What Is It? All chemical reactions take place on surfaces. The more surface area, the more reactions take place. The biological corollary to this natural law is called the edge effect: Life increases proportionately to the boundary area between different environments. More edges = more interaction between environments = more food and habitat = more varied species and larger populations.
For example, where cold ocean currents meet warm currents there is an explosion of life along the boundary layers between uniquely different ecologies. Plankton and bait fish thrive. Abundant food supplies support large populations of predatory fish which, in turn, attract apex predators like man. Fishing boats congregate in the whorls formed by mixing currents. More edges = more life.
Life Breeds Life: Every time a new species is added to an environment it provides food and habitat for numerous other species. As species diversity increases the local ecology becomes more complex, more stable, and more capable of supporting additional life. In short, life breeds life.
Practical Farm Ecology: Farming is a type of ecological management; each field, pasture, and hedgerow is a different environment with its own varied species and micro-climate. Smart farmers manipulate agricultural ecologies to achieve specific ends such as pest suppression, erosion prevention, soil development, water conservation, pollution control, and climate moderation.
How To Do It: The basic principle is simple — create as many edges as possible across the land. Establish or encourage as many species as practical. Follow the examples below and watch life flourish on your farm.
Pests Be Gone: Many modern farmers plant fence row to fence row then tear out the fence rows to make even larger fields. Wrong. Huge fields = fewer edges = more pests. A better strategy is to divide large fields into smaller units — or — plant dissimilar crops in long, narrow strips within each field. Alternate tall crops with short crops, narrow-leaved crops with broadleaf crops, nitrogen-fixing crops with non-legumes. Every field should have at least 2 unrelated species. For example, plant narrow 4-row strips of corn and soybeans rather than vast monocultures. Result: Pest populations drop 50% and corn yields rise 15% (because leaves get more sunlight).
Medieval Ecology: Back when knights went clanking around in armor, farmers grew crops in long narrow fields (because it was difficult to turn heavy wood plows). A typical 1-acre field measured 22 yards wide and 220 yards long. Adjacent fields were planted with different crops, forage plants, or fallow. This strip cropping system created many edges = large populations of beneficial insects. Medieval records rarely mention plant pests because the good bugs ate the bad bugs. No synthetic chemicals necessary.
Head Rows: Tractors and horse teams need lots of space to turn around; turning areas at field ends are called head rows. On most farms head rows are left in sod or, even worse, bare earth. Head rows are one of many unique farm environments and should be managed accordingly. There are far better and more profitable alternatives to common grass or naked ground:
(1) Expand head rows to enclose each field. This enables farm equipment to circle around crop margins, increasing mechanical efficiency and creating more edges. Result: Instead of having two isolated head rows, you now have two fields, one larger field inside a smaller border field.
(2) Plant the surrounding buffer field with quick-growing cash crops like buckwheat (Fagopyrum esculentum), bee plants like lacy phacelia (Phacelia tanacetifolia), or seed with mixed forages and clovers, wild flowers, or specialty seed crops like anise (Pimpinella anisum), dill (Anethum graveolens), caraway (Carum carvi), coriander (Coriandrum sativum), and fennel (Foeniculum vulgare). The best buffer crops have small flowers to provide pollen and nectar for beneficial insects. (Big flowers won’t work because the good bugs have small mouth parts).
(3) If money is tight, plant weeds around field borders. Grain elevator screenings are free or cheap and contain many weed seeds. Mixed weeds provide good food and habitat for predatory and parasitic insects. For example, the braconid wasp Macrocentrus ancylivorus is a major predator of Oriental Fruit Moths (Grapholita molesta) and Peach Twig Borers (Anarsia lineatella). Planting weeds and wildflowers around peach orchards not only provides pollen and nectar but also necessary alternate hosts such as Ragweed Borer (Epiblema strenuana) and Sunflower Moth (Homoeosoma electellum). Result: When the bad bugs arrive, the good bugs are already waiting to eat them.
