Field Day Focuses on Managing Ecosystem Services on Farms
Posted: September 15, 2009
Eric Nord describes how hairy vetch can be used as a weed suppressing cover crop at the field day in June.
Clean air and water, recycling of nutrients, crop pollination, weed and pest suppression: these are just a few of the services provided to us by the ecological systems that function within our agricultural fields. Learning how to manage these ecosystem services with cover crops and native plants was the subject of a field day held on June 17th at the Russel E. Larson Research and Education Center at Rock Springs and co-hosted with the Pennsylvania Association for Sustainable Agriculture.
Hands-On Assessment of Ecosystem Service Indicators
“Cover crops have long been known for their ability to protect soil from erosion and reduce nutrient leaching in the winter,” Dr. Tara Pisani Gareau, a Postdoctoral Scholar at Penn State, told field day participants. Cover crops can also provide a host of other services as well. Dr. Pisani Gareau and Dr. Rich Smith, also a Postdoctoral Scholar, led the group in a hands-on exercise to compare ecosystem service indicators of five cover crop systems: a rye/hairy vetch mixture and wheat, which were fall planted, and a pea/triticale mixture, mustard, and buckwheat, which were spring planted.
An eight sided spider plot creates a visual comparison of the ecosystem service indicators measured in different cover crops. The futher from the center the line is plotted, the greater the ecosystem service indicator is for that cover crop. (Figure by Tara Pisani Gareau, Rich Smith, and Charlie White)
Field day participants sifted through soil to count earthworms and assess the density of cover crop roots, used hand lenses to count beneficial insects, and weighed cover crop shoots to calculate the biomass and nitrogen content. To compare the ecosystem service indicators provided by each cover crop, eight sided “spider plots” were constructed with each ecosystem service as one leg of the plot. The greater the level of the ecosystem service provided by the cover crop, the further out on each leg the cover crop was plotted. “Remember,” said Smith, “the assessment of ecosystem services we conducted today is just a snapshot in time and will change through the season as the cover crops grow.” Farmers and land managers can also develop their own indicators of ecosystem services that are the most relevant to their own systems.
Floral Resources Promote Pollinators
In Pennsylvania, wild bees are significant pollinators of summer vegetable crops, so it is important to sustain them on your farm. Wild bees spend the growing season foraging for pollen and nectar from blooming flowers, so to keep them on your farm, you need to have a constant supply of flowers in bloom, according to graduate student Nelson DeBarros and weed ecologist, Dr. Dave Mortensen. If allowed to flower, cover crops like buckwheat, hairy vetch, and clover can attract pollinating insects to your farm. Another way of maintaining floral resources throughout the growing season is to manage or plant native perennial flowers around field edges, which DeBarros has been studying. Native species like talus slope penstemon, wild bergamot, common boneset, wrinkeleaf goldenrod, and New England aster are highly attractive to wild bees and can be planted on marginal farmland. Other strategies for maintaining floral resources are to plant flowering herbs or ornamentals in strips within the crop field and to allow a portion of leafy crops like lettuce to bolt and flower.
Investigating Weed Management Strategies
A roller/crimper is used at Penn State's Russel E. Larson Research and Education Center for organic no-till cover crop termination. (Photo by Dave Mortensen)
Controlling weeds is a management challenge that all farmers face. Conventional farmers often manage weeds with herbicides, which can negatively impact environmental quality and lead to herbicide resistance. Organic farmers, who don’t use herbicides, frequently rely on tillage to control weeds, which can degrade soil quality. Penn State researchers demonstrated several practices for weed control which minimize tillage in organic systems and minimize herbicide use in conventional systems.
Graduate student Ryan Bates showed how shallow cultivation with implements like a high residue rotary hoe and a high residue cultivator could be used to reduce herbicide use. Instead of broadcasting herbicides over the entire field, herbicides were applied in a 12 inch band on top of the corn row at planting and the cultivation implements were used to control weeds between the rows. This strategy reduced herbicide use by 60% while still maintaining the same level of weed control and crop yield as the broadcast herbicide treatment.
Using a thick cover crop mulch was another strategy demonstrated for controlling weeds in organic systems. Weed scientist Dr. Bill Curran, and Dr. Eric Nord, Postdoctoral Scholar, showed how cover crops such as cereal rye or hairy vetch can be planted in the fall and then rolled into a weed suppressing mat in the spring with a tractor-mounted tool called a roller/crimper. When the roller/crimper is pushed or pulled across the field by the tractor, it rolls down and crimps the cover crop stems, killing the plant and forming a compressed mat of mulch. For the roller to be effective, the cover crop must be an annual and well into flowering. As field day participants watched, it only took a few seconds to roll down a demonstration plot of hairy vetch.
Maximizing the weed control benefits of a cover crop mulch requires integrating the management of the cover crop and the cash crop. Graduate student Matt Ryan explained to the group how increasing soybean seeding rates from 75,000 seeds per acre to 300,000 seeds per acre can improve soybean yields following a rolled cereal rye cover crop. The greater soybean plant density creates a canopy that is better at shading out weeds, so there is less yield loss from weed competition. “You should also match the fertility needs of cover and cash crops,” he told participants. “Match nitrogen loving crops like corn with legume cover crops like hairy vetch. Hairy vetch is a poor cover crop for soybean because it will provide available nitrogen that will disproportionately benefit weeds over the crop. Likewise, don’t plant cereal rye before corn because it will immobilize nitrogen in the soil, making corn plants more susceptible to weed competition.”