Institutional changes in Benin have brought to light farmers' demand for varieties better suited to local growing conditions than existing ones. In response, we initiated a participatory cotton breeding experiment in 1996 to evaluate the relevance of such a methodology for the improvement of a commercial crop grown under rain-fed, semi-intensive cropping systems. This paper compares the performance of the first four mass-selection cycles, implemented by three farmer-breeders (F-B) and one formal breeder, with the original population and two commercial controls over three sites and two years. First results show that genetic changes occurred in all the F-B populations. The highest yielding F-B population (Savalou) was also more exuberant and later maturing than the others. Within the relatively narrow range of environments considered in the trial, there is no evidence that decentralized breeding results in better local adaptation. In Benin, participatory cotton breeding may be considered as complementary to formal on-station breeding and useful for enlarging the genetic variability offered to the farmers. Although the farmers want the approach to be scaled-up, its sustainability relies on a formal partnership between research and farmers institutions.

A method of estimating crop production potential was devised and tested in a number of contrasting solar radiation climates. With increasing levels of solar radiation, total dry matter yields of kale, maize and sugar beet increased, whilst energy conversion efficiency declined in kale and sugar beet but increased in maize. Maximum potential crop yields in almost all environments were achieved with a conversion efficiency of approximately 2 per cent of total radiant energy.

The discrepancy between farmers' performances and research-based recommendations in the control of cotton pests in Southern Malawi is discussed. Analysis of the former in two seasons revealed that the farmers' low levels of insecticide application approached the economic optimum, whereas several factors of economic importance were omitted from the research-based justification of high spraying levels. Recommendations for improving the applicability of research recommendations to smallholder farming are made, with particular reference to the farming risks that arise from uncertain rainfall, the wide range of farming ability encountered in practice, and the dangers of atypically high levels of management in research experiments.

Gene flow from herbicide-resistant rice (Oryza sativa L.) cultivars can affect the biodiversity of Oryza spp. and can result in the lack of opportunity to control weedy rice through selective herbicides. The aim of the present study was to quantify the outcrossing rate from the herbicide-resistant red rice and rice cultivars carrying three different ALS (acetolactate synthase) alleles using a single plant pollen donor approach. A field experiment was performed using the encircle population combination technique. The main plots comprised the pollen-receptor IRGA 417 cultivar or a susceptible biotype of weedy rice, and the subplots comprised the pollen-donor inbred cultivars IRGA 422 CL and PUITÁ INTA CL, the hybrid SATOR CL or a resistant biotype of weedy rice. Among the pollen-donors, the outcrossing rate for pollen receptor susceptible weedy rice and the IRGA 417 cultivar was 0.0344% and 0.0142%, respectively. Rice cultivars carrying the ALS gene mutations Ala122Thr, Ser653Asn and Gly654Asn showed a similar outcrossing rate of 0.0243%. The outcrossing rate decreased over a distance of up to 3.5 m from the pollen-donor and was not affected by the wind cardinal direction. The risk of gene flow of herbicide resistance from rice to weedy rice should be reduced through the development of new strategies to contain and mitigate gene flow and of the elimination of weedy rice escapees.

Farming Systems Adaptive Research (FSAR) has contributed much to the understanding of maize production constraints on smallholder farms in southern Africa in the last six to eight years. But its production impact has been constrained by the often inappropriate technology available to FSAR from component research and the ineffective use of its results by extension staff. However, FSAR has demonstrated the utility of a problem (client) orientated approach to technology development, which is now being taken up by some maize commodity research and extension programmes, though effective linkages have not usually been developed. Nevertheless, experience in southern Africa suggests that the FSAR approach can provide a framework for developing more effective integration between key groups involved in technology generation, dissemination and support.

Eighteen arabica coffee introductions from the USDA germplasm collection were planted at 23° S latitude in Brazil from 1977 to 1982 to assess their yield potential and frost hardiness, compared with the cultivar Catuai Amarelo which is extensively planted in Brazil. Nine of the introductions had similar yields to Catuai Amarelo. Erecta T966 and Harrar yielded as well as Catuai Amarelo and were also more frost hardy. Tall, early maturing coffee varieties showed the least frost injury.

Determination of canopy resistance (rc) is necessary for accurate estimating hourly latent heat flux (LET), using the Penman–Monteith (PM) model for tea crop. In this study, a non-linear relationship between rc and climatic resistance (r*) was obtained for tea plants based on micro-meteorological data and LET from the end of 2014 to the beginning of 2016 in southern China. The proposed rc model was integrated to the PM method and compared with measured LET using a Bowen ratio energy balance method. The root mean square error (RMSE) and the index of agreement (d) were calculated for assessing the accuracy of the proposed rc model. RMSE and d values for rc and LET were 167.4 s m−1 and 29.7 W m−2 and 0.93 and 0.99, respectively. As compared to data from a single season, the rc sub-model based on data from different seasons was more reliable for estimating LET of tea field when integrated to the PM model.

