Soybean Weed Management Studies

Several studies were conducted in soybeans to evaluate commercially available herbicides for weed control, crop phytotoxicity, and crop yield. Various herbicide treatment combinations and application methods were evaluated

Urea-ammonium nitrate as herbicide carrier in emerged corn

The rapid progression of corn planting followed by the current wet period prevented many growers from applying preemergence herbicides and nitrogen fertilizer when fields were planted. Both corn and weeds will have emerged in many of these fields by the time field work resumes. Growers in this predicament should adjust their weed management program rather than trying to force their previously planned herbicide treatment into the current situation

Corn Weed Management Studies

Several studies were conducted in corn to evaluate commercially available herbicides for weed control, crop phytotoxicity, and crop yield. Various herbicide treatment combinations and application methods were evaluated

Replant options following herbicide applications

Due to the recent severe weather and hail occurring throughout Iowa, there are many situations where replanting the crop may be necessary. However, it is important to remember that some herbicides limit replant options. For example, if a cornfield treated with atrazine was destroyed by hail in early June, the only crop options are corn and sorghum, regardless of the atrazine application rate. If a herbicide tank mixture was applied, the most restrictive replant label must be observed. This table lists replant options, time delays for replanting, and approximate herbicide persistence. Always refer to the herbicide label for specific information

Herbicide applications on stressed corn

The prolonged cool, wet weather has complicated application decisions for postemergence herbicides. The stressful conditions may have reduced crop tolerance and prevented timely herbicide applications. Most growers realize that it would be wise not to treat corn under these conditions, but they may not have the flexibility to delay applications because of time limitations, crop stage, or weed size. A frequently asked question is how many days of warm weather are needed before the crop will regain its vigor? Unfortunately, there is no simple answer because many interacting factors affect the crop\u27s recovery. However, the following are guidelines that may help in the decision proces

Too Much of a Good Thing: A Look at Herbicide Carryover and Mode of Action

Several herbicides commonly used in Iowa com and soybean production have sufficient persistence for soil residues to remain into the following spring. The shortage of rainfall across much of Iowa during the 2000 growing season may result in higher concentrations of these herbicides in 2001 than normally encountered, thus increasing the possibility of herbicide injury to rotational crops

Effect of the crop canopy on spray coverage

When a spray boom is set up properly, it applies the desired rate of product uniformly across the width of the boom at a specific distance below the nozzles. Uniform application can only be achieved if the boom is set at the proper height for the target. For postemergence herbicide applications, the target height is the average weed height

Application timing for preemergence herbicides

The optimum application time for preemergence herbicides is dependent upon a grower\u27s management skills, environmental conditions, and properties of the herbicide used. In an ideal situation, all herbicides would be applied at the optimum time for performance. However, due to time constraints at planting, many applications are made for convenience reasons rather than for performance