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Midwest water quality project matures.

Follow the route of ancient glaciers on a ride with Steve Workman south along U.S Route 23, down the center of Ohio from Columbus to Piketon, and you'll learn a lot about farming and clean drinking water.

Workman is an agricultural engineer hired by USDA's Agricultural Research Service to oversee the daily operations of a groundwater quality project on John Van Meter's 650-acre coern/soybean farm in Piketon.

As he leaves Columbus, Workman points to six small concrete buildings along the Scioto River, which Route 23 crisscrosses for 80 miles until it reaches the Ohio River at the Kentucky border. "Those buildings house wells that pump water from the Scioto River Valley alluvial aquifer to supply some of Columbus' drinking water," he says.

Workman notes that many cities in the United States were built near major rivers for easy transportation. Now populations have increased to the point that the groundwater found in the river valleys is needed to supplement surface supplies. In the midwestern United States, alluvial aquifers provide 90 percent of the drinking water for rural homes and about 40 percent of the urban supply.

The Ohio groundwater quality project is located above one of these alluvial valley aquifers, on 135 acres of the Van Meter farm leased by USDA. It is part of a larger departmental effort to address the public's growing concerns about the effects of farm pesticides and nitrogen from fertilizer and other sources on water quality. This departmental research and education project is known as the Management Systems Evaluation Area (MSEA) program.

The MSEA project focuses on the Midwest Corn Belt and involves eight states: Ohio, Iowa, Missouri, Minnesota, North Dakota, South Dakota, Wisconsin, and Nebraska.

Sites in the project, which is part of the USDA Water Quality Initiative, have varied susceptibility to groundwater contamination, depending on soil types and underlying geologic materials. Begun in late 1989, the initiative receives congressional funding for a coordinated seven-agency program.

Dale Bucks, ARS national program leader for water quality, says the initiative, designed to help farmers comply with voluntary state water quality provisions, is in its fourth year of research and development. "We want to find out how alternative farming systems, best management practices, and new farming system technologies are affecting the quality of water on the soil surface, in the root zone, and underground," he says.

"We're beginning the phase now of extending our results to a regional scale, which is the kind of information state environmental agencies need to do their jobs. We're also beginning to deliver technology to farmers that will help keep chemical levels within Environmental Protection Agency (EPA) guidelines. Information is being relayed to farmers through newsletters, field days, workshops, conferences, media publicity, and surveys."

The water quality initiative involves a close cooperation between USDA research agencies--ARS and the Cooperative State Research Service--as well as with the Soil Conservation Service and Extension Service, which are directly involved with farmers. The cooperation also extends to state universities, as well as to other state and federal agencies such as the U.S. Geological Survey (USGS) and EPA. Funds are pooled from the state, USDA, USGS, and EPA. Environmental and private organizations such as the Leopold Center for Sustainable Agrculture in Iowa are also involved.

"The USDA Water Quality Initiative brings the expertise and money needed to study water quality on an ambitious scale," Bucks says. "It brought funding to pay scientists such as Workman in Ohio and to install the wells needed at each site--as many as 150 in just one Iowa watershed."

An Integrated Project in Ohio

"USGS has worked closely with us in characterizing the Scioto River Valley alluvial aquifer," Workman says.

The aquifer has about 80 feet of sand and gravel deposited by drainage of meltwater from Pleistocene glaciation, with a supply potential of 1.4 billion gallons per day. The water table normally ranges from 5 to 20 feet below the soil surface. Workman explains that USGS is concerned with deep groundwater, whereas USDA's primary research interest traditionally extends only as deep as a crop's roots and to shallow groundwaters.

Typical of both the intense monitoring and close interagency cooperation, Ohio State University graduate student Abe Springer and Martha Jagucki, a USGS geologist in charge of well drilling, lived on the Van Meter farm for 2-1/2 months in the winter of 1990/ 91. They sampled the geological strata every few feet, as 41 wells were drilled in and around the area leased. Twenty-two of these wells have multiple ports for sampling, allowing for 108 sampling locations in the aquifer.

Numerous wells, drilled to various depths, are scattered throughout the research fields in different geological strata to monitor water levels and chemical concentrations. Some are computerized to take measurements automatically every half hour.

