If your measuring line uses a bead or knot, always measure by consistently counting
from a point on one side of the bead or knot. Don't use the entire bead or knot as the
"point." It's usually too big to be accurate.
Measuring Crop Residue
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Knowing how to manage crop residues is key to success with conservation
tillage. Your ability to gauge the percentage of soil surface covered by residues in a
field helps determine whether you can really plan to reap the benefits available.
For most crops, conservation tillage systems help maintain residue cover levels
well above 30%. The exceptions are crops like soybeans, cotton and sunflowers that
produce either low quantities or fragile residue which decompose quickly or are
easily incorporated by equipment.
As mentioned, the ideal conservation tillage system leaves 30% or more surface
cover after all planting operations have been completed. In many cases, much
more than 30% residue cover is required to meet tolerable soil erosion levels ("T") and
provide reasonable soil protection until the crop's canopy becomes established.
How to measure residue cover
The most commonly used technique for measuring crop residue cover is the line
transect method. This involves stretching a 50-foot tape measure or cam line at a
45-degree angle across the crop rows and counting the number of 6-inch marks
along the line that intercept a piece of crop residue. (A mark every 6 inches over a
50-foot line equals 100 marks or percentage points.) Make sure you do all your
measuring on only one side of the tape or cam line, looking straight down at the tape
or line (not at an angle or distance). A percentage point is counted only when a
piece of crop residue is directly below (touching or crossing) the mark. Figure 1
illustrates this technique.
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To ensure accurate estimates for an entire field, take three to five measurements
in areas that best represent the field. Try to avoid weedy areas or places where
larger amounts of crop residue may have been left (concentrated) by the combine.
As you gain experience, you'll find that measuring residue cover requires less time
per field.
When to measure residue cover
To ensure high levels of crop residue remain after planting is completed, residue
cover should be measured periodically, about five times a year as follows:
1 - During and after harvest.
2 - During and after any fall field
activities such as nutrient
injection or subsoiling.
3 - Near planting, before any
field activities begin (this
allows you to estimate
overwintering losses).
4 - During and after any field
activities such as tillage or
nutrient injection.
5 - During and immediately after
planting operations.
It's important to measure during a field activity since some equipment may be
burying more residue than desired. Measuring residue cover before too much
of the field has been tilled will allow you to make equipment adjustments to better
meet your crop residue goals.
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