Summary
Nitrous oxide (N2O) is a potent, globally important, greenhouse gas, predominantly released from agricultural soils during nitrogen (N) cycling. Arbuscular mycorrhizal fungi (AMF) form a mutualistic symbiosis with two‐thirds of land plants, providing phosphorus and/or N in exchange for carbon. As AMF acquire N, it was hypothesized that AMF hyphae may reduce N2O production.
AMF hyphae were either allowed (AMF) or prevented (nonAMF) access to a compartment containing an organic matter and soil patch in two independent microcosm experiments. Compartment and patch N2O production was measured both before and after addition of ammonium and nitrate.In both experiments, N2O production decreased when AMF hyphae were present before inorganic N addition. In the presence of AMF hyphae, N2O production remained low following ammonium application, but increased in the nonAMF controls. By contrast, negligible N2O was produced following nitrate application to either AMF treatment.Thus, the main N2O source in this system appeared to be via nitrification, and the production of N2O was reduced in the presence of AMF hyphae. It is hypothesized that AMF hyphae may be outcompeting slow‐growing nitrifiers for ammonium. This has significant global implications for our understanding of soil N cycling pathways and N2O production.
Bait‐delivered pharmaceuticals, increasingly used to manage populations of wild boar (Sus scrofa) and feral pigs, may be ingested by nontarget species. Species‐specificity could be achieved through a delivery system. We designed the BOSTM (Boar‐Operated‐System) as a device to deliver baits to wild pigs. The BOSTM consists of a metal pole onto which a round perforated base is attached. A metal cone with a wide rim slides up and down the pole and fully encloses the base onto which the baits are placed. We conducted a pilot, captive trial and found that captive wild boar fed from the BOSTM either directly, by lifting the cone, or indirectly, by feeding once another animal had lifted the cone. Thus, we tested whether free‐living wild boar fed from the BOSTM and whether the BOSTM could prevent bait uptake by nontarget species. We observed that free‐living wild boar fed regularly from the BOSTM and that the device successfully prevented bait uptake by nontarget species. The BOSTM should be trialed more extensively to confirm its effectiveness and species‐specificity to distribute pharmaceuticals to wild suids. If successful, the BOSTM could be used to deliver vaccines in disease control programs as well as contraceptives to manage overabundant populations of wild suids.
Worldwide, wild boar (Sus scrofa) and feral pigs are involved in environmental damage and\ud
disease transmission. These impacts are often associated with relatively high local densities of pigs, so the\ud
monitoring of population trends is important. Dung counts can be used to estimate population trends, but\ud
knowledge of daily defecation rates (DDRs) is needed to estimate absolute numbers. To address this issue, we\ud
calculated the DDRs of 18 captive, adult wild boar in July 2005 and November 2007. The mean DDR was\ud
3.8–4.3 dung/boar/day, depending on the trial. We discuss the results by comparing the DDR of wild boar to\ud
that of other ungulates and omnivores, and we consider the implications of these results for estimating feral\ud
pig and wild boar density through dung counts
Wheat bulb fly, Delia coarctata, is an important pest of winter wheat in the UK, causing significant damage of up to 4 t/ha. Accepted population thresholds for D. coarctata are 250 eggs/m 2 for crops sown up to the end of October and 100 eggs/m 2 for crops sown from November. Fields with populations of D. coarctata that exceed the thresholds are at higher risk of experiencing economically damaging infestations. In the UK, recent withdrawal of insecticides means that only a seed treatment (Signal 300 ES) is available for chemical control of D. coarctata; however, this is only effective for late-sown crops and accurate estimations of annual population levels are required to ensure a seed treatment is applied if needed. As a result of the lack of postdrilling control strategies, the management of D. coarctata is becoming reliant on nonchemical methods of control.Control strategies that are effective in managing similar stem-boring pests of wheat include sowing earlier and using higher seed rates to produce crops with greater pest tolerance. In this study, we develop two predictive models that can be used for integrated D. coarctata management. The first is an updated pest level prediction model that predicts D. coarctata populations from meteorological parameters with a predictive accuracy of 70%, a significant improvement on previous prediction models. Our second model predicts the maximum number of shoots for a winter wheat crop that would be expected at the terminal spikelet development stage.This shoot number model uses information about the thermal time from plant emergence to terminal spikelet, leaf phyllochron length, plant population and sowing date to predict the degree of tolerance a crop will have against D. coarctata.The shoot number model was calibrated against data collected from five field experiments and tested against data from four experiments. Model testing demonstrated that the shoot number model has a predictive accuracy of 65.7%. The foundation for a future decision support system using these models for the sustainable management of D. coarcata risk is described. It should be noted that these models represent a stepping-stone towards a decision support system and that further model validation over a wider geographic range is required.Daniel J. Leybourne and Kate E. Storer contributed equally to this study.
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