Now that you have a ranch established in CropManage, you are ready to add plantings to the ranch.   Each  “planting” in CropManage consists of a set of tables for keeping records of soil tests, irrigations, and fertilizer applications associated with a specific crop planted on a ranch.  

Each planting is unique, and should correspond to an actual crop planted on your farm or ranch, with a specific establishment and harvest date, field location, and acres. The planting also requires information about the irrigation system, crop type,  and previous crop residues.  This initial information is used later by CropManage to provide decision support on irrigation and fertilizer applications.  Once a planting is established in CropManage, there is no need to reenter the initial information unless updating is needed.  

After selecting a ranch, a list of current plantings will be displayed in “Ranch Home“ (Fig. 1).   Selecting new planting below the planting list table will navigate to the “new planting form”(Fig. 2). 

Figure 1.  A table in ranch home displays a list of current plantings.   Select “new planting” below the summary table to start a begin editing a new planting.

Give the planting a name and select a crop Fill in the name of the planting, start (first irrigation) and end dates (last harvest) of the crop, year, and select the field or lot from the pull down menu.  The soil type of the lot is used for irrigation, soil test, and fertilizer calculations.  If the lot is not listed, then the virtual ranch owner needs to enter the lot information in the “edit ranch” form.   Also select the crop type and planting configuration from the pull down menu.

Select save after all information is entered and a new window will display for entering additional information (Fig. 3).  In many cases, default values are provided in the forms that are typical for coastal vegetable crops.   When in doubt, use the default values.

Previous crop CropManage estimates N contribution from incorporated residue of the crop when calculating the nitrogen fertilizer needs of the current crop.  Select the type of previous crop that preceded the current planting (Fig. 3).   If the previous crop is not displayed in the pull down menu, then select a crop that approximates the amount and type of residue observed.    If no crop preceded the planting or if the interval was more than 2 months, then select “no crop residue within 2 months.”   Change the interval between residue incorporation and planting from the default value (30 days) to the actual value. 

Figure 2.  To begin a new planting, enter the name of the planting, crop type, first irrigation and end dates (harvest date) of the crop into the new planting form.

Figure 3.  Enter previous crop information so that CropManage can estimate N contribution from incorporated plant residues.

Figure 4.  Irrigation system information is entered into the new planting form for calculating the volume of water (inches) and time to irrigate. 

Irrigation information CropManage uses information about the irrigation system for calculating the amount of water and time to irrigate (Fig. 4).   If drip and sprinklers will be used for irrigating the crop, enter values for both types of irrigation methods.   Currently, CropManage does not support furrow irrigation.  

The application rate of the irrigation system in units of inches per hour must be entered to convert the volume of water applied to application time.   Default values are provided in the form, but these values may vary greatly from the actual rate if the irrigation system is atypical.  A calculator for estimating the application rate appears when the cursor is placed in the application rate form for drip or sprinkler (Fig. 5).    Application rate can be estimated for sprinklers by entering sprinkler head type, lateral pipe spacing, sprinkler head spacing, nozzle pressure, and nozzle orifice diameter (Fig. 5).   Application rate can be estimated for drip by entering the flow rate of the tape, bed width, and number of tapes per bed (Fig. 5). 

Leaching fraction for salt management  A leaching fraction value greater than default value of 0% should be entered if the irrigation water has a salinity concentration that would reduce yield (Fig. 4).   Bulk salinity is measured with an electrical conductivity (EC) meter in units of deciSiemens per meter.   EC increases with salinity content of water or soil.  The salinity threshold of irrigation water at which yield is reduced for lettuce is approximately 1 to 1.5 dS/m depending on the specific types of salts in the water.   A leaching fraction that adds an additional 15% to 30% more water to the irrigation recommendation would be typical if the irrigation water has salinity levels in the range of 1 to 2 dS/m.

Figure 5.  Calculators for drip and sprinklers can be used to estimate the application rate of the irrigation systems. 

Irrigation distribution uniformity The irrigation recommendations for the planting are adjusted for non-uniformity of the irrigation system using values entered for distribution uniformity (DU) of the drip and sprinkler systems.  Distribution uniformity is the ratio between the average application volume for the driest part of the field (typically the driest quarter) and the average application volume of the entire field:

The DU of an irrigation system that provides perfect uniformity would be equal to 100%.   Typical default values are provided for sprinklers and drip but they should be adjusted to reflect actual conditions of the crop.    Drip tape that has been retrieved and reused for more than 8 crops may have a DU substantially less than 90%.  Likewise, sprinklers that are operated under high wind conditions may have a DU lower than 75%.   

