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Source: NCDA&CS, 2/25/13
The N.C. Department of Agriculture and Consumer Services reminds growers that properly timed nitrogen applications are essential to the growth and development of wheat. Now is a good time to assess the nutrient needs to optimize yields.
An estimated 960,000 acres of wheat were planted across the state this winter. To get a quick and accurate recommendation of how much spring nitrogen to apply, agronomists advise submitting two samples of wheat leavesto the department’s Agronomic Services Division for testing. One sample will be used to measure plant nutrient content, the other to measure biomass. Both tests are necessary to obtain the most precise recommendation.
“Tissue sampling should begin when wheat reaches Zadoks growth stage 30 (GS-30),” said Kent Messick, NCDA&CS Field Services Section chief. “The rate of growth depends on variety, planting date, environmental conditions and location, with wheat in eastern counties reaching GS-30 the soonest. When wheat begins to stand up tall and straight, pull several plants, split the stems from the top to the base and look for the growing point. Before GS-30, it will be just above the roots; at GS-30, it will have moved about one-half inch up the stem.”
NCDA&CS agronomists expect most wheat in the eastern and piedmont regions of the state to reach GS-30 sometime between March 1 and 5. It isn’t advisable to apply nitrogen before then because new growth at that time would be susceptible to cold injury. On the other hand, it is a mistake to wait until after jointing to put out nitrogen because of the potential for damage by application equipment.
“Once GS-30 is reached, growers should immediately collect tissue samples and matching above-ground biomass samples,” Messick said. “This is especially true if wheat is lush due to warmer weather or early planting dates.”
At GS-30, tissue sampling involves cutting wheat plants about one-half inch above the ground from 20 to 30 representative areas throughout a field. Generally, two large fistfuls of leaves will make a good sample. Dead leaves and weeds should be removed.
Biomass samples, on the other hand, should contain all the above-ground wheat-plant tissue from one representative, 36-inch section of row. In broadcast fields where there are no rows, growers should collect all the plants from one square yard. The sample should be placed in a paper bag, with the sample ID from the corresponding tissue sample and the word “biomass” written on the bag.
The collecting of biomass samples may be fairly new to growers. The idea was based on research by Dr. Randy Weisz of N.C. State University. He developed a method of using biomass weight along with tissue test results to calculate more site-specific nitrogen recommendations. His approach takes into account crop-growth differences due to planting date, row spacing and moisture levels. For wheat grown on large acreages of poorly drained soils, however, growers should consult with an agricultural adviser about whether this method is likely to be useful.
Upon receiving their NCDA&CS plant analysis report, growers should first look for the biomass and nitrogen percentage values. These values and certain crop planting details help determine the appropriate nitrogen rate, based on Weisz’s interactive tool. This method is explained fully online at www.smallgrains.ncsu.edu/_Pubs/PG/Nitrogen.pdf.
North Carolina growers wanting more information about this method should contact their NCDA&CS regional agronomist, county Cooperative Extension agent or other agricultural adviser. Regional agronomists, in particular, can offer advice on how to collect and submit tissue and biomass samples, and how to interpret and use plant analysis report data. Contact information is available online at www.ncagr.gov/agronomi/rahome.htm.
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