Phosphorus Loss Assessment using PLATO – AgriSuite’s newest calculator

manure being applied prior to corn planting in 2020

Introducing….to your mobile device or computer, the newest in a series of on-line calculators. The phosphorus loss assessment tool for Ontario, nicknamed PLATO, will help determine the risk of phosphorus (P) loss from nutrient applications at a field scale.
PLATO takes both field characteristics, such as erosion risk and soil test level, as well as P application practices into account, and can help to verify improved phosphorus management.
PLATO confirms in numbers what consultants have been promoting for years when it comes to phosphorus management. Timing and placement are critical factors in reducing the risk of phosphorus loss. For example, the P index for manure surface applied on frozen soil will almost always trigger a high or very high risk while the same manure applied just ahead of spring planting or to a growing crop will often have a low to moderate risk.
In Figure 1, a summary screen displays the relatively low risk of P loss given the input data for the field used in this example. Information icons provide further breakdown of how P is most likely lost from a field and provides some management strategies/suggestions to consider for reducing the chance of P loss from field characteristics and/or from material applications. These suggestions do not consider what practices may already be occurring in the field.


Figure 1: Screenshot of PLATO summary where P loss risk is considered low from planter-placed starter and fall applied hog manure ahead of a corn crop

P index summary in PLATO

Field Characteristic index considers:

  • Particulate P from surface runoff/erosion
  • Dissolved P from surface runoff
  • Particulate P through tile
  • Dissolved P through tile

Application loss index

  • Phosphate contributions from surface water and through tile from fertilizer and manure application

Impact of soil test P:

The possibility of surface water contamination by phosphorus cannot be based on soil-test phosphorus level alone.  Phosphorus binds tightly to soil particles (particulate P) and the movement of eroded soil from a field by runoff (overland or through surface inlets and, in some cases, soil macropores to drainage tile) is a major factor in determining the likelihood of surface water contamination.   

When soil test results indicate that no additional phosphorus is required to achieve maximum economic yield, the risk of dissolved phosphorus movement increases in both overland and tile drainage waters.  

Manure nutrients contain nitrogen, micro nutrients and organic matter and are often applied even when phosphorus needs have been met.  Frequent manure applications can lead to a buildup of soil test phosphorus, which can increase incidental P losses.  When manure application is planned in rotation, at rates to match crop needs along with proper timing and placement, the risk of phosphorus loss can be low. 

Risk of phosphorus loss will never be totally eliminated. However, using the PLATO tool can help identify areas of greatest risk and opportunities for improvement. A crop needs-focused nutrient management planning approach, combined with 4R Nutrient Stewardship principles, is one of the best ways to minimize risk of P loss.

A step by step guide for using and interpreting the results from the PLATO calculator in agrisuite can be found at PLATO user guide

Give PLATO a try today at:

Or: Google OMAFRA AgriSuite

Or: “Hey Google/Siri:  Find OMAF’s new nutrient management software”

manure being surface applied prior to corn planting

Additional Calculators  available in AgriSuite:

Crop Nutrient Calculator – provides the crop nutrient requirements and crop removal of a crop when location, yield goal and soil test information is provided

Organic Amendment Calculator – provides available nutrients from manure or other organic amendments using analysis or data base information with timing and rate and placement of application as well as micro nutrients applied and approximate value of crop available N-P-K after cost of application

Fertilizer Calculator – provides a summary of nutrients applied from different applications or can provide a blend to supplement the difference between nutrients provided (e.g. by manure) and what is needed by the crop.

This project was funded in part through the Canadian Agricultural Partnership (the Partnership), a federal-provincial-territorial initiative.