Two different DU values can be entered for the sprinkler system if different equipment configurations are used for the germination and post establishment phases, or to reflect different tolerances for dry zones in the field during germination and post-establishment.   During crop establishment (germination or transplant establishment), one may want to assure that dry areas in the field are minimized by lowering the DU value.    A DU corresponding to the driest tenth of the field typically will be 10% to 15% less than a DU for the driest quarter of the field.     

Total amount of nitrogen taken up by the crop  The N fertilizer recommendation is based on an N uptake curve for each crop type and planting configuration.  This curve can be adjusted by increasing or decreasing the total N uptake value or increasing the interval between the first irrigation and the harvest (end of crop).  For each crop type and planting configuration supported, CropManage provides a default value for the total amount of nitrogen that the crop will take up in units of pounds of nitrogen per acre (Fig. 6).   The default values are averages of measurements from commercial fields.  The value may need to be increased or decreased to reflect factors such as a lower or higher plant population, smaller or larger than normal sized plants, or varietal differences.      

Figure 6.  Planting form entries for N fertilization recommendations: crop total N uptake, maximum fertilizer N recommendation, and days between consecutive fertilizer events.

Two other entries needed for making the fertilizer N recommendation are the maximum N recommendation and a default value for the days to next fertilization.  To prevent fertilizer N recommendations that are excessive due to incorrectly entering information, CropManage includes a maximum N recommendation value that limits the amount of N fertilizer recommended. This value may need to be increased for plantings where only 1 or 2 nitrogen fertilizer applications are made.  An estimate of the days until then next fertilizer application is needed to predict future N uptake of a crop.   A default value can be set in the planting form, but adjusted later when fertilizer events are entered.  

Flow meter data retrieval  Water applications can be monitored using a flow meter capable of producing an electronic output signal that can be recorded with a datalogger.   Currently, automated retrieval of flowmeter data to CropManage is limited to using Campbell Scientific™ dataloggers equipped with cell phone modem or radio communications.   CropManage can be configured to automatically retrieve flowmeter data for a planting at hourly intervals by entering the datalogger file name and the areas monitored under drip and/or sprinkler irrigation (Fig. 7).  Leave these entries blank if no flow meter will be used with the planting.  Contact Michael Cahn (mdcahn@ucdavis.edu) or Barry Farrara (bffarrara@ucdavis.edu) for further details on how to use flow meters for monitoring water applications using CropManage.    

Figure 7.  Form entries for flowmeter information and lot latitude and longitude coordinates.

Lot coordinates  The lot is the actual planted area within a field.  Because some fields are split into several plantings, lots can be small than the field area.  Latitude and longitude coordinates of the planting (lot) can be entered in the planting form (Fig. 7).  A mapping tool will appear to assist in locating the field when the curser is placed in the Lot Coordinates box (Fig. 8).

 Figure 8.  Mapping tool for finding the latitude and longitude coordinates of a lot

Don’t forget to save!  When satisfied with all planting entries select save at the bottom of the planting form.  Edit entries at anytime to update planting information.    

To set up a new ranch, click on the "new ranch" button at the bottom of the ranch list screen after logging on.  You can also edit existing ranches that you previously set up by clicking on the ranch and selecting "edit ranch" from the menu.  Note that you must be the "ranch owner" to edit the ranch.

Adding a new ranch or editing an existing ranch in CropManage has been made easier with the new online form under “add ranch,” which appears as an option on the left hand side of the screen (Fig 1). You can also still use the original method of filling out the downloadable spreadsheet template that can be selected on the right side of the menu. 

CropManage uses information about your farm/ranch to develop recommendations on irrigation and N fertilizer management.  Ranch data includes the main soil type and acreage of each field, well information, nearest CIMIS stations, commonly used fertilizers, and setting preferences for managing weather data and user access.   By entering the information when the ranch is set up, the data is available for all plantings on the ranch, and does not need to be reentered when using CropManage for future irrigation and fertilizer decisions.

