Environmental Issues: Health
Fields of Change
A New Crop of American Farmers Finds Alternatives to Pesticides
IOWA CORN AND SOYBEANS
Iowa, more than any other state in the nation, typifies the American vision of agriculture. It is a landscape replete with acre upon acre of grain crops interrupted only occasionally by picturesque farm houses and barns. The heartland and the bread basket, Iowa is the nation's number one corn and soybean producer. In 1995, Iowa farmers produced 1.4 billion bushels of corn on 11 million acres and 398 million bushels of soybeans on a little over 9 million acres.
Other than poor weather, weeds are the greatest threat to Iowa corn and soybean production. Herbicides and mechanical tillage are the dominant methods of weed control. In 1996, an estimated 36 million pounds of herbicides were applied to 99 percent of harvested corn acreage in Iowa. An estimated 10.8 million pounds of herbicides were applied to close to 100 percent of soybean acreage that same year. In addition, 1.8 million pounds of insecticides were applied to 17 percent of Iowa corn acreage.
Surface and groundwater contamination by herbicides is well documented in Iowa. At least 24 different herbicides have been found in Iowa's above-ground drinking water sources. And 760,000 individuals, 95 percent of the Iowa population utilizing surface water, drink from source water contaminated with herbicides.
In recent years, the use of heavy tillage practices in Iowa corn and soybean production has declined and reliance on chemical controls has increased. In response to government-sponsored soil conservation programs, farmers have adopted production practices such as "no-till" that maintain crop residue in the field as a means of reducing soil erosion. Farmers that practice no-till generally increase their use of herbicides for weed control.[25 ] A small number of farmers, such as Paul Mugge, profiled in the following section, utilize innovative methods of tillage that simultaneously reduce reliance on herbicides and prevent soil erosion.
Grasses and broadleaf weeds compete with corn and soybeans for sunlight, water, and nutrients. In a conventional system, weeds are controlled by disking the soil prior to planting, cultivating during the growing season, and applying herbicides both before and after planting. In a no-till system, weeds are primarily controlled with the use of pre-and -post emergence herbicides and limited cultivation to minimize soil erosion. A ridge-till system, in contrast, allows farmers to cut down on their use of herbicides and mechanical cultivation and reduce soil erosion at the same time.
Paul was first introduced to the system of ridge tillage at a meeting sponsored by the U.S. Department of Agriculture's Natural Resources Conservation Service (formerly called the Soil Conservation Service). He tried ridge-till on five percent of his acreage and within three to four years, had converted all of his land to this system. Weed dynamics changed during this time and Paul had to try different herbicides to find the right mix. Overall, however, the ridge-till system has worked extremely well.
In contrast to conventional and no-till systems, in which corn and soybeans are planted in rows in a relatively flat field, ridge-till involves the creation of ridges or pyramid shaped horizontal columns of soil that run the length of the field. In corn, the columns are approximately six inches high and 30 inches apart with six inches pressed flat on the top to create the ridge. In soybeans, ridge height is cut in half to avoid covering bean nodes, the site of pod formation. A crop is planted in the spring by leveling the ridges somewhat and moving residue or stubble from the previous crop into the furrow. This process helps to remove weed seeds away from the top of the ridge where the crop will be grown. Keeping the residue in the field helps to reduce soil erosion, as do the ridges themselves, which act like mini-terraces. Soil compaction in crop rows is reduced because wheel traffic remains in the furrows. Once the crop is about 12 inches high, a special cultivator is used to rebuild the ridges into the pyramid shape, smothering small weeds and reducing weed growth enough that the need for multiple cultivations and/or herbicides is reduced. After a crop is harvested, crop residue is left in the field throughout the winter, thereby minimizing soil erosion. The process begins all over again in the spring.
The creation of ridges allows Paul to continue to cultivate for weed control with minimal disruption of soil and to dramatically reduce his herbicide use. Instead of applying herbicides to the entire field, as was customary in his conventional system, Paul limits herbicide applications to a 10-inch band along the tops of the ridges. While Paul's number of herbicide applications remains the same, he has reduced the area he treats. In total, this has allowed him to reduce the amount of herbicide active ingredient applied per acre by 46 percent in corn and 26 percent in soybeans (see table below).