Soil moisture probes and other instruments track soil water movement and quality in crop root zones. Soil and water are thoroughly monitored for levels of four to six major herbicides and for nitrates from nitrogen fertilizer, manure, and other sources.

Three farming systems--continuous corn, corn-soybean rotation, and corn-soybean-wheat/hairy vetch rotation on ridges--are being evaluated for water quality impacts and economic viability.

Norm Fausey, the ARS soil scientist in charge of the Ohio research, says that five farmers in the Scioto River watershed have lent sites for demonstrations to show how actual farmers fare with the practices being tested on three 25-acre fields and eighteen 1 -acre plots on the Van Meter farm.

Routine sampling every 2 to 4 weeks includes groundwater from wells, soil water from lysimeters, aboveground plant biomass and nitrogen content, and soil, to determine water content and agrichemical concentrations. Other periodic measurements include root length, canopy cover, crop height and population, pest infestation, and weed biomass.

Fausey says that the Ohio MSEA has a very strong program investigating the influence of farm management systems on soil biological and ecological processes. Clive Edwards and Scott Subler, soil ecologists with Ohio State University (OSU), are monitoring nitrogen as it cycles through plants and soil. They are studying the activity of soil organisms and microorganisms that play a critical role in the process.

Automated weather stations in the fields keep local records around the clock. Thousands of soil samples taken from depths of 4 feet or more are frozen and sent to the ARS National Soil Tilth Laboratory at Ames, Iowa, for analysis.

The Iowa lab is fitted out with robotic equipment for 24-hour-a-day soil analysis. Each robotic system can handle 40 tubes of samples at a time, the equipment automatically performing the many steps involved in pesticide extraction. Local water quality labs analyze water samples following strict quality control standards.

Even rainfall is sampled for herbicide and nitrate content. Plants are dried in ovens, weighed, and analyzed for nutrients and chemicals. Roots are washed, weighed, counted, and measured. Liquid manure used in the corn-soybean-wheat/hairy vetch rotation is analyzed for nutrient content before application.

According to Workman, "Results to date show that the herbicides applied in 1991 have not moved below the top 12 inches of the soil, and nitrogen applied in 1991 as fertilizer has not reached the shallow water table in the aquifer as of June 1993."

OSU soil physical chemist Sam Traina and graduate student Mark Radosevich have isolated a soil microbe that degrades atrazine and its metabolites. And Fausey's counterpart at OSU, Andy Ward, says that the low-chemical-input, ridge-till-based rotation of corn-soybean-wheat/hairy vetch looks very promising from an economic standpoint, because costs are lower and there has been no difference in corn yield compared to the high-input continuous corn rotation.

In Iowa, the Focus Is on Runoff

Jerry Hatfield, head of the National Soil Tilth lab and principal investigator for the Iowa MSEA, says that runoff from heavy spring rains carried high concentrations of atrazine to tributaries of Walnut Creek in central Iowa. "These concentrations are short-lived, lasting a day or two after a rainstorm," Hatfield notes.

Hatfield says his team is evaluating different tillages to see which reduce surface runoff best. They are also testing a nitrogen management system that includes dividing fertilizer applications into several small applications. Such split applications can reduce nitrate in groundwater from more than 20 parts per million (ppm) to near 10 ppm without putting a dent in farm profitability.

The team also found that farmers can lower their fertilizer losses by making more accurate estimates of what their crops will need during the growing season.

Fertilizer applications are usually based on yield projections that may not be met because of weather or other variables. Hatfield says that over the past 12 years of research at the Treynor watersheds in southwest Iowa, farmers reached their yield goals only once. "The high soil nitrate levels we found were due to applications for a yield that was hardly ever realized," he says.

The MSEA project also includes a third major site in northeastern Iowa.

So far, results from the Iowa research show that atrazine and other herbicides are concentrated in the upper foot of topsoil, while nitrate is more uniformly distributed throughout the 4-foot depths sampled eight times a year.

Nitrate concentrations in underground tile drainage lines vary between 10 and 20 ppm, while herbicide concentrations are generally below EPA guidelines. Herbicide levels in shallow wells also fall within guidelines.