Hedge Rows: Windbreaks, greenbelts, shelter belts, and hedgerows all mean the same thing: Long, thin lines of vegetation planted to slow wind speed, raise humidity, trap snow, reduce soil erosion, and increase soil water absorption. Good windbreaks greatly multiply biological diversity and provide food and habitat for many species of beneficial birds and insects. For best results, plant hedgerows along field contours or perpendicular (at right angle) to prevailing winds or water flow. Greenbelts do not have to be wide in order to be effective; hedges 4 to 8 feet broad or strips of tall-growing perennial grass 1 to 3 feet wide are sufficient for most purposes and will save valuable land for cash crops. Space windbreaks no closer than 50 feet and no farther than 50 yards apart. Closer spacing reduces farming efficiency while wider spacing will not control wind speed effectively. Make shelter belts long to prevent wind from sweeping around the ends. Minimum length is 10 times the tallest mature tree height in the greenbelt. Ideal hedgerows contain a variety of plants selected for their economic or environmental value. Try to plant 40 or more different species per acre or linear mile of windbreak.
Ecology Math: Creating edge effects requires uncommon thinking, a different way of looking at land. Most farmers are used to broad square fields. Edge effect agriculture requires linear thinking: Thin strips and long, narrow rectangular spaces. For example, consider a 49-acre farm woodlot, 7 x 7 acres square or approximately 1,456 feet per side x 4 sides = 5,824 linear feet of forest edge. Take the same woodlot and stretch it into a narrow rectangle 1 acre wide and 49 acres long = (208 feet wide x 2 short sides) + (10,192 feet long x 2 long sides) = 416 + 20,384 = 20,800 linear feet of forest edge. The border of the narrow woodlot (3.93 miles) is more than 3 1/2 times longer than the border (1.1030 miles) of the square woodlot. More edges = more life. Wrap the narrow woodlot around the northwest corner of your farm (or divide the trees into long strips planted at right angle to prevailing winds). More trees = higher humidity = less water stress = higher crop yields.
Mixed Company: Each crop has its own architecture, its own micro-climate, and its own assortment of insects and critters that live on its leaves, stems, flowers, and roots. In short, every species creates its own micro-ecology. Combine numerous species together and each individual plant becomes an edge where many life forms interact for the benefit of all. Mixed species have more resistance to pests and more resilience to bad weather.
Ecology By Design: Mixing crop species is not a new idea; farmers sowed rye and wheat together in the Middle Ages. The mixed grain crop was called maslin and provided farmers with insurance against catastrophic loss. If disease or bad weather killed the wheat, stronger rye would survive to make a crop. Back in colonial times, Thomas Jefferson seeded mixed cover crops of buckwheat, vetch, and turnips to restore fertility to “tired fields”. Today, mixed cover crops are an essential part of modern agronomy.
Strength In Numbers: Ideal cover crop mixes contain cool and warm weather species, nitrogen fixing legumes, hardy grasses, broad leaf plants, and root crops. The idea is to mimic nature by creating an artificial jungle, a jumble of varieties adapted to a wide range of pests, diseases, and growing conditions. Plant mixtures grow with more vigor and yield than individual species grown in monoculture. This is an edge effect called synergy, a natural phenomenon where the total is more than the sum of each individual part.
Cover Crop Cocktail: To make your own cover crop mix, combine 2 cool season grasses + 2 cool season legumes + 2 cool season broad leaf plants + 2 warm season grasses + 2 warm season legumes + 2 warm season broad leaf plants + 2 root crops (tillage radish, turnip, or forage beet). Drill or broadcast at least 20 pounds seed per acre.
Life Underfoot: Most farmers think in 2 dimensions (length and width). Rarely considered is the third dimension, depth. The soil depths abound with life, and this ecology responds explosively to edge effect management. Roots need oxygen in order to absorb water and nutrients. (This is why plants wilt in flooded fields). Most agricultural soils are oxygen deficient. Gooey clays, plow pans = compacted layers, and tight subsoils starve soil organisms of essential air. Impermeable soils also restrict moisture; needed water runs off the land instead of soaking into the earth. Moisture and oxygen stress greatly reduce crop yields.
