ISSUE 5 June 12, 2008
Most areas of the state have received rain lately. There are some small grains growers who delayed N application until they could see that yield was possible in drier areas of the state. Although yield is not yet guaranteed, the prospect of at least some yield in these areas is brighter than a couple of weeks ago. With small grains at least at tillering stage, the time is right for top-dressed N applications.
The N application should be applied separately of fungicide or herbicide application using stream-bars. Low-rate, slow-release N products have been tested at NDSU for several years for their ability to increase yield and protein at 1-3 gallon rates (2-10 lb N/acre) and so far the results have not supported their marketing campaigns. Research continues this year on rates and products, but results will not be available until this fall.
Top-dress rates need to be based on about 75% of "table" rates found in our recommendations. The 75% factor is because of the high cost of N right now compared to costs of N when tables were constructed. Higher N costs (28% right now is about 75 cents/lb N) makes full N recommendations not as profitable as our table rates suggest. Applications followed by rain before the small grains mature past 6-leaf stage usually result in maximum yield for the environment. Application and rain after this time may increase protein, but will have little impact on yield.
Side-dress for corn should be made anytime that the applicator can practically be in the field. When corn is small, there is potential for covering up the plants with soil, so applications are usually made between 5-leaf and 10-leaf corn. Corn higher than this may require a liquid applicator equipped with drop hoses and orifices to dribble 28% between the rows on the soil surface and hope for rain.
Do not broadcast spray liquids, or broadcast spread dry fertilizer over the top of corn. The leaves of corn act like a funnel and you will burn the corn plants badly if this is done. Last year a few novices did this and I think they won’t do it again.
NDSU Extension Soil Specialist