Knowing a soil’s nutrient level identifies it's needs and can help maintain productivity especially in a continuous corn operation, which is something many corn growers have planned for this season.

Robert Mullen, an Ohio State University Extension soil fertility specialist, says a simple soil test can reveal all that a grower needs to know about a field’s condition, which can lead to smarter fertility management and potential alternative options, such as manure use.

Continuous corn production generally requires 40 pounds more nitrogen than in a corn/soybean rotation. With that comes higher commercial fertilizer costs. “Growers are looking for ways to not invest in as much nitrogen or to cut corners. Pay attention to soil tests. The quality of the crop is a function of the operation of the soil,” says Mullen.

Soil tests measure nutrient levels, such as phosphorus and potassium, as well as the soil pH. While corn must have nitrogen every year, growers can adjust their phosphorus and potassium levels.

“Phosphorus and potassium are nutrients that don’t deplete every year, like nitrogen. If the soil has adequate levels of those, you don’t need to add more. That money can be used to invest in more nitrogen,” says Mullen. “Additionally, growers must keep in mind that excess phosphorus can be an environmental hazard in the form of run-off. So maintaining proper soil levels is important.”

Then there's soil pH.

“Nitrogen fertilizer is a soil-acidifying reaction, so growers might think about liming more frequently to maintain the pH at around 6,” he notes. “A soil test will tell a grower the soil pH and whether he needs to add lime.”

If budgeting for additional commercial fertilizer is not an option, other alternatives might exist-- such as manure application.

“Manure is a really nice resource of nitrogen, potassium and phosphorus,” says Mullen. “Manure can be used to offset some of the commercial nitrogen fertilizer costs. It’s just a function of knowing how much to add to the soil.”

Which, again, makes soil tests important.

“Knowing which fields need the manure is an important aspect of fertility management,” he adds.

Mullen recommends that growers conduct soil tests either in the fall or spring after corn or soybeans, or in the summer after wheat harvest. The key is to be consistent about the time of sampling.

For more information on managing a continuous corn rotation, log on to Ohio State University Extension Agronomic Crops Team Web site at

Source: Ohio State University