Traveling through several Northeast states last week, many tremendously healthy stands of corn were spotted. A lot of hopes are pinned on those fields for cash income and for high-quality dairy feed that'll hold down purchased feed bills.
But across much of Pennsylvania and New York were many fields exhibiting tell-tale nitrogen deficiency symptoms – yellow leaves, particularly in slow-to-drain spots. This is not a year to be caught N-short.
Corn that hasn't reached the V8 growth stage still has potential to capitalize on corn that could be worth $7 a bushel or more by harvest. That assumes dry weather conditions continue plaguing the Corn Belt.
If corn that's only 12 inches high is deficient, there's a very high probability of getting a profitable response to sidedressing additional N, says Doug Beegle, Extension agronomist at Penn State University. "At this stage of growth, using the pre-sidedress soil nitrate test or the chlorophyll meter test (if little or no fertilizer N has been applied) would be very useful for guiding sidedress management."
Over the last two weeks, Beegle has heard that a number of fields showing N deficiency during the earlier period of rainy weather were looking a lot better once things dried out and it got warmer. "This was especially true on fields that had significant manure or were following a forage legume. The warmer, drier weather allowed [soil] microbes to go to work mineralizing the abundant organic N in these fields."
Up until the V8 growth stage (when lower leaves start breaking down and the plant begins its growth spurt), significant yield responses to extra N are likely – assuming that N is either injected into the moist soil root zone or rained into it.
Liquid N or urea are typical sidedress materials. But since both are susceptible to volatilization losses, they should be treated with an N stabilizer.
Too dry, too late for N?
Research by the Iowa Soybean Association's On-farm Network reports that lay-by nitrogen applications don't always boost corn yields. That N must first get down into the root zone, and plant roots need water to be able to access it.
This raises concerns over whether either dribbling N on the ground or injecting it behind a coulter has value in dry soils during a dry summer. If the crop is stressed because it can't take up the N from a too-dry soil, adding more N won't solve the problem, according to the report. In other words, you can't rectify an N deficiency without a little help from Mother Nature.