Experts at Iowa State University Extension advise letting the mercury drop below 50 degrees Fahrenheit to stay to maximize the effectiveness of your anhydrous application. An early start on harvest may have farmers twiddling their thumbs in the machine shed and spraying mulberry sprouts until temperatures drop. Getting an equally early start on fall fertilizer application may seem like a savings in time, but this could prove to be costly.
"With farmers finishing harvest earlier than normal, it is important that they still wait for cooler soil temps to apply anhydrous so that there is a better chance the fertilizer stays put and will be available to the crop next spring," said Bill Northey, Iowa Secretary of Agriculture. "Soil temperatures, like air temperatures, can change quickly so it is important that we wait with applications until soils are likely to remain below 50 degrees."
ISU Extension and Outreach maintains a statewide real-time soil temperature data map on their website that Ag retailers and farmers use to determine when fall N applications are appropriate. The website can be found at http://extension.agron.iastate.edu/NPKnowledge/.
In addition, note that dry soils can also be problematic for NH3 application. If soils are cloddy or very dry and cracked, ammonia can be lost at injection as it my seep too deep into the soil to be useable by next year's crop. If after application, ammonia can still be smelled in the air, adjustments to injection should be made or, better still, wait until a good rain can smooth out the clods before application.
It may be the type of year that makes it seem as if everything is ahead of schedule, but to maximize effectiveness of your NH3 application and avoid costly seepage, a savvy farmer will stay in the machine shed and wait for soil conditions to catch up with this accelerated harvest season.
For the full ISU Extension article, click here.