Hatfield and colleagues are mapping landscape variations in nitrate and atrazine levels, organic matter and other soil properties, and crop yield across fields in the 12-square-mile Walnut Creek watershed. He says that nitrate infiltration is very dependent on the geologic structure of the area.

For example, nitrate in water moves very slowly through the glacial till layers of the Walnut Creek watershed. Very little reaches deep. At levels below 50 feet in the Walnut Creek watershed, nitrate concentrations are less than 2 ppm. This watershed "has soil conditions representative of a quarter of the state," Hatfield says.

He says that research on sites much larger than normal research plots makes the results from all MSEA sites more transferable and credible to all types of farmers.

"With commercial-size fields, we can let farmers do the farming for us, with their own tractors and equipment," he says. "All the fields in the Walnut Creek watershed are operated by farmers. We give them a concept such as no-till with postemergence weed control, and they offer suggestions on ways to adapt the concept to a particular field. This is instant technology transfer."

Iowa farmers are meeting in focus groups to more formally evaluate the practices and technologies being tested and demonstrated. Hatfield says that sociologists and economists are also interviewing farmers throughout the Midwest to understand what it takes to get farmers to adopt new technology and alternative methods.

This year, the Iowa scientists began experiments with two postemergence herbicides, Accent and Pursuit, that would eliminate the need for preventive treatment before planting.

Similar tests of more environmentally friendly alternative herbicides are being done throughout the Midwest. For example, soil scientist William C. Koskinen, of St. Paul, Minnesota, found that in field tests the postemergence herbicide sethoxydim and its breakdown products leached more slowly than did atrazine or alachlor. Applied at one-tenth the rate of those herbicides, sethoxydim is quickly destroyed by light and water or is broken down by soil microbes soon after killing the weeds.

Meanwhile, Precision Farming in Missouri

In Missouri, ARS soil scientist Gene Alberts says that like Iowa, "we are working with many farmers in the 28-square-mile Goodwater Creek watershed. We have a farmer who is farming three fields for us, each 50 to 90 acres in size. The farmer maintains records of labor; costs of herbicides, fertilizer, other inputs, and machinery; and grain yields and prices. We're using these and other records to assess the profitability of each farming system."

Missouri researchers have developed a laboratory procedure to detect breakdown products formed as the herbicide atrazine degrades. To their surprise, they found these products in streams. They had thought the breakdown products were bound too tightly to soil to move into streams.

Agricultural engineers Kenneth A. Sudduth at Columbia and John W. Hummel at Urbana, Illinois, are working with AGMED, a Springfield, Illinois, company, to develop a portable near-infrared reflectance sensor that measures soil moisture and organic content. The sensor will aid in prescribing correct amounts of soil-applied herbicide. The higher the organic content, the less likely the herbicide will be to leach and the more herbicide can be safely applied. Alberts says that one strength of the Missouri project lies in assembling various technologies and tools into a prescription farming package. He says that all of the Midwest states in the project are finding ways to prescribe more precise applications of farm chemicals that take into account both plant needs and soil vulnerability to chemical leaching. Prescription farming techniques being developed in these states are contributing to a nationwide interest in the method.

The Missouri scientists have developed a tractor-mounted sensor that can detect claypan soil layers. Common in Missouri and other parts of the country, claypan inhibits yield by restricting root growth.

"We're mapping yield and soil variability within a field, as well as the claypan," Alberts says. "We want to relate these to each other and understand field variability and how it affects the movement of herbicides and nitrate to surface and groundwater."

Tillage Systems in the Northern Cornbelt Sand Plains

Robert W. Dowdy, ARS research leader in St. Paul, Minnesota, says the Northern Combelt Sand Plains MSEA project involves Minnesota, North Dakota, South Dakota, and Wisconsin. "The relatively coarse-textured, low-organic-matter soils in this project allow surface water to move down to groundwater fairly rapidly."

Dowdy says that the Northern Cornbelt Sand Plains study is unique because he and his colleagues are studying the same corn/soybean farming system in four states, representing a broad cross-section of soils, climate, and production practices for comparison. "This farming system involves several seldom-used practices that, when packaged into one system, reduce demand for herbicides and fertilizers."

The system consists of applying atrazine and alachlor herbicides in a narrow band, which reduces total chemical use by two-thirds. It also involves nitrogen application on an "as-needed" basis, irrigation timing and quantity based on crop demand, and ridge tillage.

