages between agroforesters and the private sector. The domestication activities described are relevant to the enrichment of smallholder cacao farms and agroforests. This diversification is seen as being important for the support of the cacao industry.

In view of soil fertility problems and financial constraints identified in small-scale farming, on-station investigations on Low-External-Input and Sustainable Agriculture (LEISA) were started by the Farming Systems Research Team Luapula Province (FSRT-LP) in order to assess the potential of three annual and six perennial pasture legume species for green manuring purposes. Rhodes grass (Chloris gayana cv NIRS Boma) was used as a control. Over two seasons, a pasture legume-maize rotation trial was established. Different mineral fertilizer amounts were applied to the maize. Of all the species and cultivars tested, the perennial glycine (Neonotonia wightii cv Cooper) had the strongest green manure effect when no mineral fertilizer was applied. Of the annual pasture legumes, sunn hemp (Crotalaria juncea cv. NIRS 3) and velvet bean (Mucuna pruriens cv. NIRS 16) showed the greatest green manure potential at zero mineral fertilizer level. There were strong indications that the carbon:nitrogen ratio influenced the green manure potential of a species more than its ability to produce biomass. The need to assess the economics and sustainability of current mineral fertilizer practices on maize has been identified.

The participatory approach of Farmer Research Groups (FRGs) was used in Farmer Adaptation of Starter Technology (FAST) with small-scale farmers in Luapula Province, Zambia. The introduction of a starter technology proved to be a suitable method to induce self-help initiatives with farmers. Their first move in FAST related to the improvement of food security and income generation by the cultivation and marketing of new maize (Zea mays) varieties in wetlands during the dry and early rainy seasons. By informal on-farm seed multiplication the expenditure on external agricultural inputs was reduced. The technical aspects of the starter technology began with the integration of pasture legumes as a pioneer crop for green manuring purposes in maize production. In this respect, FRGs developed individual risk-aversion strategies to ensure early planting of the maize with the onset of the rains. The groups made adaptations such as biomass transfer, intercropping and crop rotations in order to integrate pasture legumes into current cropping systems for green manuring purposes.

Manure is a key input to smallholder farming systems, especially in the semi-arid environment of West Africa where cost and availability limit the use of inorganic fertilizers. This paper considers manure management by farmers in an intensive integrated farming system in the Nigerian savanna. The paper reports farmers' indigenous knowledge concerning manure production, quality and application, chemical analysis of manure nutrient content and application rates of manure. The potential manure supply of the livestock population of the Kano close-settled zone is calculated and compared with application rates. Recommendations are made concerning methods for improving manure quality through changes in management practices.

Dry matter production and yield of tea were recorded in a genotype × environment interaction experiment with four tea clones planted at four sites at a range of altitudes in Kericho, Kenya. Large responses to environment in dry matter production and yield were found. After 34 months from planting, the total plant dry matter production ranged from 18 to 22 t ha−1 across the sites. One clone, TN14-3, produced the most dry matter, reaching 29 t ha−1 at the lowest altitude, while clone S15/10 produced the least (15 t ha−1). Analysis of genotype × environment inter actions showed that clone TN14-3 was above average stability in dry matter production across the four sites, but below average in yield. Clone S15/10 showed above average stability for tea yield, but was below average in dry matter production.

In a genotype × environment experiment at four sites with four tea (Camellia sinensis) clones in Kericho, Kenya, differences in ground cover and total dry matter production and partitioning were found between clones and between sites. The major contributor to these differences was the daily intercepted solar radiation that differed by as much as 30% between sites. Differences in radiation use efficiency (RUE) between the sites were small, but varied from 0.3 to 0.45 g MJ−1 between the clones. The rate of dry matter production was affected by the prevailing weather conditions. During the dry seasons the rate of dry matter production differed between the sites and clones by a maximum of 2 g m−2 d−1. Harvest indices were found to vary between the sites and increased with time. Partitioning to harvested shoots ranged from 10% for clone TN14-3 to a maximum of 19% in clone S15/10 at site 4. Partitioning to roots showed distinct differences between clones, being least in clone S15/10 (10–20%) compared with 15–32% in other clones. Rooting depths were greatly influenced by the prevailing temperatures.

In an experiment on genotype × environment interactions in tea (Camellia sinensis), yield differed between the genotypes at all sites. The highest yield in the third year after planting was 3760 kg ha−1 for clone S15/10 at site 4 (1800 m altitude), while the lowest was 1610 kg ha−1 for clone 6/8 at site 1 (2200 m). The dry matter contents of harvested shoots from each clone ranged from 0.24 for clone TN14-3 down to 0.19 for clone S15/10. Yield response to soil water deficits was more pronounced at site 4, where larger deficits were observed. Hail damage affected the yield of two sites and a temperature influence on recovery was evident.

Growth variability in pearl millet (Pennisetum glaucum) over short distances is a severe constraint on the interpretation of agricultural experiments in the West African Sahel. The purpose of this study, therefore, was to compare different non-destructive methods to estimate, spatially, millet growth and final yields. Aerial photography, georeferenced radiometric measurements and a chlorophyll meter were tested during three rainy seasons in a nitrogen rate×density×genotype experiment in western Niger. For the radiometric measurements, normalized difference vegetation indices (NDVI) obtained and calibrated for individual millet hills spaced 1.5 m apart were aggregated for the entire experiment with 6000 samples per hectare. A simple calibration procedure was used to correct for variation in soil background reflectance and incident light. For NDVI measurements of individual planting hills, the correlation between plant total dry matter (TDM), leaf weight, leaf area and NDVI was high (r2 = 0.89–0.91) and regression parameters were genotype-specific. Aggregated georeferenced NDVI measurements at the plot level correlated with grain and TDM at harvest (r2 = 0.40–0.87). The analysis of true-colour and infrared aerial photographs permitted the monitoring of millet growth and the quantitative evaluation of treatment responses throughout the growing season. The infrared images were the most efficient in the detection of vegetation followed by the normalized green band of true-colour images. The red band was the least effective because of the influence of soil albedo and image vignetting. Although chlorophyll meter measurements reflected relative differences in plant nitrogen status between treatments, their interpretation required destructive sampling and proved unsuitable to predict millet yields. The results demonstrate the potential of georeferenced radiometric data and aerial photographs to improve soil sampling strategies, sequential plant growth monitoring and the statistical design and analysis of experiments. By providing intermediate data sets, the tested tools can also help in the upscaling of ground truth to satellite data in yield prediction studies.

