Field margins are the boundaries between a field and other land uses, such as another field with a different crop, a road, a trail, a stream, a wetland—anything, really. They are not often considered very carefully. Even their name implies that they are somewhere off to the side, on the edge of what’s important, in the periphery of our attention—certainly not the focus.
But those margins offer varied and considerable benefits at all scales, from landscapes of large grain fields to market gardens and small horticultural acreages. The importance of field margins in crop production has long been recognized for serving as windbreaks for snow-trapping and protection against wind erosion, two very useful ecosystem services to agriculture.
In recent years, we’ve learned much more about the potential for these habitats to provide many more ecosystem services to agricultural production. As it turns out, they can do a great deal to enhance agriculture (see Table 1).
Table 1: Summary of Ecosystem Services that Field Margins Can Provide
- Create and provide habitat for the common mycorrhizal fungi network to increase nutrient cycling in adjacent cultivated fields
- Provide movement corridors and shelter for desirable wildlife species
- Protect soil from wind erosion
- Provide shelter for crops and livestock
- Create microclimate conditions that reduce heating and cooling energy needs and costs
- Manage the capture and distribution of snow
- Create and provide habitat for wild pollinators to increase pollination services
- to nearby crops
- Create and provide habitat that favours the natural enemies of pests to increase pest suppression services to nearby crops
- Slow surface water movement to increase ground/soil water storage and mitigate water erosion
- Treat overland agricultural wastewater flows to reduce contamination risk in downstream surface and groundwater
- Reduce the effects of dust, odour and pesticide drift
- Provide useable and marketable products (e.g., berries, nuts, wood, biofuels, floral products)
- Provide visual screening and increase the aesthetic quality of the farm landscape
Margins for Specific Functions
This table of ecosystem services illustrates that there is much more to field margins than meets the eye, and they can be designed for specific functions. Any existing field margin is likely already delivering some functions. With tweaking, their performance can be vastly improved, and some field margins can be designed to provide several functions.
Field Margins on Organic Farms
The Canadian Organic Standards state that “ [i]f unintended contact with prohibited substances is possible, distinct buffer zones or other features sufficient to prevent contamination are required” (CAN/CGSB-32.310-2015, section 5.2.2).
Often organic farmers meet this requirement by establishing 8-metre buffer zones around organic production areas adjacent to potential sources of contamination. These buffer zones must be managed organically but any products from these areas are considered conventional. Producing crops on these areas creates logistical challenges (since products must be kept separate) and may not be economically viable.
This buffer zone requirement may seem like an inconvenience or economic burden to organic farmers, but it can also present an opportunity to harness beneficial ecological processes, which are the cornerstone of holistic organic systems. In fact, the Canadian Organic Standards also state that: “Organic products referenced in this standard are derived from a production system that:
a) seeks to nurture ecosystems through its management practices in order to achieve sustainable productivity; and
b) provides weed, pest and disease control through enhancement of biodiversity, recycling of plant and animal residues, crop selection and rotation, water management, tillage and cultivation” (CAN/CGSB- 32.310-2015, section 1.2).
With some strategic planning and management, buffer zones can provide any of the benefits outlined in Table 1. These services will indirectly support the production of organic crops while benefitting the whole ecosystem.
If any edible species such as fruit or nuts are included in the buffer zone, however, it is important to remember than these products will not be considered organic.
To gain benefits from wild pollinators such as native bees, you need to provide them access to nectar and pollen, nesting sites and materials, and overwintering habitat. This can be done by:
• planting your field margins with diverse native flowering species that will bloom throughout the entire growing period;
• including/maintaining hollow-stemmed plants (such as raspberry and elderberry), bunch grasses and rotting logs and snags in the margin; and
• maintaining areas of thick leaf litter (for bumblebee overwintering) and sunny patches of bare soil (for soil-nesting bees).
The bees will use the field margins for much of their lives, but they will also readily venture about 150 metres, on average, into flowering crops, providing the pollination service the crops need.
Taking It to the Next Level
To add pest suppression services, you need to create habitat that favours the natural enemies of the pests of concern. In Canadian agricultural settings, the most important natural enemies of pests are insects (e.g., predatory beetles, parasitoid wasps, and seed-eating insects), although spiders and birds can also be important. The habitat requirements for these beneficial insects can be similar to that of bees, but more care and monitoring is necessary to avoid unintentionally creating habitat that favours the pest species more than their natural enemies.
Theoretically, then, if you know which pest you want to control and which species or even group of species you want to promote, you should be able to design field margins to tip the balance in favour of the natural enemies of the pest. But because nature is inherently complex and often acts in ways that are difficult to predict, we need to rely on general design principles and experimentation.
Research suggests that an effective natural enemy community is made up of species that:
• prey on several different species;
• have life cycles that are not perfectly synchronized with that of any one prey species;
• consume several prey individuals in a lifetime;
• are capable of dispersal, rapid recolonization and reproduction; and
• are effective in finding and capturing prey
This suggests that a diverse natural enemy community and, therefore, a diverse farm landscape are desirable. A review of studies on this premise showed that more than 70% of the time, a more diverse natural enemy community corresponds with increased pest suppression. That said, almost all of the remaining 30% of studies showed less effective pest suppression with greater natural enemy diversity. This study also found that when habitat and natural enemy diversity worked well, it worked very well, but when it didn’t work, the impacts were mild. So, while there is some risk that diverse field margin habitats might favour pests over natural enemies, generally the benefits tend to outweigh the risk.
Whole Farm Design
No single field margin can meet all needs, but across a farm landscape more things are possible. Designing for multiple ecosystem services on a farm is sometimes referred to as “farmscaping,” which involves the modification of the overall farm setting, including the management of cover crops, field margins, roadside verges, wetlands, watercourses and adjoining wild areas.
Farmscaping design is highly specific to each farm. For example, to determine where you need water treatment, water storage or flood protection on your farm and how to best get these services, you must consider many factors, including your topography, the water source, quantity and timing, where it goes, and landscapes surrounding your farm. For pest suppression and pollination services, your local insect fauna will have particular habitat requirements. So, effective farmscaping depends on what ecosystem services you need as well as your farming context.
Fortunately, there are resources to help guide you in designing your farm to take best advantage of particular ecosystem services (see resource list, page 23). Putting all the elements together for a particular farm is less well understood, which means you will need to create your own unique design. While there is some risk in such a venture, the potential rewards are substantial, and you will learn a great deal about your land and your place in it.
Learn more about how providing habitat for beneficial bugs can help protect blueberries from pests in the Summer 2017 edition of the TCOG magazine!