**TECHNICAL NOTES**

**USDA-Natural Resources Conservation Service**

**Boise, Idaho**

TN AGRONOMY NO. 43 May 20, 1983

Prepared by Floyd G. Bailey, State Conservation Agronomist

STANDARD METHODS OF MEASURING

CROP VEGETATION RESIDUES, YIELDS

As greater emphasis is placed on conservation tillage, crop residue use
and stubble mulching in soil erosion control systems, soil
conservationists need to have available acceptable methods for measuring
and estimating amounts of crop residues. This technical note contains
instructions on the commonly used methods of measuring and estimating
crop residues. Its objective is to encourage improved sampling
procedures and accuracy in crop residue measurements.

[The Hand Clipping Method]{.underline}

This method consists of hand clipping and weighing crop residues. It
requires a fixed guide consisting of a square or ring containing 9.6
square feet inside the frame. A square with 37.2 inches per side or a
ring having a 42-inch inside diameter is used to get a 9.6 square feet
template. Measurements are made in grams for easy conversion to pounds
per acre. To use, place the ring or square on the ground and collect all
visible parts of plant vegetation or residue above the ground within the
ring or square. Clip off all attached or partially buried vegetation at
the soil surface. Materials such as weeds should be included when the
sample is for erosion control purposes. When the sample area contains
small pieces of vegeta­tion that are difficult to pick up, the soil
conservationist should esti­mate the amount (in grams) remaining on the
soil surface. Do not include soil particles in the sample.

Weigh all samples in an air-dry condition. When samples are wet, they
should be air-dried under natural weather conditions or oven-dried at
approximately 700 C. until the weight has become stable. Use a gram
scale to weigh the sample. To convert the sample weight to pounds per
acre, multiply the sample gram weight by 10.

A minimum of four samples per field should be collected using a random
method of sampling. When the field contains chaff or straw rows, one of
the four samples should include the chaff row.

[The Line and Point Method]{.underline}

This method requires crop residues to be flattened and uniformly
distrib­uted across the field.

The line consists of a cord 50 feet long with 100 knots or beads spaced
6 inches apart. Lines can be easily made from a piece of 1/8 or 3/16
inch nylon rope about 70 feet long and two metal pegs or stakes.
Overhand knots are tied in the rope on 6 inch centers. The end product
is a 50 foot cord with 100 points on it. The two metal pegs are attached
to the ends of the rope. They are used to stake the line out.

In the field, the line is stretched out across the field at about a 45
degree angle to the crop rows. Both end pegs are pushed into the soil to
hold the line straight.

To estimate residue on the soil, walk along the line and count the
number of knots that lie on top of a piece of crop residue. Ignore small
pieces of residue that will decay before the critical erosion period or
are not large enough to intercept a raindrop. The number of knots
directly over residue will tell the percentage of the surface covered
with residue. Tables 1 and 2 can be used to convert percent cover to
pounds of cover per acre.

To improve accuracy, three or more randomly selected samples should be
taken and results averaged.

[The Weight Estimate System]{.underline}

The weight estimate system is similar to the hand clipping method. It is
faster but less accurate; however, it is accurate enough for planning
purposes.

This system uses a 9.6 square foot or ring. The square or ring is placed
on the ground. Then the soil conservationist selects a handful of the
same type of material located outside the square or ring. This sample
should be large enough to weigh, but not too much to easily handle in
one hand. Holding the sample in one hand, the soil conservationist uses
the other hand to estimate the number of "like handfuls" of residue
contained within the square or ring by grasping handfuls inside the
template. The hand sample is then weighed in grams and the weight
multiplied by the number of "like handfuls" to determine the estimated
weight of the residues within the square or ring. The weight in grams is
multiplied by 10 to give pounds per acre.

This procedure should be randomly repeated over the field to get a
proper representation of the field. Weight estimates should periodically
be checked against actual clipping weights to maintain accuracy.

[Row-Length Method]{.underline}

Where row crops are grown, it is often desirable to use the row-length
method to measure residue. This is accomplished by measuring the row
spacing and marking off the row length required to give the proper size
sample. The sample area should be a minimum of 1 square yard for small
grains and grasses and a minimum of 2 square yards for corn. The
following table is used to determine row length needed when the row
spacing is known.

+-----------------------+----------------------+----------------------+
| Row spacing           | Length of row to     | Length of row to     |
| center-to-center      | make 2               | make 1               |
|                       |                      |                      |
|                       | square yards         | square yard          |
+-----------------------+----------------------+----------------------+
| Inches                | Feet                 | Feet                 |
+-----------------------+----------------------+----------------------+
| 20                    | 11                   | 5.5                  |
+-----------------------+----------------------+----------------------+
| 24                    | 9                    | 4.5                  |
+-----------------------+----------------------+----------------------+
| 30                    | 7                    | 3.5                  |
+-----------------------+----------------------+----------------------+
| 36                    | 7                    | 3.0                  |
+-----------------------+----------------------+----------------------+
| 42                    | 5                    | 2.5                  |
+-----------------------+----------------------+----------------------+

All above ground vegetation or residue is collected and weighed. Samples
are weighed air-dry. Sufficient samples should be measured to get a good
representation of the field. Sample weights are averaged to gain the
weight of the average 1 square yard sample. When the weight is in grams,
multiply average sample weight by 10.66 to convert to pounds per acre.

[Rod Row Sampling]{.underline}

This method consists of cutting a measured length of drill row and
weighing the grain or straw yield. Any length of row can be cut, but the
following row lengths are recommended because they produce an
easily-managed bundle or sheath, and the data is easily converted to
pounds or bushels per acre.