To assist commercial producers with optimizing the use of irrigation water, the responses to drought of mature and young tea (Camellia sinensis) crops (22 and 5 years after field planting respectively) were compared using data from two adjacent long-term irrigation experiments in southern Tanzania. Providing the maximum potential soil water deficit was below about 400–500 mm for mature, and 200–250 mm for young plants (clone 6/8), annual yields of dry tea from rainfed or partially irrigated crops were similar to those from the corresponding well-watered crops. At deficits greater than this, annual yields declined rapidly in young tea (up to 22 kg ha−1 mm−1) but relatively slowly in mature tea (up to 6.5 kg ha−1 mm−1). This apparent insensitivity of the mature crop to drought was principally due to compensation during the rains for yield lost in the dry season. Differences in dry matter distribution and shoot:root ratios contributed to these contrasting responses. Thus, the total above-ground dry mass of well-irrigated, mature plants was about twice that for young plants. Similarly, the total mass of structural roots (>1 mm diameter) to 3 m depth was four times greater in the mature crop than in the young crop and, for fine roots (<1 mm diameter), eight times greater. The corresponding shoot:root ratios (dry mass) were about 1:1 and 2:1 respectively. In addition, each unit area of leaf in the canopy of a mature plant had six times (by weight) more fine roots available to extract and supply water than did a young plant. These results show that young tea should be irrigated in preference to mature tea, especially where the maximum soil water deficit is likely to exceed 250 mm.

The mean time for 50% germination at 20 °C of 12 Indian wheat (Triticum aestivum) cultivars was nearly halved, from 51 h to 27 h, by soaking seed in water for 8 h prior to sowing. A delay of 24 h without further soaking, intended to simulate postponement of sowing, reduced the time saved by priming to 16%. Priming had no effect on final germination percentage. These results were used in the design of 275 on-farm, farmer-managed, participatory trials of seed priming in wheat during the 1997–98 and 1998–99 rabi (post-monsoon) seasons. In forty-one trials in tribal areas of Bihar and West Bengal states of India, seed priming gave a 13% grain yield advantage for farmers growing wheat in marginal areas with low levels of agricultural inputs. Mean benefits from seed priming of wheat in nine trials in Chitwan, Nepal were 17%. In high potential areas of Gujarat, India, 205 trials had higher rates of input use. Yield benefit from priming in these trials averaged only 5% but constituted an extra 200 kg ha−1 grain at little or no cost. In 20 trials on marginal land, with slightly saline irrigation water in Ahmadwala, Pakistan, an average yield increase of 36% was obtained using seed primed with a 0.2% gypsum solution. Collaborating farmers reported that priming wheat seed overnight resulted in faster, more complete emergence, more vigorous early growth, better tillering, earlier flowering, larger ears, earlier maturity and higher yields. In addition, many farmers also reported that foliage in primed plots was a darker shade of green than that in non-primed plots, suggesting that primed plants may have been using nitrogen more efficiently. Seed priming was popular with farmers, most of whom reported that they would prime wheat seed the following year. A survey in Gujarat in 1998–99 of 63 farmers who had tested priming in 1997–98 showed that, while 65% had primed some of their own seed, none had primed more than 50 kg, suggesting that there were practical difficulties in priming larger volumes of seed.

A field experiment to evaluate the effect of N, K and time of K application on the growth, yield and chemical composition of wheat (Triticum aestivum) grown in saline soil with subsurface drainage, was conducted at the Central Soil Salinity Research Institute, Karnal Research Farm, Sampla during the winter seasons of 1992–93 to 1994–95. The treatments consisted of three levels each of N (0, 120 and 150 kg ha−1) and K (0, 50 and 75 kg ha−1) with the K applied at two different times (full basal and half basal + half top dressed 30 d after sowing). The growth characteristics (plant height, number of tillers and dry matter weight m−2 recorded at 60 d after sowing) and yield-attributing parameters (number of productive tillers and length of spikes) increased significantly with increasing N levels up to 150 kg ha−1 and K levels up to 50 kg ha−1. Similar responses of N and K were also observed on grain and straw yields of wheat. Time of K application had no significant effect on growth and yields. The N concentration in grain and straw increased significantly with the application of 120 kg N ha−1 over control. Application of K had no significant effect on the concentration of N in grain and straw. The K concentration in grain and straw increased significantly due to the application of 50 kg K ha−1 but it was unaffected by the time of K application. Application of K increased the efficiency of utilization of applied N. A trend towards declining salinity of the soil profile due to leaching through the subsurface drainage system was observed from 1992–93 to 1994–95. For three consecutive years the status of available N and K in surface soil (0–30 cm depth) increased due to their respective applications. This field study indicates that 150 kg N and 50 kg K ha−1 should be applied under canal-irrigated conditions to get the sustainable and optimum yield of wheat in saline soils.