1995 Annual Report for LNC95-086
Reduced Chemical Inputs in Alternative Potato Farming Systems
In Wisconsin, dairy farms epitomize the image of sustainable family farming. However, dairy
farms are being lost rapidly due to several factors. The dairy farm has specialized in the
production of a single commodity, milk. Crops grown on most dairy farms have primary value
only as on-farm inputs for milk production. Corn and forage prices preclude these crops as
significant sources of cash receipts. As the price of milk has stagnated and costs have gone up,
economic hard times have resulted. A solution for some may be diversification to eliminate total
dependence on one commodity. To be sustainable, diversification should result in
complementarily between the subsystems on the farm. The potato subsystem and the diary
subsystem on a diversified farm have great complementary potential that could allow the
reduction in off-farm costs.
1) To establish, monitor and demonstrate field scale reduced chemical potato plots on farms
outside the central sands potato region of Wisconsin with the participation of dairy/livestock
farmers and potato growers.
2) To demonstrate the potential of using alternative row spacing and mechanical vine removal as
advantages of growing potatoes in a mixed crop/livestock farming system.
A combination of field size plots on farms and research size plots on farms and experiment
stations were utilized. Two dairy farmers established potato fields of approximately 40 acres
each in 1996. Data were collected weekly on pest infestation levels. Yields and economic data
were collected in the fall. Replicated field plots were established for the purpose of determining
the impact of vine removal on early blight and early dying. Treatments included a check with no
potatoes the previous year, plots with vines from the previous year, and plots with vines removed
from the previous year. Four methods of removing vines were tested, including: a modified sweet
potato vine puller, a commercial vine puller from Europe, a corn silage chopper with a knife for
cutting the stems, and a flail chopper. Each implement was modified to allow vines to be picked
up from the furrows between the rows.
Silage was produced in the fall of 1995 by hand harvesting and mixing vines with other materials
in mini silos for potential use as livestock feed.
Fields grown by the dairy farmers produced approximately 300cwt per acre at a cost of
approximately $900 per acre. The average cost of potato production in the central sands regions
was estimated by the Wisconsin Potato and Vegetable Growers Association to be $1,700. The
difference in production costs was due in part to reduced pesticide usage (approximately $250),
reduced equipment costs (e.g. tractors were used most of the year for the dairy operation and
were prorated for time spent on potatoes), and labor costs. Late blight did not occur on these
farms while it was prevalent in the commercial production regions. Unfortunately,
overproduction on a national basis dramatically depressed prices received by farmers.
Nevertheless, the diversified farming systems absorbed the loss better than some potato growers.
Pesticide inputs were reduced by over 50 percent compared with the central sands production
area. Chemical fertilizer was not reduced since neither farmer took advantage of rotation
following alfalfa in 1996. This was due in part to the scarcity of alfalfa and its price.
Several methods of harvesting potato vines were demonstrated to be feasible. The corn chopper
with a scissors type cutting mechanism worked well and was preferable because it did not result
in dirt contaminating the chopped vines. In experiments to determine if skin set was effected by
vine removal it was found that a small effect occurred. Potatoes set skins slightly faster when
vines were pulled as opposed to not removed but killed with a vine desiccant.
Silage production potential was clearly demonstrated by the experiments with mini silos. While
ash content and non-digestible fiber were higher in silage made with potato vines, the overall
quality was quite good. Moisture content was easily controlled by blending vines with other
Potential Contributions and Practical Applications:
The work to date demonstrates the feasibility of growing potatoes in conjunction with livestock
to take advantage of ecological services provided by each subsystem to the other. Pesticide and
chemical fertilizer use is reduced significantly. Cull potatoes and potato vines provide
inexpensive feed. Removing vines may reduce future disease. These results are not only
applicable to dairy farmers but to current commercial potato growers as well.
Areas Needing Further Study:
The economic documentation needs to be improved, and more research is needed on the impact
of vine removal on disease. A prototype machine for harvesting vines is desperately needed
before potato growers can recognize the possible benefits of removing vines.