Software allows wheat farmers to streamline soil tests

Wheat farmers can more easily save on fertilizer costs and produce better crops because of recently refined tools that make it possible to interpret the results of a field test for soil nitrate quickly and easily.

The latest wrinkle in University of California research on the soil nitrate quick test is the development of software that fine-tunes the results based on the soil type at any location in the state and translates the strip test color change into the pounds of nitrogen per acre already available to the crop.

"The soil nitrate quick test is a simple and low-cost test," said Mark Lundy, UC Cooperative Extension grain cropping systems specialist. "It provides a ballpark estimate of the soil nitrate-nitrogen concentration in the rootzone."

Lundy described nitrate as "a highly plant-available form" of nitrogen.

"Using the soil nitrate quick test when nitrogen fertilizer decisions are being made will help define a range of fertilizer rates appropriate for that field," he said.

Lundy is part of a team of researchers that includes UC Davis graduate student Taylor Nelsen and UCCE farm advisors Konrad Mathesius, Nicholas Clark, Sarah Light and Michelle Leinfelder-Miles, all working to make the quick test more useful for grain growers.

A soil test can help farmers save the cost of a fertilizer application with confidence they will not reduce yields or crop quality.

Recent UC research on the Central Coast vegetable territory showed there is even greater potential savings from avoiding regulatory restrictions if farmers in a region generally monitor their nitrogen applications well enough to avoid groundwater nitrate infiltration.

The team presented its latest work, including software that provides field-specific interpretations, during a webinar in place of the traditional small-grains field day on the Davis campus.

As a result of the latest research, farmers and pest control advisors could make informed fertilizer decisions, without going to a lab, using a cylindrical bottle with a cap, a gallon of distilled water, some calcium chloride, a few test strips, a container with a solution of known nitrate content and a smartphone.

"Over the past several years, UC Cooperative Extension agronomists have been developing and refining information about the accuracy of the soil nitrate quick test compared to laboratory tests across different soil types and users," the researchers said. "Based on more than 300 samples taken from 19 sites across California, we have developed a strong quantitative relationship between the value measured from an in-field soil nitrate quick test and an estimate of fertilizer equivalence."

The newest research tool involves software that lets a farmer enter the color change of the test strip and quickly receive site-specific information on how much nitrogen is already available to the crop. The Soil Nitrate Quick Test Web Tool is available at n-quick-test.plantsciences.ucdavis.edu.

A user enters into the program the nitrates parts per million in the top foot of soil from the test strip, checks whether the test was done using calcium chloride or just water, locates the field on a map, and the software reveals how much nitrogen is already available.

To begin the test, a user combines soil from the top foot in a 1-to-3 ratio with distilled water that works best if sodium chloride is added, shakes the mixture vigorously for 3 minutes, and dips a color-coded test strip that reveals how many parts per million nitrate-nitrogen are in the soil.

The container with a known concentration of nitrate serves to confirm that the test strips are still accurate.

The researchers said the software serves to adjust the reading to account for the soil qualities in the particular area or field, and to translate the results into practical terms of how much nitrogen per acre is already available to the crop before any fertilizer is applied.

"The webtools are notable because they provide automated conversion of quick-test values to fertilizer equivalence based on map-enabled, site-specific soil information," according to the researchers.

The UC team said its goal in developing the resource "was to simplify and improve the process of measuring and interpreting soil nitrate values so that soil nitrate testing would become a more widely used tool when fertilizing California small grains."

In addition to the software tool that calculates available nitrogen values, the online presentation includes other information to ease soil testing.

There are step-by-step instructions on how to perform the test, including a list of necessary materials, to serve as a brief refresher course or a manual for newcomers, and there is a longer version of the instructions presented in a four-page guide that includes tips on how to best ensure accuracy of the sample.

In addition, there is also a 12-minute video showing how the soil quick test is conducted.

All of the pamphlets, videos and software may be accessed from a UC small grains website at smallgrains.ucanr.edu/Nutrient_Management/snqt.

The California Department of Food and Agriculture Fertilizer Research and Education Program, California Crop Improvement Association, California Wheat Commission, UC Agriculture and Natural Resources, and the UC Davis Department of Plant Sciences are all involved in the ongoing effort to develop tools that make it possible for farmers to precisely target how much fertilizer to apply, and when.

(Bob Johnson is a reporter in Sacramento. He may be contacted at bjohn11135@gmail.com.)