CALIFORNIA
Field Crops A SPECIAL GROWERS’ REPORT OF AG ALERT ®
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Having current information on nitrogen levels in soil is key for wheat growers because concentrations vary widely in the growing season. Quick tests can help farmers know when more nitrogen is needed.
Updated nitrate test can assist small-grain growers By Vicky Boyd
The soil quick test was not designed as a stand-alone assay, Nelsen said. Instead, it was intended to be part of a suite of nitrogen management tools that pair plant nitrogen sufficiency measurements based on nitrogen-rich reference strips with the soil quick test measurement. The quick test, which can be performed in the field, gives producers and CCAs an accurate real-time estimate of the amount of soil nitrate-nitrogen—a nitrogen form usually most available to plants. Having up-to-date information is important because soil nitrate concentrations can change significantly as the season progresses, bringing about variations in soil moisture levels and plant nitrogen demand. Much of the state’s wheat crop is planted in late fall. Because the plants don’t grow much over the winter, they use only about 20% to 25% of their total nitrogen require- ments before the start of stem elongation—a critical growth stage when the heads begin to form deep in the main stem. This is when growers follow up with in-season nitrogen applications referred to as topdressing. Depending on growers’ goals and cultural practices, Nelsen said they may make possibly one to several topdress applications. By conducting the quick test shortly before topdressing, growers can determine
University of California researchers have updated a soil nitrogen quick test orig- inally developed for lettuce in the 1990s to make it more applicable to the state’s small-grain producers. Not only can the nitrate test potentially save small-grain growers the cost of unneces- sary nitrogen applications, but it also can help maximize fertilizer efficiency and minimize nitrogen losses, said Taylor Nelsen, a UC Davis research scientist. “The growers we worked with and the people we surveyed through our three-year FREP (Fertilizer Research and Education Program) grant said this was one of the most useful tools,” she said. Konrad Mathesius, UC Cooperative Extension agronomy advisor for Sacramento, Solano and Yolo counties, agreed, saying growers and certified crop advisors overall have been receptive. “It’s really a positive tool that can save people a lot of money, and I think they just need a chance to get used to it,” said Mathesius, who was part of the FREP project. “It’s not just a feel-good thing. This is like real cash, especially now with nitrogen prices.” In addition, reducing potential nitrate leaching into surface water and groundwater has become more important as the Irrigated Lands Management Program now requires growers to annually report nitrogen efficiency practices.
See NITROGEN, Page 8
January 18, 2023 Ag Alert 7
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