By Don Donovan
Farmers today say new “racehorse” corn hybrids make use of available nitrogen in the soil much later than some older hybrids. Studies show that nitrogen uptake may occur until shortly before black layer, when corn reaches its full maturity.
What does this mean for the farmer? It probably means you need to consider how you put on nitrogen, when you put it on, and maybe even what form of N you use. A careful review of your nitrogen program for corn will improve nutrient use efficiency of the applied nitrogen.
What does this mean for you as you manage your N application? How can you tell if you have enough N?
Get out in the field and check your corn as it matures. You may need to pull some tissue samples. A drone flying over the field can tell you some things about how healthy your corn is and whether it’s lacking in available nitrogen.
Late need for nitrogen may mean you should consider applying part of your N after plant emergence. This is especially true if you’ve been putting on most N in the fall or early spring 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 the nitrogen. You can improve potential yield without applying more N than you have in the past.
Nitrogen application methods
Some Indiana farmers are finding that a very late application of nitrogen right before tasseling, using a high-clearance sprayer with either a coulter unit that injects N or Y-Drop applicators, has provided a yield boost. (Editor’s note: Not every study finds this yield increase every year.)
If you use cover crops or would like to add cover crops, nitrogen management is one of the benefits of their use. Legumes produce N. Other cover crops scavenge available N in the soil and make it available later in the growing season. A challenge is knowing how much of this N is available to the cash crop, and when it is available. Some planning in using cover crops in your system can help provide late-season nitrogen for your corn crop to use.
Effective scouting of corn for any signs of nitrogen deficiency will help you make your decision. With profit margins as tight as they are now, you can’t leave any yield on the table due to corn running out of nitrogen. At the same time, you can’t afford to apply N that will not be available when the crop needs it.
Look at your nitrogen application program. Can you change your system to one where nitrogen is put on in multiple applications, closer to the time corn needs it? Increasing nitrogen management can help improve profit margins while also potentially improving water quality through less loss of N into water supplies.
Donovan is a district conservationist for the Natural Resources Conservation Service. He writes on behalf of the Indiana Conservation Partnership.