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Serving: IN
corn plants showing nitrogen deficiency
COSTLY SIGN: These corn plants are showing classic signs of nitrogen deficiency, with yellowing starting at the tips of the leaves and running down the midribs. A deficiency this pronounced can shave off bushels and profit.

Last-minute refresher on nitrogen for corn

You can’t afford to waste it, but you can’t afford to see nitrogen-deficient plants either.

By Don Donovan

Farmers are finding some new “racehorse” hybrids use soil-available nitrogen much later than older hybrids. Studies show nitrogen uptake may occur until shortly before black layer, when corn reaches full maturity. 

What does this mean to you? A full review of your nitrogen management strategy may be necessary. Here are steps to get you started:

Consider key questions. How and when have you been putting on nitrogen? What form of nitrogen are you using? Especially during these times of narrow profit margins, you want to get everything you can out of your nitrogen dollar.

Assess nitrogen status. How can you tell if you have enough nitrogen? Get out in the field and check corn as it matures. You may need to pull tissue samples. A drone flying over the field can tell you some things about how healthy corn is and whether it’s lacking in available nitrogen. You can also check chlorophyll levels in corn leaves to get an idea of nitrogen deficiency.

Consider late-season options. Need for nitrogen later in the season may mean applying part of your nitrogen after plant emergence — if you’ve been putting most of your nitrogen on in the fall or early spring as preplant. Depending on weather and soil conditions, a large portion of nitrogen applied early can be lost to volatilization or leaching below the root zone. By splitting applications, you can make more effective use of nitrogen. You can improve potential yield without applying more units of nitrogen than in the past.

Look at viable alternatives. Some farmers are finding that a very late application of nitrogen right before tassel, using a high-clearance sprayer with Y-drop applicators, has provided a yield boost. 

Take advantage of cover crops. If you’re using cover crops or would like to add cover crops to your system, nitrogen management is one benefit. Legumes produce nitrogen, and other cover crops scavenge available nitrogen in the soil and make it available later in the growing season. A challenge is knowing how much of this nitrogen is available to the cash crop and when it’s available. Planning when using cover crops can help provide late-season nitrogen for your corn crop.

Scout to make decisions. Effective scouting of corn for any signs of nitrogen deficiency will help you make decisions. With profit margins in corn as tight as they are, you cannot afford to leave any yield on the table due to corn running out of nitrogen. At the same time, you cannot afford to apply nitrogen that will not be available when the corn needs it. 

Review application timing. See if you can change your system to make multiple nitrogen applications closer to the time corn needs it. Increasing nitrogen management can help improve profit margins while also potentially improving water quality through reduced nitrogen runoff and leaching.

Donovan is a district conservationist with the Natural Resources Conservation Service. He writes on behalf of the Indiana Conservation Partnership.

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