Two sets of on-farm trials, each covering two years, were conducted in the northern Guinea savannah of Nigeria over the period 1999–2001, the objective being to compare integrated Striga hermonthica control measures (soybean or cowpea trap crops followed by maize resistant to Striga) with farmers' traditional cereal-based cropping systems. In both sets of trials, this proved to be highly effective in increasing productivity over the two year period, especially where soybean was used as a trap crop. Resistant maize after a trap crop increased the net benefit over the two cropping seasons in both trials by over 100% over farmer practice. However, in the second set of trials there was no significant increase in productivity between a trap crop followed by Striga resistant maize, and a trap crop followed by local maize especially where legume intercropping and fertilizer had been applied in the farmer practice. There was also no increase in productivity between two years' traditional cereal cropping and one year's local maize followed by Striga resistant maize. This indicates the importance of a legume trap crop in the first year in order to ensure high productivity in the second year, regardless of variety. Up to 20% of farmers obtained higher productivity from their own practices, notably intercropping of cereals with legumes and use of inorganic fertilizers. Leguminous trap crops and Striga resistant maize, together with two key management practices (increased soybean planting density and hand-roguing) were seen to be spreading both within and beyond the research villages, indicating that farmers see the economic benefits of controlling Striga. Survey findings show that explaining the reasons why control practices work can greatly increase the adoption of these practices. Wider adoption of Striga control will therefore require an extension approach that provides this training as well as encouraging farmers to experiment and adapt Striga control options for their local farming systems.

A three-year trial was conducted on a degraded soil in the moist Guinea savanna of northern Nigeria to assess the possibility of improving productivity and economic viability of maize-based systems by incorporating short-season legumes and green manure crops into the cropping pattern. Treatments included double cropping legume-maize systems, full-season sole maize receiving various amounts of nitrogen, green manure crop mucuna (Mucuna pruriens var. utilis) followed by sole maize and a legume-maize system receiving additional rice mill waste. In comparison with full-season maize, the use of early-season cowpea followed by maize improved productivity as well as economic returns of the cropping system, while the use of mucuna, grown as an early-season crop or full-season crop, resulted in poor overall productivity of the system. The addition of rice mill waste as a soil amendment in cowpea–maize systems stimulated maize yields and rice mill waste can form a cheap source of organic inputs for farmers living nearby rice mills. Given the limited growing season of the northern Guinea savanna, it is concluded that timing of field operations is crucial for the successful application of double cropping systems. In addition, high labour requirements are a serious constraint for wide-scale adoption of double cropping systems by small-scale farmers, stressing the need to reduce soil cultivation operations, for example by maintaining a uniform ridge distance for all crops in the rotation.

Canavalia ensiformis, Crotalaria grahamiana, Dolichos lablab, Mucuna pruriens, Tephrosia vogellii and Tithonia diversifolia were evaluated as potential species for soil fertility replenishment in on-farm adaptive trials, farm visits and field days in Tororo District, eastern Uganda. Farmers used multiple criteria for assessing and selecting those species that fitted within their production systems and production objectives. Farmers also adapted the technologies to allow for local opportunities and constraints. A preference ranking and logit regression analysis of probabilities of acceptance of the species conducted in 19 farmer groups showed that Mucuna had high, Tithonia and Crotalaria intermediate, and Canavalia, Lablab and Tephrosia low probabilities of being accepted or adopted. The evaluations showed that whilst technologies need to be adapted, a single-use technology had little chance of large-scale adoption. This paper highlights adaptations/innovations by farmers, and opportunities for participatory action research targeting farmers' production objectives.

The effect of ‘on-farm’ seed priming – soaking seeds in water before surface-drying and sowing them – was tested for mungbean (Vigna radiata) in 15 irrigated on-station trials and four sets of rainfed, paired-plot, farmer-participatory trials over four contrasting years from 1999 to 2002 in the North West Frontier Province of Pakistan. The optimum soaking time was found to be between six and eight hours; eight hours was used in all the trials. Of the 19 trials, priming was significantly better than non-priming in 14 with a mean yield increase of 56%. In the remaining five trials there was no difference between treatments but in no case was priming worse than not priming. In a subset of 11 on-station trials in which management was considered to be optimal, yield declined in a linear fashion as the date of sowing was delayed. The rate of decline of about 30 kg ha−1 d−1 after 1st June was similar for both non-primed and primed crops, although the latter declined from a higher base. Farmers' yields were proportional to rainfall over the four years and the mean increase in grain yield due to priming in the 39 trials was 30%. Benefits from priming were the result of a combination of faster germination and emergence and more vigorous growth and development, leading to better crop stands and bigger, more productive plants. It was concluded that ‘on-farm’ seed priming is a low-cost, low-risk technology that has the potential to raise mungbean yields substantially thus making it a more attractive crop for farmers.