In 1993, the mid-west experienced an extremely wet year. This made it difficult for most farmers to find a dry window of time to get into the field and cultivate and/or apply herbicides to control weeds. Paul believes that his weed "clean up" job was much less difficult than it would have been because he was using the ridge-till system rather than farming conventionally.
|IOWA CORN AND SOYBEANS|
Ridge-Till Reduces Herbicide Use
|Material||Rate of Application
(pints per acre)
|Rate of Application|
(pints per acre)
|Total Amount Applied Per Acrea||3.25||1.75|
|Material||Rate of Application
(pints per acre)
|Rate of Application|
(pints per acre)
|Total Amount Applied Per Acreb||2.50||1.84|
|a. The frequency of applications was constant and Paul estimated the reduction in rate of application based on reducing the amount of acreage treated|
b. The frequency of applications was constant and Paul estimated the reduction in rate of application based on reducing the amount of acreage treated
Added Benefit: More Earthworms
Since he began using ridge-till, Paul has seen a tremendous increase in earthworm populations in his soil. He attributes this to the fact that he rarely disturbs the soil, thus making it a more hospitable environment for worm reproduction and activities. Earthworms increase soil productivity and structure. Compared to the soil itself, earthworm casts, formed and deposited in the soil as they ingest organic matter, are higher in organic matter and available plant nutrients. The holes left in the soil from earthworm activity serve to increase aeration and drainage which improves crop production. According to Paul, "Earthworms are one of Earth's most under-valued creatures. You could not buy me a big enough tractor to replicate the tillage earthworms create."
Paul has also noticed more abundant wildlife in his fields, particularly deer, since he began using ridge-till. "They come in for the ears of corn left on the ground because we no longer plow those under. They trample crops a bit but don't reduce yields much." He also regularly spots pheasants, partridge, and wild turkeys.
The use of ridge-till is one reason that Paul has seen the organic matter content in his soils rise 20 percent over what they were when he farmed conventionally. Soils high in organic matter have better soil structure allowing for improved water penetration and infiltration. Soils high in organic matter are beneficial for crop production in other ways as well, including generally higher levels of plant nutrients in the soil.
Raising Hogs and Reaping Manure
Hogs are an essential component of Paul's farming operation and he specializes in weaning young hogs. In any given month, Paul has approximately 800 hogs, at least half of which are two to three weeks old. The hogs are born on a separate farm and are brought to Paul's farm to be weaned to avoid catching diseases from their mothers. At the end of the month, Paul sells half the pigs to other farmers who raise them to maturity and he keeps the rest until they are ready for sale to meat packers. Paul feeds the hogs at least six times a day and most of the corn that he grows is fed to the hogs. The manure generated by the hogs is "recycled" and spread on the fields. It has proven to be an excellent source of plant nutrients, particularly, phosphorous and nitrogen. The manure also returns valuable organic matter to Paul's soils.
Testing for Targeted Nitrogen Application
Soil nutrients, particularly nitrogen, are critical for adequate growth of corn and soybean plants. As a conventional farmer, Paul applied nitrogen fertilizers according to a formula recommended by the Iowa State University Extension Service. If his overall yield goal was 150 bushels of corn per acre, then he applied approximately 125 pounds of nitrogen fertilizer per acre. Ten years ago, when the house still received its water from a shallow well, Paul grew concerned about possible nitrate contamination resulting from fertilizer use. He had his water tested and found nitrate and coliform bacteria at levels considered unsafe for adult and infant consumption. When Iowa State University asked him if he was interested in trying out a new soil nitrate test as a means of applying fertilizer more efficiently, Paul jumped at the chance. Now he tests his soil every spring and only applies as much nitrogen as is needed. In the past 6 years since he began using the test, Paul has been able to reduce his nitrogen fertilizer use by 40 percent. Paul also applies nitrogen fertilizers in several smaller applications rather than one or two large applications thereby decreasing the chance that nitrogen left unused by the plant will end up in water supplies.
