Three renovated Mississippi lakes have been restocked with fish in a long-term research program to track the nation's water quality. In the Mississippi Delta Management Systems Evaluation Area project, ARS scientists are obtaining new information on controlling detrimental environmental effects of sediment, fertilizer and pesticides from farmland. The scientists already see one strong trend: improved farm practices mean less sediment is reaching the lakes. Sediment is a prime factor limiting fish production. It will take several years, however, to measure comprehensively how farm practices affect water quality and fish populations. The information will be used to develop educational and public awareness programs. ARS scientists worked with the Mississippi Department of Wildlife Fisheries and Parks to restock the lakes with bluegill and redear sunfish fingerlings and channel catfish in fall 1996 and with bass in spring 1997. Stocking rates were as follows: Thighman Lake (Sunflower Co.) 16,250 bluegill/redear, 1,250 catfish, 2,500 bass; Beasley Lake (Sunflower Co.), 39,000 bluegill/redear, 3,000 catfish, 4,000 bass; Deep Hollow Lake (Lefore Co.), 13,000 bluegill/redear, 1,000 catfish, 2,000 bass.
National Sedimentation Lab, Oxford, MS
Scott Knight, (601) 232-2934, knight@sedlab.olemiss.edu

Crop residue left on the soil may lower the amount of atrazine, a weed-killing chemical, in runoff to surface waters or leached into ground water. That's because the residue eventually boosts the soil's organic matter. An ARS study has shown that landscape position and soil organic carbon content greatly influence the amount of atrazine absorbed by the soil. The study focused on absorption of atrazine in glacial soils in Iowa and sandy soil in South Carolina under various tillage practices, including conservation tillage that leaves crop stubble on the ground. The researchers selected atrazine because of its heavy use and frequent detection in ground and surface water, especially in corn-growing states like Illinois, Iowa, and Nebraska. Although conservation tillage may not solve pesticide leaching problems in all soils, researchers can use these findings to help farmers fine- tune tillage practices to reduce contamination of ground and surface waters. The residue cover from conservation tillage has the potential to reduce atrazine runoff to surface waters in early spring.
Coastal Plains Soil, Water and Plant Research Center, Florence, SC
Jeffrey M. Novak, (803) 669-5203, novak@florence.ars.usda.gov

Farmers who irrigate their crops could save more than $9 per acre each year by using ARS-developed computer programs to schedule irrigation. That's the finding from an 10-year ARS study in Kansas. Researchers hope data from the study will convince other farmers to schedule irrigation. The ARS scheduling programs calculate water needs by incorporating local weather data with complex equations that account for all water used—including moisture transpired from plant leaves and evaporated from the soil. The study on a 4,200-acre farm in south-central Kansas revealed that farmers who use scheduling programs apply about 20 percent less water than neighbors who water when crops "look thirsty." Pumping less water cuts energy use and reduces the risk of flushing fertilizer below crop roots. Wasted fertilizer not only costs farmers directly but also is a potential contaminant to water supplies. Five percent of the 190,000 irrigated farms in the 27 leading agricultural states use a commercial scheduling service. Another 2.5 percent use their own computers to generate a schedule.
Water Management Research, Fort Collins, CO
Gerald W. Buchleiter, phone (970) 491-8213, jerry@lily.colostate.edu

A new tillage technique combines the best of conventional and conservation tillage techniques to control both weeds and erosion. With the new "mow-plow" method, a standard moldboard plow, pulled by a tractor, deeply tills the soil and buries weed seeds so they don't sprout. However, soil-protecting stems, stalks and other residue from a previous crop don't get buried. That's because of a modified combine header attached to the tractor's front end. The header cuts and lifts old stubble that lies in the plow's path, then dumps it on the adjacent, freshly plowed furrows. There, it shields the soil from erosion. ARS scientists developed the technique for the 4.5-million-acre wheat-growing region of Washington, Oregon, and Idaho. The region receives little rainfall; land is left fallow every other year to collect water for the next year's wheat crop. But the soil often freezes during winter, so rain and melting snow water don't soak into the soil. Instead, the water washes away soil--up to 150 tons an acre. Normally, farmers leave crop residue on the field as long as possible, but weeds can take over during the fallow year. With the mow-plow method, growers should be able to manage both weeds and erosion.
Columbia Plateau Conservation Research Center, Pendleton, OR
Dale E. Wilkins, (541) 278-3292, wilkinsd@ccmail.orst.edu

Advances in understanding of the positive relationship between the ecology of soil microbes and nutrient availability could someday enable farmers to take better advantage of stored nutrients in soil and use less commercial fertilizer. For the past 10 years, ARS scientists have been studying prairie-derived Midwestern agricultural soils as well as soils from the North American Great Plains and other sites across the United States. They examine soil organic matter, nutrient cycling, and tiny soil clumps called aggregates. Unbroken, intact aggregates are "glued" together by organic material produced by soil microbes as they dine on bits of decaying roots and transform them into particulate organic matter or POM—a rich source of nutrients. The scientists found that when tillage breaks up soil aggregates, the nutrient- rich organic matter that was within them quickly decomposes. The nutrients are released when no plants are growing that can use them. These nutrients are often lost to leaching. By contrast, in untilled native prairie, nutrient-use is efficient and, as a result, leaching losses are low. In undisturbed prairies, microbes and plants are "in sync"—nutrients are released when and where the plants are ready to use them.
National Soil Tilth Lab, Ames, IA
Cynthia Cambardella, (515) 294-2921, cindyc@nstl.gov

