Have you ever wondered, am I losing nitrogen from my field?
retaiN seeks to give farmers and landowners the tools and information they need to make the best decisions on their land, starting by helping to test for, understand, and retain their nitrogen.
retaiN is a compact kit that includes nitrate test strips. Nitrogen is vital for crop growth and is taken up by plants primarily as nitrate (NO3-). Use this kit to understand if nitrogen is staying in your field where your crops need it most.
How to use this kit - - -
What's included?
The kit includes 10 - 12 nitrate test strips in an air-tight plastic tube. Make sure that you keep the desiccant in the tube, and the caps securely on the tube to ensure that the strips do not activate before you are ready to use them.
The kit also includes a one-page guide on using the kit and a test card to interpret your results.
Where should you take your water sample from?
We recommend sampling the outlet of tile lines leaving your fields (see photo below), as that will have the greatest relationship to your land management practices. Make sure that you continue to use the same tile outlet each time you sample.
As you gain experience with the kit consider testing two fields with different management. Make sure that you test both fields on the same day to ensure that you're comparing management rather than other variables like precipitation.
When should you sample?
The majority of nitrogen loss occurs in the Spring when no crops are actively growing (see figure below). A smaller amount of nitrogen is lost in the Fall for the same reason. Nitrogen loss can also occur when fertilizer or manure is applied when the crop is not actively growing, or when it is applied in excess of what the crop needs.
Choose a sampling strategy that will work with your schedule. We recommend, at minimum, sampling once per month when tile lines are running. Prioritize March, April, May and June – and secondarily, October and November so you can understand the maximum extent of potential nitrogen loss.
This figure illustrates the times of year when corn and soybean fields are the most vulnerable to nitrogen loss through leaching (red shaded area). In Iowa, the primary way that nitrate is lost is through tile lines. Figure taken from ISU Extension Publication CROP 3162: "Field Crop Production Handbook."
How do you sample?
Step #1: Dip strip into water for 1 second (or pass under gentle water stream) and remove. Do not shake excess water from the test strip.
Step #2: Hold the strip level, with pad side up, for 30 seconds. Compare the NITRATE test pad (top pad) to the color chart. Estimate results if the color on the test pad falls between two color blocks.
Remove sunglasses before reading the strip. The pad will continue to change color, so make a determination immediately after 30 seconds.
Record results.
Interpreting your results
Nitrate loss will vary depending on time of year, rainfall, soil properties, and perhaps most importantly, land management. Use this kit to understand if, and when, you’re losing nitrogen from your field. Nitrate that leaves your field can also have negative impacts on human health and the environment.
Nitrate loss is highly dependent on rainfall. In general, as precipitation increases, tile flow increases, and total nitrate loss increases. Be aware that your test strip is measuring the current concentration of nitrate leaving your tile line; it is a “snapshot in time” and can change year to year based on rainfall and land management.
How do you retain nitrogen in your field?
There are a suite of technologies and practices to help retain nitrogen in your field. One example is cover crops which are designed to grow at the times of year when corn and soybeans do not. These additional living roots help to hold nitrogen in place. Another option is to apply nitrogen closer to when the crop will take it up in the Spring or Summer. Below you will find information on the average nitrate reduction potential of various practices.
*www.cornnratecalc.org
Information collected from ISU Extension Publication SP 435 A: “Reducing Nutrient Loss: Science Shows What Works”
Would you like to request a kit?
retaiN kits are currently being prioritized for direct distribution to farmers and agricultural landowners to test nitrate leaving their tile outlets. You can request a kit here: https://iastate.qualtrics.com/jfe/form/SV_6MzibLsWqUMFrjo. You will be asked to provide your name, email address, mailing address and reason for requesting a kit. All recipients will be asked to take a brief email survey 6 - 9 months after recieving the kit.
If you would like to test a public waterway or another public water source, you can request a free kit from the Izaak Walton League of America's Nitrate Watch program: https://www.iwla.org/water/stream-monitoring/nitrate-watch.
