Permaculture Designers Manual
CHAPTER 10 –
THE HUMID TROPICS IN PERMACULTURE
Section 10.12 –
Animal Tractor Systems in the Humid Tropics in Permaculture
Following are two examples of animal tractor systems, either of which can be used to prepare soils and remove grasses or persistent weeds for evolution to garden and tree crop.
Confined chicken flocks will remove all green ground cover and surface bulbils, depending on how many are confined and the size of area, thus killing out or consuming such plants as Oxalis, nut-grass, kikuyu, onion weed and pasture species of Convolvulus.
Dano Gorisch, on a 0.5ha farm on Molokai, Hawaii, has planned and executed a successful chicken tractor/garden system on a stony hillside site.
The process is to fence 5-6 plots and rotate a 40-Chicken flock on these plots over a period of 18 months. As each fenced area is scratched bore, it is limed, raked and sowed immediately to vegetable crop (typically Brassica, beans, peas, amaranth, cucurbits, radish or root crop).
The chickens are moved to Plot 2, and in about 6-8 weeks vegetables are in full production on Plot 1.
As Dano also needs a cash crop, he has inter-planted young papaya in Plot 1 amongst the vegetables.
These grow strongly and succeed the vegetable layer, giving high shade and (from the waste fruit), chicken forage in later rotations.
Thus the tractor system proceeds.
Chickens pioneer the weeds, with vegetables and papaya succeeding them.
In about 18 months to 2 years, a more perennial system succeeds the weed layer.
Eggs, chickens, vegetables and papaya are at modest commercial level and both milk goats and chickens are let out onto the paths to eat greens when the pens are bare.
Even rocky or rough country is so prepared for crop by chickens, the main cost being secure pen fencing.
Strong fences also support vine crop and a few larger legume trees provide high shade (Tijuana tipu, larger Albizzia) for pens and crops.
I have now seen numerous chicken tractors, all different, some with passion fruit fence/trellis crop, some just as vegetable gardens and some for small fruit or herbaceous orchard.
All are remarkable for lack of weeds and high production. In the more mature cycles, buckwheat, comfrey, millet, sunflower and sorghum can be sown in the pens a few weeks before the chickens are returned, providing greens and grains.
Where chickens are to be the main crop, chicken forage plants replace vegetables and some fruit crop and the system then provides all food.
Near the house, a few small top-netted and secure rearing pens allow broody hens to replace the chickens culled.
Normal weeds such as Oxalis, cleavers, dandelion, onion weed, nettle and nut grass are excellent chicken fodders, as are any of the Solanum family (huckleberry, black nightshade, pepino, kangaroo apple, tomato, husk berry, Sodom apple. etc.)
The pig tractor follows the same technique but is more suited to 1-40ha properties.
Larger shrub-weeds (Lantana, gorse, and blackberry) or deep-rooted weeds (Convolvulus, rhizomatous grasses, and comfrey) call for a pig tractor.
The density of pigs per pen should be at the proportion of 50/ha for full clearance of weeds.
In practice, 0.5-2ha plots are fenced, most economically using permanent electric fencing, which is much cheaper than chicken mesh fencing.
Once each pen is bare (6-10 weeks) and rough-plowed by rooting pigs, it is easy to plant lucerne, comfrey sets, sunroot (Jerusalem artichoke), sweet potato, Inga trees, papaya, banana and similar crops for pig forages and to keep up this rotation until the pigs return to the pen.
On a large scale (20-40ha), the pig tractor system can pioneer high-quality milk-cow pasture of chicory, dandelion, comfrey, dock, grasses and clover and cows follow along 2-3 months behind the pig tractor.
A continuous rotation is set up, and excess milk product (whey, skim milk) fed to the pigs as accessory food.
Piglets ranging over such pasture rarely show iron anemia deficiency, parasite cycles are broken and the soil constantly improves in humus.
Such large animals as pigs and cows need fenced tree strips, tree guards and border hedgerow to supply tree forage crop.
Obviously, these intensive animal tractor systems can be a phase followed by tree crop, an accessory to tree crop or a permanent feature on the mixed farm or used seasonally to remove crop wastes and fallen fruits.
Chickens, I feel, should be a permanent forage system in all mixed orchards.