KanSched An ET-Based Irrigation Scheduling Tool
for Kansas Summer Annual Crops

August 2002

Gary A. Clark, Danny H. Rogers, and Steven Briggeman
Biological and Agricultural Engineering
K-State Research and Extension

 
Printable KanSched User Guide (PDF Format)

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Introduction TOP OF PAGE

KanSched is a program that is designed to help monitor the root zone soil profile water balance and schedule irrigation events on a field using evapotranspiration (ET) data. The program can also be used to monitor the soil profile water content of non-irrigated fields. ET-based irrigation scheduling is a tool that can help you determine when and how much irrigation water to apply. The basic process involves using data on crop water use (crop evapotranspiration or ETc), rainfall, and soil water storage to assess when an irrigation event is needed and how much water could be applied.

This program was developed as part of the Mobile Irrigation Lab, which is supported by a partnership between K-State Research and Extension, the Kansas Water Office with State Water Plan Funds, Kansas Water Resources Research Institute, and the Kansas Corn Commission.


Disclaimer: Use of trade names does not imply endorsement of named product or criticism of others.

General Overview TOP OF PAGE

Irrigation scheduling that uses evapotranspiration (ET) information is much like checkbook accounting procedures where the valued commodities are tracked. In this case, soil water, rather than money, is the valued commodity and the debit is crop water use while credits are rainfall and irrigation. One notable difference is that the water balance can be too high as well as deficient. ETc, short for crop evapotranspiration, is the amount of water that a crop withdraws from the soil water reserve. Deposits to the soil water reserve are rainfall and applied irrigation. The major goal of the accounting procedure is to help the irrigation manager keep the amount of water in reserve above a minimum soil water balance level to prevent water stress to the growing crop. The upper limit to the account is the amount of water that can be physically stored in the root zone area of the soil profile. Deposits of water, once the upper limit is exceeded, result in the water being lost as either deep percolation or surface runoff.

Irrigation scheduling can help minimize deep percolation losses, although even the most rigorously followed schedule cannot prevent all losses since large rainfall events can exceed soil water storage capacity by themselves. The benefits of irrigation scheduling generally translate into increased net returns through several possible avenues. Irrigation scheduling may also reduce irrigation labor and equipment operation pumping cost, and may also result in improved yields due to less water stress or less loss of fertilizer due to leaching.

One of the major obstacles to adoption of on-farm irrigation scheduling has been the time management problem of gathering, processing, and implementing scheduling on a daily irrigation cycle period. Computer technology presents the opportunity for information gathering, transferring, and processing to be done much more easily, efficiently, and sometimes automatically. Scheduling software, communication, and control technology exists that can provide management recommendations which could then be remotely implemented. This manual will help to step you through the KanSched program, input windows, and help screens.

The Start Screen TOP OF PAGE

Each time you start KanSched, you’ll begin with the screen pictured in Figure 1. From this point, you have several options to choose from depending on how you want to use the program. The following sections will describe each of these options in detail and how you can use them to your advantage when using KanSched.

Figure 1 – The start screen of KanSched

The Menu Bar TOP OF PAGE

At the top of each window in KanSched is the menu bar. The start screen’s menu bar has three main menus: File, Information, and Demo. The File menu simply offers an Exit option for quitting KanSched; although, you can always exit KanSched by clicking the button at the top right corner of the KanSched window. The Information menu provides two choices: Contact Information and Credits and Version Information. The Contact Information and Credits option gives you the names and phone numbers of individuals who can assist you with any KanSched related questions you might have. The Version Information option displays the version number of the KanSched program you are running. The Demo menu allows you to use a demo field that is fully functional with all field and weather information pre-entered, making it easy to quickly become acquainted with the functions of KanSched.

Start a new field TOP OF PAGE

To initialize a new field, click the green button labeled “Start a new field”. A new window will appear displaying the input boxes for the initial field information and soil information (Figure 2). The input screen will be discussed in detail later on in this manual.



Figure 2 - The input data screen of KanSched
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Quick ET TOP OF PAGE

To quickly enter daily reference ET data for a group of fields that are in the same region, click the green button labeled “Quick ET Update.” The Quick ET feature makes the daily process of updating your fields’ reference ET values quick and easy. When you click on the Quick ET Update button, you’ll see the window in Figure 3. Select the desired ET Field Group (the process of creating an ET Field group will be discussed later in the manual) from the list. When a group is selected, the fields within the group will be listed in the “Fields in this group” list. On the right side of the window you’ll see the input boxes for the daily reference ET values. Simply enter the required reference ET values and all of the fields in that ET field group will be automatically updated. Be sure to click the green “Save Group ET Data” button to save the reference ET info that you just entered.

