Water Testing Calculator

This calculator was developed to support the water testing program now available in 21 counties in Illinois that have access to nitrate sensors. Farmers can bring in tile, stream, or surface water samples from their farms and have them tested – for free, and confidentially – for nitrate concentration.

A nitrate concentration from one sample simply shows a snapshot in time. Nitrate concentrations can vary considerably based on recent weather events, soil types, crops, and other in-field practices. While this calculator uses results from one nitrate concentration to project nitrate losses, it is simply meant to start a conversation with a farmer and put nitrate loss into a context they are familiar with – pounds of nitrogen lost per acre, and the monetary loss that goes along with it.

This calculator takes the nitrate concentration from a farmer’s sample, as well as flow and acreage data, and projects the following, assuming their concentration and flow remained the same:

  • How many pounds of nitrogen they might lose per day
  • How many pounds of nitrogen they might lose per acre, per day
  • How much money* they might be losing per day
  • How much money* they might be losing per acre, per day
  • How much money* they might lose over the course of a year (if conditions were the same every day for the number of months specified for tile or ditch flow)

* It should be noted that a significant portion of tile drainage nitrate loss each year comes from soil organic nitrogen that has naturally mineralized. Applied fertilizer is not the only source of nitrate in drainage. It is well established that if you're growing an annual crop like corn or soybeans, you could still lose nitrate in drainage water without applying any fertilizer. 

To achieve the most meaningful results, a farmer should collect samples weekly or biweekly and monitor changes in nitrate loss over a season.

Print this table so you can keep track of your results over time. 


Nitrate Load Calculations

Nitrate-Nitrogen Concentration from sample:  
(mg/L, also ppm)

Collection Method: *The default calculation uses 2 gallon buckets

Flow Rate:  

Acres Drained:

How many months of the year do you have flowing
water at the point where you collected your sample?

Enter your nitrogen costs per ton below for anhydrous ammonia OR liquid nitrogen 28% (but not both). You can also check current average prices via the link. Average prices for these products are listed in the middle column on the site.

Anhydrous Ammonia
  Check Current Prices   

Liquid Nitrogen 28%
  Check Current Prices   

Concerned about your numbers? Talk to your local NRCS or SWCD office, Certified Crop Adviser, or research your BMP options here.