##### TECHNICAL NOTES

**US DEPARTMENT OF AGRICULTURE NATURAL RESOURCES CONSERVATION SERVICE**

**AGRONOMY - 55 Albuquerque, New Mexico**

**January, 2005**

**WIND EROSION EQUATION**

### USE OF MICROSOFT EXCEL SPREADSHEET

**Mike Sporcic Leigh Nelson**

**State Agronomist Ag Engineer**

**Albuquerque, NM Central Basin Team**

**Ephrata, WA**

-   **Purpose** This note will give the background and basic
    instructions to use the Wind Erosion Equation (WEQ) Microsoft Excel
    spreadsheet computer version. To operate the equation the user will
    need to have a good understanding of Part 502 of the National
    Agronomy Manual. User will need a computer with at least a 486/33 or
    better (586 is better); Windows, 95, 98; or NT, MS Excel version 7.0
    or better; 64 meg of RAM or better; a copy of the spreadsheet
    (**WEQv9.00.xls**) from the following web site:
    [http://www.nm.nrcs.usda.gov/technical/tech-notes/agro/ag55.xls](http://www.nm.nrcs.usda.gov/technical/tech-notes/agro/ag55.xls )

-   **Background** In the late 1980s a computer version of WEQ was
    developed for the UNIX based 3b2 commuters. It allowed us to run a
    management period method calculation in a fraction of the time a
    long hand version could be done. We have used this version until
    recently. Circular No. 2 (amendment to the NAM) came out Sept.
    12, 1997. It **added** an adjustment for irrigated fields (Lowering
    the I for irrigated fields and reducing Erosive Wind Energy (EWE)
    for surface wetness), an adjustment for random roughness (RR), and a
    way to interpolate the Climate (C) factors. When this happened we
    were unable to use the new WEQ module in FOCS. FOCS was not able to
    compute the Circular No. 2 changes, and no one will be doing this in
    FOCS in the future. In about 2 years we will be going to a windows
    based computing system, the Wind Erosion Prediction System (WEPS).
    **WEQ vs 9.00 xls** **was created to fill the two-year gap and
    incorporate Circular 2 changes**.

-   **General --** The WEQ management period method spreadsheet can be
    in states that use the management period method to estimate wind
    erosion.

To operate the equation the user will need to have a good understanding
of Part 502 of the National Agronomy Manual (NAM). Planners will be able
to use this spreadsheet, **if they have a basic understanding of the
wind erosion equation, can do a residue reduction calculation,
understand irrigation (where the land is irrigated), and have basic
Excel spreadsheet skills**. The State Agronomist will need to set up the
wind climate data, crop data and operation (tillage) files. Cropping
systems developed on the model (WEQ Input Worksheet) can be saved to a
file and used as templates for future use by the client or for new
planning. The light yellow shaded areas are the **only** "user" data
required to run the program. The worksheet is "protected". This is not
because the user is not trustworthy; it is because some of the data
should only be changed state wide, and mostly because if a formula is
lost it can be very difficult to replace.

-   **Irrigated Circles -** Many irrigation circles in are planted in a
    circular pattern. To estimate wind erosion on fields planted and/or
    tilled in a circular pattern, two estimates need to be made. The
    first estimate should be made after selecting a NS tillage direction
    and the second should be an EW direction. The average of the two
    estimates is the correct soil loss value. In the example it does not
    make a difference, but when making other erosion estimates on
    circular tilled fields this averaging procedure should be completed.

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-   **Definitions -** The first sheet in the spreadsheet (**Instr**) has
    most of the column headings defined and an explanation of the
    information required for the spreadsheet to run. Please print a
    blank worksheet (**Res Wks**) and the calculation sheet (**Calc**)
    before reading the **Instr** sheet. **Remember only the shaded area
    cells need input data.** Please read the **Instr** sheet before
    starting.

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-   **Circular Reference Bug -** There is a circular reference bug in
    the sheet. As you enter data for the first time you will find an
    error caution will come up and tell you there is a circular formula
    error in the sheet. **DO NOT** **PANIC** and call for help! Just
    close the warning box when it pops up and continue to add the data
    needed for the run. The error warning will stop when the first
    harvest is entered.

