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Online calculators help growers improve nitrogen, water efficiency - meet regulatory requirements

Almonds in hand
Harvested almonds.
The Almond Board of California has created a tool - the Almond Nitrogen Calculator - which not only helps you manage your nitrogen applications for efficient fertilizer use, but also generates a Nitrogen Management Plan as required by the Irrigated Lands Regulatory Program.

As we await proposed changes to the Irrigated Lands Regulatory Program (ILRP), current requirements are still in place for all Central Valley Water Quality Coalitions, including farm evaluations, nitrogen summary reports, and a sediment and erosion plan.

In high-vulnerability groundwater areas, growers are required to submit certified summary reports annually. In low-vulnerability areas, the report must be kept on-site and certification is not required.

It is important to comply with these requirements as the Central Valley Regional Water Board is actively enforcing the program with heavy fines for growers who have not signed up for a coalition or who have not submitted a Nitrogen Management Plan (NMP).


The Almond Board of California (ABC) has created a tool - the Almond Nitrogen Calculator - that not only helps you manage your nitrogen applications for efficient fertilizer use, but also generates a NMP as required by ILRP.

The N Calculator:

  • Calculates fertilization rates based on newest University of California nitrogen management research;
  • Follows the Four R’s of nutrient management (right source, right rate, right timing and right location);
  • Is based on crop demand and accounts for tree demand as well;
  • Enables efficient fertilizer use;
  • Has a library of fertilizers in pull-down menus for easy rate calculations, based on data you enter in the system;
  • Calculates nitrogen contributions from non-fertilizer sources, including groundwater, compost, and legume cover crops;
  • Recalculates fertilizer rates as April leaf sample data and/or better yield estimates become available during the season; and
  • Can clone the N budget from one orchard to another within and between years if orchards are similar.

This Nitrogen Calculator uses models based on measuring demand throughout the Central Valley and developed by UC Davis plant scientist Patrick Brown and colleagues to predict how much nitrogen to apply and when to apply it to meet yield-based demand.

To use the tool, growers enter their yield estimates pre- and post-bloom, including any additional sources of N including groundwater and organic matter. The calculator then provides recommended N to be applied for the growing season.

Post-bloom, estimates can be updated with better data, including yield estimates, amounts of groundwater applied (to account for N in groundwater), and to add early-season tissue sampling results. The yield estimate can be revised as many times as necessary between post-bloom and final harvest.

Growers enter when and how much fertilizer was applied; ideally, during the recommended timing of early spring after leaf-out, fruit growth, kernel fill, and fruit maturity/early post-harvest.

At the end of the season, actual yields are entered, along with the actual amount of water applied if groundwater is the source, and the tool will recalculate the efficiency for the season.


The Mapping Tool, also part of the N Calculator, allows users to draw boundaries of their fields and enter assessor’s parcel numbers (APNs), and then drop pins to plot the locations of active or abandoned wells or observation wells, plus discharge points and any other feature you wish to record.

When you have that map along with borders or APNs, you can create a map report required as Part D of the ILRP farm evaluation plan, and is also required to be on file for your NMP. The Mapping Tool and Nitrogen Calculator are integrated so the information does not have to be entered twice.

For growers who have fields in multiple coalitions, which may have different reporting requirements, the Mapping Tool and the Nitrogen Calculator allow you to enter the name of the coalition and create separate reports for each coalition.


For efficient nitrogen management, efficient irrigation management is essential.

Today, most nitrogen applications in almonds are made by fertigation. Key areas that affect nitrogen efficiency are irrigation distribution uniformity and applying the right amount of water by using an irrigation frequency adapted to your soils to avoid water moving below the root zone.

To accomplish the latter, consider adding nitrogen later in the irrigation run to keep it closer to the roots.


When using fertigation, growers are relying on the applied water to move the nitrogen into the soil in the root zone. A key assumption is that the irrigation system is applying the same amount of water throughout the system, and that it is applying a defined amount of water per hour.

Unless you are regularly checking and maintaining the irrigation system, the assumptions of uniformity and rate of application are likely incorrect. If so, parts of the orchard may be under-or over irrigated and consequently under-or-over fertilized.

To find out more about maintaining an irrigation system, please refer to the Almond Irrigation Improvement Continuum at An important step in improving both irrigation and nitrogen efficiency is to test your irrigation system for pressure variation and distribution uniformity, and make adjustments as necessary.


Another online tool, the Irrigation Calculator, can be used to increase irrigation efficiency by recommending the amount and timing of water to be applied to almond orchards based on evapotranspiration (ET), and taking into consideration information about the individual orchard and irrigation system.

By automating the recommendation, growers can save time, and because the tool is integrated with active CIMIS stations to calculate ETo, you’re assured that the trees are neither overwatered nor under-watered.


The Nitrogen Calculator, Irrigation Calculator and Mapping Tool are available at the California Almond Sustainability Program (CASP) website, Once there, take the time to fill out some of the CASP modules, which are being used to demonstrate the sustainability of the California almond industry.

This website has recently been relaunched with reactive web design, which means now it is accessible using mobile devices for login, navigation, assessment, reporting, and the calculators.

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