Despite previous research on mycorrhizal association with plants, the data on associations with coffee (Coffea species) are very sparse despite the great economic importance of this crop for many tropical developing countries. The present paper reviews the main aspects of the association between arbuscular mycorrhizal fungi (AMF) and coffee plants. This review includes topics on mycorrhizal effects on coffee nutritional status, pathogen–AMF interactions and responses to several environmental stresses. It also summarizes findings about the natural occurrence of AMF in different soils in which coffee is cultivated, some ecological aspects of this specific association and outlines trends for future investigations, which must elucidate the real benefits of mycorrhizae to coffee plants.

Regardless of the irrigation system deployed, rice production requires a variety of farm energy inputs. The present study estimated and compared greenhouse gas (GHG) emissions from rice farming practices, resulting from various farm inputs and irrigation systems in Pakistan, the Philippines, China, Indonesia, Myanmar, Nepal, Australia and the USA. Results indicate that, on aggregate, emissions related to farm machinery, fuels, agrochemicals and animal labour accounted for 0·018, 0·307, 0·666 and 0·008, respectively. Emissions from tubewell irrigation systems were the highest, followed by canal and rainfed irrigation systems. Average emissions from all selected countries with tubewell irrigation systems were 1·64 times greater than canal irrigation systems and 2·64 times greater than rainfed irrigation systems. When considering GHG emission efficiencies (emissions/kg of rice yield), developing countries were found to be less efficient than developed countries in both canal and tubewell irrigation systems. The relationship between GHG emissions and rice yield was statistically significant (P<0·01), with results indicating that a yield increase of 100 kg would increase GHG emissions by 16·51 kg CO2e (kg carbon dioxide equivalent).

Winter waterlogging is expected to become an increasingly serious problem due to climate change. It is therefore important to find whether differences in tolerance to waterlogging exist between wheat cultivars grown in the UK. Screening experiments were conducted outdoors and in a glasshouse to investigate the yield response to waterlogging and waterlogging tolerance at the seedling stage. The experiments suggested that differences in tolerance existed between cultivars, in the form of digression of some cultivars from their expected yield in the outdoor experiment and a significant interaction between cultivar and waterlogging for shoot and root dry weight in the seedling experiment. Cultivars that appeared to differ in their responses to waterlogging were further tested in a field experiment over two seasons and in a second glasshouse seedling experiment. However, there was no significant relationship between measurements taken at the seedling stage and grain yield at maturity; also the field experiment did not provide compelling evidence of differences in tolerance. Cultivars with the largest yield suffered the largest decrease due to waterlogging, and the yield of the cultivar with the lowest yield potential was unaffected. All cultivars showed considerable ability to compensate for winter waterlogging damage by vigorous spring growth. All cultivars produced nodal roots in response to waterlogging, and these displayed evidence of aerenchyma tissue by penetrating below the water level, but no cultivar was any better in this respect than any other. The results of these experiments suggest that screening for waterlogging tolerance at the seedling stage is not representative of final yield. It is suggested that the lack of diversity for tolerance is a result of the inbred nature of UK wheat cultivars and that the overall good level of tolerance and ability to compensate has been selected for, either inadvertently, or as a result of selecting the best cultivars in UK conditions, where tolerance to waterlogging is a part of the general winter hardiness required.

Wheat (Triticum aestivum L.) variety mixtures represent a relatively unexplored avenue for maintaining and stabilizing yield for both organic and conventional producers. The present study examined the responses of three Canadian western red spring wheat varieties in sole crop and in variety mixtures to varying levels of simulated and natural competition, as well as environmental stress at one conventionally and two organically managed locations in central Alberta, Canada, between 2003 and 2005. Three modern hard red spring wheat varieties (Superb, semi-dwarf; AC Intrepid, early maturing and 5600HR, tall), along with 13 two- and three-way variety mixtures, were planted under two levels of simulated weed (Brassica juncea L.) competition at each of the eight location-years. The B. juncea weed competition treatment decreased yields at all locations. Overall yield was lowest at the certified organic farm and highest under conventional management. Sole-crop semi-dwarf Superb and all three Superb–Intrepid mixture entries consistently yielded among the highest, regardless of management system, testing location or competition treatment. The 1:1 and 1:2 Superb–Intrepid mixture entries were the most stable of all entries tested. Early season vigour was strongly associated with yield, with the strongest correlation occurring under low-moisture, low-nutrient, high-competition conditions at the certified organic farm. Spring wheat variety mixtures may provide greater stability with little or no reduction in yield, while providing greater competitive ability.

