Exercise 3 - South Dakota: Templates and Add Irrigation

Skill Building: This exercise will call up a template management run with fallow, make a run, calibrate the run, replace the fallow with sorghum, make two more runs (one calibration), and then add irrigation.

Scenario: The field is located in Haakon County, South Dakota. The CLIGEN station is Milesville. The WINDGEN station is Pierre Municipal. The critical dominate Soil Map Unit is CRAFT_Cv_85_VFSL. The existing cropping system is Winter Wheat-Fallow. Consider adding sorghum dry land or corn if irrigated. The field size is a 160 ac square. The field orientation is 45 degrees from North. Management includes fall chisel at a 45 degree angle to the field borders after the winter wheat harvest, producing about 40 bu/ac/yr. The dryland yield for sudangrass will be 1.5 ton/ac/yr. The crop management file we will start with is Wheat, winter; fallow; Conv, CMZ5.man.

Getting Started

Step 1: Make sure you are in the Student project. Enter all the needed data mentioned above into the interface. Be sure to change the field Orientation to 45.0 degrees in the Simulation Region Information panel. You will see the field orientation rotate in the Field View panel. Open a template file by clicking the Management Template Folder icon and clicking 'Example Mgt. Files' then select WWheat-fallow, Conv, CMZ5.man. An alternative way to open the template file is to open the MCREW Management editor by clicking the 'Man' button. Click 'File', then 'Open Copy of Template' and load WWheat-fallow, Conv, CMZ5.man into the editor. Be sure to highlight all the operations, right click in the Row/Ridge Dir. (Deg.) column, and select Set to 45 deg. See Figure 1.42.

Note: All degree settings, including field orientation and tillage direction, are measured from 0 degrees (i.e., North). The fall chisel (Oct 20, 01) direction should be 0 or North because the field angle is 45 degrees. If you do not make these changes the answer will be different.

Select the soil Craft_Cv_85_VFSL.ifc. Click Yield Calibrate button to turn on the yield function and click the Return button to return to the main interface.

Step 2: Make a Yield Calibration WEPS Run and name the run WWheat-Follow, Conv, CMZ5 cal. The soil loss is 8.0 ton/ac and the Biomass Adjustment Factor is 0.930. Use this Biomass Adjustment Factor in the project.

Add Sudangrass

Now replace the fallow with a short sudangrass forage crop. Note that forage crops are not calibrated. WEPS will grow the crop without calibration. This may change in future versions, but for now (Version 1) do not calibrate forage crops.

Step 1: Open up the management editor again. Make a new management file called Wheat, winter-Sudangrass, forage, Conv, CMZ5.man, by clicking 'File', 'Save as...' and type the new name and click 'Save'.

Edit the file to add in the sudangrass. Planting time for sudangrass is April 15, so we need to add a chisel and a field cultivator to the file before we plant the sudangrass. Schedule these operations with two days between each operation. We will start in the spring time of the second year. Change the date of the spring chisel from 'May 01, 02' to 'Apr 11, 02' (right click the date cell on the May 1 Chisel line and select 'Calendar Date' to change the date).

Now change the operation to a Chisel, sweep shovel by right clicking on the operation name and clicking "Change Operation". Right click the date on the next line (June 1), and change the date to 'Apr 13, 02'. Then change the operation to Cultivator, field 6-12 in sweeps.

On the next line, change the date to 'Apr 15,02' and the operation to Drill or airseeder, double disk. We will have to add the sudangrass hay crop. In this case, the name for the crops is Sorghum, forage. Sudangrass is a type of sorghum.

Next, change the 'Aug 15,02' line to a hay harvest line with a 'Sep 01, 02' harvest date. Change the operation to Harvest, hay, no regrowth.

Now we want to add a Chisel, sweep shovel before the Cultivator, field 6-12 in sweeps. Right click the Chisel, sweep shovel operation on the second row and copy rows(s). Right click the 'Sep 01, 02' Cultivator, field 6-12 in sweeps and paste row(s). Now change the date of the chisel to 'Sep 03, 02' and the cultivator to 'Sep 05, 02'. Be sure to change the year on the Chisel from year 1 to year 2.

The last thing to do is to change all the direction of tillage operations to 45 degrees except for the 'Oct 20, 01' chisel, should stay at 0 degrees. The updated management file should look as in Figure 1.43. Finally 'Save' the management.

Step 2: Make the run and call it Winter Wheat-Sudangrass, forage, conv, CMZ5. Be sure that the winter wheat has the 0.93 value in the Bio Adj. Factor column in the MCREW management editor screen. The soil loss is now 3.9 ton/ac (Figure 1.44). This is a good reduction of the erosion rate.

Note: If a disk had been used to prepare the seed bed for the hay, the soil loss would be 4 ton/acre more. The 2.3 ton/ac yield of sudangrass hay seems reasonable.

Add Supplemental Irrigation

The producer can apply about 12 inches of water per year to the crops and would like to see the effect of this in the yield. This is a relatively easy question to answer.

Step 1: Open up the last management we ran: Wheat, winter-Sudangrass, forage, Conv, CMZ5.man. Save a new version of this rotation by clicking 'File', 'Save as...' and adding irrigation to the name: Wheat, winter-Sudangrass, forage, Conv, irr supplemental, CMZ5.man.

The producer wants to add supplemental irrigation to see the effect on yields. Right click the third line in the Operation Name column and insert an operation. Select, Irrigation (2 inch, Pivot, Linear, Wheelline), and change the date to 'Apr 01' and year to '01'. Now use the copy-paste function by right clicking on the irrigation operation just created and click 'Copy Row(s)'. Now right click in the same row and click 'Paste Row(s)'. Repeat this to give six irrigation operations and change the dates to 'Apr 01', 'Apr 20', 'May 15', 'Jun 15', 'Jul 15', and 'Aug 15' with year of '01'. The wheat also needs the two inch irrigations on 'Sep 15', 'Mar 01', 'Apr 01', 'May 01', 'Jun 01', and Jun 15' of year '02'. You can copy the six lines of irrigation for the sudangrass by left clicking and dragging the mouse over the six sudangrass irrigations to highlight them, copy, and paste at the end of the file. Then change the dates for wheat. The last thing to do is to sort the file by clicking the sort button, on the top of the tool bar, then save the file. The completed management window should look like Figure 1.45.

Note: This example shows how to use supplemental irrigation. If you want to use full irrigation to meet crop consumptive use, put a Start Monitor (Pivot, Linear, Wheelline) operation just after planting and an Irritation, Stop Monitor operation 15 days before harvest. This will auto-irrigate the crop during the growing season similar to the way Exercise 1 was run.

Step 2: Return to the main interface and make the run without calibration (Biomass Adjustment Factor set to 1.0 for wheat) to see how much additional yield the producer may get with the supplemental irrigation. This time, show the Simulation Region as a circle by changing the "Shape" to circle, and typing 120 ac in the area box. Call the run: Wheat, winter-Sudangrass, forage, Conv, irr supplemental, CMZ5.

Note that the wheat yield increased to 55.6 bu/ac and the sudangrass hay only increased 249 lbs/ac (Figure 1.47). This may not be a good investment of the 12 inches of water per year. The soil loss dropped to 0.7 ton/ac/yr.