High yields pull out nutrients

Corn is king for Tom Boyd, his son Trent, and
son-in-law, Logan Graber, Washington. A large percentage of their flat, productive soils consistently produce above-average yields.

With success comes responsibility, Trent emphasizes. He believes it’s critical to monitor how many nutrients are removed through soil test results. When warranted, it’s important to add fertilizer, whether it’s commercial fertilizer or manure, he adds.

Key Points

Big corn yields remove lots of nutrients from the soil.

Soil test levels help determine how much fertilizer to apply.

Sampling every other year helps keep a better eye on pH levels.

Work with consultant

How many nutrients big crops remove is one of the lessons Trent learned working with Shannon Morrison, a local crops consultant. “If you’re going to haul off big yields, you’re going to take off lots of nutrients too,” Trent says. “You have to pay attention to how many nutrients you’re pulling out.”

The Purdue University Corn and Soybean Field Guide indicates how much of each nutrient you will haul off per bushel. For example, each bushel of corn grain removes 0.37 pound per acre of phosphate equivalent and 0.27 pound of potash equivalent.

“At one time Dad’s goal was to average 160 bushels per acre on better ground,” Trent observes. “Now we sometimes hit 240 bushels per acre. That’s a significant increase not only in yield, but in nutrients you’re taking off the field.”

Here’s the math based on the Purdue field guide figures. At 160 bushels per acre, you remove just over 59 pounds of phosphate per acre per year. At 240 bushels per acre, it’s nearly 90 pounds per acre.

For potash, a 160-bushel-per-acre corn crop on average would remove about 43 pounds. But a 240-bushel-per-acre crop could take off 65 pounds.

The numbers are even more striking for soybeans. Each bushel hauled to town removes about 0.8 pound of phosphate and 1.4 pounds per bushel of potash equivalent.

Crop removal is not the only factor that will determine how much fertilizer should be applied, the guide notes. It also depends on how much is supplied by the soil, which is linked to soil test levels and efficiency of use in any season.

Morrison samples on 2.5-acre grids. Working together, he and Trent monitor removal of nutrients, especially on high-yielding fields. They determine how much fertilizer should be applied.

Recently, Trent decided to switch to sampling fields every other year instead of once every three years.

“The main reason for sampling more often was keeping a closer eye on pH levels,” he says. “I don’t like them to change so much in a three-year period that I must apply up to 3 tons per acre. We were seeing quite a bit of pH change, so we decided to pull samples more often and monitor pH closely.”

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Big yield believer: Trent Boyd knows big yields are possible on good soils, but he also knows they pull out lots of nutrients.

This article published in the May, 2011 edition of INDIANA PRAIRIE FARMER.

All rights reserved. Copyright Farm Progress Cos. 2011.