Through years of research, the Ethiopian Agricultural Research Organization has recommended a number of improved bread-wheat varieties for production in the different climatic zones, along with accompanying technology packages. In areas such as the Jijiga plains, however, adoption of these varieties by the farmers has been very limited. The principal objective of the study was, therefore, to investigate the reasons why farmers are reluctant to adopt high-yielding improved wheat varieties, and to identify farmers' preferences. An assessment study followed by participatory evaluation of the performance of five improved bread-wheat (Triticum aestivum) varieties and a local control was carried out under farmers' management practices. The trial was conducted at 10 locations (across three districts) on the Jijiga plains for two consecutive years (the 1999 and 2000 cropping seasons) and involved 30 farmers. Farmers' preferred varieties were identified using preference ranking. The results showed that farmers refrained from the adoption of some ‘improved’ varieties of bread wheat that were provided through the extension services because the varieties performed poorly under farmers' conditions. The study also showed that farmers do have multiple criteria for evaluating the varieties apart from yield, though the latter was the major parameter for recommending and releasing varieties for multi-locations. Farmers identified earliness, yield, and quality as the main criteria for adoption of wheat varieties. Accordingly, variety HAR-710 stood first in terms of yield (2.56 t ha−1) and other parameters, followed by PAVON -76 (2.49 t ha−1). Though its grain yield was relatively lower than the improved ones, the local control was preferred to some improved varieties used in this study for other quality parameters. The study highlighted the need for re-orienting agricultural research towards involving farmers at the appropriate stages of technology identification.

In general, olive trees are self-compatible, but under some climatic conditions a number of cultivars have demonstrated problems with pollination and fruit set. The Manzanillo cultivar is usually self-pollinating, but under hot conditions its pollen develops slowly, resulting in little or no fertilization. Trials were carried out in two hot, arid ecosystems (Arid Chaco in La Rioja, Argentina and Sonoran Desert in Arizona, USA) to determine if supplemental pollination of a Manzanillo cultivar has the potential to increase yields, and to assess the effectiveness of three different cultivars as sources of pollen. Branches that received supplemental pollination produced 21% more total olives than the control. In Arizona, total olive and shotberry (unpollinated olive) production were significantly different between treatments. Branches that received supplemental pollination produced 98% more olives, and had 58% fewer shotberries than did branches in the control rows. Significantly more olives were produced on branches pollinated with Sevillano and Arbequina pollen, compared with those pollinated with Ascolano pollen and with the control.

Mineral fertilizer application and consequent plant nutrition has long been observed to influence associated plant-parasitic nematode population densities, offering the potential as a nematode management option. Observations were made on the influence of mineral fertilizer application on nematode populations on three separate long-term rice experiments, (differential mineral application on upland and on lowland rice, and P application on upland rice) undertaken between 1994 and 1997 in Côte d'Ivoire. In 1995, on upland rice, treatments with K or N withheld from the comprehensive mineral application treatment (range of elements including N, P, K, Ca, Mg and Zn) led to lower densities of Pratylenchus zeae at harvest than the comprehensive mineral application. By withholding K or Mg, Helicotylenchus pseudorobustus densities were greater than with either the control (no mineral application) or comprehensive mineral application in the same year. No differences were observed between treatments in 1994, or between treatments for densities of other nematode species present (Meloidogyne incognita, Criconemella tescorum) or for total nematode density. In the lowland rice trial, no treatment effects on nematode species (Hirschmanniella oryzae and Uliginotylenchus palustris) were observed. In the P application trial on a P-deficient Ultisol, Heterodera sacchari densities were lower in treatments receiving 180 kg P ha−1, than untreated in 1995; in 1996 no differences were observed between untreated and 135 kg P ha−1, while in 1997 higher densities of H. sacchari were present in 135 kg P ha−1 than untreated. Regression analysis of nematode densities against the mineral straw content in the P application trial revealed a negative correlation between M. incognita and Mn and Ca, and between P. zeae and Zn or Fe. A positive correlation was observed between Helicotylenchus spp. and Mg. This study provides strong arguments for taking plant parasitic nematodes into account when planning and executing long-term research trials.

The two years on-farm tillage research during the 1999 and 2000 cropping seasons in Ethiopian highland Vertisol area demonstrated the importance of adapting cultural practices into participatory trials. The minimum tillage package could be an effective intervention for soil conservation due to the early-vegetative cover of the soil. Based on farmers' application of ash on Vertisols at Chefe Donsa, the incorporation of 50 kg ha−1 of potassium sulphate (K2SO4) in the on-farm trial significantly increased grain and straw yields of wheat. The nitrogen levels in the grain and straw of wheat on plots given K2SO4 were higher than those without. The nitrogen level for both wheat grain and straw was even higher when grown on plots previously growing legumes that received K2SO4. This showed that the availability of extra potassium in these soils improved the extraction of nitrogen by the wheat crop, thus improving the grain yield. The findings indicate the need to reassess the traditionally-practised system of not applying potassium fertilizer to Ethiopian soils.