Ridge tillage involves growing crops on raised seedbeds. Farmers typically apply fertilizers and herbicides to the ridges and control weeds between ridges by cultivating.

At the principal research site in Minnesota, this total cropping system is being compared with a more conventional corn production system using full-width tillage, herbicide sprayed across fields, and typical nitrogen applications.

Dowdy says that no atrazine or alachlor attributable to either cropping system has yet been detected in groundwater.

But John A. Lamb, University of Minnesota soil scientist, says that nitrate levels have increased in groundwater under conventional cornfields. He also reports that nitrogen uptake by plants can vary by as much as 35 pounds per acre over a distance of 800 feet in the fine sandy soil that is not as uniform as it looks.

Another source of variability, Dowdy says, is associated with the fact that rainfall moving through the crop canopy (throughfall) is not uniformly delivered to the soil surface. The least throughfall occurs on the downwind side of ridges in the ridge-tillage fields. Cropping systems can be designed to take advantage of this situation to minimize leaching of chemicals. "One example is placing fertilizer on the downwind side," he says.

ARS soil scientists working with University of Minnesota colleagues are measuring soil water distribution in two dimensions, using time-domain reflectometry (TDR). TDR is a modem technique using radar signals sent through electrical cables to measure water movement. So far, their data confirm the throughfall distribution patterns noted by Dowdy. . The technique is also providing information needed to develop predictive models that extrapolate data to other regions of the country.

"Through further studies on the placement of agricultural chemicals, application rates, and tillage practices, we hope to help farmers increase crop production efficiency while minimizing the pollution hazard," Dowdy says. And in Nebraska, Managing Water and Nitrogen

Similar results are coming out of Nebraska. Jim Schepers, the ARS project leader in Nebraska, says that the combination of irrigation with sandy, highly permeable soils makes aquifers in his state particularly vulnerable to nitrate contamination.

Schepers says the researchers have found ways to strategically add nitrogen to irrigation water after analyzing for plant nitrogen status. The addition of nitrogen to irrigation water is currently being used by farmers, but often without monitoring for actual plant needs.

"Instead of applying 150 pounds of fertilizer per acre all at once," Schepers says, "we add just enough to start the seedlings out and then add more once a week or so, but only if plant tissue monitoring calls for it."

"The combination of improving irrigation techniques and adding nitrogen to irrigation water has reduced both water and nitrogen use by up to 50 percent, compared to current practices," he says. "We're finding reduced levels of nitrate in groundwater after 2 years."

Schepers says another strategy under evaluation is placing nitrogen in alternate rows and irrigating only those rows without nitrogen so it is not moved out of the root zone by the water.

"We are also testing deep-rooted crops like alfalfa in rotation with corn, to scavenge nitrate left in the soil."

Putting It All Together

ARS' water quality program leader Bucks says the strength of all the MSEA projects is that they look at the ecosystem as a whole, instead of having individual researchers working on different parts of a system at different locations, with little communication.

"We're studying farming practices and chemicals and their interactions with plants, the soil, soil organisms, and surface and groundwater quality. We're learning that there is considerable variation up and down, as well as side to side, no matter how close or similar two locations are."

Bucks points out that researchers in all the MSEA's have worked together from the beginning of the project to develop common sampling methods and techniques. This uniformity aids in sharing information among the sites.

One common finding has been that herbicides are more often found in streams and lakes, while nitrate is more common in groundwater.

"We're finding that nitrate-nitrogen levels in groundwater periodically exceed the EPA guideline for drinking water--10 parts per million--at certain locations in all the states studied, with levels of 30 to 40 ppm more common in the irrigated sands of Nebraska," he says. "And Iowa has found nitrate levels as high as 35 ppm in streams after heavy spring rains.

"We generally aren't finding any herbicides in deep groundwater, but we've detected some in shallow groundwater," he says. "In surface water, we've found atrazine levels as high as 75 parts per billion (ppb) in spring runoff in Iowa, with 3 ppb being the EPA guideline for drinking water. We've found metolachlor levels up to 29 parts per billion, above the EPA guideline of 10 ppb. But the seasonal averages of it and the other herbicides are usually below EPA guidelines. We must recognize that there is tremendous variability in the timing, amounts, and distribution of herbicides being found in surface and groundwater."