The duration of the residual effect of sesbania (Sesbania sesban) fallow on subsequent crops will determine the interval at which sesbania must be grown to replenish N in a planted fallow–crop rotation cycle. An experiment was conducted from 1995 to 1998 (seven cropping seasons) on two farms in western Kenya, an area subject to a bimodal annual rainfall pattern. The aim was to compare the effect of a single-season sesbania fallow with continuous annual cropping with and without phosphorus fertilizer, on a P-deficient soil. Phosphorus was applied at a rate of 500 kg ha−1 in a single application to meet the phosphorus needs of subsequent crops for the next five to ten years. Sesbania was established simultaneously with maize by direct seeding in the first rainy season of 1995 and allowed to grow as a pure fallow through the second rainy season. Following the harvest of this fallow crop, sole maize in the first post-fallow season and maize-bean intercrops in the subsequent four seasons were grown with and without nitrogen at a rate of 100 kg ha−1. Added phosphorus on average increased maize yields by 3.7 times over the control, indicating that phosphorus fertilizer is essential for good yields. The amount of phosphorus recycled by sesbania fallow was inadequate to meet the crop needs in P-deficient soils. While continuously cropped maize in the presence of phosphorus responded to nitrogen in all seasons, the crop following sesbania responded only from the third season. In the first post-fallow season, sesbania increased maize grain yields over continuous maize by 1.4 t ha−1 with phosphorus fertilizer and by 1.3 t ha−1 without phosphorus fertilizer. The residual effect of sesbania with phosphorus fertilizer lasted for two seasons, while without phosphorus it lasted for only one. In these Kenyan highlands, farmers who can afford fertilizer should buy phosphorus fertilizer and rely for nitrogen on planted fallow with species such as sesbania grown for one season every two years. For farmers who cannot afford fertilizer, one-season fallow every year may be more attractive because of labour savings and the firewood produced by sesbania.

Resilient cropping systems are required to achieve food security in the presence of climate change, and so several long-term conservation agriculture (CA) trials have been established in southern Africa – one of them at the Chitedze Agriculture Research Station in Malawi in 2007. The present study focused on a longitudinal analysis of 10 years of data from the trial to better understand the joint effects of variations between the seasons and particular contrasts among treatments on yield of maize. Of further interest was the variability of treatment responses in time and space and the implications for design of future trials with adequate statistical power. The analysis shows treatment differences of the mean effect which vary according to cropping season. There was a strong treatment effect between rotational treatments and other treatments and a weak effect between intercropping and monocropping. There was no evidence for an overall advantage of systems where residues are retained (in combination with direct seeding or planting basins) over conventional management with respect to maize yield. A season effect was evident although the strong benefit of rotation in El Niño season was also reduced, highlighting the strong interaction between treatment and climatic conditions. The power analysis shows that treatment effects of practically significant magnitude may be unlikely to be detected with just four replicates, as at Chitedze, under either a simple randomised control trial or a factorial experiment. Given logistical and financial constraints, it is important to design trials with fewer treatments but more replicates to gain enough statistical power and to pay attention to the selection of treatments to given an informative outcome.

Leaves of Coffea arabica L. were sampled from an artificial shade trial to examine the effects of two levels of shade, compared with full exposure, on size, structure and chlorophyll content. A grid was designed for the rapid measurement of leaf areas in the field, and individual leaf areas were found to increase progressively with shading. Since dry weight per leaf was not affected, an increase in specific leaf area was entailed. Leaf size varied greatly with season of formation, a wider range occurring in selection N39 than KP162, but the reasons for the variation were not clear. Neither lamina thickness nor proportion of palisade tissue varied with shade treatment. Chlorophyll per unit weight increased with shade in KP162 but with N39 was only greater under dense shade. Chlorophyll per unit area did not alter with shade, but N39 had significantly more chlorophyll than KP162 on both a weight and an area basis.

Studies on the effect of nanofertilizers (NF) in physiological performance of plants is scarce, especially that related to substances encapsulated into silicon dioxide (SiO2) nanoparticles in cocoa plants. The effect of foliar application of SiO2-NF on nutrient contents, gas exchange, photochemical activity, photosynthetic pigments, total soluble protein (TSP), photosynthetic nitrogen use efficiency (PNUE), and growth in seedlings of two cocoa clones (OC-61 and BR-05) in a greenhouse was assessed. Spraying with SiO2-NF increased net photosynthetic rate (A) by 16 and 60% and electron transport rate (J) by 52 and 162% in clones OC-61 and BR-05, respectively, without changes in photosynthetic pigment concentration in either clone. The SiO2-NF caused a decrease of 37 and 22% in stomatal conductance in OC-61 and BR-05, respectively; a similar trend was observed in transpiration rate, causing an increase of 42 and 100% in water use efficiency in OC-61 and BR-05, respectively. In both clones, diameter of graft increased on average 28% with SiO2-NF. Higher photosynthetic capacity was related to an increase in leaf N, P, and TSP. A significant reduction in PNUE (A/N ratio) was found in OC-61, whereas in BR-05 PNUE increased after spraying with SiO2-NF. Overall, spraying with SiO2-NF had a positive effect on photosynthetic processes in both cocoa clones, associated with an increase in nutrients content, which translated into improved growth. A differential physiological response to spraying with SiO2-NF between clones was also found, with BR-05 being the clone with a better physiological response during the establishment and development stages.