Figure 3 – The Quick ET update screen

View ET Field Groups TOP OF PAGE

Fields that you enter in KanSched can be grouped together according to their source of reference ET data, making it quick and easy to make one daily ET entry for the entire group. By clicking the “View ET Field Groups” button, you can view each group you created, along with the fields they contain. A sample of the ET Field Groups screen is shown in Figure 4. As you can see, there are two field groups, East Group and West Group. The East Group contains one field, called Demo Field. The West Group also contains just one field, called Demo Field #2. If any fields existed that were not associated with a field group, they would be listed in the “Individual Fields” section.

Also available from the Field Groups screen are the options found just below the list of field groups: Create a new group, Rename this group, and Delete this group. These options will be discussed in detail later in this manual.

Figure 4 – The ET Field Groups screen

Delete an Existing Field TOP OF PAGE

Sometimes while using KanSched, you will want to delete a field. This option is available throughout the software, as well as on the Start screen. Clicking the “Delete an existing field” button will display the window shown in Figure 5. The deletion process is described below the list of fields. When you’re finished, simply click the Done button or close the window. Remember, once a field is deleted, it cannot be recovered!

Figure 5 – The ‘Delete a Field’ screen

Entering Information Into KanSched TOP OF PAGE

Before KanSched can begin tracking the field’s soil water content and crop water usage, you need to provide it with information about the soil type, growing season, and crop for each field. The following sections will guide you through the input entering process required to begin using KanSched. This section starts with the main Input screen, the first screen you see when starting a new field or opening a previously created field.

The Input Screen TOP OF PAGE

The Input screen (Figure 2) requires some information that characterizes the soil type, growing season, and crop type for a field. All of the inputs on this screen must be entered before KanSched can track your field’s soil water content and crop water usage. If some of these values are unknown to you, simply click the question mark button in the lower right corner of the screen. After pushing this button, the help options will be enabled and you will see three horizontal blue bars appear behind the sections that have a help section. To get help with any of those sections, simply click on the question mark button associated with each section. Help screens are available for soil characteristics, crop growth characteristics, and crop coefficients.

The following section will describe each input required:

Field Name or ID: TOP OF PAGE

Enter the name of the field in this box. KanSched uses this name to keep track of your field. This name can also be changed at any time during the software’s use.

Soil Available Water Holding Capacity and Soil Permanent Wilting Point: TOP OF PAGE

The soil available water (AW) holding capacity value is a measure of the maximum amount of water your soil can hold that is usable to the crop. The soil permanent wilting point (PWP) value is the water content of the soil when the crop cannot pull the water from the soil, causing the plant to wilt. Both of these values are measured in inches of water per inch of soil. If you are unsure of one or both of these values, simply click the help button in the lower right hand corner of the input screen to enable the help options, then select the help button in the soil characteristics section. The help screen for the soil section is shown in Figure 6. To automatically calculate your soil’s water holding characteristic values, simply select your soil texture from the drop-down list at the top of the screen. The default values on this help page are from the NRCS soil characteristic database.


Figure 6 – The Soil Help Screen

Emergence Date: TOP OF PAGE

KanSched needs to know the emergence date of the crop in order to start tracking water usage. The emergence date is simply the date your crop emerges from the ground after planting.

Date to Start the Water Budget: TOP OF PAGE

The water budget start date is the date that KanSched will actually start tracking the soil water content. This date must be after the emergence date.

Root Depth on the Start Date: TOP OF PAGE

KanSched tracks root growth throughout the season. In order to do this, it must know the root depth on the date it starts the water budget. This can be determined by going out to the field on the start day and dig around the crop to measure the root depth. As an early season guess, use 6 inches.

Maximum Managed Root Zone: TOP OF PAGE

Entering a maximum managed root zone lets KanSched calculate the maximum depth of the soil profile that your crop can draw water from. While the actual root depth may be deeper, this value is the managed depth for the crop’s roots. Normally, managed root zone depth is 3 to 4 feet unless the root-depth is limited by restrictive soils.

Date the Crop Canopy Cover Exceeds 10% of the field area,
Date the Crop Canopy Cover Exceeds 70-80% of the field area,
Date when the Crop is at Initial Maturation, and
Date of the End of the Growing Season :
TOP OF PAGE

The above dates are required by KanSched in order to monitor the growth stages of the crop and to create a crop coefficient curve. If you need assistance with calculating these values, simply enable the help options and click the question mark button in this section. The Date Help screen, shown in Figure 7, will automatically calculate these dates. Select the crop type, enter the season length and emergence date, then press the Calculate Values button. The calculated values are displayed at the bottom of the screen. Click the “Use these values on the input page” button to automatically enter these values on the input screen; however, they can be adjusted later if needed.

