Water requirement of Aloe vera in a dry caribbean climate     

Willem B. M. Genet  Cok A. M. van Schooten 《Irrigation Science》1992,13(2):81-85

Summary As hardly any data can be found on the water requirement and yield response to water of Aloe vera, an irrigation experiment on transplanted aloe poles was conducted on the Caribbean island of Aruba. Compared to non-irrigated treatments irrigation shows a positive influence on growth, number of developed leaves, raw gel figure and gel production per plant. The amount of irrigation water to apply can be best calculated based on crop coefficients (K_c) between 0.20 and 0.30. Treatment based on a K_c value higher than 0.30 did not further increase production. A lysimeter study conducted over a relatively short period revealed that the crop coefficient for Aloe vera varied between 0.25 and 0.40 which is characteristic of the so-called agave/pineapple group.  相似文献   

Analysis of the uncertainty associated with the estimation of nitrogen losses from farming systems     

Sylvain Payraudeau  Hayo M.G. van der Werf  Françoise Vertès 《Agricultural Systems》2007

This work describes the analysis of the uncertainty linked to the annual direct and indirect losses of different nitrogenous compounds at the scale of a group of farms. The nitrogen (N) forms taken into account are: ammonia (NH₃), nitric oxide (NO), nitrous oxide (N₂O), dinitrogen (N₂) and nitrate (NO₃). The gaseous N emissions for the different components of the farms are estimated with a selection of adapted emission factors. The NO₃ losses at the farm scale are calculated as the difference between the surplus of the farm-gate N balance and the gaseous N emissions.  相似文献   

Finding niches for whole-farm design models – contradictio in terminis?     

B. Sterk  M.K. van Ittersum  C. Leeuwis  W.A.H. Rossing  H. van Keulen  G.W.J. van de Ven 《Agricultural Systems》2006

Whole-farm design models quantitatively analyze the effects of a variety of potential changes at the farm system level. Science-driven technical information is confronted with value-driven objectives of farmers or other social groupings under explicit assumptions with respect to exogenous variables that are important drivers of agricultural systems (e.g., market conditions). Hence, farm design is an outcome of objective specification and the potential of a system. In recent publications, whole-farm design modelling has been proposed to enhance (farm) innovation processes. A number of operational modelling tools now offers the opportunity to assess the true potential of whole-farm design modelling to enhance innovation. In this paper, we demonstrate that it is not trivial to find niches for the application of goal-based farm models. Model outcomes appeared not to match questions of farm managers monitoring and learning from their own and other farmers’ practices. However, our research indicates that whole-farm design modelling possesses the capabilities to make a valuable contribution to reframing. Reframing is the phenomenon that people feel an urge to discuss and reconsider current objectives and perspectives on a problem. Reframing might take place in a situation (i) of mutually felt dependency between stakeholders, (ii) in which there is sufficient pressure and urgency for stakeholders to explore new problem definitions and make progress. Furthermore, our research suggests that the way the researcher enters a likely niche to introduce a model and/or his or her position in this niche may have significant implications for the potential of models to enhance an innovation process. Therefore, we hypothesize that the chances of capitalizing on modelling expertise are likely to be higher when researchers with such expertise are a logical and more or less permanent component of ongoing trajectories than when these researchers come from outside to purposefully search for a niche.  相似文献   

Mitigating nitrous oxide emissions from agricultural soils by precision management     

Robert M. REES  Juliette MAIRE  Anna FLORENCE  Nicholas COWAN  Ute SKIBA  Tony van der WEERDEN  Xiaotang JU 《农业科学与工程前沿(英文版)》2020,7(1):75-80

Nitrous oxide (N₂O) emissions make up a significant part of agricultural greenhouse gas emissions. There is an urgent need to identify new approaches to the mitigation of these emissions with emerging technology. In this short review four approaches to precision managements of agricultural systems are described based on examples of work being undertaken in the UK and New Zealand. They offer the opportunity for N₂O mitigation without any reduction in productivity. These approaches depend upon new sensor technology, modeling and spatial information with which to make management decisions and interventions that can both improve agricultural productivity and environmental protection.  相似文献   

Hypovirulent effect of the Cryphonectria hypovirus 1 in British isolates of Cryphonectria parasitica     

Pedro Romon‐Ochoa  Caroline Gorton  Alex Lewis  Sietse van der Linde  Joan Webber  Ana Prez‐Sierra 《Pest management science》2020,76(4):1333-1343

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Mosquito repellent thermal stability,permeability and air volatility     

Antnio B Mapossa  Alcides Sitoe  Walter W Focke  Homa Izadi  Elizabeth L du Toit  Ren Androsch  Chanita Sungkapreecha  Elizabet M van der Merwe 《Pest management science》2020,76(3):1112-1120

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Variation in parasitoid attraction to herbivore-infested plants and alternative host plant cover mediate tritrophic interactions at the landscape scale     

