By Justin Petrosino, OSU Extension Darke County
After last year’s wheat crop, many growers are wondering if this year’s crop will do any better. The crop this year was planted on time thanks to last year’s early soybean harvest, but suffered through somewhat dry fall conditions. This winter seemed very harsh and spring doesn’t seem to be going any easier on the wheat.
Thankfully over the winter we had good snow cover and wheat is a very resilient crop.
In early winter, wheat goes into a period of dormancy where metabolic processes are decreased, water content of leaves is decreased, and the plants ability to survive freezing temperatures increases. The growing point of wheat during dormancy and tillering is safely protected below the soil surface. It takes temperatures as low as -9 to -11 F to kill the growing point of wheat. A stress that may cause some losses this spring is ponding. If there is standing water in the field that persists for more than a few days anoxic conditions (lack of oxygen) and root diseases like Pythium may take a toll. Unfortunately by now, our seed treatments have worn off and there are no fungicides labeled for such a condition with Pythium.
Thankfully any losses caused by these conditions typically don’t warrant abandoning the crop because they only affect a small portion of the field. A final assessment of the state of the crop will be made as the wheat continues green-up.
Come April wheat management becomes all about timing. The majority of our wheat receives a spring top dress of nitrogen. Spring nitrogen applications should be down before April 15, but can be made as late as April 30, as long as wheat isn’t past Feekes 6. If N as 28% UAN is applied after Feekes 6, the application can cause significant leaf burn. Burn before this point generally does not affect yield. To minimize foliar burn with applications of N you can dribble band apply 28% rather than broadcast or use urea. Another unique method of applying spring N is a broadcast or dragline application of manure. Glen Arnold, Extension AgNR Educator in Putnam County, has some great research available from the On Farm Research section of the OSU Agronomic Crops Web site at http://agcrops.osu.edu/.
As a reminder on N application rates for wheat, below is the recommendation table from the Ohio Agronomy Guide for yield based N rates. These rates are for total N for the season so remember to subtract the amount of N fertilizer you applied last fall as a starter.
Table 6-6: Nitrogen Recommendations for Wheat
Yield Potential Pound N to Apply
(bu/acre) (lb N/acre)
With our fertilizer applications in the spring we have a high potential for nutrient loss. In the cool, wet conditions typically seen in spring there is a potential to lose N through leaching of the nitrate portion of UAN and from runoff of dissolved fertilizer. Dr. Robert
Mullen, our state Extension soil fertility expert, says urea losses are typically low for wheat topdress because losses would more likely happen during warm, dry conditions, not typically seen this time of year.
There are several best management practices to help minimize nutrient losses. If urea is used and warm, dry, windy conditions are expected a urease inhibitor may be beneficial. Applying nitrogen closer to Feekes 6 will help minimize leaching losses. Wheat does not take up a significant amount of nitrogen until it starts to elongate the stem, typically around Feekes 6. To minimize the potential for runoff losses at application try to avoid applying right before major rainfall events where runoff and ponding can occur. Only about a half inch of rainfall is needed to incorporate broadcast N. The problem here is finding a weather forecast accurate enough on which to base a decision. Some good advice comes from Jon Rausch, AgNR Educator in Union County, who says to, “use your best judgment.”
Herbicides and fungicides can be effective management tools if they are needed. A spring application of a growth regulator herbicide like 2,4-D can provide cheap, effective control of most broadleaf weeds, including marestail; do not apply if you have frost-seeded clover. Application costscan be decreased by applying the herbicide with the N application. However, growth regulators need to be applied before wheat begins jointing at Feekes 6, usually by mid April. For more information on weed control in wheat you can pick up a copy of the 2011 Ohio & Indiana Weed Control Guide at your local extension office or you can view the guide online at: http://ohioline.osu.edu/b789/index.html.
Of all the management tools, timing is most critical for fungicides. Just a reminder – fungicides are needed when we have a susceptible variety, a disease organism present, and the weather conditions are right for growth of this organism and infection of the plant.
On-farm research by Dr. Pierce Paul, our state Extension wheat pathologist, and many others in the academic community shows that if disease conditions are right a fungicide application between Feekes 8 and 10 growth stage will protect the flag leaf and return more dollars than green-up or split applications. Protecting the flag leaf helps prevent losses from foliar diseases like Stagonospora and powdery mildew. For head scab, effective fungicides need to be applied when wheat is flowering. Because this is a very narrow window and our best fungicides, Caramba, Proline 480 SC, and Prosaro 421 SC, only give about 50-55% control of scab, combining varietal resistance with a fungicide application is our best management option for scab. For more information on disease management in wheat consult the Ohio Agronomy Guide available for sale in Extension
offices or online at http://ohioline.osu.edu/b472/index.html, the Ohio Corn, Soybean, Wheat & Alfalfa Field Guide, or visit the Plant Pathology Web site maintained by Dr. Pierce Paul at http://www.oardc.ohiostate.edu/ohiofieldcropdisease/wheat/wheat1.htm.
Wheat is a very resilient crop. I’ve seen it survive temperature swings from the mid 80s down to 16 F overnight followed by a week in the 20s and 30s only to see it pounded by hail two days before harvest. With a little fertilizer, herbicide, and fungicide, if they are needed, and a lot of luck this year’s crop can rebound.