Tubers of Dioscorea alata L. cv White Lisbon, affected by Internal Brown Spot (IBS) disease, and stored under ambient conditions on wooden or wire racks, did not show significant increases in IBS incidence and mean lesions over storage periods of up to 18 weeks. Storage under different conditions of temperature (13, 20 and 28 ± 3°C) did not have any significant effect on IBS incidence; but tubers stored under conditions of high relative humidity (95 ± 2%) showed less IBS and greater mean lesion diameters. Although a significant reduction in disease incidence occurred during storage under the latter conditions, the effects of increased lesion size resulted in some deterioration of tuber quality.

Cotton–wheat (CW) is an important cropping system in South Asia. Wheat yields under a conventional CW system are generally lower compared to a rice–wheat system due to delayed seeding. Relay seeding of wheat can help timely sowing, capturing residual soil moisture of last irrigation to cotton, and increase the productivity and profitability of CW system. The field experiment included two Bt-cotton genotypes having different canopy cover (RCH 776 and MRC 7017), two types of relay seeders (RSs) for cotton planted at 67.5-cm and 101-cm row spacing and four types of relay seeding methods (manual broadcast, strip rotor (SR) and zero-till double disc and conventional till). Relay planting of wheat allowed one additional boll picking, which increased seed cotton yield by 12% compared with conventional tillage wheat. Cotton genotypes and RSs had no effect on emergence and yield of wheat. The RSs with SR and zero till double disc furrow openers performed better in terms of wheat emergence and grain yield compared to zero-till tine openers. Under relay seeding, wheat sowing was advanced by 31 days, which increased grain yield by 18.8% compared with conventional tillage practice. Net returns from the CW system with relay seeding of wheat were higher by US$ 311 to 425 ha−1 compared with the conventional CW system.

The presence of free water on both surfaces of the leaves of shaded and unshaded coffee trees was evaluated at Cenicafé, Colombia. Rainfall was the main source of humidity and dew was not registered during the experiment. Five mm of rain caused canopy saturation and water began to reach the underside of the leaves. The period of wetness lasted 9.7 hours on average and no significant moisture differences were found between leaves on east or west facing branches, at different levels within the tree, or externally or internally positioned on the branches, either for exposed or shaded trees. Between 1700 and 0500 h (local time), a close relation was found between the time of rain initiation and the duration of the period of wetness. Leaves dried out at approximately 1000 h.

Instruments and techniques are reviewed for measuring the content and potential of water in the soil, the water potential and solute potential of plant tissue, and the diffusive resistance of leaves. Emphasis is placed on difficulties encountered in the field and in the interpretation of measurements. References are given to recent technical papers and reviews dealing with the principles and construction of individual instruments.

Sorghum landraces from contrasting districts of northern Nigeria were grown during the 1990 rainy season to describe their physiological and morphological features. Changes in their dry matter production and yield could be predicted from thermal time to flowering (based on response to a fixed daylength) and partitioning indices. Many other morphological and physiological features, such as light-extinction coefficient, light-use efficiency, plant height, leaf area and leaf number, were either stable or varied systematically with time to flowering. Grain yields of early maturing lines were limited by low light interception from flowering to physiological maturity and those of later maturing lines by highly site-specific drought stress.

Following a survey of fertilizer use on farmers' barley fields in northern Syria and very positive results from barley fertilizer trials on ICARDA research stations, a programme of researcher managed trials on farmers' fields indicated considerable potential for yield increase from the use of nitrogen and phosphorus fertilizers across a range of environments. It was then necessary to test and demonstrate the effectiveness of fertilizers in farmers' hands. A researcher managed trial (RMT) and a farmer managed trial (FMT), with similar fertilizer treatments, were compared over the winter cropping season on each of 10 on-farm sites in 1987/88 and 20 sites in 1988/1989. Despite large differences in rainfall between the two seasons (means across sites, 422 mm in 1987/88 and 174 mm in 1988/89), yield responses to fertilizer were similar in both seasons, with only marginal yield differences between researcher and farmer managed trials. Crop sequence had no effect on the pattern of fertilizer response in either type of trial. Once the effectiveness of fertilizers had been tested in farmers' hands, demonstration trials were conducted in the following two years to transfer the technology to farmers in the barley growing areas of northern Syria.

Ensayos conducidos por agricultores e investigadores en Siria