1\. On 14-inch drill row spacing - Cut two adjacent rows in 9 feet 4
inches long. To convert yield to pounds per acre, multiply results by
2000.

2\. On a 7-inch drill row spacing - Cut two adjacent rows 9 feet 4
inches long. To convert yield to pounds per acre, multiply results by
4000.

3\. On a 6-inch drill row spacing - Cut two adjacent rows 8 feet 8½
inches long. To convert yield to pounds per acre, multiply results by
5000.

Cutting two adjacent drill rows is better than cutting only a single row
because drill skips in the row are usually compensated for by heavier
tillering in the adjacent row.

[Photo Comparisons]{.underline}

Photographs of different amounts of crop residue can be compared to
field situations to estimate the amount of crop residues on the field.
This method is accurate enough for general planning purposes, but should
not be used for certifying practice compliance. Soil conservationists
using photo-comparison should frequently check themselves by clipping
samples using the square or ring method to maintain accuracy at a high
level.

The attached photographs can be used for making photo comparisons.

![](media/image1.png){width="5.2340277777777775in"
height="4.270138888888889in"}

![](media/image2.png){width="5.233333333333333in"
height="4.613888888888889in"}

![](media/image3.png){width="5.226388888888889in"
height="3.9694444444444446in"}

![](media/image4.png){width="6.10625in" height="5.093055555555556in"}

![](media/image5.png){width="5.102083333333334in"
height="3.8569444444444443in"}

![](media/image6.png){width="5.604166666666667in"
height="4.864583333333333in"}

![](media/image7.png){width="5.229166666666667in"
height="3.972916666666667in"}

![](media/image8.png){width="5.607638888888889in"
height="4.622222222222222in"}

![](media/image9.png){width="5.23125in" height="4.102083333333334in"}

![](media/image10.png){width="5.48125in" height="4.748611111111111in"}

![](media/image11.png){width="5.358333333333333in"
height="4.102777777777778in"}

![](media/image12.png){width="5.60625in" height="3.7583333333333333in"}

![](media/image13.png){width="5.615972222222222in"
height="4.608333333333333in"}

![](media/image14.png){width="5.985416666666667in"
height="4.292361111111111in"}

![](media/image15.png){width="5.457638888888889in"
height="4.854861111111111in"}

![](media/image16.png){width="5.969444444444444in"
height="4.207638888888889in"}

![](media/image17.png){width="5.509722222222222in"
height="4.730555555555555in"}

![](media/image18.png){width="5.754861111111111in"
height="4.093055555555556in"}

![](media/image19.png){width="5.509722222222222in"
height="4.604166666666667in"}

![](media/image20.png){width="5.875694444444444in"
height="3.9277777777777776in"}

![](media/image21.png){width="5.602777777777778in"
height="4.481944444444444in"}

![](media/image22.png){width="5.698611111111111in"
height="4.072222222222222in"}

**TABLE 1 Cover/Residue Table for Wheat, Barley, Oats, Soybeans or
Similar Small Diameter Stalk**

  -------------- --------------------- ------------- ---------------------
  **Percent      **Pounds of           **Percent     **Pounds of
  Cover**        Residue/Acre**        Cover**       Residue/Acre**

  1              16                    51            1107

  2              31                    52            1139

  3              47                    53            1172

  4              63                    54            1205

  5              80                    55            1233

  6              96                    56            1274

  7              113                   57            1310

  8              129                   58            1346

  9              146                   59            1384

  10             164                   60            1422

  11             181                   61            1461

  12             198                   62            1502

  13             216                   63            1543

  14             234                   64            1586

  15             252                   65            1629

  16             271                   66            1674

  17             289                   67            1721

  18             308                   68            1768

  19             327                   69            1818

  20             346                   70            1868

  21             366                   71            1921

  22             386                   72            1976

  23             406                   73            2032

  24             426                   74            2091

  25             446                   75            2151

  26             467                   76            2215

  27             488                   77            2281

  28             510                   78            2350

  29             532                   79            2422

  30             554                   80            2498

  31             576                   81            2577

  32             599                   82            2661

  33             622                   83            2750

  34             645                   84            2844

  35             669                   85            2944

  36             693                   86            3051

  37             717                   87            3166

  38             742                   88            3291

  39             767                   89            3426

  40             793                   90            3573

  41             819                   91            3737

  42             845                   92            3920

  43             872                   93            4127

  44             900                   94            4366

  45             928                   95            4649

  46             956                   96            4995

  47             985                   97            5442

  48             1015                  98            6071

  49             1045                  99            7147

  50             1076                  100           9999
  -------------- --------------------- ------------- ---------------------

**TABLE 2 Relation of Percentage of Surface Cover to Mulch Rate**

![](media/image23.png){width="6.697222222222222in"
height="4.596527777777778in"}

Curve A is for small-grain straw. Curve B is for chopped cornstalks.

[Acknowledgements]{.underline}

This material was developed from the following references:

"A Standardized Procedure for Residue Sampling." USDA-ARS 41-68.

''Methods of Measuring or Estimating Amounts of Crop Residue Per Acre."
WTSC Agronomy Note No. 23, November 1965 by J.W. Turelle.

"Weight-Estimate System of Sampling Crop Residues." (unpublished) by
Evan L. Murray.

"Predicting Rainfall Erosion Losses, A Guide to Conservation Planning."
USDA Handbook No. 537, prepared by Science and Education Administration
(ARS), 1978.

Plant Science Handbook, Washington State University.

"Measuring Crop Residue Cover." Laflen, J.M. et al, Journal of Soil and
Water Conservation, November-December 1981.