In sub-Saharan Africa, the bollworm complex, including Helicoverpa armigera, Diparopsis watersi and Earias spp., threatens the continued success of cotton production. Pyrethroid resistance in H. armigera led to serious crop losses while endosulfan, a suitable alternative to pyrethroids, was banned for cotton pest management. Five candidates with no cross-resistance to pyrethroids were evaluated in both on-station and on-farm trials from 2002 to 2006. Two applications were made at the early peak of H. armigera infestation in September, the period when pyrethroid use should be restricted for resistance management purposes. Results showed that, as expected, bollworm infestation consistently peaked from mid-September to mid-October. Spinosad, thiodicarb and emamectin-benzoate were the most suitable alternatives to reduce damage, regardless of the cotton bollworm species. Indoxacarb and lufenuron were less effective in controlling D. watersi. On-farm experiments confirmed the suitability of spinosad for control of pyrethroid-resistant H. armigera, particularly on late sown fields. These new chemistries offer control of bollworms which justify their relevance for pyrethroid resistance management in Cameroon and sub-Saharan Africa.

On-farm participatory varietal selection (PVS) trials are often of two types: mother trials (with all of the entries) and baby trials (each having one, or very few of the entries from the mother trials). We conducted PVS trials on 17 wheat varieties in 12 villages of four districts of Bangladesh over three years but the data were highly unbalanced. Both quantitative and qualitative traits were measured in the on-farm trials. The factors in the trials were both fixed effects (varieties and districts) and random (years and farmers). We used the residual or restricted maximum likelihood (REML) analysis for the mixed model for quantitative traits. For qualitative data on farmers' perceptions, logistic regression procedures were used that are equally applicable to balanced and unbalanced data sets. The REML analysis provided adjusted mean values for quantitative traits for all the varieties, for the mother and baby trials separately, using the data from all years and all locations. It identified varieties BAW 1006 and BAW 1008 that yielded 19–30% more than the control Kanchan and also had a higher 1000-grain weight, were at least as early to flower and had a high overall ranking by farmers in the mother trials. The logistic regression analysis of perception data agreed with the results of the REML analysis as these varieties were most preferred by farmers for grain yield, earlier maturity and better chapatti making quality. The less labour-intensive method of recording qualitative perceptions can usefully replace actual yield measurements, particularly when validated by other participatory measures such as intended and actual adoption. In 2005, BAW 1006 was released as BARI Gom 23 or Bijoy and BAW 1008 as BARI Gom 24 or Prodip for the whole of Bangladesh. The validity of the results of the REML analysis was confirmed by the high early adoption trends of the identified varieties. Since REML is an effective analysis for unbalanced PVS trial data using a mixed model, its wider use by researchers would increase the value of the PVS process.

The arid zone of northwestern India is a unique adaptation zone for crop plants because of its pervasive severe moisture stress and high temperatures. Pearl millet (Pennisetum glaucum) is a major cereal in this zone as it represents approximately 25% of the total acreage of the crop in the country. Pearl millet hybrid cultivars, which have gained widespread acceptance from farmers elsewhere in the country, have not been adopted in the arid zone. Farmers continue to sow their traditional landraces because the yield advantage of current hybrids is not expressed in this zone, and the risk of failure in poor years with the hybrids is unacceptably high. The International Crops Research Institute for the Semi-Arid Tropics and the Indian Council of Agricultural Research have been collaborating to understand the unique nature of pearl millet in the arid zone since the late 1980s. This collaboration has produced a better understanding of how arid zone farmers manage their germplasm, of the unique features of this invaluable resource and of a range of ways of using this germplasm to produce well-adapted new varieties and hybrids that will meet the requirements of the farmers of the arid zone. It has been shown that new cultivars for the arid zone need to be based on parental materials, including traditional landraces that are specifically adapted to the arid zone. This paper summarizes the main lessons of nearly 20 years of this collaborative research.

Daily courses of leaf gas exchange and leaf water potential (Ψleaf) of green dwarf coconut palm (Cocos nucifera) were measured in irrigated plantations on the wet coastal plateau and in a dry semi-arid area of northeast Brazil. At both sites, significant correlations were obtained between stomatal conductance (gs) and vapour pressure deficit (VPDair), Ψleaf and VPDair, leaf transpiration (E) and gs, and E-Ψleaf. Despite these similar relationships between sites, stronger correlations involving gs-VPDair and E-Ψleaf were found at the semi-arid site, where whole-plant hydraulic conductance (gp) was correlated significantly with VPDair. In addition, at the semi-arid site, only, the net photosynthesis (PN) was not correlated with E and Ψleaf, and the intrinsic water use efficiency (WUEi) was disconnected from VPDair and Ψleaf. The different behaviour of leaf gas exchange and Ψleaf between sites was probably caused by low gs in response to high VPDair at the semi-arid site. Our results indicate potential for significant alterations in the pattern of leaf gas exchange during future climatic changes with increasing temperature and concomitant increases in VPDair. The atmospheric water stress will probably reinforce the strength of connection among water relation variables (E, Ψleaf, gs, gp, and VPDair), but it will disrupt the linear relationship between net CO2 assimilation and leaf water relations such as PN-E, PN-Ψleaf, WUEi-VPDair and WUEi-Ψleaf.

