Nitrogen Continued from Page 7
high probability that additional nitrogen would increase yields. The researchers followed up their initial research with a three-year FREP demonstration project that compared growers’ standard practices to plots managed according to a suite of ni- trogen-management tools, including the quick test. The Natural Resources Conservation Service also was involved. What the researchers found was con- verting quick test results into a form growers and CCAs could readily use was cumbersome, so Nelsen developed a simple web-based application to do the work. The app includes a map that users click on to record their sample site loca- tion. It automatically loads site-specific soil bulk density, a soil property. Users then input the test strip color score, and the app converts the values into an ap- proximate nitrate fertilizer equivalent in pounds per acre. “We tried to make it as easy as possi- ble,” Nelsen said. In addition, the team compiled step- by-step guides and YouTube instruc- tional quick test videos as well as a list of suppliers for test materials at UC’s small grain nutrient management website, https://bit.ly/3ZHhogf. (Vicky Boyd is a reporter in Modesto. She may be contacted at vlboyd@att.net.)
whether they’ll need more nitrogen to maximize crop yield potential or whether the soil has an ample supply and they can forgo an application, she said. “Some found they had nothing there,” Nelsen said of growers collaborating in the FREP project. “Their regular fertiliz- er practices were pretty much what they needed. Others—if they followed toma- toes—had a lot of residual nitrate from the previous crop, and they didn’t need to topdress it.” To conduct the quick test, growers or CCAs collect at least 10 to 20 soil samples from the top 12 inches of representative areas of a field and put them in a clean 5-gallon bucket, breaking up clods and mixing the soil. Then they add one teaspoon per gallon of calcium chloride to a jug of purified water. From there, they pour three parts of the solution into a clean 500-millili- ter—roughly 16-ounce—sample bottle followed by one part soil. After shaking the bottle vigorously for at least three minutes based on a timer, users let it settle for two to five minutes before dipping a WaterWorks nitrate and nitrite test strip into the top, clear portion of the solution and letting it wick up. After about 60 seconds, the strip turns a shade of light pink to magenta. By
University of California Cooperative Extension researchers developed a rapid test to obtain nitrate scores to help growers determine if they’ll need more nitrogen to maximize crop yield.
matching the color to a chart on the test strip bottle, users obtain a nitrate parts- per-million score. Research into updating the soil quick test was conducted from 2014 to 2019 by a large team led by UCCE grain cropping systems specialist Mark Lundy. The researchers collected more than 300 soil samples from 19 site-year tests across the state’s small-grain production regions to reflect variations in soil types
and production practices, Nelsen said. Using the test previously developed by UC vegetable specialist Tim Hartz for let- tuce, they found his 20 parts-per-million nitrate threshold also was applicable to small grains. If quick test results were more than 20 ppm, odds were slim that additional nitrogen applications would result in a yield increase. Conversely, if the results were below the threshold, there was a
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