Pests such as corn borer and corn rootworm can be a serious problem in some corn-producing regions. Paul has rarely ever had to use an insecticide because he rotates his corn with soybeans every other year, which helps destroy over-wintering and potentially damaging pest populations. Occasionally, Paul has problems with the northern corn rootworm, which has developed an extended "diapause," or resting state, to adapt to the corn/soybean rotation. He has sprayed his corn fields twice in the past 20 years for corn borer and his soybean fields once for spider mites. He always makes a practice of scouting his fields to determine pest levels and treating only when populations are considerably above economic thresholds.
Yields and Quality
Although it varies by year, Paul yields approximately 150 bushels of corn per acre and 50 bushels of soybeans per acre, matching average yields for his region. His yields did not change when he converted to the ridge-till system. The quality of his corn and soybeans also remained unchanged.
Paul made an initial investment in the purchase of a special cultivator and attachments for his ridge-till system. Although it cost twice as much as a regular cultivator, Paul has found this investment worthwhile. For the past six years, he has been able to reduce his weed management costs in corn by 17 percent and in soybeans by 46 percent. This is due to reducing the amount of herbicides applied and making fewer trips into the field to disk and cultivate. Paul notes that farms larger than his 320 acres may not lower production costs because they would need to hire additional labor, which is almost always more expensive than applying an herbicide.
|IOWA CORN AND SOYBEANS|
Ridge-Till Lowers Per-Acre Weed Management Costs
Concerns and Recommendations
One of Paul's biggest concerns is his ability to stay in the hog business. Without the hogs, the diversity of his operation is limited and his income is reduced to the sale of cash grains, which are much less profitable than hogs. All around him, small farmers are being replaced by industrial farms that raise a minimum of 1,000 hogs at a time. Paul knows he produces good quality, competitive hogs but he is afraid that it will be increasingly difficult for small farmers, like himself, to have access to hog markets. He has noticed, for example, that some meat packing plants are owned, or at least influenced, by the same people who own the hogs and are obligated, contractually or otherwise, to buy these hogs first.
He plans to continue to reduce pesticide use and would like to see more research directed toward the development of non-chemical weed control practices. He sees promise in new and improved methods of cultivation and the use of cover crops. His biggest hope rests with groups such as the Practical Farmers of Iowa (PFI) and the Leopold Center for Sustainable Agriculture at Iowa State University (ISU). PFI is a non-profit research and education organization that funds on-farm research and Paul has been a board member for the past seven years. "Many people associated with PFI, both farmers, researchers and extension agents at ISU have influenced my philosophy and my farming practices. For example, PFI cooperators, like myself, helped ISU researchers calibrate the late spring nitrate test that has allowed me to reduce fertilizer rates," says Paul.
Paul also recently accepted a position on the Advisory Committee for the University of Iowa's Leopold Center. As one of the only farmers on the committee, he provides a reality check for the applicability of different research projects. For his part, he gets a kick out of interacting with scientists.
Reflecting on the Chief Joseph quote, "Whatever befalls the earth, befalls the children of the earth," Paul notes that we still have a long way to go before we adequately understand ecology and the interrelationship of various biological systems on the farm. In the long run, he believes we need to convert mid-western farms from cash grain producers to renewable energy producers. Paul points to a 1993 report by the Union of Concerned Scientists that provides a road map for reducing the Midwest's reliance on fossil fuels and developing renewable-electric technologies and resources. Because of the Midwest's vast agricultural resources, there is tremendous potential to expand the production of energy crops, including trees and grasses grown specifically for energy.
22. U.S. Department of Agriculture, Agricultural Statistics 1995Ð1996, National Agricultural Statistics Service, 1997, p. IÐ27.
23. U.S. Department of Agriculture, Agricultural Chemical Usage: 1996 Field Crops Summary.
24. Wiles, Richard, et. al., Tap Water Blues: Herbicides in Drinking Water, p. 142.
25. Duffy, Michael, Developing the Next Generation of Weed Management Systems: Economic and Social Challenges, 1996 (draft).
26. Brady, Nyle C., The Nature and Properties of Soils (Tenth Edition) Macmillan Publishing Company: New York, 1990, pp. 250Ð259.
27. Brower, Michael C., et. al., Powering the Midwest: Renewable Electricity for the Economy and the Environment (Executive Summary), Union of Concerned Scientists, 1993, pp.1Ð11.