Bucks says that "to transfer technology to farmers, people in different agencies and disciplines--ecologists, agronomists, soil scientists, engineers, geologists, computer modelers--have to talk to each other and combine their work into a package farmers can use.

"Besides the unusually extensive instrumentation and sampling involved, the MSEA projects are unique in that they approach research problems from a variety of perspectives. For example, soil ecosystem scientists examine the effects of different practices on soil biological processes. The results of their work are in turn used by soil physicists and agricultural engineers to model the movement of nitrates under fields. This information is then combined with that of hydrogeologists who evaluate nitrate transport in groundwater under entire landscapes.

"In this way," Bucks says, "a complete picture is developed of the movement of nitrates and herbicides from the soil surface to deep aquifers and across crop rows and landscapes. The ecosystem perspective requires integrating diverse research activities into a meaningful whole."

A Dip-Stick Test for Soil Nitrogen

Scientists in the Nebraska MSEA unit are evaluating a "last-minute" soil nitrate test as a promising means of reducing nitrogen use by corn farmers.

The overnight test, called the presidedress soil nitrate test (PSNT) was developed by University of Vermont researcher Fred Magdoff. It is done after the corn has grown about a foot tall, rather than before planting as is traditionally done. The test allows farmers to avoid applying large quantities of fertilizer at planting time, based on estimates of what might be appropriate. Instead, it tells them if soil nitrogen is adequate for the crop, or if sidedress nitrogen is needed.

Corn uses large amounts of nitrogen, phosphorus, and potassium--the key ingredients in commercial fertilizers. But the only thing constant about nitrogen is the fact that it's always moving and changing.

When fertilizer nitrogen is added to corn before planting, the nitrogen can leach through the soil and be lost or tied up by soil microorganisms before the plant is ready to use it. So farmers from east to west who planted an estimated 76,486,000 acres of corn for grain use in the 1993 crop year have planned their nitrogen applications carefully--whether, when, and how much to apply.

ARS soil scientist James S. Schepers in Lincoln, Nebraska, serves on a regional committee that devotes at least half its time to evaluating the PSNT. The committee is made up of ARS and university researchers from Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Missouri, Ohio, Nebraska, North and South Dakota, and Wisconsin.

Schepers and University of Nebraska researchers have been evaluating the test for the last 6 years. It has been in limited use east of the Mississippi for about 9.

Each PSNT sample is taken from a 1-foot depth, dried overnight, and mixed with an extraction solution provided in the the kit. A nitrate test strip is dipped in the solution and then checked with a digital meter that indicates the color intensity: the mom purple, the more nitrate is in the sample.

Commercial soil testing laboratories can also perform this chemical test.

In Beltsville, Maryland, ARS soil scientist Jack Meisinger, who works with the regional committee, has been evaluating the test in cooperative studies with the University of Maryland in an effort to reduce nitrate concentrations that end up in the Chesapeake Bay.

"It really helps identify fields that don't need extra nitrogen fertilizer," Meisinger says.

Schepers also uses a chlorophyll meter to check corn for greenness, which indicates nitrogen status. it gives farmers guidance as to when to liquid nitrogen to irrigation water More than 5 million acres of corn are irrigated in the state of Nebraska alone, so fine-tuning inputs could reduce costly excesses.

But he says that using the chlorophyll meter doesn't mean that farmers shouldn't apply starter fertilizer. "With this method, early-season application of nitrogen is still needed to get the plant to 18 inches in height That's when the chlorophyll meter becomes reliable and remains a good management tool until after corn silking," says Schepers.

To contact scientists mentioned in this article, write or telephone Don Comis, Room 446, 6303 Ivy Lane, Greenbelt, MD 20770; phone (301) 344-2748, fax (301) 344-2311.
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Title Annotation:also includes related article on soil nitrate testing
Author:Comis, Don; Hardin, Ben; Cooke, Linda
Publication:Agricultural Research
Date:Sep 1, 1993
Previous Article:The MSEA water quality research program.
Next Article:Shrinking screwworm's domain: ARS assists FAO in groundwork for eradication effort.

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