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Texas:

Increased Costs Make Management Key When Fertilizing Wheat

By Kay Ledbetter

Texas A & M

AMARILLO, Texas (August 14, 2008) – The increasing costs of nitrogen and phosphorous during the last year have made it more important than ever to use fertilizer as efficiently as possible, said a Texas AgriLife Extension Service specialist.

Dr. Brent Bean, AgriLife Extension agronomist, said a good soil test is essential to determine the most efficient nitrogen use and proper rates of other nutrients.

“It is important to remember that yields are limited by the most limiting nutrient, whether that is nitrogen, phosphorous or other nutrients,” Bean said. “Applications of nitrogen when phosphorous or other nutrients are deficient, is wasting money.”

He said where possible, the collection of deep soil samples is best and could potentially save producers a significant amount of money in fertilizer costs. “It is not unusual to find 30 pounds or more of nitrogen in the soil at depths below 1 foot,” Bean said, adding wheat can easily use nitrogen from a soil depth of 3 feet.

Wheat needs 1.5 pounds of nitrogen for every bushel, regardless of the nitrogen source, said Dr. Gaylon Morgan, AgriLife Extension small grains specialist. It also needs approximately 0.75 pounds of phosphate for every bushel of yield.

“If phosphorous is needed, it is best to apply it in the fall,” Morgan said.

Phosphorous must be incorporated or injected into the soil because it is not mobile in the soil like nitrogen, he said. The highest efficiency rates are received when phosphorous is applied in band.

“Phosphorous can be applied with wheat seed, but make sure any nitrogen or potassium applied with it does not exceed 18 pounds, or seed germination may be hampered,” Morgan said.

Nitrogen can be applied either all in the fall, as a split application between fall and spring, or all in the spring to maximize nitrogen use efficiency, Dr. Todd Baughman, AgriLife Extension agronomist said.

“Unless the nitrogen level is very low in the soil, dryland wheat producers should consider applying all of their nitrogen in the spring when they will have a better estimate of their yield potential,” Baughman said.

Nitrogen should be applied as a top-dress application at least two weeks prior to jointing, Bean said. This will promote tillering and wheat head size. If the wheat will be grazed, he said, then at least one-third of the nitrogen needs should be applied in fall.

“If manure or compost is available, producers should compare cost with inorganic fertilizer needs,” Bean said. “In many cases, manure or compost may be the most economical form of fertilizer.”

But he also suggested producers have the manure or compost tested for nutrients, as only about half of the nitrogen content will be available the first year.