A potassium fertilizer field trial of rain-fed cotton crop was carried out on ferrasols at two sites in Benin. The measurements focused on leaf formation patterns and their ability to convert intercepted photosynthetically active radiation (PAR) into biomass. The results highlighted the role of K in plant architecture and leaf area development. On K deficient plots, the reduction in leaf area was mostly the result of a decreased number of leaves and, to a lesser extent, leaves of a smaller individual size. During vegetative growth, leaf senescence did not differ between treatments. Biomass partitioning to different plant compartments was found to be affected by potassium deficiency, in favour of leaves. No significant effect of K treatment was observed on the conversion of intercepted radiation into biomass.

Parameterization in crop simulation modelling is a general procedure to calibrate a crop model to explore the best fit for a certain regional environment of interest. The parameters of radiation use efficiency (RUE) and light interception coefficient (k) of cotton (Gossypium hirsutum) for different cultivars were estimated under various irrigation conditions in South Texas in 2006 and 2007. A calibration procedure was then performed for determination of RUE using the environmental policy impact calculator (EPIC) crop model (Williams et al.1984). This was carried out using data sets obtained separately from the data for parameter estimation. The estimates of k and RUE were 0·63 and 2·5 g/MJ, respectively, which were determined based on the field experiment and variation of simulated lint yield. When the parameters were used with EPIC to simulate the variability in lint yields, a correlation coefficient of 0·86 and root mean square error (RMSE) of 0·22 t/ha were obtained, presenting no significant differences (paired t-test: P=0·282) between simulation and measurement. The results demonstrate that an appropriate estimate of the model parameters including RUE is essential in order to make crop models reproduce field conditions properly in simulating crop growth, yield and other variables.

Groundnut or peanut (Arachis hypogaea L.) is a valuable food and forage crop in West Africa. It is important to determine yield-limiting factors and to develop suitable management practices to improve groundnut productivity. The objective of the present research was to determine the influence of fungicide application at different sowing densities on growth, biomass and yield of early and late maturing groundnut under rainfed conditions. Two groundnut cultivars (Chinese, 90 days duration and Manipinter, 120 days duration) were grown at low (8 plants/m2), medium (12 plants/m2) and high density (20 plants/m2), with and without fungicide application, for two growing seasons (2004 and 2005). Data on leaf area index (LAI), light interception (LI) and total biomass were measured at different stages of crop development. Haulm (stem and leaf), pod and seed yields were measured at maturity. Fungicide application increased LAI, LI and total biomass of both cultivars from 65 days after sowing (DAS) until maturity. Fungicide application significantly increased pod and seed yields by 95 and 103%, respectively, on average. In both years, the long duration cultivar Manipinter had significantly greater LAI, LI and total biomass at later stages of crop development when compared with the short-duration cultivar Chinese. The growth and yield of both cultivars were significantly less at the lowest population density when compared with medium or high population densities. There was no significant difference between medium and high population densities in haulm, pod and seed yield at maturity. It is concluded that sowing a long-duration cultivar at a density of 12 plants/m2 with fungicide application significantly improved groundnut yields under rainfed conditions in Ghana.

The export of Ataulfo mangoes to the US market involves a mandatory hot water treatment and further handling at 13°C for 4 days. These treatments have proven to adversely affect fruit ripening, mainly in colour and flavour development, and their nutritional quality. The application of exogenous ethylene (100 μl/l of air for 12 h at 25°C) to Ataulfo mangoes that were treated with hot water after storage for 4 days at 13°C, and then transferred to 25°C for ripening, was evaluated. Sugar content, colour development and textural firmness were monitored. Control fruit were held at 25°C with no previous refrigeration or ethylene exposure; another batch was kept refrigerated for 4 days at 13°C, not treated with ethylene and ripened at 25°C. Synthesis of fructose (30 g/kg fresh weight (FW)), glucose (38 g/kg FW), sucrose (120 g/kg FW) and β-carotene (0·026 g/kg FW) in the last day of storage was greater in fruits treated with ethylene than on refrigerated mangoes (RM). Loss of firmness (9·3 Newtons) coincided with the highest pectinmethylesterase and polygalacturonase activities, 53·24 and 37·92 U/mg protein, respectively, and eventually led to collapse of cell structure. Results suggest that sugars and carotenoid content can be increased, along with an accelerated ripening by application of exogenous ethylene on mangoes that were refrigerated for 4 days.

