Applying fertilizer and herbicide together may reduce costs and trips around the field, but it often damages winter wheat, says Bob Klein, University of Nebraska cropping systems specialist in North Platte.
Based on at the UNL West Central Research and Extension Center, Klein recommends against mixing these agricultural materials.
"We know this practice causes more damage when the wheat's under stress and we think we can tell when wheat's stressed," Klein says. "But, over the years, we haven't been as successful as we thought.
"Since we can't figure that out, we recommend separate applications of fertilizer and herbicide," Klein says.
Producers can apply fertilizer in fall or late winter, but many farmers prefer to wait until early spring, a little closer to harvest, so they can check the wheat stand, the soil moisture, wheat prices and the price of fertilizer. They feel they can make a better estimate on the most cost effective rate of fertilizer to apply.
Klein said that the best time to fertilize with nitrogen (phosphorus would have been applied before or during planting) in late winter or early spring is as soon as the applicator can get into the field without making tracks, but after the ground thaws. If the ground is frozen, any additional moisture will wash the fertilizer away.
He recommends strip banding rather than broadcasting liquid fertilizer. That concentrates the fertilizer and reduces the rate of loss through volatilization and it doesn't burn as much total leaf surface.
Herbicide should go on a little later. "We like to have the weeds in the rosette stage. Once they bolt, they're very hard to control."
Weeds such as blue mustard have to be controlled early. Winter annual weeds, like pennycress and some other winter annuals that emerge with or after winter wheat emerges, need to be controlled in the fall. Be careful about choosing herbicides because some of them can do a lot of damage to the winter wheat, even causing winter kill.
"Be sure to apply the herbicide at the appropriate time; most should be applied before the joint stage," Klein says.