Soil - Agroecology: The Ecology of Sustainable Food Systems - page 112

REDUCED TILLAGE ON THE THOMPSON FARM

Farmers who want to reduce the frequency and intensity of cultivation and soil disturbance face a major quandary:
how to cultivate less without simultaneously increasing herbicide use? Decades ago, Dick Thompson, a farmer in
Boone, Iowa, realized this was a false choice — it should be possible to reduce both tillage and herbicide use and
yet still control weeds effectively. Dick reasoned that while cultivation killed weeds, it also created the ideal disturbed
environment for their regrowth. The solution must involve cultivating less, and doing so in a way that aided crops
but deterred weeds.
Through extensive experimentation and tinkering, Dick has developed a modified ridge tillage system that,
combined with other farming practices, produces the desired result: the Thompson Farm uses virtually no herbicides,
the soil is tilled much less frequently and intensively than conventional wisdom would dictate, and weeds are not
a problem. In addition, the Thompsons generate about $147 more profit per acre than their conventional neighbors,
and their soil contains about twice as much organic matter.
The ridge tillage works like this: in the spring, special planters shave a little soil — and the weeds and cover
crop growing in it — off the top of each ridge, burying plant residue, weed seeds, and previously applied compost
in the inter-row zone. There, the allelopathic effect of the residue suppresses weed germination. Later, a rotary hoe
lifts soil up around the crops planted in the weed-free area in the middle of the ridges. Weeds are controlled by this
process until the crop is developed enough to suppress weeds itself.
The Thompson's modified ridge tillage system is the centerpiece of their farming operation — or at least the
part that differs most from conventional practice — but it is only one part of a broader management system with
many components.

• Rotations . Whereas many conventional farms in Iowa grow corn continuously, the Thompsons always

rotate their crops. One rotation they've used with success is the five-year sequence of corn-soy-
beans-corn-oats-hay. Rotating crops avoids problems with soil pests and helps maintain soil fertility.
The rotation has a direct connection with the ridge-till system as well: after the four years of row crops
planted on minimally tilled ridgetops, the ridges are flattened for the final crop of hay, which is a
mixture of grasses and legumes. This crop is cut multiple times to help control weeds. During this
ridgeless period, the field is cultivated conventionally, with incorporation of manure deep into the soil
where its fertility is most needed by crops. Then the ridges are re-formed for the corn that begins the
cycle again.

• Cover crops . During winter, the soil in the fields is always covered by a cover crop. At first, the

Thompsons used winter rye and hairy vetch, but after much experimentation, they found that grains
worked best as cover crops. They now plant oats ahead of corn, and rye ahead of soybeans. At the
point in the rotation when hay will be followed by corn, however, they plant a cover crop of rye. In
addition to reducing erosion and nitrate leaching, these cover crops suppress weed growth allelopath-
ically. The weeds that do grow with the cover crop are treated as part of the cover vegetation — they
help provide cover, suppress later-germinating weeds, and contribute organic matter to the soil after
cultivation.

• Livestock integration . The Thompsons raise both beef cattle and hogs, and all their manure — composted

aerobically in special containers — goes into the fields as organic fertilizer. To complete the nutrient
cycling, the livestock are fed hay and crop residue from the crop fields.

Combined, these principles result in both profitability and sustainability, making the Thompson Farm an excellent
model. Every year, hundreds of visitors — ranging from college professors to organic farmers — tour the farm to
learn alternative practices for soil management, erosion control, weed management, and reduced tillage.

featured in the Case Study, is a well-known example of a
successful diversified farm operation that has as its
centerpiece the use of a modified ridge tillage program
(Practical Farmers of Iowa, 2002).
The challenge for research on reduced tillage systems
is how to find ways to reduce tillage without increasing

input costs elsewhere in the system, especially those
involving the use of chemicals or fossil fuels.

S USTAINABLE S OIL M ANAGEMENT

When soil is understood to be a living, dynamic system —
an ecosystem — management for sustainability becomes