Focus on fertility to prevent pollution and boost profits

The basics of elementary education typically center around the three Rs: reading, writing and ’rithmetic. In the field, farmers need to focus on the four Rs of fertility management: the right product, right rate, right time and right place.

"Choosing the right product and then applying it at the right time, at the right rate and in the right place makes you money by using fertilizer more efficiently," says Farm Journal Field Agronomist Ken Ferrie. "It also makes you a better environmental steward by preventing unused nutrients from escaping and getting into water sources."

The four Rs, developed by the fertilizer industry, are so important that Farm Journal is launching a new series called Nutrient Navigator to help put the concept into motion on your own farm.

The key to the four Rs of fertility is that all of the components are applied together. "If just  one—the product, the rate, the timing or the placement—is off, you miss out on the benefits of the whole process," Ferrie says.

To set the stage for fertilizer success, let’s look at the role of rate, timing, product and placement.

Rate and timing. Rate and timing are related. To understand rates, you must understand when each crop, as well as soil microorganisms, needs nutrients. For example, both corn plants and
microorganisms need nitrogen early in the growing season.

"When we talk rates, we’re talking about the rate for a certain window of time," Ferrie says. "Your total nitrogen application for a corn crop might be 200 lb. per acre. However, you might
need 50 lb. of that nitrogen applied in late fall or early spring to pay the carbon penalty."

The carbon penalty results from microorganisms decomposing old crop residue. The penalty is greater when residue is incorporated with tillage.

"The corn needs nitrogen for early growth and plant health—a crucial time when yield is being set," Ferrie says. "Microorganisms need nitrogen to promote the breakdown of old crop residue. This triggers the mineralization of nutrients and makes them available to the growing crop.

"You might need to apply 10 lb. of your total nitrogen application as starter fertilizer to make sure the roots of your young corn plants can reach it," Ferrie continues. "You might also need to put some phosphorus in your starter to make sure it is available to the young plants early in the season, when cold, wet conditions might cause phosphorus in the soil to be tied up."

Learn when each crop needs each nutrient. "For example, phosphate, sulfur and zinc need to be taken up by plants early in their lives," Ferrie says. "Those nutrients are not mobile, and they must be present in the plant to satisfy its vegetative growth needs early in the season."

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