Farmers will have to pull two samples, one from the usual zero to six-inch depth to determine nitrogen, phosphorus, potassium calcium, magnesium, sulfur, micronutrients, and pH. They’ll need to take a second sample from zero to 18 or 24 inches to determine residual nutrient levels with depth. He also suggested farmers use N-rich strips in season to judge the proper amount of topdress nitrogen. N-rich strips consist of narrow strips laid out in the wheat field with each strip receiving a different rate of pre-plant fertilizer. Strips are fertilized with increasing rates of nitrogen (for example zero, 40, 80, and 120 pounds per acre) up to the maximum rate for the expected yield.

Producers evaluate each strip to determine between which increments there is no difference in plant growth. They use the last discernible improvement to establish topdress rate. If the last strip to show a yield advantage is 80 pounds per acre, and the grower applied 40 pounds per acre at planting, he needs to topdress his field with 40 pounds to bring the total to 80 pounds.

Phosphorus also makes a difference. “Phosphorus stimulates early root formation, increases tillering and increases seed size.”

But, unlike nitrogen, phosphorus is stable. “It stays put. If farmers apply phosphorus to the surface it doesn’t migrate into the root zone,” he said.

“We need to incorporate phosphorus to five or six inches. That will improve uptake substantially and increases production potential. Phosphorus prices are close to nitrogen costs, so we need to put it where the plant can take advantage of it.”

McFarland said he’s seen more potassium deficiencies than usual the past few years. “And I’m not sure why. It could be that fields have been cropped for many years, and natural soil levels are decreasing.  And, under dry conditions, root uptake of soil potassium already is limited. But potassium is important. It plays a role in cold hardiness and water use efficiency.”

He also cautioned growers about “non-traditional” fertilizer products. “With current high nutrient prices, silver bullets are being marketed to producers to enhance fertilizer efficiency. The problem is that often no research is available to back up many of these claims. Be sure to have independent, nonbiased research before using a new product.”

Humic acid is a product that’s been touted in recent years as a means of enhancing fertility. “We’ve looked at it in cotton, corn and grain sorghum and saw no response compared to traditional products.”

He said humic acids occur naturally in the soil anyway, “probably from one-half to one ton per acre. So if we only add one to three gallons per acre it’s not likely to have much impact.

“Look for sound scientific data before deciding to use any new product.”

Organic nutrient sources, such as chicken litter, can offer “real bargains.” The biggest factors will be transportation cost and moisture content. If a farmer can have chicken litter delivered and spread for $65 to $75 a ton, he should do the math and see how it compares to standard inorganic products. “Also, do an analysis on compost or manure to determine what’s in it and then compare that dollar to dollar with inorganic fertilizers.”

But, whether it’s chicken litter, compost or typical fertilizer products, McFarland says the keys remain the same. Select the type of fertilizer, the rate, the method and the time of applications based on crop conditions, moisture and intended crop use. And measure—soil sample—to make certain that what you apply is exactly what you need.