Source:  NCDA&CS, 7/8/11

Wheat producer Warren Hardy is pleased with his crop this year. The Wayne County farmer put out less fertilizer and achieved a yield of about 80 bushels per acre over 160 acres.

Hardy did this by applying spring nitrogen based on the results of an agronomic test known as plant tissue analysis, which is available through the N.C. Department of Agriculture and Consumer Services.
“I had taken tissue samples sporadically in previous years,” Hardy said, “but it was mostly for diagnostic purposes. I was doing it to identify problems. My fertilization program had been based on soil samples and standard recommendations alone.”

Plant tissue analysis involves collecting representative plant leaves from random locations throughout a reasonably uniform field. The sample is sent to a laboratory, which measures plant-nutrient content. The test is so sensitive that it can detect nutrient deficiencies before plants display any visible symptoms. Even so, the best use of tissue analysis is as a monitoring tool to prevent problems in the first place.

In early March, NCDA&CS regional agronomist Dianne Farrer encouraged Hardy to use tissue analysis to fine-tune his spring nitrogen application. She demonstrated the sample collection process, which involves not only routine tissue samples to measure nutrient content but also corresponding biomass samples to estimate crop growth and vigor. Both types of data, along with information about row spacing, can be used together to arrive at precise, field-specific nitrogen recommendations, using a method developed by Drs. Randy Weisz and Ron Heiniger at N.C. State University.

“I advise growers to take advantage of tissue testing because soil tests do not actually measure nitrogen,” Farrer said. “Soil reports suggest a nitrogen application of 80 to 100 pounds per acre for all wheat fields, regardless of rainfall, soil type, winter temperatures, planting date or any of a number of other factors that can affect crop nutrient needs. Tissue testing, on the other hand, is precise and situation-specific. It tells you how much nitrogen a crop contains, and that is a good basis for determining how much more it needs.”

Hardy took Farrer’s advice and collected tissue samples with the intention of applying nitrogen based on the test results. However, because of an extended forecast of rain, Hardy chose to fertilize some fields immediately, using standard rates. For the remaining fields, he applied nitrogen later, calculating the rate using information from his NCDA&CS Plant Analysis Report.

“If I’d have sampled earlier and gotten the recommendations back before the rain, I would have applied less nitrogen to all my fields,” Hardy said. “In certain fields that I fertilized first, I used a higher rate, plants lodged and yield was lower. In the other fields, yields were as good or better even though less nitrogen was applied.”

Hardy’s records indicate that fields fertilized according to tissue test recommendations out-yielded similar tracts nearby that had received an additional 10 pounds of nitrogen per acre. Next year Hardy hopes to fertilize his entire wheat acreage based on tissue-test results.

In an unpredictable and volatile economy in which nitrogen prices can fluctuate dramatically, knowing the precise fertilizer needs of a crop is critical for optimizing production costs. This March, nitrogen prices were about 15 cents per pound higher than last year. That may not sound like much, but for Hardy, the possibility of cutting back 10 units of nitrogen over 700 acres represents a significant savings. Adhering to precise agronomic rates also helps safeguard environmental quality.

Tissue testing through the NCDA&CS lab is a quick and economical way to assess crop nutrient needs. It costs only $5 for each pair of tissue and biomass samples, and the lab completes the analysis within two business days. Results are posted online at the Agronomic Services Division’s website, www.ncagr.gov/agronomi, under the “Find Your Report (PALS)” option. If growers have questions, regional agronomists are available to provide guidance.

For more information on the Agronomic Services Division’s tissue testing service, visit www.ncagr.gov/agronomi/uyrplant.htm. Select the “Nitrogen Management for Small Grains” link for an in-depth description of how to use test results to determine a nitrogen recommendation. Any N.C. grower interested in using tissue analysis to determine fertilizer needs of wheat is encouraged to consult with a regional agronomist early in the growing season to get a detailed explanation of the process. Contact information is available online at www.ncagr.gov/agronomi/rahome.htm.