Overstory #180 - Animal tractor systems
When planned and managed properly, animals can be key components in sustainable farming systems, enhancing important cycles of nature such as nutrient cycling and balancing of insect populations. A well-designed system with animals can also greatly reduce the human labor required to care for the animals and to prepare and maintain crop areas.
Animal tractor systems are a sustainable, cost-effective, and humane way to integrate animals into an agricultural system. Although the term "tractor" can be confusing, animal tractor systems do not involve draft animals.
Animal tractors are shelter-pen systems where animals such as chickens, turkeys, geese, ducks, pigs, or goats become integral parts of agricultural environments. In animal tractor systems, the animals are managed for productivity of eggs, milk, or meat. At the same time, the scratching, pecking, tilling, and manure spreading behavior of animals is used to prepare, clean, or maintain planting areas.
In this issue of The Overstory, special guest author Andy Lee shares his extensive personal experience working with animals including chickens, pigs, turkeys, and goats in effective animal tractor systems. He describes animal tractors for many purposes, including market garden operations, orchard settings, pond preparation, land clearing, and pasture improvement/diversification.
The key to creating an effective animal tractor system is to integrate the needs, behaviors, and products of the animals with the farm system as a whole. An animal tractor locates animals where its food is abundant, where the animal enjoys relative freedom, and where the natural behaviors of the animal are put to best use. By having an animal in the right location, the need to be fed, watered, and cared for by humans is minimized.
Animal tractors bring into harmony the relationships between farmers, the agroecosystem, and animals. The animal provides a handy tillage tool with its continual scratching, pecking, or rooting behavior. It becomes a biomass recycler, consuming excess weeds, grasses, insects, etc. The manure returns to the earth as fertility for the crops.
Animal tractor systems can be very effective for ground cover maintenance, and work well with orchard or tree crops. In an orchard animal tractor system, the animals are rotated through the orchard, either in movable pens or in a series of fixed paddocks. When at the proper density, the animals clean the area between and under the trees of grasses, weeds, and weed seeds, scavenge wastes and windfall fruits, and eat insects and their larvae. At the same time, the animals add their manure to help fertilize the crops. When the pen area has been cleared and fertilized by the animals, they are moved on to the next section of orchard.
With the appropriate combination of animals and crop trees, this system has been effective with chickens, guinea fowl, turkey, pheasant, quail, sheep, and pigs. On a healthy mixed diet from the orchard, animals tend to have less disease problems.
Lighter animals such as chickens or other poultry can be rotated permanently through an orchard system. More intensive animal tractor systems, for example with pigs, can be very useful in orchard establishment as well as for seasonal maintenance. The system can be further adapted to be more productive by mixing tree species that provide additional food for the animals; for example papaya, banana, and inga (ice cream bean).
Poultry such as chickens and turkeys are excellent for preparing and fertilizing garden areas. In such systems, the poultry are confined to an area in sufficient density to remove virtually all green matter, fallen fruit, insects, etc. When an area is grazed clean, the animals are moved to a fresh area.
In our case, we use turkeys to fertilize and prepare our market gardens. At the end of each garden season in the Fall we herd turkeys into our enclosed gardens to graze. They eat crop residue and weeds right down to bare ground in no time. Then we harvest the turkeys for the holidays and unroll round bales of hay to mulch the gardens for the winter. The following spring we transplant our garden crops right into the mulch.
To establish a new garden site we use a tractor-powered spading machine to work up the plot. In following years we rely solely upon the turkeys for clean up and fertilizing, and the mulch for soil stability and weed control. Underneath the mulch the soil stays wonderfully loose, sopping up rain and providing a great habitat for soil dwellers and plant roots. Our yields are always well above national averages, and our soil gets richer year by year.
Portable tractor systems are also very effective with chickens. For household production, 120 sq. foot (11 sq. meter) pasture pens are just fine for up to 30 layers or 80 broilers. On a commercial scale, such small pens are too costly and labor intensive for the number of birds each can house. We use a portable ranging system, where we house the birds at night and enclose them in a 1700 sq. foot (160 sq. meter) area during the day inside a portable electric netting. This way we can double or even triple the number of birds per shelter, and still be able to move them easily on a daily or weekly basis.
Removing deep rooted woody weeds requires the power of a pig tractor. A pig tractor works much the same as poultry tractors. Instead of scratching, it is the rooting behavior of the pigs which is used. Pig tractors can be used to prepare land for permanent tree crops or rotated seasonally to clean up crop wastes or fallen fruits.
My father used pigs to root out a pasture in a cut over wood lot on our farm in Southwest Missouri. To encourage the pigs to root at the stumps, he dug holes around the roots of oak and hickory and filled them with shell corn. He then turned in the hogs.