Figure 7 – The Crop Date Help Screen

The Initial Crop Coefficient,
The Maximum Crop Coefficient, and
The Final Crop Coefficient: TOP OF PAGE

To determine how much water the crop is using, KanSched uses crop coefficients. The crop coefficient changes over the season; starting very small, increasing as the crop grows, peaking at the beginning of reproduction, then declining as the plant’s water usage stops with maturation. To gain assistance with calculating these values, enable the help options and click the associated question mark button. The Crop Coefficient Help screen is shown in Figure 8. Select your crop type from the dropdown list. If necessary, select your reference ET system if it isn’t a grass based reference. Because crop coefficients are adjusted according to different reference ET bases (grass or alfalfa), you need to determine and then select the appropriate reference ET system. This information should be available from your automated weather station or reference ET information source.

Figure 8 – The Crop Coefficient Help Screen

Management Allowed Deficit (MAD): TOP OF PAGE

The Management Allowed is the percentage of the available water in the soil that will be removed by the crop before you decide to irrigate. The MAD value will vary across different crops and according to how risk adverse you are as a producer. For high value crops, the MAD may be 40 percent or less. For lower value crops, the MAD may be 60 percent. A MAD of 50 percent is reasonable for most row crops.


Initial Soil Water Availability: TOP OF PAGE

Before KanSched starts tracking your soil water content, it must have an initial value to start with. The initial soil water availability is the percentage of available water to the crop on the budget start date entered earlier. A value of zero (0%) is associated with the permanent wilting point water content while a value of 100% represents a full profile at the field capacity level. KanSched defaults to 100%, but this value usually needs to be changed to reflect your initial soil water value.

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The Budget Screen TOP OF PAGE

The Budget screen (Figure 9) consists of rows of input for each day. These inputs include reference ET, rainfall, and gross irrigation. When these inputs are entered into KanSched, it can track the soil water that is available to your crop. The following sections describe the individual inputs needed and the program’s output.

Figure 9 – The Budget Sheet

Reference ET TOP OF PAGE

The reference ET values can be obtained from on-site measurements or from an automated weather station in your county or region. This value needs to be entered for each day of the season as KanSched tracks the water content. However, you can also enter the ET values from several days at one time. The reference ET can also be updated using the Quick ET button from the start screen.

Crop ET TOP OF PAGE

After the daily reference ET value is entered, KanSched will calculate and display the crop ET. This value is the amount of water (in inches) your crop used during each of the listed days. KanSched uses the crop coefficient values and the reference ET values to calculate the crop ET value.

Rain TOP OF PAGE

Whenever the crop receives rainfall, enter the value for the appropriate day in KanSched. This value will then be used to calculate your soil’s current water content. Rainfall is entered as a previous day value, as reference ET. So, if it rains on May 29th, enter that rainfall amount in the ‘Rain’ input cell for May 30th.

Gross Irrigation TOP OF PAGE

Input gross irrigation amounts into KanSched every time you irrigate your crop. You will notice that this is a gross irrigation amount. At the top of the budget sheet (Figure 9) is an input box labeled Irrigation System Efficiency. By default, a value of 100% is entered, meaning that KanSched uses the exact value entered into the Gross Irrigation box. If you know the efficiency of your irrigation system, you can enter it in the box at the top of the budget sheet. Then, each Gross Irrigation value will be recalculated to a Net Irrigation value (e.g. if you set the irrigation system efficiency at 80% and you enter 1.0 inch in the gross irrigation box, KanSched will use the Net Irrigation amount of 0.8 inches). Most sprinkler systems will have system efficiency values that range from 80% to 90%. If you are unsure, try 85%.

Measured Soil Water Availability TOP OF PAGE

KanSched gives you the option of entering your own value for the Soil Water Availability. KanSched tends to be a conservative estimate of soil water. Therefore, if KanSched is indicating that the soil is drier than it actually is, you can simply enter a new value for the soil water availability, automatically recalibrating KanSched to the accurate field-based values.

Calculated Soil Water Availability TOP OF PAGE

KanSched’s calculation of the available water in the soil is displayed in the Calculated Soil Water Availability column. This value can be defined as the percent of water that is available for the crop to use from the available water profile. When this value drops below your MAD value, the Calculating Soil Water Availability numbers turn red, alerting you to the current situation. A value of zero (0%) represents PWP while 100% represents field capacity.