A newly discovered protein produced by fungi may be the "glue" that holds soils together in granules, making it easier for air and water to move through the soil. This improved circulation helps water move down to plant roots and creates a healthier environment for plants and beneficial microorganisms in the soil. The ARS scientist who discovered the new protein named it "glomalin" for the Glomales fungi that secrete the gooey substance. One early discovery: Farming practices can affect glomalin levels. In tests, the granules from no-till corn plots were more stable and contained more glomalin than those from tilled plots. Soils with well-stabilized granular structure are less prone to erosion by wind or water. Tests of soils from across the United States show glomalin is most abundant in eastern soils, accounting for up to 2 percent of the weight of a soil granule. ARS scientists have also related glomalin to stability of soil granules from samples sent from around the world.
Soil Microbial Systems Lab, Beltsville, MD
Sara E. Wright, (301) 504-8156, swright@asrr.arsuda.gov

Simulated rainfall studies show farmers who take land out of USDA's Conservation Reserve Program (CRP) should minimize cultivation and plant cover crops. This will hold down soil erosion and boost the soil's ability to retain vital water. Another recommendation: Plant hay and graze pastures instead of growing row crops such as corn. ARS scientists used rainfall simulators to measure soil and water movement on plots of former CRP land. They found a rapid increase in soil erosion on environmentally fragile land. The multistate studies focused mostly on areas west of the Mississippi River where CRP acreage is widespread. Under the CRP, farmers voluntarily sign a 10-year contract to take environmentally fragile land out of production. Approximately 36 million acres of land west of the Mississippi River have been enrolled in CRP since the program began in 1986. The first contracts expired Dec. 31, 1995. Tillage on former CRP land without protective conservation practices could accelerate soil erosion and nonpoint water pollution, wiping out environmental gains accrued during participation in the program.
Soil and Water Conservation Research, Lincoln, NE
John E. Gilley, (402) 472-2975, jgilley@unlinfo.unl.edu

Thanks largely to ARS research, 13 western States in the past 3 years have approved farm use of an erosion- fighting white powder called polyacrylamide, or PAM. State regulatory agencies made their decisions using data from large-scale field tests by ARS scientists in Idaho. The tests showed that an ounce of water-soluble, negatively charged PAM mixed with irrigation water anchors as much as 1,000 pounds of topsoil that might otherwise be swept away when irrigation water rushes down furrows. ARS scientists also developed a new test to detect PAM residue in runoff water. The assay showed that 99 percent of the applied PAM remains on treated fields to safely biodegrade if mixed with irrigation water at the prescribed rate of 10 parts per million. That's a tablespoon of PAM for every 750 gallons of irrigation water until the first of this water reaches the end of the furrow. The efficient, cost-effective techniques that the scientists produced for using PAM on furrow-irrigated fields boosted use of the soil-saver on U.S. farms to more than 400,000 acres in 1996.
Northwest Irrigation and Soils Research Lab, Kimberly, ID
Rodrick D. Lentz (208) 423-5582, lentz@kimberly.ars.pn.usbr.gov

Over the next 50 to 100 years, western mountain snowpacks may gradually supply less water from melting snow in late spring because of global warming. That's because the warmer year-round temperatures could result in winter precipitation in the form of rain rather than snow, and the rainwater runs off immediately. The warmer winter temperatures also would increase snowpack moisture loss from melting and evaporation. Those are just two of the predictions from new ARS computer modeling studies. The ARS researchers used three different computer-based mathematical models to predict potential snowmelt changes in seven basins. They assumed an average temperature increase of 5 to 9 degrees F, a range used by many climate researchers worldwide. The ARS analysis was the first of its kind to represent a diverse array of western watersheds. One finding: Overall yield from watersheds—measured by water flow from rain- and snow-fed streams—might be up to 30 percent less than in 1975, the year the scientists selected for comparison. High-elevation watersheds provide 50 to 80 percent of the West's water for farmers, city dwellers, and other downstream users. Since the changes should be gradual, farmers and others have time to prepare. Farmers, for example, will need to know what kinds of crops could perform best under the changed conditions. The scientists are expanding and fine-tuning the forecast models. Northwest Watershed Research Center, Boise ID
Keith R. Cooley, (208) 422-0719, kcooley@nwrc.ars.pn.usbr.gov
Hydrology Lab, Beltsville, MD
Albert Rango, (301) 504-8700, alrango@hydrolab.arsusda.gov

An experimental irrigation system is applying precise amounts of water and chemicals to a Colorado corn field to hold down costs and maximize farm profits while protecting the environment. Engineers with ARS and Valmont Industries developed the applicators to apply water and dissolved fertilizer or herbicide at rates ranging from 3 to 200 gallons per acre in a single pass. Application rates vary according to plant needs in different areas of the 26-acre test field. One part of the system is a modification of a self-propelled linear sprinkler—basically a big pipe that passes over the crop from one end of the field to the other. Groups of computer-controlled conventional sprinkler heads operate independently, delivering precise but varying amounts of water as needed across the field. The system's second part is a low-volume applicator with smaller sprinkler heads programmed to spray at intervals ranging from 4 seconds to 1 minute to apply agricultural chemicals. Computers and a commercial radio telemetry system control the application patterns for both parts of the system. After three growing seasons, researchers are encouraged by the savings in water and chemical use. Future modifications could incorporate satellite images to better target and control water applications.
Water Management Research, Fort Collins, CO
Harold R. Duke, (970) 491-8230, hrduke@aerc.colostate.edu

Last Updated: October 28, 1997
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