Fig. 1.  Two options for adding a new ranch include using the online form or importing ranch information using the downloadable excel spreadsheet.

Step 1: Ranch Info Tab  Add ranch name, ranch owner, and total acreage of ranch under the “info” tab (Fig. 2.)  The ranch owner does not need to be the actual ranch owner.  This should be the person that has the responsibility of managing the ranch information on CropManage and who will be responsible for granting access and permission to users.  If you would like the ranch information to remain anonymous, then use a pseudonym for the ranch name and do not enter the ranch latitude and longitude coordinates.   Keep in mind that ranch location information is need for importing spatial CIMIS reference evapotranspiration (ET) data. 

Fig. 2.  Information tab on the online ranch form.

Getting lat and long coordinates of a ranch If you will be using Spatial CIMIS, you must enter the ranch latitude and longitude coordinates.  If you do not know the coordinates, then you can use a tool for locating the ranch by clicking in the ranch coordinates box (Fig. 3.)  Using the Google map tool, you can zoom to the location of the ranch.  Switch the display to satellite to see field boundaries.  Click on the thumbtack in the upper left hand corner to activate coordinate selection, and then click on the map where the ranch is located.  Choose save to import the lat. and long.  coordinates into CropManage.  

Fig. 3.  Google map tool for selecting latitude and longitude coordinates of a ranch.

Step 2: Ranch Options  Select the CIMIS weather and privacy options under the “options” tab (Fig. 4.)  Choose if you want to get reference ET data directly from CIMIS weather stations or from Spatial CIMIS.  Note that spatial CIMIS needs latitude and longitude coordinates of your ranch to function.  Choose if you want to use CIMIS ET data from a particular weather station and set an order of preference for back up stations if data is not available from the first station (sequential mode) or average ET data from several stations.   

The ranch owner can decide if latitude and longitude coordinates can be entered for the ranch by selecting in the coordinates option.  By selecting” no coordinates entry” option no user with access to the ranch can enter latitude and longitude coordinates.  This option will keep the location of the ranch anonymous.  Again, Spatial CIMIS needs the location coordinates to function.  If you choose the “no coordinate entry” option then you will need to choose a specific CIMIS station for the ET data.

Fig. 4.  Options tab for selecting preferences for CIMIS weather data and privacy.

Step 3.  Choose CIMIS stations   The CIMIS stations tab (Fig. 5) is used to enter active CIMIS weather stations that will provide reference ET data for all plantings associated with the ranch.   Even if you choose to use Spatial CIMIS, it is a good idea to enter the closest stations  to the ranch in case spatial CIMIS data is not available or you want to change ET options at a future time.    Use the “add station” button at the bottom left to see a list of all active CIMIS stations that are not currently associated with the ranch.  You can sort the list by county or station number by selecting the list heading.   After locating the station of interest, select the station number to add it to the ranch.  Repeat this process for all stations .  If you selected the sequential mode, the station at the top of the list will be the first station that CropManage uses for ET data to calculate the irrigation schedule.  You can change the station preference order by selecting the arrows on the far right of the table (Fig. 5)

Fig. 5. CIMIS station tab for associating CIMIS weather stations with the ranch.

Step 4.  Add field/lots to ranch   Field or lot names are designated on the “Lot” tab   (Fig. 6).  Select “new lot” from the bottom left of the screen to enter a new field.  Add a name and area (acres) of the field and then enter the soil type.  If you do not know the soil type, then use the “find soil type” tool to the right of the form to determine the soil type of the lot.   The tool links to the UC Davis SoilWeb using a google map application.   Switch to satellite view to see field boundaries and click on the location of the field to obtain the soil properties needed for CropManage (Fig. 7.)  A table will appear with the soil properties for the 1 and 2 foot depths (Fig 8.)   By clicking on “Select this data,” you can associate the soil properties with the field.  To save the soil properties, select OK in the window that appears asking to update soil properties.  Be sure to click the “save lot” button on the bottom left of the screen before continuing.

Fig. 6. Lots/fields are added or edited in the “Lot”  tab.

Fig. 7. Use the “Find Soil Type” tool to determine soil properties of the field.

Fig. 8.  Soil property table is displayed after selecting the soil type using the Google map tool.