The aim of this work was to determine the importance of the genotype-by-environment interaction in true potato seed breeding. In order to establish the importance of this type of interaction, experiments were sited across three Peruvian locations, San Ramon (warm mid-altitude slopes), Huancayo (cool Andean highlands), and La Molina (coastal desert). The genotype by environment interaction significantly affected tuber yield in all breeding materials (4x-4x from random or selected parents, and 4x-2x crosses). For example, the 10 most outstanding 4x-2x crosses for tuber yield were different when tested in warm and cool locations. Similarly, two clones derived from 4x-4x crosses were among the best 15 hybrids assessed in the two lower altitude locations. These two offspring provide examples of crossover genotype-by-environment interaction for tuber set, non-cross order genotype-by-environment interaction for tuber yield and lack of genotype-by-environment interaction for days to flowering. Because top yielding true potato seed offspring for each location were locally adapted, cultivars or advanced selections from the target area should be the parental sources of true potato seed offspring.

The legume Arachis pintoi has a number of characteristics which enable it to make a valuable contribution to the development of sustainable and productive pastures in the tropics. It was introduced to Costa Rica for this reason, in 1987. The objective of this study was to analyse the adoption of A. pintoi as a forage legume in Huetar Norte, a region in the north of Costa Rica. The adoption process was analysed to identify the contributory factors and to make recommendations for measures which could be taken to promote the process. To collect the data, 115 randomly selected livestock holders and an additional 34 farmers known to have planted A. pintoi were interviewed. Farmers see improved pastures to be the most important technology to enhance forage and cattle production. It was confirmed that A. pintoi is a potential improved pasture alternative. Although A. pintoi was well known., the adoption rate was low. Lack of availability of seed, technical assistance and information about the use and management of A. pintoi hinder adoption. Difficulties in establishment and maintenance were also recorded.

The influence of a growth regulator, chlorocholine chloride (commercial name Cycocel 75) on plant growth, (yield) and quality of late-seeded (mid-December) cotton (Gossypium hirsutum) was studied in the Río Dulce Irrigation Area, northwest Argentina, during three growth cycles (1998–2001). Cycocel 75 reduced plant height and node number as well as the total production of aerial biomass, thus increasing the harvest index. Due to an increase in the boll weight and boll number per plant, the yield of treated plots increased by an average of 35% in comparison with the control. Cycocel 75 improved fibre strength significantly, although other parameters of fibre quality, such as length, uniformity, elongation, and micronaire index were not affected. This study indicated that late-planted cotton responds favourably to the application of Cycocel 75, especially when its development cycle is extended due to low air temperatures during the latter part of the growing season.

The changes taking place in the mixed farming systems of northwest Syria were examined by re-visiting, in 1996 and 2000, five villages along a rainfall gradient. The villages had been surveyed first in 1977–79. In those villages with moderate rainfall, intensification of crop production, namely a trend towards cereal monoculture and the planting of tree crops, did not lead to specialization in cropping at the expense of sheep ownership. In contrast, households in the areas too dry for most rainfed crops except barley (Hordeum vulgare) were more likely to sell their sheep because they depended heavily on off-farm income. Increases in crop yields were found but these only benefited the families in villages in the higher rainfall zones. Conversely, with the exception of ewe fertility, there was little evidence of improvements in sheep productivity. The mixed farming systems in the five villages sampled are still passing through a period of transition, and the cropping component will undoubtedly continue to change. This is less likely to happen to the small ruminant component in the near future unless the sector is given higher priority in national policy. As a strategy to increase feed production and balance the crop rotations, the prospects for closer crop/livestock integration at the farm level are limited by the many difficulties associated with the introduction of leguminous pasture and forage crops.

There are currently concerns within some sugar industries that long-term monoculture has led to soil degradation and consequent yield decline. An investigation was conducted in Swaziland to assess the effects of fallowing and green manuring practices, over a seven-month period, on sugarcane yields and the physical properties of a poorly draining clay soil. In the subsequent first sugarcane crop after planting, yields were improved from 129 t ha−1 under continuous sugarcane to 141–144 t ha−1 after fallowing and green manuring, but there were no significant responses in the first and second ratoon crops. Also, in the first crop after planting, root length index increased from 3.5 km m−2 under continuous sugarcane to 5.2–6.8 km m−2 after fallowing, and improved rooting was still evident in the first ratoon crop where there had been soil drying during the fallow period. Soil bulk density, total porosity and water-holding capacity were not affected by the fallowing practices. However, air-filled porosity increased from 11 % under continuous sugarcane to 16% after fallowing, and steady state ponded infiltration rates were increased from 0.61 mm h−1 to 1.34 mm h−1, but these improvements were no longer evident after a year back under sugarcane. Levels of soil organic matter were reduced in all cases, probably as a result of the tillage operations involved. In the plant crop, root length was well correlated with air-filled porosity, indicating the importance of improving belowground air supply for crop production on poorly draining clay soils.