Effect of Planting Sequence and Time, and Nitrogen on Maize Legume Intercrop Yield

Productivity of maize ( Zea mays L.) legume intercrops is determined by soil, management, and environment. Planting sequence and time and N fertilization are easily controlled management factors but their effects on intercrop yields are not well understood. Maize grown in monoculture or intercropped with polebean ( Phaseolus vulgaris L.) or cowpea ( Vigna unguiculata [L.] Warp.) was studied for two growing seasons at Morgantown, WV. Crops were seeded in the following sequences: maize before legume, both at the same time, and legume before maize. Planting times were early May or mid June. Nitrogen was applied at 0 or 160 kg ha⁻¹. Maize grain and forage, legume grain and forage, and total forage production were determined on a dry matter basis. Intercropping (average of all treatments) reduced maize grain and forage yields compared to maize in monoculture but had no effect on total forage production. However, total forage production was greatest when the seeding sequence was maize intercropped at the same time or before cowpea. Cowpea never produced grain, but forage production was almost double that of polebean. Maize produced most forage when seeded before the legumes, and the legumes produced most forage when seeded before maize. Early planting increased maize production and decreased legume production. Nitrogen increased maize grain, maize forage, and total forage yields but had not effect on legume forage production. It is concluded that maize/legume intercrops show promise for increasing forage production in temperate areas and more research on planting times and densities, weed control, harvesting and management is needed.     

Antigenic relationship of turkey coronavirus isolates from different geographic locations in the United States

The purpose of the present study was to examine the antigenicity of turkey coronavirus (TCV) isolates from various geographic areas with antibodies to different viruses. Seventeen isolates of TCV were recovered from intestinal samples submitted to Animal Disease Diagnostic Laboratory, Purdue University, from turkey farms located in different geographic areas. The prototype TCV Minnesota isolate (TCV-ATCC) was obtained from the American Type Culture Collection. Intestinal sections were prepared from turkey embryos infected with different TCV isolates and reacted with polyclonal or monoclonal antibodies to TCV, infectious bronchitis virus (IBV), bovine coronavirus (BCV), transmissible gastroenteritis virus (TGEV), reovirus, rotavirus, adenovirus, or enterovirus in immunofluorescent antibody staining. All 18 TCV isolates have the same antigenic reactivity pattern with the same panel of antibodies. Positive reactivity was seen with polyclonal antibodies to the TCV Indiana isolate, the TCV Virginia isolate, TCV-ATCC, and the IBV Massachusetts strain as well as monoclonal antibodies to the TCV North Carolina isolate or the membrane protein of IBV. Antibodies to BCV or TGEV were not reactive with any of the TCV isolates. Reactivity of antibodies to unrelated virus, rotavirus, reovirus, adenovirus, or enterovirus with different TCV isolates was all negative, except positive response was seen between enterovirus antibody and a TCV western North Carolina isolate, suggesting coinfection of turkeys with TCV and enterovirus in that particular case. The results indicated that the TCV isolates from these geographic locations in the U.S. shared close antigenicity and were antigenically related to IBV.     

The effect of immunosuppression on protective immunity of turkey poults against infection with turkey coronavirus

The objective of the present study was to evaluate the protective effect of humoral and cellular immunities on turkeys infected with turkey coronavirus (TCV). Two trials were conducted with two separate hatches of turkey poults. Turkey's were experimentally immunosuppressed with cyclosporin A (CsA) or cyclophosphamide (CY) and infected with TCV. Prior to infection, treatment with CsA selectively suppressed T cell activity as revealed by 2-3 fold decreased (p < 0.1) lymphocyte proliferation responses to a T cell mitogen, concanavalin A (Con A). Treatment with CY mainly induced B cell deficiency as indicated by significant reductions (p < 0.05) in antibody responses to sheep erythrocytes 7 days after injection. Body weight gain of turkeys treated with CY was significantly lower (p < 0.05) than that of untreated turkeys at 9 days post-infection (PI). Turkeys treated with CY had 1-2 fold higher immunofluorescent antibody assay (IFA) scores for TCV antigens (p < 0.05) in the intestine than untreated turkeys at 9 or 14 days PI. These results suggested that humoral immunity against TCV infection may be important in turkeys.     