Step 5.  Enter wells   Using the “well” tab, well names and average salinity and nitrate concentration of the water can be added to the ranch (Fig. 9.)    Although currently not available, we plan to add algorithms that determine the nitrogen contribution of the irrigation water to the crop and also determine an appropriate leaching fraction to apply to minimize salinity effects on the crop. 

Fig. 9.  The “Well” tab allows entry of ranch well information.

Step 6.  Add/Edit users  Using the “user” tab the ranch owner can determine which CropManage users can have access to their ranch and planting information and also set the level of access to the data (Fig. 10.)     The ranch owner may decide that some users cannot have access to specific information, or can only view the data. 

Fig. 10.  The user tab allows the ranch owner to customize the level of permission for users.  

Step 7.  Add Fertilizers  Customize a list of the commonly used fertilizers for the ranch in the “Fertilizer” tab by selecting  “add”  in the far right column (Fig. 11.)  The selected fertilizers will display in a drop down menu when entering fertilizer events for the plantings.   The database automatically converts between gallons or lbs of fertilizer to lbs of nitrogen using the conversions shown in the table.  You can also enter fertilizers not shown on the tab using the “create fertilizer” button at the bottom left of the screen.  

Fig. 11.  A fertilizer list can be customized for a ranch under the “Fertilizers” tab.  

Summary 

Although setting up the ranch information requires some upfront investment of time, this base information eliminates the need to reenter data required later for calculating fertilizer N and irrigation recommendations.  At anytime, ranch information can be edited or updated.    If you are in a hurry, then just enter the minimal data needed.  For example, you do not need to enter information for all fields on the ranch or add all the fertilizers to the fertilizer list.  These can be added at a later time. 

Now that the ranch information is updated, you are ready to start adding new plantings and using the soil test, fertilizer and irrigation functions of CropManage.   

Understanding the nutrient value of nitrate in irrigation water often leads to confusion. Laboratories commonly report nitrate concentration of water samples in parts per million of nitrate (PPM NO₃).  However, as shown in Table 1, the reported nitrate value must be multiplied by 0.225 to express it in equivalents of nitrogen (PPM NO₃-N).   This conversion is required because the nitrate molecule has three oxygen atoms for every nitrogen atom, meaning that the nitrate molecule is 22.5% N by weight. 

Several more calculations must be made to determine the pounds of N contained in a volume of water.   Factors for converting PPM NO₃ or PPM NO₃-N to lbs of N per acre-foot (or acre-inch) are presented in Table 2.   For example, multiplying a water test of 45 PPM NO₃ by 0.62 would determine that an acre-foot of water contained about 28 lbs of N.  If the same water test was reported as PPM Nitrate-N it would be equivalent to about 10 PPM N and would be multiplied by 2.72 to convert to lbs of N per acre-foot of water. 

How much of the nitrogen in irrigation water should be credited as fertilizer value to a crop is debatable, especially for shallow rooted vegetables such as leafy greens.   It is unclear if leafy green crops can make use of nitrate in irrigation water when concentrations are less than 20 ppm NO₃-N.  The soil nitrate level that optimizes lettuce growth is considered to be in the range of 15 to 25 ppm NO₃-N.   But this concentration is expressed in terms of weight of nitrogen per weight of soil (mg of N/kg of soil).  Since soil is about 20% to 25% water by weight, the nitrate concentration in the soil water of most commercial lettuce fields would range between 60 to 120 ppm NO₃-N.   Field monitoring of nitrate concentration in soil water using suction lysimeter tubes installed in the root zone of lettuce has confirmed that most commercial fields are in the range of 50 to 150 ppm NO₃-N, which is substantially higher than the concentration of nitrate found in most irrigation water.   

Applying a leaching fraction to minimize the build-up of salt in the soil would also affect how to credit the fertilizer value of nitrate in irrigation water.  Much of the nitrogen contained in the extra water applied to leach salts would presumably percolate beyond the root zone and not be available to the crop.    In the Salinas Valley, growers report that ground water with a high nitrate concentration often has high levels of sodium and chloride salts.   These water sources are often from shallow wells, where both salt and nitrate have leached over time into the aquifer.    In these circumstances where elevated levels of salts are associated with high nitrate concentrations, a greater leaching fraction may be required and therefore less of the nitrate can be credited to the crop.

