Skyrocketing fertilizer prices and the current drought make it important for wheat producers to gauge nitrogen needs accurately this year. The North Carolina Department of Agriculture and Consumer Services is advising growers to base upcoming fertilizer decisions on tiller counts and plant tissue analysis results.
“Last fall, nitrogen was selling for $180 per ton. This year the price is up to $320,” said Ben Knox, a regional agronomist with the department. “No one wants to apply more than is necessary, especially when it's likely some fields still contain residual nitrogen from the previous crop. This year growers really need to get into the field and scout early and often.”
The time to count tillers is in late January or early February when wheat begins to green up. At this stage, 50 to 70 tillers per square foot is optimum. If wheat was planted late, tiller counts may be significantly lower. In that case, it is appropriate to apply 30 to 40 pounds of nitrogen per acre right away. This application will enhance tillering on warm days without fostering excessive growth.
Tissue testing should be on the calendar in late February or early March. Precise timing will depend on weather and crop growth stage. Tissue sampling to evaluate nitrogen levels in wheat should coincide with Zadoks Growth Stage 30, also known as Feekes Stage 4-5. At this stage, wheat is usually 5 to 6 inches tall, stems are upright, and tillering has stopped.
To determine whether wheat has reached this growth stage, dig up a plant, slice it down the middle and measure the distance from the bottom of the plant to the top of the growing point. If the measurement is one-half inch, it is time to sample.
Because of the ongoing drought, tissue testing is a must this year. Plants need water to use nitrogen, and the lack of rain means it is likely nitrogen from the previous crop is still in the soil. If wheat is thriving on residual nitrogen, tissue test results will point that out and you will be able to adjust spring application rates accordingly.
Brenda Cleveland, chief of the NCDA&CS Plant, Waste and Solution Section, said tissue testing is crucial to appropriate nitrogen fertilization, but it often uncovers other nutrient problems, too.
“Wheat producers are most concerned about nitrogen,” Cleveland said. “If they apply too little, there will be fewer heads and fewer and smaller kernels. If they put out too much, there may be problems with lodging, disease, leaching or runoff. At least half of our tissue tests, however, reveal that potassium, magnesium or sulfur levels are also low enough to limit yield. With wheat prices remaining favorable this year, growers have extra incentive to follow all plant report recommendations carefully.”
To collect tissue samples, break plants off about one-half inch above the ground. A good sample consists of about two handfuls of plants gathered from 20 to 30 areas throughout the field.
In early 2008, the NCDA&CS Agronomic Division will hold training sessions in the eastern part of the state on how to count tillers, identify wheat growth stages and collect tissue samples. For training dates and locations, contact regional agronomist Wayne Nixon at (252) 335-4142 or Kent Yarborough at (252) 793-4118, ext. 122.