Available Soil Water Content Above PWP TOP OF PAGE

Another way that KanSched interprets the soil’s current water content is in the Available Soil Water Content Above PWP column. This figure gives you an estimate of approximately how much water is in the soil that your crop can use before it enters the permanent wilting point (e.g. if the Available Soil Water Content Above PWP value is 1.5 inches, this means that 1.5 inches of water is available in the soil for the crop to use). Keep in mind that when the water content reaches the MAD value, crop stress is beginning to occur.

Root Zone Water Deficit TOP OF PAGE

How much water will it take to fill the soil profile to full capacity? The Root Zone Water Deficit value answers that question by displaying how much water (in inches) the managed root zone soil profile needs before the water would be lost either to runoff or deep percolation.

Effective Rain TOP OF PAGE

How does KanSched handle rainfall events on a soil that is already at field capacity? Basically, when the soil profile is at field capacity, any water that is applied to the field will either run off or be lost in the soil through deep percolation. KanSched keeps track of the soil’s current profile status and will ignore any rainfall or irrigation events that occur on the soil when it has reached field capacity. This ensures that the program won’t credit the soil with more water than it can hold when it receives many rainfall events (or one large rainfall event) in a short period of time.



The Summary Screen TOP OF PAGE

The summary screen (Figure 10) gives you a snapshot of the current total season amounts for your crop. You can get total reference ET, crop ET, rainfall, effective rainfall, gross irrigation amounts, and net irrigation amounts. A periodic check-up on this screen will let you know your current water-use statistics at a glance. As shown in Figure 10, even though actual rainfall was recorded as 2.00 inches, the field soil profile must have been wet and only 0.04 inches was effective.

Figure 10 – The Summary Sheet

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Soil Water Chart TOP OF PAGE

One of KanSched’s most useful features is the Soil Water Chart, shown in Figure 11. This chart shows a visual representation of the field soil water content as it changes throughout the season. In addition, each rainfall and irrigation event are displayed at the bottom of the chart. The horizontal axis of the chart is labeled with the dates of the crop season, while the vertical axis is in units of inches of water contained within the defined soil profile. Before fully utilizing the Soil Water Chart, one must understand how to read the chart. The following section describes each component of the Soil Water Chart.

The Soil Water Chart has the ability to get detailed information about any point on the chart. Using your mouse, position the cursor arrow and click on any line or column in the chart to get information about that point. This is an easy way to see how much rain or irrigation you received on a particular day, without having to scroll through the budget page to find the information.

Figure 11 – Soil Water Management Chart

Soil Water Storage at Field Capacity- TOP OF PAGE

The dark blue line that forms the upper boundary of the chart is called the Soil Water Storage at Field Capacity line. This line represents the total amount of water that your soil can hold before runoff or deep percolation occurs. This line also represents a water availability value of 100%. This value is determined using the soil characteristics from the input screen and the depth of the root zone, as are the PWP and MAD values described next.

Soil Water Storage at PWP- TOP OF PAGE

The dark red line that forms the lower boundary of the chart is called the Soil Water Storage at PWP line. This line represents the moisture content of the soil where plants are unable to pull the water from the soil, causing them to wilt and die. This line also represents a water availability value of 0%.

Soil Water Storage at MAD- TOP OF PAGE

The dotted red line represents the MAD level that you chose during the initial input process for your field. One way to manage your field’s soil water content is to attempt to keep the dotted green line (the calculated soil water content) close to the dotted red line (the MAD value). Of course, the MAD value is a simple visual representation of your management preferences, so you can ultimately manage the soil’s water content in any manner you wish. As the water content goes below the MAD value, plants may wilt and experience some stress. Therefore, KanSched derates or reduces crop coefficients when this occurs and simulated crop water use is reduced.

Soil Water- TOP OF PAGE

The dotted green line represents the calculated soil water content of the soil. As the days in the season progress, you can watch the status of your soil’s water content by monitoring this dotted green line. As the line increases, approaching the upper dark blue line, the soil’s water content is increasing. Likewise, as the dotted green line falls, approaching the lower dark red line, the soil’s water content is decreasing. A quick glance at the trend in the dotted green line will let you know the status of your soil water content and how much water might be available to the crop. One of the general management goals is to maintain the field water content above the MAD value until the end of the season.

Gross Irrigation- TOP OF PAGE

Each irrigation event is represented by a dark blue column on the date the irrigation was received. The height of the column reflects the amount of the irrigation event.

