By Carl Majewski
Checking your corn to see if it’s likely to have enough nitrogen for the remainder of the season is a good idea any year, but it’s likely to be especially important this summer. The high amounts of rainfall we’ve had throughout May – nearly twice the normal amount - and June has greatly increased the chance for nitrogen losses from leaching or denitrification.
And yet, there may be at least some remaining in the soil. There’s a reservoir of organic nitrogen temporarily stored in manure or crop residues that gets released once those materials decompose when the soil warms up. Given the weather we’ve had so far it may not be much, but you’ll still want to take it into account when figuring out whether to sidedress fields. That’s where mid-season testing comes in, and there are a couple different methods to choose from.
SPAD chlorophyll meter readings measure the concentration of chlorophyll in leaves, which is tied to how much nitrogen the crop has taken up. They have the advantage of giving you results as soon as you exit the field, but the meter itself is too expensive for most farms to justify the expense. Instead, talk to your crop advisor (or us!) about arranging to take some readings.
Source : unh.edu