The objective of the current study was to evaluate the effects of calcium propionate supplementation on rumen fermentation, urinary excretion of purine derivatives (PD) and feed digestibility in the total gastrointestinal tract of steers. Eight ruminally cannulated Simmental steers (462±14 kg) were used in a replicated 4×4 Latin square arrangement of treatments with experimental periods of 21 days. The treatments were: control (without calcium propionate), LCaP (calcium propionate – low), MCaP (calcium propionate – medium) and HCaP (calcium propionate – high) with 100, 200 and 300 g calcium propionate per steer per day. Diet consisted of 0·60 maize stover and 0·40 concentrate (dry matter (DM) basis). DM intake (average 9 kg/day) was restricted to a maximum of 0·90 of ad libitum intake. Ruminal pH (range of 6·7–6·5) linearly (P<0·003) and quadratically (P<0·005) decreased, and total volatile fatty acid (VFA) concentration (range of 64·4–67·1 mm) tended (P<0·087) to increase linearly with rising calcium propionate supplementation. Ratio of acetate to propionate fell linearly (P<0·006) and quadratically (P<0·008) from 3·5 to 2·6 as calcium propionate supplementation increased due to the additional propionate supplementation. In situ ruminal neutral detergent fibre (NDF) degradation of maize stover and crude protein (CP) degradability of concentrate mix were improved with increasing concentration of calcium propionate. Urinary excretion of PD was linearly (P<0·032) and quadratically (P<0·048) increased with greater calcium propionate supplementation (72, 74, 77 and 76 mmol/day for control, LCaP, MCaP and HCaP, respectively). Similarly, digestibilities of organic matter (OM), NDF and CP in the total tract were also linearly and quadratically improved with increasing calcium propionate. The results indicate that the calcium propionate supplementation potentially improves rumen fermentation and feed digestion in beef cattle. It is speculated that calcium propionate stimulates the digestive microorganisms or enzymes in a dose-dependent manner. In the experimental conditions of the current trial, the optimum calcium propionate dose was about 200 g calcium propionate per steer per day.

In previous work, administration of a commercial tannin preparation, quebracho, as oral drench was shown to reduce significantly faecal egg counts (FEC) and worm burdens of temperate sheep with experimental Haemonchus contortus infection. In the current work carried out in Morogoro, Tanzania, three separate animal trials were carried out to investigate the effect of drenches of wattle tannin (WT), a similar tannin preparation that is readily available in the tropics, on nematodes of tropical goats and sheep. In the first trial, 36 young Small East African (SEA) goats were experimentally infected with a single dose of mixed nematode larvae and FEC were monitored regularly. On day 30 post-infection (p.i.), the animals were blocked on the basis of their FEC and randomly assigned into three equal groups (n=12). For 3 consecutive days, two groups received low and high doses of drench at a rate of 1·2 and 2·4 g WT/kg bodyweight, respectively, whereas the third group received a placebo drench (i.e. water). All goats were humanely slaughtered on day 42 p.i. and their worm burdens were assessed. Neither FEC nor worm burdens were significantly reduced by the administration of the low or high dose of WT. The second trial had an identical design but two groups (n=14) of growing Black Head Persian (BHP) sheep were used instead. One group received the drench at 1·5 g WT/kg body wt for 3 consecutive days, whereas the other group received a placebo. Unlike in goats, worm burdens and FEC were significantly reduced (P<0·001) by the drench administration. In the third trial, the effect of WT drench against a naturally acquired nematode infestation in a flock of 34 BHP sheep was determined. FEC were examined three times in a 2-week period and the egg counts were used to block the sheep before being randomly assigned into two groups (n=17). The treated group received the drench at 1·0 g WT/kg bodyweight for 3 consecutive days, while the remaining half was given a placebo. The two groups continued to graze together as FEC were being monitored. Results indicated a significant (P<0·001) reduction in egg counts, which remained low for at least 3 weeks after the drench. The current study demonstrated that the WT drench had significant anthelmintic activity against important nematodes in sheep but not in goats, suggesting an existence of species differences between the two hosts. It was concluded that WT drenches could be used in combination with other worm control strategies to reduce or control nematode infections, at least in sheep.