A survey of helminth control practices in equine establishments in Ireland

We report the results of a survey to assess the attitudes of horse owners and managers of equine businesses in Ireland to the control of helminth parasites, and the extent to which veterinary practitioners are involved in providing advice on parasite control of horses.Replies to our questionnaire indicated that there is a high level of awareness on the need for helminth control, typically leading to several doses of anthelmintic being administered to each animal every year. While a majority of respondents (61%) were concerned about the issue of anthelmintic resistance, only a few were of the opinion that it was a problem on their establishment. Measures to minimise the development of resistance, such as decreasing the frequency of dosing, optimising non-drug-based control strategies and assessing the need for dosing by faecal egg counts (FECs), were not widely employed in a strategic manner. Just over half (54%) of respondents indicated that they devised worming control programmes based on veterinary advice, and a large majority did not perceive any need for modification of their current worm control programmes.We concluded that there is considerable scope for increased veterinary involvement in the design and implementation of control programmes for helminths in horses, and that veterinarians do not always provide advice in accordance with "best practice" in helminth control.     

The ecological sustainability of tropical forest management: evaluation of the national forest management standards of Costa Rica and Nicaragua, with emphasis on the need for adaptive management

From a conceptual point of view, national forest management standards in Latin American countries have progressed significantly in recent years. Examples include the Costa Rican Standards and Procedures for Sustainable Forest Management and Certification, developed by the National Commission for Forest Certification and in Nicaragua, the National Institute of Forestry proposal of principles, criteria and indicators for sustainable forest management. In line with general approaches worldwide, these national standards primarily focus on the fulfillment of sound forest practice. There is comparatively little emphasis on the assessment of management outcomes or changes in key components of the eco- and social-systems that result from management impacts. Essentially, there is little emphasis on adaptive management, though arguments that management cannot be sustainable if it is not adaptive are persuasive. This study sought to contribute to the development of standards that include elements for adaptive management that define, communicate and evaluate sustainable forest management in Costa Rica and Nicaragua. Elements from the national standards and the CIFOR generic C&I template (predominantly focused on forest management outcomes) were used as a starting point. The basic research process consisted of three phases of evaluation (in-office, desk and field). The evaluations were carried out by multidisciplinary, international groups of experts in forest ecology, management and policy. This study demonstrated the value of forums and workshops that facilitate exchange between forest scientists and policymakers; the innovation and application of a practical, applicable and scientifically based methodology for developing national level C&I; and acceptance of this methodology by key players in the fields of forest management and policy. These experiences and the resulting proposals of C&I for the evaluation of ecologically sustainable forest management are expected to be used as points of reference for future development of forest policy in Costa Rica and Nicaragua, and to contribute to the overall understanding of C&I development processes in the region.     

Estimating root mass in young hybrid poplar trees using the electrical capacitance method

A preliminary field study was conducted on root mass of young hybrid polar trees (Populus deltoides x P. nigra) using the electrical capacitance method. The objective of this study was to develop a simple calibration relationship that would enable root mass (fresh or dry) to be estimated for young hybrid poplar trees grown in mineral soils using simple, non-intrusive measurements of electrical capacitance. For first-year potted saplings (n = 33), strong linear and positive correlations were found between both root dry mass (adjusted r² = 0.895, P<0.001) and root fresh mass (adjusted r² = 0.866, P<0.001) and root electrical capacitance for the particular DN hybrid poplar clone studied. When augmented with data from third-year DN saplings grown in a more harsh landfill environment, a somewhat less strong curvilinear relationship was indicated with root dry mass (adjusted r² = 0.780, P<0.001, n = 50). This rapid field method may be capable of providing adequate estimates of root mass for young trees in a variety of applications, such as afforestation, agroforestry or phytoremediation studies. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effects of white-tailed deer on vegetation structure and woody seedling composition in three forest types on the Piedmont Plateau

White-tailed deer (Ododcoileus virginiana) can substantially affect the structure and species composition of a forest. The tolerance of a forest community to browsing may vary by type as a result of varying biotic and abiotic factors of the environment. To date, no studies have compared the effects of browsing among forest communities within a physiographic region. We investigated the effects of browsing on vegetation structure and woody seedling composition in three forest types (oak–hickory, Virginia pine–eastern red cedar, bottomland hardwood) in Manassas National Battlefield Park (MNBP), Virginia, USA. We compared forb cover, vertical plant cover (0–1.5 m tall), and survival of tagged seedlings in 10 exclosed (2 m × 6 m) and 10 unexclosed plots in each forest type during a 5-year period. No differential effects of browsing were found among forest types. In all forest types, deer (67 deer/km²) suppressed forb and vertical plant cover to levels less than would be expected in the absence of deer. Seedling survival rates of most species were significantly reduced by browsing. By the 4th year of the study, box elder (Acer negundo), hickory (Carya spp.), and red maple (Acer rubrum) had been eliminated from unexclosed plots, and red and white oaks (Quercus spp.) dramatically reduced. Ash (Fraxinus spp.), black cherry (Prunus serotina), and hackberry (Celtis occidentalis), although significantly impacted, remained the most abundant species throughout the study. These findings suggest that white-tailed deer may be modifying the structure of the forest interior to the extent that it adversely affects wildlife species dependent on a dense understory to thrive. We predict that the future composition of forests in MNBP will shift towards stands with fewer species and a greater dominance of ash, black cherry, and hackberry, particularly in the oak–hickory and bottomland hardwood forests, where the majority of current dominants are most affected.     