Rain- TOP OF PAGE

Much like the irrigation events, a light blue column represents the rainfall events on the date the rainfall was received. The height of the column reflects the amount of rain received.

Using ET Groups with KanSched TOP OF PAGE

Often times, you will be managing many fields within KanSched that all require the same daily reference ET value. If all of your fields are within the same general area where you get your daily reference ET value, you can place all of your fields into one ET Group. Managing multiple fields in KanSched is an easy task with the use of ET Groups. Initially, every new field is identified as an Individial Field, meaning each field’s reference ET values are unique to that field alone. Basically, once you create an ET Group and add your fields to the group, each field’s daily reference ET values can be automatically updated by entering the value just once. The following section will describe how to create an ET Group, place your fields within the group, and update the daily reference ET for the group.

Creating an ET Group TOP OF PAGE

You can create an ET Group and place fields within that group any time during the season. However, you may find it easiest to create an ET group for your fields at the beginning of the season. The following steps will guide you through the ET Group creation process.

1.) Start KanSched and select Start a New Field from the menu on the start screen (Figure 1.)

2.) Select the Create a New Group from the Field ET Info box on the right side of the main input screen.

3.) The Create a New ET Group window will now be displayed on your screen (Figure 12). Enter a name for your ET Group in the box labeled New Group Name. Give the group any name you want; however, it’s handy to name the group according to the region it represents (i.e. fields from the eastern part of your production area could be placed in a group called Eastern Group, or the name may be associated with a specific weather station). Once you have entered a name, click the Create this new group button.

Figure 12 – The Create a New ET Group window

Your new group will appear in the Field ET Info box on the main screen. When you create a new field, or open another field already created, you can simply click on the ET Group from the list to assign the field to that group.

*If you have already entered reference ET data into a field and try to assign that field to a new ET Group, the following window will appear (Figure 13).

Figure 13. Change ET Group Screen

Since the field has never been in an ET Group, it was assigned the Individual Field status, this window (Figure 13) appears. To place the field into the new ET Group (in this example, Demo Group), click the Yes button. If the field already contains some reference ET values, the window in Figure 14 will appear. To have the new ET Group copy the existing reference ET values from the field, simply click the Yes button. This feature is convenient if you create the ET Group halfway through the season and do not want to reenter every value, you can simply have the group copy the values from an existing field. If the No button is pushed, the new ET Group will not have any reference ET values associated with it and any existing reference ET values in the field that is being placed into the group will be erased.

Figure 14. Copy ET Values Screen

Managing ET Field Groups TOP OF PAGE

As mentioned earlier, you can view, rename, and delete ET Field groups from the View ET Field Groups button on the start screen, or from the ET Field Groups menu at the top of the main screen. It is important to note that when you delete an ET Field Group, the fields within the ET Field Group are NOT deleted! They are simply reassigned as Individual Fields, using their own reference ET data instead of the group’s data.

To enter daily reference ET values, review the section entitled Quick ET .

Extra Features in KanSched TOP OF PAGE

KanSched has several built in utilities to increase the functionality of the program. The following section will describe each of these utilities.

Archiving a Field TOP OF PAGE

When you have completed one season and you are ready to start entering data for the next season, you can begin a new season for the same field without having to create a new field or delete the old data. Archiving a field is easy. At the end of the crop season, or before you start entering data for the next season, select Start a New Season and Archive Current Season from the Options menu at the top of the main screen. Archiving safely stores all of your field’s information and can easily be recalled for viewing by selecting View an Archived Field from the Options menu. Once your field is archived, KanSched automatically prepares your field for a new season by advancing all of the dates by one year. Obviously, those dates are likely to change, as well some of the other inputs. You will need to double check all of the field input information to ensure it still reflects your crop and season information.

Export Season Data to Text File TOP OF PAGE

If you are familiar with using spreadsheets to analyze data, you will find KanSched’s Export Season Data to Text File very useful. This feature is found in the File menu at the top of the main screen, under the item Export Season Data to Text File. When you select this option, you will be given the option of where to save the text file. After designating where you want to save it, and the name of the text file, KanSched will automatically generate a fixed width text file with all of the daily season values (Date, Reference ET, Crop ET, Rain, Gross Irrigation, Measured Soil Water Content, Calculate Soil Water Content, Root Zone Water Deficit, and Effective Rain). This text file can then be imported into any spreadsheet program you desire to use.

Still Have Questions? TOP OF PAGE

If you have a problem operating KanSched, or another KanSched related question, you can check with your local county extension agent. Many agents are familiar with KanSched and can refer any questions on to the MIL Team members for you.