Not all soils are created equal, and that simple realization will go a long way in helping you determine yield goals and fertilizer needs.

“Whatever you’re growing, you need to take into consideration what your land is capable of producing,” says Charles Mitchell, Auburn University Extension agronomist.

“In Alabama, we have a lot of varying soil types with different mineral and chemical properties and yield potentials, so we need to take into consideration all these factors.”

For example, growers need to ask themselves if their land is capable of producing 200 bushels of corn per acre. Sometimes, says Mitchell, the answer will surprise you.

“I never thought you could produce 200-bushel corn on Black Belt Prairie soils in Alabama. But the Dee family in Pickens County has proven me wrong on that, on several occasions. Annie Dee has asked me what nutrients to put out to produce 300-bushel corn, and I can’t tell her.

Some soils are well-drained and others are not, and that’s an important consideration,” he says.

In Alabama, the most limiting factor in crop production is water, according to Mitchell. “It suddenly hit me a few years ago why we are so successful in growing cotton in Alabama, but we’re a total failure at growing dryland corn, and that’s because corn is a determinate plant.

“It’s genetically set to produce a crop in a specific number of days. If anything slows down the growth — if anything affects photosynthesis during the span of 120 days or so — you’ll lose yield, and yield potential will decrease.

“Whenever you see corn wilting, that means photosynthesis has shut down. When corn is wilting it is no longer producing sugars, and it is no longer growing. So if it’s wilting today, that’s one day out of 120 or a little less than 1 percent yield loss already. If it wilts for 10 days, that’s a little less than 10-percent yield loss, assuming everything else is perfect,” he says.

Cotton, on the other hand, is an indeterminate plant, so it’ll just keep growing, he adds.

“If cotton goes through a drought, it’ll start to set bolls whenever it starts to rain. You might lose some yield, but it can compensate for some of those days of drought. Peanuts are the same way, but soybeans are less so.”

These differences have been evident, says Mitchell, on the Old Rotation, a crop fertility experiment begun on the Auburn University campus in 1896.

“Before we installed irrigation, we were probably averaging 70 to 80 bushels of corn per acre, and doing everything we knew how to do.

“Now, with irrigation, we’re pushing 200 bushels per acre each year. With soybeans, we were down to 30 to 40 bushels per acre and now we’re up to 60 to 70 bushels. The difference with cotton has not been as dramatic as with corn or soybeans.

One thing we can do to increase our yield potential is to irrigate. Eliminating water as a yield-limiting factor is a first step, but it’s not always easy.