# Step by Step

This is a step by step process to show how to use the program. Start the
step by step process after reading the **Instr** sheet (the tab at the
bottom of the WEQ Excel spreadsheet).

**Step 1 -** Fill in the **Producer**, **Planner**, **Location** (Farm
Unit or Sec., Town., Range), **Tract**, **Field**, and **Crop Rotation**
boxes.

**Step 2 -** Use the drop down menu to select the **Climate Data
Station**. The climate data is pulled from the **Climate** sheet (see
the tab at the bottom of the worksheet).

**Step 3 -** Fill in the **C Value** (in whole numbers. Divide the
isobar interval only once from the C factor map)**,** **Field Width** of
short side of field (ft)**, Tillage Direct.** (EW or NS, drop down)**,
Length/Width Ratio** (number equal to or greater than one, drop down),
**Field Direction** (EW or NS, drop down)**, Irrigation** (Y/N, pull
down)**,** and **Soil "I"** (drop down).

**Step 4 -** Determine the **Wind Erodibility Group** (WEG) from the
FOTG soil survey, and fill in the number (1-7 or 4L, drop down).

**Step 5 -** Place **1/1/xxxx** on the first line of worksheet (next to
Start Rotation). Start the first management period on January 2,
(current year) with an **Over winter** **loss** operation. Go to the
**Operation Date** column on row 13. Put in the date **1/2/xxxx**. Next
place the cursor in the **Crop** column next to the date, left click in
the box to activate the pull down and select the previous crop harvested
(select from the list). Move to the **Operation** column. In cell C13,
click the pull-down and select the **Over winter loss, fragile (F) or
non-fragile** **(N)** **operation** (see NAM Part 503 Subpart E, table 1
& 2, for definition), repeat these steps with correct dates until all
tillage operations, planting operations, and harvests are completed. As
you select the planting operation change the crop to the new crop
beginning with the planting operation.

**Step 6 -** The next date after planting will be the end of the first
15-day growth period. The date can be entered as a formula. In the blank
date column A, type **=**, then point and click on the cell just above,
then type **+15**, then hit the return key. This will enter a formula
that tells the computer, to type the date above and add 15 days. All
growth periods are 15 days except winter wheat or other winter crops,
which have a 60-day growth period over winter (see the **Crop** table
for details). The 15-day date formula can be copied down for the number
of growth periods for the crop planted. Next, in the **Crop** column
click and select the growing crop name with a number **(15 to 75)** next
to it. Continue to select down the column a series of growth periods.
Example: **Bean 15**, **Bean 30**, **Bean 45**, **Bean 60**, and **Bean
75** can be copied and moved at the same time to the **Crop Name**
column of the **Res Wks**. This must be done using the **paste special**
function. Select the Crop Tab and find the correct series of grow names,
highlight them and copy them. Change back to the **Res Wks** sheet,
place the cursor in the first cell under **Crop** (column B) where crop
growth begins, right click and click on **paste special**, then select
the radio button for **value** under the paste section, and click OK. In
the **Operation** column enter (click and select) **"Grow"** for all the
growth periods. **"Grow"** can be pasted in the first cell for "Grow"
and then copied down the sheet (**Res Wks**) as needed**.** All growth
series of data can be copy from the tables in groups and **paste
special** used to paste only the **values** to the **Res Wks**. If you
copy and paste normal you will lose the formatting in the cells.

**Step 7** - Enter the **Harvest date**, the harvested **crop name**
(without a number extension), and the word "**Harvest**" for above
ground crops or "**Harvest, root crop**" for root crops in the
**operation column**.

**Step 8** - Enter the **date** of any post harvest tillage**, crop
name** (residue just harvested), and the name of the **operation.**
Repeat step 5, 6, 7, and 8 for any additional crops in the rotation. 100
management periods can be used in each calculation. If more are needed
try removing lines where there is no erosion. An example would be to
reduce the number of operations of **"Grow"** to just what is needed to
take erosion to zero for the rest of crop growth period.

**Step 9 -** End the run with a **12/31/xxxx date,** last harvested
**crop name**, and the **End Rotation** operation.

**Step 10 -** Enter any **irrigations** for the periods listed. Enter
the **number** of irrigations in each period (This is NOT the cumulative
number of irrigations). Keep in mind the stage of growth and the
consumptive use of the crop during the management period. See table 1.

