During corn silking or even before, too many Northeast corn fields turned yellow – out of "gas", better known as nitrogen. Fields receiving much higher than usual rainfall suffered much higher than usual N losses, reports Penn State University Agronomist Doug Beegle. A few farmers saw it coming and late-applied extra N.
With today's corn input costs and current grain prices, you can't afford to get caught short on nitrogen, especially during a higher-yielding growing season. So, American Agriculturist queried Beegle and Greg Roth, corn specialist also at Penn State, for their advice on planning ahead for 2014. The lead questions were: How can you tell how much N is left for next year? And, when's the best time to test?
Gauge in-field variability
Roth also spotted in-field variability and questions whether any patterns reflect other management factors. A late-season cornstalk nitrate test might help rule out solely blaming nitrogen losses. And it could determine if this year's corn received the proper amount.
"I'd use the results as part of my future N management strategy, knowing that in some years with heavy crops and a wet June what you did this year might not work," cautions Roth. "How often do these conditions occur? Do they warrant bumping up your strategy? Or, are there ways to sidedress late to overcome early wet conditions?"
You can visually assess N status as the crop reaches silage harvest maturity by the number of green leaves below the ear, says Beegle. "If you have at least four green leaves at and below the ear at silage harvest time, the crop had adequate N. That assumes the yellow or brown leaves at the bottom of the plant are due to N deficiency.
Be careful to not confuse N deficiency with disease and dry conditions. The latter also cause lower leaves to senesce (turn yellow).
Nitrogen deficiency is characterized by a distinct "V" shaped pattern starting at the tip of the leaf and going back the mid-rib. Drought senescence and diseases usually don't follow this very distinct pattern, he adds.