Stephen Holland
Graduate Program: Soil Science
Advisor: Joshua Heitman
Poster Number: 64
Title: Measuring the Influence of an Inter-row Fescue Crop on the Below-Canopy Humidity in a North Carolina Vineyard
Abstract
Growing European grape varieties for wine making is an expanding industry in the southeastern U.S. However, the southeastern climate differs from climates where European grapes are traditionally grown.
The southeast has high precipitation and soils with poor internal drainage, which lead to high humidity. High humidity, in turn,
|
|
creates ideal conditions for fungal diseases. Without adaptations to management practices to reduce canopy humidity, fungal diseases will continue to limit the local wine grape industry. Altering inter-row management practices may offer a solution.
|
typically fescue, serve as a pump extracting water from the soil, which increases below canopy humidity. The following objectives seek to test this hypothesis: |
We hypothesize that inter-row crops
(1) estimate and compare surface water vapor flux under (i) bare soil conditions and (ii) fescue cover crop conditions in the inter-row and in the vine row and (2) characterize and compare the humidity profile from the ground surface to the upper canopy for bare soil conditions and fescue cover crop conditions. Research will be conducted at a commercial vineyard in the Yadkin Valley Appellation. Measurements of below canopy water vapor flux will be collected with a micro-Bowen ratio system. To support this calculation, soil heat flux density, net radiation, and an air temperature gradient will be measured. We will also use microlysimeters and profile water content measurements to monitor soil water dynamics within the vineyard. Below-canopy humidity will be monitored at several heights. Together, these data will be used to compare the inter-row water balance between treatments. Measurements will be collected starting in March 2011.
|
Nape Mothapo
Graduate Program: Soil Science
Advisor: Julie Grossman
Poster Number: 120
Title: Hairy Vetch Use History Affects Nodulation and Diversity of Rhizobium leguminosarum
Abstract
Contribution of biological nitrogen fixation to soil fertility can be improved through functional knowledge of nodulation and rhizobia diversity associated with popular legume cover crops, such as hairy vetch (HV; Vicia villosa Roth).
The objective of this study was to evaluate nodulation effectiveness and diversity of rhizobia isolated from soils with and without history of HV 10 cultivation with distinct HV
|
|
genotypes. Soils from six paired fields, three with 10-yr HV history and three with no history, were collected from three organic farms across North Carolina. Five distinct HV genotypes were inoculated with soil dilutions from the six fields and used to trap rhizobia over a 6-wk period in a growth chamber. Nodulation efficacy was equated to nodule number and mass, and nitrogen-fixation efficiency to legume growth and development. Rhizobia diversity was evaluated through DNA analysis using repetitive element polymerase chain reaction (rep-PCR). Plant biomass was linearly correlated to nodule mass (r2 = 0.79). The rep-PCR analysis showed that fields with HV history exhibit higher rhizobia diversity than fields without HV history.
|
Nonetheless, strains isolated from one of the fields with HV history had surprisingly lower rhizobia diversity than the other two, possibly due to strain domination from prior
inoculant. |
Rhizobia grouping based on cluster analysis indicated five genetic groups and suggested rhizobia diversity to be most impacted by site, followed by hairy vetch field history. Overall, results suggest that HV use provides an environment that enhances diversity of rhizobia populations capable of high nodulation.
|