Soil crusting from cropped soils can cause serious erosion problems due to increased runoff water. The best way to overcome this is by applying chemicals like gypsum and polyarcylamide (PAM) and increasing plant canopy surface cover. The two together, say ARS scientists who tested several solutions to surface soil crusting, are very effective in combating water runoff and soil loss on cultivated soils. After studying four crust-preventing practices (tillage, canopy cover, gypsum, and PAM) on six 11.5-by 3-foot field plots of Cecil soil under natural rainfall conditions, they found gypsum and PAM were effective in reducing both runoff and soil loss. Breaking surface crust by tillage worked for short, mild storms but was not as effective for high intensity storms. Canopy cover was much more efficient in reducing soil loss than in reducing runoff. By controlling surface sealing and crusting, more water infiltrates soil and less soil is lost by surface sealing. This information will be useful to farmers and land planners.
National Soil Erosion Research, West Lafayette, IN
Mark Nearing, (317) 494-8683

Native shrubs can be successfully planted on western lands being reclaimed after strip-mining operations. However, seeding rates may need to be increased and seeding methods may have to be improved to comply with reclamation requirements. ARS scientists examined seedings made by strip mining companies 10 to 15 years ago at 14 reclaimed sites throughout Wyoming. Areas seeded at 1,000 shrub seeds per square meter now have shrub densities of 0.6 per square meter. Areas seeded at lower rates had lower densities. The Wyoming state reclamation requirement is for one (1.0) shrub per square meter on 20 percent of the reclaimed surface. The scientists do not advise mining companies to seed at rates higher than 1000 seeds per square meter because that does not appear to substantially increase shrub density. The original seedings were of fourwing saltbush, sagebrush, grass or a combination of these plants. Shrub density and composition varied by site, but typically reflected the seed mixtures used. Scientists say precipitation and temperature are significant variables in seeding success, especially with sagebrush. Some years, like 1993, are just right for sagebrush survival while other years resulted in less success. Scientists can't do much to control the weather but they are looking for methods to substitute for the 1993-like conditions. One such possibility might be to use a mulch to slow moisture loss and keep temperatures cooler in the summer.
High Plains Grasslands Research Station, Cheyenne, WY
D. Terrance Booth, (307) 772-2433, tbooth@lamar.colostate.edu

Careful timing of corn ridge-till cultivation could allow farmers to cut back on insecticide treatments against corn rootworms. In ridge tilling, the cultivator throws dirt up around the base of the corn plant. Corn plants that had at least seven leaves before ridge tilling produced more brace roots, scientists found. Corn with a stronger brace root system is less likely to fall to the ground after rootworm damage. Because rootworm damage is usually restricted to older roots that are lower on the stem, new brace roots higher up on the plant may help corn plants tolerate some rootworm damage. In the three-year experiment, researchers found grain yields generally unaffected by ridge tilling. But when the tilling was postponed to the seven-leaf stage, ridging the soil increased the number of brace roots by five to eight roots.
National Soil Tilth Laboratory, Ames, IA
Thomas C. Kaspar, (515) 294-8873, kaspar@nstl.gov

For the first time, research has revealed how a small stream can contaminate an aquifer with agricultural chemicals. Walnut Creek, a tributary of the South Skunk River near Ames, Iowa, is a typical small stream. Before flowing into the river, the creek passes over a sand and gravel aquifer. ARS scientists confirmed the movement of water through the creek bed and into the underlying aquifer by measuring water levels in the aquifer and flow in the stream on two sampling dates. Chemical analyses of 24 water samples showed that the water entering the aquifer contained nitrate and herbicides, including atrazine. The researchers estimate that the creek could contribute up to 10,000 times more atrazine to the aquifer than leaching through a field with an area equal to that of the stream bed. The stream and aquifer conditions studied are common in the Corn Belt. Alluvial aquifers, sometimes called "buried valley aquifers," are found near most major rivers in the Corn Belt.
National Soil Tilth Laboratory, Ames, IA
Michael R. Burkart, (515) 294-5809

The soil's ability to absorb sound waves can provide major clues to its physical characteristics, such as porosity or resistance to air flow. ARS scientists collaborated with specialists at the University of Mississippi's National Center for Physical Acoustics, Oxford, Mississippi, to develop a probe microphone and a procedure to help measure these characteristics. The procedure determines how well sound waves penetrate up to 4 inches of soil. The new technology allows the soil properties to be measured quickly without disturbing the soil profile by digging. The same technology also could help determine sediment concentrations in water flow--useful information in devising strategies for protecting stream beds from filling up with sediment.
National Sedimentation Laboratory, Oxford, MS
Mathias J. Romkens, (601) 232-2927

Last Updated: April 25, 1997
Return to: Quarterly Report Table of Contents