The present study evaluated the pest constraints of an innovative crop management system in Cameroon involving conservation tillage and direct seeding mulch-based strategies. We hypothesized that the presence of mulch (i) would support a higher density of phytophagous arthropods particularly millipedes as well as pathogenic fungi that cause severe damage to cotton seedlings and (ii) would reduce early aphid infestations. The impact of two cover-crop mulches Calopogonium mucunoides and Brachiaria ruziziensis on the vigour of seedling cotton stands and arthropod damage was assessed in two independent field experiments conducted in 2001 and 2002 respectively. In both experiments the presence of mulch negatively affected cotton seedling stand by 13–14% compared to non-mulched plots and the proportion of damaged seedlings was higher in mulched than in non-mulched plots supporting the hypothesis that mulch favoured soil pest damage. In both experiments insecticidal seed dressing increased the seedling stand and the number of dead millipedes collected and fungicide had little or no effect on seedling stand and vigour. It was however observed in 2002 that the fungicide seed dressing had a positive effect on seedling stand in non-mulched plots but not in mulched plots suggesting that fungi may have been naturally inhibited by B. ruziziensis mulch. The dynamics of aphid colonization was not influenced by the presence of mulch. In 2001 taller seedlings were found in mulched than non-mulched plots probably due to greater water and nutrient availability in C. mucunoides-mulched plots than in non-mulched plots.

This study investigated the feasibility of using sole organics or a combination of organics with inorganic fertilizer to improve maize production in on-station and on-farm experiments in central Kenya. In the on-station experiment, combined application of Calliandra calothyrsus, Leucaena trichandra and Tithonia diversifolia at 30 kg N ha−1 plus inorganic fertilizer (30 kg N ha−1) consistently gave significantly higher maize grain yields than the recommended rate of inorganic fertilizer (60 kg N ha−1). Sole application of calliandra, leucaena and tithonia also increased maize yields more than the recommended rate of inorganic fertilizer. In the on-farm experiment, calliandra, leucaena, tithonia and cattle manure either alone or combined with inorganic fertilizer increased maize yields with a similar magnitude to that of inorganic fertilizer. These organic resources could therefore be used to supplement inorganic fertilizer as a whole or in part. There was a yield gap between on-station and on-farm trials with on-station yields having, on average, 65% greater yields than the on-farm yields. There is therefore potential for increasing yields at the farm level by closing the yield gap.

This study investigated the effects of harvesting at different plant maturation stages on the yield and component compositions of aniseed. It was carried out on the Harran Plain (Sanliurfa, Turkey) in the 2002 and 2003 growing seasons. A randomized complete block design was used. The plants were harvested at 10 different growth stages and determinations were made of the yields of seed, the essential oil and its main component (E)-anethole, the weight of 1000 seeds, the number of umbels per plant, the number of seedless umbels per plant and number of seeds per umbel. Statistical analyses indicated that all properties studied were affected by the harvesting stage. The fourth harvesting stage gave the highest yields of seed, essential oil and (E)-anethole. The first and second harvesting stages provided the best quality of essential oils with a high (E)-anethole content.

Farmer participatory research (FPR) approaches are now considered mainstream and are especially applicable for developing appropriate technology options in complex, diverse and risk-prone regions, where local adaptations are crucial. Although the advantages of using farmer knowledge to guide scientific research are numerous and well documented, the challenges and potential pitfalls that befall biophysical researchers, in particular, when using FPR approaches have received much less attention, especially in sub-Saharan Africa. Our experiences show that in certain cases, the methods used to collect farmer knowledge are flawed, leading to inaccurate or incomplete information being gathered. This potentially leads to the development and promotion of unsustainable, unprofitable or socially unacceptable technologies. This paper uses a series of examples to illustrate that discrepancies between farmer and researcher observations may occur because (i) farmers and scientists may not have sufficient insight into the systems complexity, (ii) farmers and scientists use different reference frameworks, and (iii) methodological errors may lead to farmers intentionally or unintentionally providing false or ‘desired’ information to achieve (short-term) benefits. This paper concludes by providing guidelines to improve the integration of farmer and scientific knowledge in order to develop appropriate technology options that are both environmentally sound and adaptable to local conditions.