Irrigation efficiency can also factor into estimating the fertilizer value of nitrate in irrigation water.  Fields with irrigation systems that apply water with poor uniformity would have areas where water drains below the root zone and other areas where less than the desired volume of water is applied.     

Considering the above concerns, perhaps the fairest way to value nitrate in irrigation water is to take credit for the water that the crop uses for evapotranspiration (ET).  This would be equivalent to the volume of water that enters the plant roots or evaporates from the soil surface leaving salts including nitrate behind.   Lettuce transpires 5 to 8 inches of water between germination and maturity in the lower Salinas Valley during the summer.   Factoring in irrigation system uniformity also makes sense.   If the irrigation system uniformity is 80%, one may assume that 20% of the N in the applied water would likely percolate below the root zone and would not be available to the crop.  For a crop that has a seasonal ET of 7 inches and an irrigation uniformity of 80%, the following values (Table 3) would approximate the N contribution of irrigation water for the indicated range of nitrate concentrations.   Most wells in the Salinas Valley with elevated concentrations of nitrate are less 20 PPM NO₃-N; therefore, we would expect that for most wells with this range of nitrate concentration, the irrigation water would contribute 20 to 30 lbs of N/Acre to a lettuce crop.

Conclusions

Growers have long been advised to reduce their standard nitrogen fertilizer rate if their irrigation water is high in nitrates.    Extension publications commonly suggest that one can credit the nitrogen in irrigation water by multiplying the concentration of nitrate by the volume of water applied to a crop.   As can be seen from the above estimates, water containing less than 45 ppm NO₃ generally does not contribute a significant amount of nitrogen to crop growth (< 15 lbs N/acre). However, if well waters contain more than that amount, irrigation water may contribute greater amounts of nitrogen for crop production.  In the future, we hope to conduct field trials to verify these estimates of the fertilizer value of nitrate in irrigation water.

Irrigation water is only one of several possible sources of nitrogen for a crop.  The soil organic matter, added organic amendments, and previous crop residues continuingly mineralize releasing nitrogen.  Fertilizer N is also periodically applied through sidedress and fertigation applications or as a slow release product.   The good news is that you can account for the N contribution from the nitrate in the applied irrigation water as well as these other sources by using the quick nitrate soil test.  However, keep in mind that this test only shows what has happened, and will not estimate the contribution of N from these sources, including irrigation water, to predict future crop N needs.  

Table 1.  Conversion factors between NO₃ and NO₃-N

 Conversion between nitrate (NO₃) and nitrate-nitrogen (NO₃-N):

Table 2.  Factors for converting between nitrate concentration in irrigation water and pounds of N per volume of water.

Nitrogen content of irrigation water*

* water analyses from most labs report NO₃  in units of ppm, but it is very important to pay attention to which units the results are reported.

Table 3.  Estimated fertilizer N value of nitrate in irrigation water for lettuce production.

* multiplied by 0.8 to account for the irrigation system efficiency

CropManage Workshop

Monterey County Agricultural Center Conference Room

 1432 Abbott St, Salinas CA 93901

Wednesday, March 13^th / Tuesday, April 2^nd 2013

(9 am – 11 am)

We will offer two hands-on workshops to learn in depth about the features of CropManage, a new Web-tool that provides decision support on irrigation and N management of lettuce.   Learn how to use CropManage for improving the efficiency of your farming operations or for adding value to your consulting services.  Wi-Fi internet access is available at our conference room so you are welcomed to bring a laptop or tablet computer so that you can follow along as we tour through the features of the software.   There should be sufficient time to answer questions as we cover the following topics: 

1. Purpose and main features of software
2. Getting started with CropManage (login, setting up new ranches, adding new plantings, fertilizers).
3. Using CropManage for decision support and record keeping (soil nitrate quick test, recommendations on N fertilizer and irrigation schedules, maintaining fertilizer and irrigation records).
4. Additional features (advanced settings, exporting data, integrating flow meter data).
5. Discussion of new features or changes needed.

To keep the group size manageable so that we can provide individual help, we would like to limit each workshop to 20 participants.  Please RSVP in advance by sending an email to  larriaga@ucdavis.edu with the subject heading “CropManage workshop” and let us know which workshop (March 13 or April 2) you will be attending and the number of participants in your group.  We will email you a confirmation

Hope to see you soon,

Michael Cahn