Aartsma  Yavanna  Hao  Yueyi  Dicke  Marcel  van der Werf  Wopke  Poelman  Erik H.  Bianchi  Felix J. J. A. 《Landscape Ecology》2020,35(4):907-919

Landscape Ecology - Tritrophic interactions may be affected by local factors and the broader landscape context. At small spatial scales, carnivorous enemies of herbivorous insects use...  相似文献   

Projecting the suitability of global and local habitats for myrtle rust (Austropuccinia psidii) using model consensus     

H. A. Narouei-Khandan  S. P. Worner  S. L. H. Viljanen  A. H. C. van Bruggen  E. E. Jones 《Plant pathology》2020,69(1):17-27

Myrtle rust (caused by Austropuccinia psidii) affects more than 500 known host species in the Myrtaceae family. Three different modelling approaches (CLIMEX, MaxEnt and Multi-Model Framework) were used to project the habitat suitability for myrtle rust at both global and local scales. Current data on the global occurrence of myrtle rust were collected from online literature and expert solicitation. Long-term averages of climate data (1960–1990) were sourced from WorldClim and CliMond websites. Recent reports of myrtle rust in New Zealand were used for validation of model outputs but not in model training and testing. The model outputs were combined into a consensus model to identify localities projected to be suitable for myrtle rust according to two or three models (hotspots). In addition to the locations where the pathogen is currently present, all models successfully projected independent occurrence data in New Zealand suitable for establishment of the pathogen. Climate suitability for the pathogen was primarily related to temperature followed by rainfall in MaxEnt and the CLIMEX model. The results confirmed the optimum temperature range of this pathogen in the literature (15–25 °C). Additional analysis of the precipitation variables indicated that excessive rain (more than 2000 mm in warmest quarter of the year) combined with high temperatures (>30 °C) constrain pathogen establishment. The results of the current study can be useful for countries such as New Zealand, China, South Africa and Singapore where the pathogen has not fully spread or established.  相似文献   

Improved detection of Mycobacterium tuberculosis and M. bovis in African wildlife samples using cationic peptide decontamination and mycobacterial culture supplementation     

Wynand J. Goosen  Lanie Kleynhans  Tanya J. Kerr  Paul D. van Helden  Peter Buss  Robin M. Warren  Michele A. Miller 《Journal of veterinary diagnostic investigation》2022,34(1):61

In South Africa, mycobacterial culture is regarded as the gold standard for the detection of Mycobacterium tuberculosis complex (MTBC) infection in wildlife even though it is regarded as “imperfect.” We compared a novel decontamination and mycobacterial culture technique (TiKa) to the conventional mycobacterium growth indicator tube (MGIT) system using known amounts of bacilli and clinical samples from MTBC-infected African buffaloes (Syncerus caffer), white rhinoceros (Ceratotherium simum), and African elephants (Loxodonta africana). Use of the TiKa-KiC decontamination agent on samples spiked with 10,000 to 10 colony forming units (cfu) of M. bovis (SB0121) and M. tuberculosis (H37Rv) had no effect on isolate recovery in culture. In contrast, decontamination with MGIT MycoPrep resulted in no growth of M. bovis samples at concentrations < 1,000 cfu and M. tuberculosis samples < 100 cfu. Subsequently, we used the TiKa system with stored clinical samples (various lymphatic tissues) collected from wildlife and paucibacillary bronchoalveolar lavage fluid, trunk washes, and endotracheal tube washes from 3 species with known MTBC infections. Overall, MTBC recovery by culture was improved significantly (p < 0.01) by using TiKa compared to conventional MGIT, with 54 of 57 positive specimens versus 25 of 57 positive specimens, respectively. The TiKa mycobacterial growth system appears to significantly enhance the recovery of MTBC members from tissue and paucibacillary respiratory samples collected from African buffaloes, African elephants, and white rhinoceros. Moreover, the TiKa system may improve success of MTBC culture from various sample types previously deemed unculturable from other species.  相似文献   

Modelling optimal timing and frequency of insecticide sprays for knockdown in preparation for other control measures     

Hugh J. Barclay  John W. Hargrove  Robert Steacy  P. van den Driessche 《国际虫害防治杂志》2019,65(2):114-129

A modelling investigation was conducted into optimizing the number of sprays and inter-spray interval to reduce an insect population to a low level, for example, prior to pheromone trapping or the release of sterile males. The model population was age-structured and density-dependent. If spray mortality is 100% for each spray, then the ideal spraying schedule is easily determined from the durations of the various life stages. For spray mortality of less than 100%, a simulation was used to determine optimal spraying schedules. Relative length of the larval period, fertility rate and age to first oviposition were found to be the most important biotic parameters for this determination. Their importance is magnified as spray mortality decreases. The stage targeted by sprays and the percent mortality caused by each spray are also important in determining the required number of sprays. Using medfly (Ceratitis capitata Wiedmann) biotic parameters as an example when the spray targets adults, it appeared that neither the stage at which density-dependent mortality takes effect, nor the form of the adult survivorship curve are important in determining the optimal spray schedule.  相似文献