Sidedressing nitrogen and small grains diseases were topics of discussion on the June 4, University of Minnesota Extension Strategic Farming: Field Notes program.
Nitrogen sidedressing tips If you haven’t applied all your N needs yet, corn will be growing very quickly once temperatures warm up. It is better to apply N needs sooner than later, so the N is there when the crop needs it. N uptake by corn rises greatly around the V6 stage of corn, with the sweet spot for sidedressing N being between the V4 to V8 stages of corn. It is important to note that research is not really showing a benefit to applying N past the V12 stage, and corn yield could actually be hurt by delaying applications this late.
Sources of N vary in their loss potential. If UAN is applied on the soil surface without incorporation, N could be lost through volatilization. Urea, which makes up 50% of UAN, can be lost through volatilization if it is not incorporated by at least 0.25 to 0.50 inches of rain. Knifing in UAN or injecting it into the soil are good practices to reduce loss risks.
When sidedressing anhydrous ammonia, applying when corn is at the V4 to the V8 stage is ideal, although it is best to be on the earlier side of this window than later. Corn roots will start to grow between the corn rows, so you can damage the roots by later application. It is not expected to pay off to use a nitrification inhibitor when sidedressing N unless we get radically wet, as the chance of N loss through denitrification and leaching is low this time of the season.
Forecasting small grain disease Robust weather-based models help assess the risk of infection for several economically important fungal diseases, including fusarium head blight (FHB), in small grains. The Small Grain Disease Forecasting Model at https://www.ag.ndsu.edu/cropdisease/ works in conjunction with the North Dakota Agricultural Weather Network (https:// ndawn.ndsu.nodak.edu/ ) and the Minnesota Agricultural Weather Network (https://www. mda.state.mn.us/minnesotaag- weather-network). This system is expanded beyond North Dakota and northwestern MN.
To use the model, input the weather station location closest to you and the growth stage of the crop. This will produce a table that calculates the risk of economic losses caused by fusarium head blight (FHB) and/ or the number of days favorable for infection for tan spot, Septoria and leaf rust over the last 10 days.
FHB has a wide host range, and we have learned that the spores are pretty much always around. Consequently, the weather conditions during the crop’s most vulnerable stage drive the need for a fungicide application. If you find that the model has your variety at a moderate to high risk for 3 or more consecutive days before heading, a timely fungicide application is needed.
It is a bit more complicated to predict the need for a fungicide for tan spot, Septoria and leaf rust. The presence of the spores is not as ubiquitous as it is for FHB. Spores from tan spot and Septoria are produced on last year’s wheat residue and do not travel very far, while spores of leaf rust have to be blown up by southerly winds from states like NE and SD. This means you need to scout to determine whether the disease is even present in your field. Wheat following wheat is at greatest risk. Luckily, it takes a couple of in-season disease cycles (or generations) for these diseases to reach economically damaging levels, giving you time to combine the information of the disease risk models with the in-field information to make an informed decision.
Listen to the full program through your preferred podcasting platform or at the Strategic Farming: Field Notes website (www.strategicfarming. transistor.fm).