Conservation and management of the rivers of the Kruger National Park: Suggested methods for calculating instream flow needs

1. Six major river systems flow west to east across the Kruger National Park (South Africa). All arise outside the western boundary of the KNP, and are outside the jurisdiction of the Park authorities. 2. Growing human populations to the west of the Park are placing increasing demands on the water resources of these rivers, and a variety of artificial changes threaten the ecological integrity of the rivers. 3. As a result, the Luvuvhu and Letaba Rivers to the north no longer have a perennial flow, while the flow of the Crocodile River on the southern boundary of the Park has been regulated to a more constant regime due to irrigation demands. The Letaba, Olifants, and Crocodile Rivers all receive diverse pollutants. The Sabie River, at present the least disturbed system, and biologically the most diverse in South Africa, is threatened with multiple regulation within the next five years. 4. The paper describes the development of initial protocols for the assessment of instream flow needs for the Luvuvhu and Sabie Rivers. These methods require an extension of existing methods developed in the USA to ensure the maintenance of ecological processes, rather than the maintenance of single target species. 5. Two methods are described: one that identifies the consumptive and non-consumptive water requirements of the rivers, adding all consumptive to the limiting non-consumptive quantity to give a base-flow requirement. 6. A second method uses a conservation status model to assess the ecological consequences of flow reductions generated through a hydrological model, in response to different impoundment conditions. 7. Both methods are successful in appropriate circumstances, but we conclude that the proposed impoundment and agricultural development of the Sabie River, in particular, is an inappropriate use of this unique resource, and that the catchment would be more advantageously developed for tourism, recreation, and nature conservation.     

Palaeoecological insights for the conservation of aquatic ecosystems in dryland environments: A case study of the Verlorenvlei system,South Africa

Verlorenvlei, a dryland aquatic ecosystem in South Africa, has been identified as having enormous conservation importance. Although the system has Ramsar status and is widely regarded as being in ‘pristine' condition, neither statutory control nor any form of management is currently in existence. Based on the analysis of fossil pollen derived from the sediments of Verlorenvlei, a sequence of rapid changes within the riparian and aquatic vegetation is identified. Synchronous changes in the rate of sedimentation suggest a threefold increase in annual sediment deposition since the mid-18th century—the onset of colonial settlement. The pollen spectra prior to the arrival of colonial settlers suggest that abundant Poaceae (grasses) and rooted aquatic plants dominated the vegetation of the site. Radical changes in the pollen record become evident after the time of European colonization. Aquatic vegetation, including Gentianaceae (water lilies) and Potamogetonaceae, show a marked decrease while riparian vegetation, particularly reed elements such as Cyperaceae, Typhaceae and Juncaceae, are seen to increase progressively. Terrestrial pollen indicators reveal an expansion in the vegetation of classic disturbance indicators such as Asteraceae, Oxalidaceae and Scrophulariaceae. As the wetland has already endured rapid ecological adjustments in the face of colonial (and more recent) occupation of the broader landscape, it cannot be regarded as being in a ‘pristine’ state. Indeed, Verlorenvlei is interpreted as having reached a state of ‘transitional’ ecological equilibrium in which it continues to endure a number of rapid ecological changes; nonetheless, it is still worthy of conservation and management, not least because of its role as a strategic wetland in a dryland environment. Failing the timely implementation of remedial action in the form of an integrated conservation and management plan, Verlorenvlei appears destined to become irreversibly altered. Dryland aquatic ecosystems are vital aquatic resources in so called ‘Third World’ regions of the world yet, paradoxically, scientific research on, and the conservation of, these environments in the Southern Hemisphere are rare by comparison to wetland environments in the northern temperate zones. Although many dryland aquatic systems may already be altered, most are worthy of urgent management and conservation action, bearing in mind the fundamental question: ‘What is it that we wish to conserve?’. A number of recommendations for the management of dryland aquatic ecosystems such as Verlorenvlei are listed.