In the past, North Carolina growers had to rely on spring nitrogen recommendations that had been developed in Virginia. Now they can generate their own site-specific recommendations. This approach is more precise because it 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.

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. In general, two large fistfuls of leaves 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.

Upon receiving their NCDA&CS plant analysis report, growers should first look for the biomass and nitrogen percentage values. Then, they should use an interpretive tool developed by Randy Weisz of North Carolina State University to determine the appropriate nitrogen rate. This tool is available online at www.smallgrains.ncsu.edu/_Pubs/PG/Nitrogen.pdf.

Weisz’ interpretive tool uses the biomass value from the plant analysis report along with planting details, such as the crop’s row spacing or whether it was broadcast, to rank biomass as low, medium or high. Having made that determination, the grower can locate the nitrogen percentage value from the plant analysis report on the appropriate biomass graph to find the site-specific nitrogen recommendation.

North Carolina growers who want to know more 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.