In a few months the stumps were rooted out and the ground was completely churned up. After taking out the stumps, the bare ground was disc harrowed and planted to permanent pasture with scattered trees. The whole process took about a year, but the results were excellent. I returned to my father's farm forty years later, and found the pasture is still thriving, with cattle grazing amongst the trees that offer shelter and shade.
Another application for the pig tractor is in pond preparation. In this case the wallowing and rooting behavior of the pigs, along with their manure and trampled crop residue combine to make a watertight pond bottom.
In my family's case, we have had very good results turning boggy garden areas into ponds. First, we turn feeder pigs into the garden and let them eat crop residue and weeds. The pigs love to wallow and root in the boggy areas. After the area is thoroughly worked over by the pigs, we use a grader to scoop out the pond. We then return the pigs to wallow some more.
The combination of compaction and gleying (similar to gluing) of manure and plant residue creates a perfect pond bottom that holds water for years. Any time the pond starts to leak, we'd just put a pig or two in there for a few days. Ponds usually leak at the water level, and that's where the pigs do the most good. Half in and half out of the water they lay there for hours just slicking the pond side to a impermeable surface, fixing leaks we can't see.
Pasture improvement and diversification
Animal tractors can be used very effectively to revitalize and diversify pasture. Using pig and chicken tractors in mobile enclosures can greatly enhance the pasture.
We use beef cattle followed by a chicken tractor to improve our pasture. We only raise a few cattle inside portable electric sheep netting (7000 sq. ft or 650 sq meters). We stock the enclosures so that the cattle daily chew the grass down low enough for the chickens to graze on it. The chickens follow the beef by a week. The time between gives the manure pats time to dry out, for seeds to germinate, and for parasites to become larvae. The chickens scratch the cow pats completely apart, spreading the fertility of the cow pat over a much larger area and eliminating the large cow-pats found in conventionally grazed fields. At the same time, the chickens sanitize the pasture by eating weed seeds and grain that passed through the cows, and eating the parasite larvae. This breaks up the parasite cycle and makes it safe to graze the cattle across the field in controlled rotations without concern for reinfecting them with stomach parasites.
We also use pig tractors in our permanent pasture. Each tractor occupies 130 sq. feet (12 sq. meters), and is roofed and enclosed on one end with sheet metal roofing to shelter the pigs. The pig tractor is on wheels so we can move it easily each morning when we do chores. Leaving the pigs at any one place for just one day churns up a small area of pasture. As soon as we move the pig tractor to its next spot we throw grass and clover seed on the rooted up area to diversify the pasture vegetation.
Various animals can be used to prepare land, depending on the condition of the vegetation. For lightly vegetated land prone to erosion, a movable poultry tractor works well to quickly remove the tops of weeds and lay down a light coat of manure, in preparation for planting permanent ground covers such as grass, legumes or other protective plants.
Where vegetation is too rough for poultry, pigs, goats or cattle can be used to prepare land for production. For example, on parts of our land crowded with red cedar and black locust sprouts, Virginia creeper, honeysuckle and multi-flora rose, we use goats to clean up the vegetation (Boar meat goats). We use the goats to prepare the land ahead of the chickens, again relying on the poultry to spread the manure and break up parasite cycles.
Here at Good Earth Farm in Central Virginia, USA, our livestock and poultry are reclaiming a 40-acre Shenandoah Valley farm. The results we are seeing are gratifying, especially knowing that we have not spent any money on fertilizer, and in all likelihood we'll never have to, as long as we keep rotating the animals to where they are needed.
The livestock and poultry are also our cash income, to pay for the land and house, and to keep us clothed. Without them we would both have to work off the farm to make ends meet. Instead, we live the kind of life we have always dreamed about, and look forward to sharing our knowledge with others who are ready to learn.
Lee, A. 1998. Chicken Tractor, The Permaculture Guide to Happy Hens and Healthy Soils, 2nd ed. Good Earth Publications, Buena Vista, VA.
Mollison, B. 1990. Permaculture A Practical Guide for a Sustainable Future. Island Press, Washington, DC.
Morrow, R. 2000. Earth User's Guide to Permaculture. Simon & Schuster, Australia.
This article was originally published in The Overstory
Lee, A. 2000. Animal tractor systems. The Overstory #50. Permanent Agriculture Resources, Holualoa, Hawaii. http//www.agroforestry.net/overstory/overstory50.html
For more information about the author and his publications, see
About the author
Andy Lee is a well known speaker and small farm advocate, and the author of Backyard Market Gardening. He and his business partner Patricia Foreman authored Chicken Tractor, The Permaculture Guide to Happy Hens and Healthy Soils. Their books are available at Good Earth Publications Company, which publishes books on self-reliant living and sustainable small-scale agriculture. You can reach Andy at