1. Enter your pad value from the soil nitrate quick test (ppm). Results are based on top 0-12 in of soil.
Alternatively, if you have a lab value you may select it here. Results are based on nitrate-N (ppm) in the top 0-12 inches of soil (to translate nitrate to nitrate-N multiply by 0.23).
2. Click or move the marker to the field where the soil sample was taken. You must choose a field within the wheat-growing region of CA (colored area).
3. The results are based on the in situ bulk density (g/cm3) from the SSURGO database. Values used and presented here are a weighted average of the component types present in the top 0-12 in of soil. SSURGO-estimated bulk density may not accurately represent the bulk density at a site. For better accuracy, update the SSURGO estimate with a recently-measured bulk density value.
False positives and false negatives. The nitrate quick test is useful for providing a ballpark estimate of whether your soil nitrogen status is high, medium or low. Generally speaking, this test doesn’t yield false positives. That is, if your soil sampling techniques are representative of your field conditions, high values are probably real. Whereas, medium and low values may be harder to interpret because false negatives (because the test wasn’t conducted properly or your strips aren’t working) are more of a possibility.
Final considerations. It is important to remember that this test is a snapshot in time of one important and highly plant-available form of nitrogen (nitrate-N). However, nitrogen has many forms and is very dynamic in cropping systems. So, a measurement taken at a particular moment in time may not reflect future conditions, especially if rainfall, irrigation or other environmental changes occur subsequent to the test. Nevertheless, when taken at a time when an N fertilizer application decision is being made, it can help to narrow or modify the range of rates that may be appropriate. For small grains in California, when nitrate-N values in the top foot of soil are 20ppm (lab equivalent) or higher, there is little probability of crop response to fertilization in the near-term. Because the test is unlikely to yield false positives, if you measure a reading of 20ppm lab equivalent or higher, fertilization can probably be delayed and/or rates should be adjusted to reflect the fertilizer-equivalent nitrate-N (estimated above) that is immediately available in the top foot of soil.
Links to test materials:WaterWorks Nitrate/Nitrite Nitrogen test strips (50 pack)
Related Resources:Sampling for Soil Nitrate Determination
Acknowledgments:A wide range of University of California Cooperative Extension personnel have contributed to the development of this information, including: Taylor Nelsen, Konrad Mathesius, Michael Rodriguez, Jessica Schweiger, Ethan McCullough, Taylor Becker, Nicholas Clark, Sarah Light, Michelle Leinfelder-Miles, Thomas Getts, Giuliano Galdi, Jessica Henriquez, Rozana Moe, Leah Puro, Jonathan Slocum, Eric Williams, Quinn Levin, Steven Spivak, Maria Sandate-Reyes, Serena Lewin, Ryan Byrnes, Jason Tsichlis, Katherine Mulligan, Nic George, Darrin Culp, Steve Orloff, Steven Wright, Robert Hutmacher, Gabriel Rosa, and Mark Lundy.
Printable Copy available at: https://ucanr.edu/sites/small-grains/files/324074.pdf