Photocopying a 13' section of farmland to measure crop residue is the latest tool in studying erosion control.

USDA is using a stubble scanner, a combination 35mm camera and low-power laser beam to measure image elevation. More than 3,000 elevation points are scanned per second and measured in thousandths of an inch to profile approximately 26 sq ft of field surface.

The profiles created by the stubble scanner are being used by USDA scientists in Kansas and Indiana to study the effectiveness of standing crop residue at preventing erosion.

"Measuring the amount of residue in a field is a key to determining its effectiveness for erosion control," says Denise McWilliams, agronomist for the University of Minnesota Extension Service.

For crop residue to be most effective in controlling erosion, it must be left standing after harvest, she adds.

"Residue left standing can be 10 times more effective at reducing erosion than if it's chopped or tilled," says McWilliams.

New Conservation Tillage Book A publication on crop tillage systems that save soil and improve water quality is available from the Midwest Plan Service.

The second edition of Conservation Tillage Systems and Management: Crop Residue Management with No-Till, Ridge-Till, Mulch-Till and Strip-till includes 120 line drawings and color photos and 72 tables.

Contained in the 29 chapters are sections dealing with conservation tillage, tillage system definitions, wind erosion, water erosion, crop residue, irrigation water management and water quality.

The book also covers costs and returns, estimating residue cover, harvest residue management, crop response to tillage, soil compaction, controlled traffic, and converting CRP acres to production.

More than 60 specialists contributed to the book, which is available for $25 per copy plus sales tax from MWPS, 219 BioAgEng, University of Minnesota, 1390 Eckles Ave., St. Paul, MN 55108; e-mail mwps@gaia.bae.umn.edu or phone 612-625-9733.