Vertical Tillage: The conventional solution to compacted soils is deep tillage = subsoiling. Unfortunately, this procedure requires expensive plows and enormous amounts of horse power = BIG tractors or bulldozers. The effects are also temporary and must be repeated every few years. A better solution is vertical tillage = verti-tillage = slicing thin crevices into the soil with minimum disturbance to surface vegetation. Each slit is 3/4 inch wide, 12 to 16 inches deep, and 2 feet apart. Verti-till fields along the contour for the first 4 or 5 years until soils develop their full potential. Thereafter, till every few years as needed. Each slit is like a high-capacity artery supplying water and air directly to the subsoil. Plant roots flourish along crevice edges. More roots = higher yields.
Vertical Mulching: In areas with poor soils, torrential rains, steep slopes or frequent droughts, use vertical mulching to bring problem fields into high production. Vertical mulching = drilling deep holes or digging deep trenches along the contour or perpendicular (at right angle) to water flow across the land. Fill the holes or trenches with manure, compost, stable bedding, wood chips, tree bark, coarse peat moss, straw, leaf mold, spoiled hay or similar organic matter. The holes and trenches conduct air and water deep into the soil so plant roots thrive. 100% to 800% yield increases are frequent, especially in arid lands or difficult soils like heavy clays or stony ground.
Soil Engineering: For best results use mechanical trenchers and rotary post hole diggers to prepare land for vertical mulching. Excavations should be as deep as practical, 3 to 8 feet is ideal. Best holes are 8 to 16 inches in diameter; trenches should be 4 to 12 inches wide. Space holes and trenches as convenient (as close as 40 inches = 3.3 feet, or as wide as 13.3 to 26.6 feet = 4 to 8 rows 40-inches apart. Even trenches spaced 50 feet = 15 rows 40-inches apart can dramatically improve yields). Exact spacing is not essential as more holes and trenches can be dug next season or periodically as time and resources permit. (Vertical mulching is a LONG TERM soil management technology).
For transplanted crops like tomatoes, peppers, cabbage and melons, space trenches or holes accordingly then fill with compost, potting soil or similar media (1 sand : 1 topsoil : 1 peat is a good mix). Plant roots quickly grow deep into the subsoil and resulting crops are nearly drought-proof.
If organic matter is scarce or expensive, fill holes or trenches with river sand, river pebbles, or river cobblestones. (This technique works especially well when trenches are placed directly under permanent tractor paths to prevent soil compaction). Tree prunings, grain straw, spoiled hay, and green chop or silage make adequate substitutes for compost when treating large fields. (Any medium will work as long as it has many large holes that allow unrestricted entry of air and water. In extremis, leave holes and trenches empty; they will eventually fill themselves with eroded soil and plant litter). Each hole or trench is a high-volume conduit channeling air and water deep into the soil. Every excavation is another edge between different ecologies and life will proliferate along these boundaries. More air = more roots = more absorption = higher yields.
Tillage Crops: In the 1500’s farmers without draft animals used deep rooted crops to “plow” their fields. They did not have much choice because the alternative was digging fields by hand — a lengthy and laborious task which severely limited the amount of land that could grow food. It was much easier to sow stock beet = mangle-wurzel (Beta vulgaris) or forage radish (Raphaus sativus variety longipinnatus) and let the plants break up the earth. Modern farmers call these specialized plants tillage crops or bio-drills because of their ability to penetrate subsoils to depths of 6 feet = 2 meters or more.
The advantage of tillage crops is that they leave tens of thousands of holes (vertical edges) across a field and each hole is a pipeline carrying water and air direct to waiting roots. Soil life proliferates around these breathing tubes resulting in better plant growth. For example, average yields increase 15% when upland rice follows a forage radish tillage crop. As an added benefit, soil erosion is nearly zero because rainwater soaks into the sponge-like earth rather than running off the land.
