Growers have an opportunity today to make money in the grain markets, but they must find solutions to issues like rising fertilizer prices, says Ron Heininger, crop system specialist with North Carolina State University.
“The increase in the price of nitrogen and fuels is part and parcel of the opportunity we have,” says Heininger. “So we have to look at our nitrogen issues in a new light.”
Producers have always looked at nitrogen from the standpoint of how much fertilizer they should apply he says. “Now that we're looking at the juxtaposition of the cost of nitrogen against the opportunity we have to make money in grain production, we must look at things from a different angle.”
Looking at the components that make up the fertilizer recommendations for corn, it's important to ask how much nitrogen is really needed to grow a 150 or 200-bushel corn crop, he says.
“We focus not only on the fertilizer we're going to apply, but also on what is supplied by the soil. Now, more than ever before, we need to take advantage of that. Once we take the amount we need for that 200-bushel crop and subtract what we have in the soil, we're going to put on our fertilizer. But how efficient is that pound of fertilizer? Is 1 pound going to match our requirement or do we need to put on 1.25 to 1.5 pounds? How much do we really need?” he asks.
It takes about 1.5 pounds of nitrogen to make a bushel of corn, says Heininger. If a grower has a goal of making 200 bushels per acre, basic recommendations would dictate that he needs 300 pounds of nitrogen. If it's all put on as fertilizer, the cost adds up quickly, he says.
Fortunately, he adds, there are other ways of doing it.
The problem with growers simply calculating their nitrogen needs and using that as a starting point is they don't know what their yields will be, says Heininger. “We don't know if we need 300 or 250 or 200 pounds of nitrogen because we don't know what our final yields will be. Many factors impact final yields, including temperature, rainfall and genetics. We see some Bt hybrids that are a little more efficient in nitrogen use than it used to be,” he says.
It's difficult, he continues, to determine how much nitrogen the soil will supply. “Soil is dynamic, and that's the problem with measuring nitrogen in the soil. It's changing all the time, especially when it's wet and warm. We have all of those interactions, such as nitrification and the breakdown of organic matter. So the nitrate available to that crop changes. That's why we need to pick a time or find a way to measure that nitrogen to tell us the soil N,” he says.
The good news, says Heininger, is that unlike what we've been taught and led to believe over the years, soil actually is a major supplier of nitrogen to the crop.
“Manure can give us a lot of soil nitrogen. We need to start thinking about what we can do today to build our nitrogen supply in the soil — taking the emphasis off of fertilizer and starting to build our soil to supply that nitrogen,” he says.
Finally, he says, there's the nitrogen use factor — finding a way to put on nitrogen when it's needed by the crop so there's an adequate supply during the critical growth periods. “How do we design a system that we can use in the field and that will give us some relief from high nitrogen prices?”
Currently, some North Carolina growers use the realistic yield estimate (RYE) method to determine the crop's nitrogen needs, says Heininger. The RYE uses an average yield based on three out five years multiplied by a nitrogen factor and taking into account what the soil might supply.
“The RYE doesn't measure N crop, and that's particularly important for dryland growers. You know your yields have gone up over the past several years, and yet the RYE is understating what N crop is. And where is the soil factor? We're not accounting for residual N — maybe a little but not truly. There's also no adjustment for manure. It does a pretty good job if we assume the soil doesn't give us much.
“The other problem with our current system is especially evident as we get into higher nitrogen prices in relation to corn prices. As long as we stay in our normal range — whether in high or low-yield situations — we only change our nitrogen rate by about by about 10 pounds, by going from 10:1 to 15:1.”
The deficiencies in RYE can be solved by designing a different system that uses a step-by-step approach through the growth of the crop, says Heininger.
“We can start out with an estimate of what our N crop is going to be, or how much our crop will require. Then, we can step forward in time, each time know a little more about what our crop requirement might be. At planting, assume you're looking at a 200-bushel corn crop. N crop will be about 300 pounds. Then assume, based on a previous history of a legume crop, that you're getting about 50 pounds out of the soil.
“We take that out, so out of 300 pounds, I've got to put on a 250-pound application rate. So I'm going to start off with enough nitrogen that will make that yield happen for me. In other words, to begin with, we'll apply 50 pounds or about one-third to one-fourth of the total needs of the crop.”
Growers know they'll have to make another application at layby, says Heininger. “It would be good here if we had a soil test that would work for us and help to quantify the soil nitrogen that is available. We can then take a look at the needs of the crop. If weather conditions have been poor, we can consider dropping the yield estimate to 150 bushels per acre. With this system, we're going forward, one step at a time, closing in on what we think we really require.”
There might then be an opportunity, he says, to take a “final shot” at the pre-tassel stage. “Our N crop has further eroded because of weather, so we make an estimate and finally put on the rest of our fertilizer to meet the needs of the crop.
“We need to look at this type of system in our nitrogen management if we're ever going to get an accurate supply of nitrogen to the crop.”
To make such a system practical, growers will need to start the season by looking first at the soil. “What will it take to get all of the nitrogen that the soil has to apply to the crop? That means we need to make sure it's all taken up by maximizing root growth. We do things to improve root growth so we can get all of the soil nitrogen that is available. We've done a lot of root studies in North Carolina, and starter fertilizer makes a difference in root mass and root ball size. It is especially helpful in high-population, intensive management systems.”
One reason for wanting the crop to get off to a quick start is rainfall, says Heininger. “The best rain we got in North Carolina last year was in early June. We made a corn crop last year on 2 inches or rain in June because we got our roots developed.”
Other ways of preparing the soil so that it'll provide the maximum amount of nitrogen to the crop include using manure and cover crops, he says.