Optimizing Environmental Benefits From Riparian Buffers in Maryland
Riparian grass buffers enrolled in the Conservation Reserve Enhancement Program (CREP) are becoming a major part of the agricultural landscape in Maryland and thus have the potential to be propagation areas for insect populations that could have major effects on agricultural production.
This project focuses on three design elements of grass buffers, vegetation composition, timing of mowing, and adjacent crop type, and examines their effects on both pest and beneficial insect populations. Monitoring data from buffers and adjacent crops at 44 farm sites will document relationships between buffer design elements and management practices, natural enemy communities, and pest problems.
This project will show that riparian buffers of native warm-season grasses with an appropriate level of flowering plant biodiversity can foster large multi-species populations of natural enemies to immigrate into adjacent crops and to suppress pest populations that may originate from buffers. Using monitoring results, questionnaire surveys, direct contacts, an extension fact sheet, extension talks, and other ways to engage target groups, the project will institute changes toward increased use of more sustainable warm-season grasses, improved buffer management to minimize ecological disturbances, and over-seeding practices to maintain plant diversity and enhance conservation biological control.
Adoption of these practices, ultimately reducing the proportion of non-native, cool-season grasses planted, will enhance the environmental benefits of riparian grass buffers without sacrificing their primary water quality functions. Results will influence state and district soil conservation leaders to incorporate the information into policy, resulting in modified buffer design and management guidelines. Changes in buffer management implemented by cooperators will lead directly to improved and more profitable farming practices and enhanced environmental quality.
The major aim of this project is to demonstrate that the design and management of CREP riparian grass buffers can be modified to enhance conservation of natural enemy communities and reduce pest outbreaks without sacrificing their water quality functions. Using on-farm data from research activities and various ways to engage the target groups in the project, we will institute changes in the types of buffers and management practices used by landowners. Anticipated performance targets are:
1. Fifty percent of the cooperating landowners will transition to improved design features in newly established buffers, and at least 30% of all participants in the CREP program will adopt some of these practices after the project is over.
2. Project results will bring about an 80 percent increase in over-seeding practices on existing buffers to enhance biodiversity with flowering forbs as alternate food sources for natural enemies.
3. Of the farmers/landowners in the project with cool-season buffers, one-third will reduce their use of non-native grasses, and two-thirds will delay mowing of buffers to avoid removal of food sources for pollinators and adult parasitoids.
4. Training and project results will influence state conservation leaders and county conservation planners to incorporate the information into policy, resulting in modified buffer design and best management guidelines.
In this first year of the project, 44 buffer/crop sites were monitored three times during June, July, and August to describe the natural enemy communities in warm-season versus cool-season grass buffers and determine if differences exist in community structure in corn and soybean fields bordered by these grass buffers. Study sites were located on eleven farms in Caroline, Queen Anne’s, and Talbot Counties on the Eastern Shore of Maryland. Sticky-card and pitfall trap samples were collected at three locations (6m into buffer, 6m and 46m into crop) along 2-3 transects perpendicular to the buffer-crop edge at each site.
The processing of samples and the data analysis are still in progress. A preliminary summary indicated that over 150 families of arthropods were identified. Arthropod communities in crops adjacent to warm-season buffers were significantly different from communities in crops associated with cool-season buffers. Differences appeared to be due primarily to several taxonomic groups of herbivores and saprovores, all of which occurred at higher densities in cool-season grasses. Further analysis of the 2004 data will focus on differences in beneficial arthropod densities between the two grass buffer systems.
Another demonstration project that will complement the SARE riparian buffer project was initiated in 2004 to evaluate perennial wildflower species for use as beneficial insectary plants in farmscapes to enhance biological control. Replicated clumps of 25 plant species were established in an organic transition field of orchard grass at the Wye Research and Education Center on the Eastern Shore. In 2005 and subsequent years, the relative efficiency of these perennials to provide nectar, pollen, and non-pest prey or hosts for natural enemies will be determined.
In 2004, two training events were conducted in October to explain the objectives and anticipated outcomes of the project to soil conservation district personnel throughout the state. Thirty-five conservation planners attended the event in Denton, MD on the Eastern Shore, while 52 planners received the same training in Westminster, MD. The presentation and informal discussion focused on how riparian grass buffers can affect pest populations both positively and negatively, and anticipated practices that can enhance sustainability of grass buffers as habitats to conserve natural enemies. Attendees were asked for constructive feedback on the feasibility of the proposed changes in grass buffer design and management. Additionally, a three-hour workshop was conducted prior to the Future Harvest Annual Sustainable Agricultural Conference held in Hagerstown in January 2005. Twenty-five participants, primarily organic farmers, paid a registration fee to receive training on arthropod natural enemies. Though the workshop focused on the biology, identification, and practical use of natural enemies, emphasis was given to flowering annuals and perennials in non-crop habitats to provide alternate food and shelter for natural enemies.
Two other sources of funding were sought for and awarded to support additional studies related to the SARE riparian grass buffer project. A grant for $100,000 was obtained from the NRCS Wildlife Habitat Management Institute to conduct a 3-year study of the use of riparian grass buffers by breeding and wintering birds. Supported by this grant, graduate student, Peter Blank, is addressing the following questions: Which bird species are using riparian grass buffers in summer and winter? Which birds prefer buffers containing warm season grasses versus cool season grasses? How does vegetation composition and structure affect bird response? How does buffer width affect bird response? The products of this research will include a comprehensive assessment of the bird use in riparian grass buffers, as well as management recommendations designed to meet specific bird conservation objectives. A second grant from the Maryland Soybean Board for $14,529 was provided to determine if soybean insect pest problems are linked to riparian grass buffers and ascertain if changes in buffer design and management can minimize these problems.