He says 25 of 26 (96 percent) of the corn locations tested showed that using residual nitrogen plus enough to get to typical fertility rate produced yield goal. For sorghum trials, 14 of 16 locations produced yield using residual nitrogen as part of the total fertility program.

McFarland says some fields show more than $100 per acre in residual nitrogen available. “Typical is $30 to $35 per acre. Consequently, farmers may want to consider deep sampling this year. They may be able to reduce nitrogen expenses.”

But farmers can’t substitute the deep sample for the zero to 6-inch standard test. “They still need that to get the base,” he says. “Then they can sample deeper, as deep as they can go. The deeper you can test the more money you’ll save.”

He recommends sampling with two buckets, one for the shallow sample and another for the deep one.

He says phosphorus and potassium also may be available at depth.

McFarland says growers may check a Texas A&M website, http://soilcrop.tamu.edu to help calculate how much fertilizer they need.

He says timing fertilizer applications also affects efficiency. “Crops don’t need a lot of nutrients in the early stages of development. Consider delaying full fertilizer application, especially nitrogen, and apply as a sidedress. That gives you an opportunity to look at the crop and adjust fertility to realistic yield potential.”

He says phosphorus is also expensive and is different from nitrogen. “It is not very soluble and stays where it’s placed. So, if you apply it in the middles, it will not do much good this year. We need to put it close to the plant and incorporate it, preferably 5 to 6 inches deep, in the active root zone.”

He says 20 years of research have shown that if farmers place phosphorus 5 or 6 inches deep they can reduce the broadcast rate by half and achieve “the same or better yields.” With phosphorus prices ranging from 85 cents to 90 cents a pound, a half-rate can make a big difference.

Potassium deficiencies, McFarland says, are showing up in some Blacklands fields. Drought last year may have been a contributing factor because potassium needs moisture to move through the soil. He says it gets trapped between dry layers of clay. “It’s like an Oreo. The potassium is the crème center. If the outside layers are moist, it can seep through. If it’s dry, it’s trapped. Soil compaction also sets us up for trouble.”

McFarland says soil and foliar-applied potassium have not been successful. “We have seen no response and don’t see an extra application of potassium as necessary. Heavy soils typically have sufficient potassium; medium textured soils may be deficient. Soil tests may indicate that marginal potassium sufficiency may justify fertilizer applications.” Deep soil testing may help identify these deficiencies, he says.

McFarland says farmers should test fields where silage has been removed. “Silage takes out a lot of nutrients.”

He also cautioned farmers about nontraditional fertilizer products. “There are no silver bullets. We’ve looked at a few of these and have not found any benefits.”

He recommends that if farmers want to try something non-traditional they should look for scientific data to back up claims and then test only on small plots.