**Step 11** -- In the **Flat Res.** column on each line of the run enter
**0** when residue is 100% standing (no flat residue), and 100 when all
the residue is flat (as in heavy inversion tillage). Example, if 60% of
the residue is standing after a tillage, then enter 40 or 0.4 and hit
the return key. The number will be in percent.

**Step 12** - Finally, adjust any **yield values** that are different
than the default yields in column G-H. You can change the yield by 50%
up or down by using the drop down in the **Yield Adjustment** column
(F).

## Example

-   Iam Windy farms, tract 123 on an irrigated circle (field 1) of
    continuous grain corn, where the soil has an I of 56. The circle
    field has a diameter of 2640 ft, and is near Clovis, NM. The C
    is 100. The grower tills and/or plants approximately perpendicular
    to the damaging winds from the west during the spring critical
    period. The field is farmed north and south. Iam plants corn on 4/15
    and harvests 10/15. The stalks are disked with an offset disk and
    packer on 11/1. In the spring the field is disked and packed again
    on 3/15. On 4/1 the circle is moldboard plowed, conventionally and
    packed. Then, on 4/10 a seedbed maker is used to set up the field
    for the corn planter. The corn is cultivated on 5/15. His average
    yield has been 200 bushels/acre.

**Step 1** - Fill in: **Iam Windy**, **MAS**, **Clovis, NM**, tract
**123**, field **1**, and **Corn, grain** in the rotation box.

**Step 2 -** Select the climate data station of **Clovis, NM** from the
pull down list.

**Step 3 -** Put **100** in the C box, **2640** feet in the width box,
**NS** for tillage direction, length width ratio is **1.0**, field
direction is **EW**, Irrigation is **Y**, and soil I is **56**.

**Step 4 -** WEG is **5**.

**Step 5 -** Enter **1/1/1999** in the first line (cell A13) of the
table, and select (cell B13) **Corn, grain, high yield** from the
**Crop** table drop-down list. Enter **1/2/1999**, copy **Corn, grain,
high yield** from the above cell to row 14 in the crop column, select
**Over winter loss N** in the **operation** column. Enter the first
tillage on **3/15/1999**, copy **Corn, grain, high yield** from the cell
above, select **Disk, offset, heavy N** from the **Oper** drop down
list. Do the same for the **Packer, roller** on the same date**.** Enter
**4/1/1999** and put in the **Plow, moldboard, conventional** and
**Packer, roller.** Enter **4/10/1999** and copy **Corn, grain, high
yield**. There is no seedbed maker operation, but a
**Chisel-disk-harrow-packer (comb) N** is close, so use it. Enter
**4/15/1999**, **Corn, grain, high yield** and **Planter, DD opener, 30
in sp N**.

**Step 6 -** Copy the 4/15 date and add 15 days to the formula. Copy or
select **Corn, grain 15** through **Corn, grain 75** from the **Crop**
table to the crop column. Type or select **Grow** in the **Operation**
column and copy down to match the **Crop** column. Copy down the
**Operation Date** column to match the growth cells. Note that there is
a cultivation on the second growth date. Copy the six columns of data
from 5/15 down one line to add the cultivation. On the second 5/15 date
in the **Operation** column copy and paste or select the **Cultivator,
rowcrop, 3** **in ridge** operation.

**Step 7 -** Enter the harvest date **10/15/1999**, copy down the crop
**Corn, grain, high yield** and type or select the word **Harvest**.

**Step 8 -** Add the post harvest tillage on **11/1/1999**. Copy both
tillage operations from the cells above.

**Step 9 -** End the run by entering **12/31/1999**, copy **Corn, grain,
high yield** and copy or select the **End Rotation** operation.

**Step 10 -** In the NM FOTG, sec I, in the Irrigation Guide we find
that the Consumptive Use (CU) irrigation requirement for **Corn, grain**
is 32.4 inches of water per year. We also know that peak daily CU is
about 0.30 inches for Corn (by dividing the highest month by 30). Most
circle systems are set up to meet the peak CU. We can estimate the
number of irrigations needed for each growth period or use Iam's records
for each period. To estimate divide the 32.4 in. by 0.30 in/day and we
find we need 108 irrigation days. See Table 1 for the number or
irrigation per month estimated.