Agroforestry: Sunlight is very intense — it contains much more energy than any one crop can absorb. Thus, it is possible to stack multiple crops on top of each other so that more energy is collected and higher yields obtained. For example: Pole Apples grow mostly straight up with very little horizontal spread. Rows of pole apples planted in a hay field yield 2 crops (fruit and forage) with very little competition between plants. Edge effects increase dramatically because vertical space is used more efficiently; taller growing fruit trees and ground hugging forage plants are different micro-ecologies. There are many possible combinations of tree crops and field crops: Mulberry trees in pasture and English walnut trees in wheat fields are just two examples. Walk about your farm and look for ways to use vertical spaces = create more edges to increase biodiversity and farm profits.
Water Is Life: Most crops are water stressed at some point in their growth, usually at critical times like germination, flowering, or fruit development. The solution to inadequate soil moisture is water management, either active (irrigation) or passive (water conservation). To ensure ample water supply, every farm should have a watershed management plan; the goal is to trap every drop of water that falls on the land.
The best way to develop a watershed management plan is to don your poncho and walk about the farm while it is raining. The harder it rains the more you will learn. Watch where the water comes from and where it goes. Any place water flows across the land is an EDGE that requires management.
For example, water running down a gully to a stream is wasted moisture = reduced plant growth = lost profits. Solution: Top seed low growing clovers to halt water before it runs off your corn field; then build weirs to stop any water that reaches the gully. (Each row of corn in clover is an edge between different species; every gully and weir is an edge defining separate micro-environments). Plant useful trees and shrubs behind each weir to take advantage of trapped rainfall. Stand at the bottom of the gully and watch the results. If any water escapes then more aggressive management = more edges are needed.
Remember: The goal of every watershed management plan is zero runoff. More edges = more trapped water = more life.
Hungry Mouths: Agriculture is a dirty business that generates substantial pollution. Smart farmers use edge effects to clean up the mess. The principle is simple: For every pollutant there are a host of organisms waiting to eat it. The trick is to bring food and hungry mouths together; this is best accomplished by creating ecological edges where life thrives. More edges = more life = more pollutants eaten.
For example, stockyard effluent needs cleaning: Run dirty water through a sedimentation pond (8 feet deep), aeration lagoon (3 feet deep), filtration marsh (6 inches deep), then into a fish pond or irrigation reservoir. Result: Potable water without a costly waste water treatment plant. 4 separate environments each with many edges and different ecologies filled with hungry life forms. What does not get eaten is absorbed. Plants, fish and plankton flourish. Germs and parasites die.
Problem: The stream running through your property is polluted by an upstream hog farm. Solution: Build artificial rapids. Erect a series of weirs the entire length of the stream. Each weir is an edge supporting a unique ecology of organisms that thrive in high-oxygen water. Excess nutrients and harmful microbes are consumed. 1 mile of rapids has the cleansing power of a modern sewage treatment plant.
Mother Nature is quite capable of clearing up the worst pollution; all she needs are places to work. Provide edges and biology will supply the magic. More edges = more cleaning power.
Heat On Demand: Problem: The fruit industry is 300 miles south of your farm, but you want to grow grapes and peaches. Solution: Use edge effects to create favorable micro-climates for trees and vines. Walk about your farm and wherever there is sufficient catchment area build a pond. Each pond does not have to be large, but the cumulative effects will be significant. Water holds lots of heat and each pond acts like a radiator to warm its local environment. Plant fruit crops on the southeast side of ponds and lakes where temperatures are most favorable. Every pond is an edge, a boundary between separate ecologies each with its own micro-climate. Mulch trees and vines with heat-retaining rocks = more edges. Combining water and rocks can raise canopy temperatures by 5 degrees or more. A few degrees are all that is needed to protect blossoms from frost.
Linear Agriculture: Edge effect farming is all about surfaces = boundaries between different ecologies. Creating more edges fosters more life which in turn enables the environment to support more life. As life abounds the local ecology grows stronger and more stable. Crops become more resistant to insects and more resilient to adverse weather. Result: Farmers make more money.
Would You Like To Know More? Please contact the Author directly if you have any questions or need additional information about edge effect agriculture.
Eric Koperek = firstname.lastname@example.org
About The Author: Mr. Koperek is a plant breeder who farms in Pennsylvania during the summer and Florida during the winter. (Growing two generations each year greatly speeds development of new crop varieties).