The time to make rescue operations for nitrogen is growing short. For some fields, the window may be closed. For later-planted corn, there may still be time. Regardless of what stage of growth your corn is at, wouldn't you like to know if it has sufficient N at this point in the season? Did you put on enough N? Did you lose more than you expected in a wetter than normal spring?

One new, relatively inexpensive tool to use to do that is the Green Indexing system, offed by Spectrum Technologies. It was featured as an 'Editor's Choice' item in Indiana Prairie Farmer in June.

Why use this system when a spectrometer, basically a chlorophyll meter, can do the same thing faster? The chlorophyll meter costs about 15 times more than this simple system, even if it is a $100 app. It could be a handy tool for farmers who want an indication of how nitrogen levels are holding up in their field.

The system consists of a pink board with green, yellow and gray areas. You can purchase it for around $50. The brain of the system is an app for your iPhone, which you order through Spectrum Technologies. Eventually you download it from the App store. It's about a $100 app.

That gave my son, Daniel, pause. The young generation is used to apps that don't cost much. In this case the brains that make the whole thing work are in the app. The board provides a background for the app to calibrate itself, and a consistent background for determining color of the lead.

Related: Corn Nutrition, Nitrogen Use Varies Between Fields

Jeff Phillips, Tippecanoe County Extension ag educator, helped try out the system in the field. First he pulled leaves and worked in the shade of the truck cab because it was hard to see the phone screen in bright daylight. After about 15 minutes he figured out how it worked. He also adjusted to reading the screen.

The suggested method is to use the system on plants without removing leaves. Phillips tried it on leaves on plants, holding the board under the leaf and shooting pictures with the camera. The app then provides readout. He says he didn't find it to be that awkward and once he had the methodology down, he could get readings fairly quickly.

He tested green, yellow and in-between leaves and the readings lined up accordingly. Earlier in the season before sidedressing time, it could be used to get a handle on recommendations. Data to do that is supplied with the app. We didn't try that part since the corn was tasseling.

From the corn hybrid you select to the seeding rate and row width you choose, every decision you make influences the size and scope for corn yields. Download our FREE report: Maximizing Your Corn Yield.