Cover Crops for Sustainable Pest Management and Soil Quality in Production Nurseries
In spring 2010 the project leaders met face to face and discussed progress made in 2009 (first full field season), and to refine the research and demonstration protocol aimed at identifying and implementing the use of cover crops in field production nurseries to determine their benefits to pest management and soil quality for the 2010 season. On-farm visits and email interactions also took place with the 3 nursery cooperators to obtain their input on the project to date. The four studies implemented in fall 2008 and 2009 were repeated in the 2010 field season (spring/summer and fall). Three of the studies consisted of spring / summer and fall cover crop treatments. In all three nurseries studies on cover crops took place in the tree bare zone areas and fallow tree rows (trees have been harvested over time). In one of the three nurseries 2 additional studies were implemented: 1 is evaluating cover crops in open field plots of the nursery, and the 2nd is evaluating 3 turf types, each with and without cover crops in grass alleys of the nursery. Data were collected through out the summer and fall and are currently being analyzed. Project PD’s presented several talks at conferences targeting stakeholders on sustainable practices for production nurseries.
Of the 150 MD growers trained at field days and other events, a minimum of 25 that have never used cover crops in their nursery will use cover crops in at least one production field, and five nurseries will adopt one new ecologically based pest or soil management practice to reduce pest pressure or improve soil quality.
In the 3rd year (2010, 2nd full year) of the proposed project milestones 3, 4, and 7 were addressed. The PD’s implemented a change in the original proposal in that we decided to conduct a full year of field research and demonstration in 2010 since the grant started in fall of 2008 rather than the summer. This will provide 2 full years and one fall season of data that will give more rigorous data to address the proposal objectives. This shifted milestones 5 and 6 to a later time frame. An additional experiment was added to address the question of soil loss during B&B harvesting of trees. Three nursery growers worked with project leaders implementing the proposed research in 2010. Data are still being analyzed (prior to addressing milestone 5). Presentations on sustainable practices were given at green industry conferences by project PDs.
Impacts and Contributions/Outcomes
Data from fall 2008 and two full years (2009 and 2010) have been completed and are currently being evaluated and analyzed. At this time only preliminary results have been summarized for the cover crop selection and establishment, and the soil quality and pest management components of the project.
Cover crop treatments for both the spring/summer and fall plantings overall did not establish as well as hoped. This was the case in the open field, tree row zone, and fallow row studies. Sampling for cover crop establishment in all 4 studies was conducted in early and late summer, and again in the fall. Although data on establishment is still being evaluated, preliminary observations suggest that forage radish, crimson clover, cowpea, and Austrian winter pea have promise. Vacuum sampling was conducted in early and late summer and fall of the cover crop treatments and trees to determine arthropod composition and abundance. A predation study in tree rows with and without cover crops was conducted and data are currently being analyzed. Grass alley studies compared 3 grass mixes with and without cover crops added. The hard fescue mix and no-mow mix seem to establish as well as the industry standard of tall fescue, and require less mowing. Additional data is still being analysed on soil attributes of the grasses and cover crops.
Several sampling methods were conducted on soils of all studies. Soils were sampled in June 2010 from the surface 10 cm of all plots. Samples were weighed and air dried, and bulk density calculated. 2010 samples were tested by permanganate oxidation for active carbon content, in an effort to determine differences in soil available carbon after 1 ½ years of conventional versus cover crop treatments. Permanganate tests for active soil carbon are being completed, and statistical analysis of the results is still to be conducted. It may be expected that treatment effects will be weak, because of the overall poor establishment and low biomass production of cover crops in most locations in most seasons of the study. Final soil samples are being taken following the last cover crop season for the Fallow Rows experiment Fall 2010, and for Open Fields and Bare Zones experiments Spring 2011. Analysis of these soils will be made if warranted by 2010 cover crop performance. Observation of cover crop establishment and growth during the study period so far suggests that initially in the first season there may have been enough available nitrogen in the surface soil to allowed reasonable cover crop growth. Cover crop later plantings appeared to be limited by nitrogen as well as poor establishment. As nitrate is a very dynamic soil property and the soil sampling was not specifically timed for nitrate analysis, we cannot reliably estimate the actual role of N availability. In planning the research we had assumed that N fertility would be higher in the surface soils of nurseries, especially in fertilized tree rows.
To respond to the question of soil loss from nurseries that use balled and burlap harvest methods, direct measurement was made in September 2010 of the soil and roots present in a set of 12 root balls (6 each of two tree species, using standard tree spades of two different geometries). The amount of soil vs. tree roots in the ball was evaluated. As expected, the volume of fresh roots in a soil root ball was negligible (<5%) compared with the total volume of the root ball, as was the dry weight of roots compared with the total dry weight of the root ball. The quality of soil being lost was evaluated by LECO analysis of carbon content of A and B horizon soil in the root balls. Statistical analysis is yet to be conducted, but the results are likely to confirm that calculating soil loss based on tree spade volume and field soil bulk density is generally valid.
Approximately 125 green industry stakeholders were informed on sustainable practices via presentations given by project PDs at conferences.
University of Maryland
Department of Environmental Science and Technology
1109 H.J. Patterson Hall
College Park, MD 20742
Office Phone: 3014051314
University of Maryland
11975-A Homewood Road
Ellicott City, MD 21042
Office Phone: 3015969413
University of Maryland
Montgomery County Extension
18410 Muncaster Road
Derwood, MD 20855
Office Phone: 3015902807