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ARS Home » Research » Publications at this Location » Publication #63695
Title: MEASUREMENT OF WHEAT RESIDUE COVER IN GREAT PLAINS AND PACIFIC NORTHWEST

Author
item Morrison Jr, John
item Rickman, Ronald
item McCool, Donald
item PFEIFFER, K - NRCS

Submitted to: Journal of Soil and Water Conservation Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/11/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: When the residues from previous crops are left on the surface of fields, the soil is more protected from the forces of erosion. Several different methods and devices are currently being used to measure the degree of surface cover provided by crop residues. This study evaluated nine visual device/methods of residue cover measurement on wheatlands of the Great Plains and the Pacific Northwest. The study sites ranged in residue cover from a meager 6 percent-cover where intensive tillage had been conducted, to 84 percent-cover for no-tillage cropping practices. We found that all nine devices seemed to produce similar measurements, because any differences were masked by substantial variability among operators and spatial variability across the field sites. It was concluded that the criteria needs to be better defined as to what is acceptable measurement precision, or better instrumentation should be developed to replace human vision-judgement with objective sensors.

Technical Abstract: Nine devices were used to visually measure percent residue cover on fields following a wheat crop. Three observers took 1000 point readings with each device on each field. Residue cover varied from 6 to 84 percent with some fields having been fallow-tilled with as many as seven operations, compared to one field which was long-term no-till. The devices were four lines with various arrangements of bead markers, a measuring tape, and four wheels with markers located on or near the wheel perimeter. Measurement precision among devices was only different for the deeply tilled low-residue sites on Oregon wheatlands. For that special condition, the line-type devices produced cover values which were statistically lower than the wheel-type devices. Otherwise, the nine devices produced similar values for residue cover. Any differences in measured cover caused by the line bead arrangements or wheel designs, were either small or masked by large variations among observation and spatial variations across the fields. Operation time was generally similar for the four line and wheel type devices. The measuring tape took 50 percent more field time and is not recommended for use in measuring cover. Other factors, including length of pieces of residue, height or row spacing of stubble, and initial amount of residue, as well as line height above the surface were also either masked or not important. Results showed that fields with low amounts of old wheat residues may be measured with the same devices and methods as fields with higher amounts of cover and fresher residues. Because the field sites spanned a wide range of conditions, the results should apply to most dryland wheat production areas.