#### Table 1 Consumptive Use for Corn at Clovis NM

+---------+----------+-----------+-----------+----------+-----------+
| ####    |          |           |           |          |           |
| ## Corn |          |           |           |          |           |
|  Irriga |          |           |           |          |           |
| tion Wa |          |           |           |          |           |
| ter Use |          |           |           |          |           |
|  at Clo |          |           |           |          |           |
| vis, NM |          |           |           |          |           |
+---------+----------+-----------+-----------+----------+-----------+
| **      | **Month  | **Co      | **Co      | **Number | **Number  |
| Month** | by       | nsumptive | nsumptive | of       | of        |
|         | period** | Us        | Use/Day** | Irriga   | irriga    |
| (mo)    |          | e/Month** |           | itons/** | tions/Mgt |
|         | (date)   |           | (in/day)  |          | period**  |
|         |          | (in/mo)   |           | *        |           |
|         |          |           |           | *Month** | (number)  |
|         |          |           |           |          |           |
|         |          |           |           | (nu      |           |
|         |          |           |           | mber/mo) |           |
+---------+----------+-----------+-----------+----------+-----------+
| **      | **4/10   | **1.5**   | **0.05**  | **5**    | **2**     |
| April** | to       |           |           |          |           |
|         | 4/15**   |           |           |          |           |
+---------+----------+-----------+-----------+----------+-----------+
|         | **4/15   |           |           |          | **3**     |
|         | to       |           |           |          |           |
|         | 4/30**   |           |           |          |           |
+---------+----------+-----------+-----------+----------+-----------+
| **May** | **4/30   | **3.3**   | **0.11**  | **11**   | **5**     |
|         | to       |           |           |          |           |
|         | 5/15**   |           |           |          |           |
+---------+----------+-----------+-----------+----------+-----------+
|         | **5/15   |           |           |          | **6**     |
|         | to       |           |           |          |           |
|         | 5/30**   |           |           |          |           |
+---------+----------+-----------+-----------+----------+-----------+
| *       | **5/30   | **6.6**   | **0.22**  | **22**   | **11**    |
| *June** | to       |           |           |          |           |
|         | 6/14**   |           |           |          |           |
+---------+----------+-----------+-----------+----------+-----------+
|         | **6/14   |           |           |          | **11**    |
|         | to       |           |           |          |           |
|         | 6/29**   |           |           |          |           |
+---------+----------+-----------+-----------+----------+-----------+
| *       | **7/1 to | **8.7**   | **0.29**  | **29**   | **70**    |
| *July** | 10/15**  |           |           |          |           |
+---------+----------+-----------+-----------+----------+-----------+
| **A     |          | **7.5**   | **0.25**  | **25**   |           |
| ugust** |          |           |           |          |           |
+---------+----------+-----------+-----------+----------+-----------+
| **Sept  |          | **4.8**   | **0.16**  | **16**   |           |
| ember** |          |           |           |          |           |
+---------+----------+-----------+-----------+----------+-----------+
| **Oc    |          | **0**     | **0**     | **0**    |           |
| tober** |          |           |           |          |           |
+---------+----------+-----------+-----------+----------+-----------+
|         |          |           |           |          | **Total   |
|         |          |           |           |          | 108**     |
+---------+----------+-----------+-----------+----------+-----------+

The number of irrigation per month can then be entered by each growth
period. Estimate 2 irrigations for preplant, 2 in the first period, 3 in
the second, 5 in the third, 6 in the fourth, 11 in the fifth, 11 in
sixth and 70 in the last (the remaining of the year). Leave the period
just before the cultivation blank since both operations occur on the
same day.

**Step 11 -** Go down the **Flat Res** column and estimate the **percent
flat residue**. Start on the Harvest Operation. Estimate about 50% of
the residue is standing after harvest and 0% is standing after the fall
tillage. Enter **50** at the harvest, and 100 in the management period
after the fall packing. Note only the 1^st^ period after harvest has
standing residue.

#### Step 12 -- Select .5 on the drop down in column F. This increases the 135 bu/ac to 200 bu/ac.

See the attached example.

![](media/image1.wmf){width="6.9in" height="3.861111111111111in"}