From Agronomists of the
Potash & Phosphate Institute
655 Engineering Drive, Suite 110
Norcross, Georgia 30092-2837
Phone (770) 447-0335

Summer 1996, No. 7


The outlook for tight wheat supplies and good wheat prices for 1996 and 1997 indicates that growers need to be planning now to capitalize on the situation. Good soil fertility management is a key in that planning. Here are some things to think about.

Nitrogen. In the Great Plains, short moisture, poor stands and uncertainty about the 1996 crop caused a cut back on both preplant and top-dressed nitrogen applications. That means little carryover for the 1997 crop ...even if that crop is poor. Soil testing for residual nitrate-nitrogen is one way to tell how much nitrogen remains in the soil following the preceeding crop or fallow. Remember, each bushel of yield requires about 2.2 pounds of nitrogen from somewhere...soil, fertilizer or irrigation produce the roots and top growth needed to produce grain. Grazing increases the amount needed.

Nitrogen affects water use efficiency...the amount of grain produced per inch of available better root growth allows the plants to better utilize the moisture that is in the soil. Adequate nitrogen is also key to tillering and has to be available in adequate amounts when the plant is deciding how many tillers to produce. Fewer tillers mean lower yields. This year is a good example of that effect.

Phosphorus. Wheat simply can’t get by with short supplies of available phosphorus...both forage and grain production suffer without adequate amounts. Each bushel of grain harvested removes about one-half pound of phosphate. But the only way to determine how much fertilizer phosphorus the crop needs is to soil test. Otherwise, you’re just guessing. There’s no question, phosphorus is the second limiting nutrient behind nitrogen for wheat production from Texas to Alberta. Short supplies mean poor root growth, less forage production and grazing, poorer nitrogen use efficiency and lower grain yields. That all translates to reduced profit potential at a time when profit potential for grain was never higher!

Soil testing can also give you some important tips about phosphorus management. Very low soil tests, particularly on high pH or low pH soils, mean that broadcast phosphorus prior to planting isn’t going to be as effective as some sort of placement...banding preplant with nitrogen or application at planting in seed contact. Banded phosphorus is often more effective on medium testing soils but is less important at higher soil tests.

Potassium, Sulfur, Chloride. Soil testing is the key to determining needs for these nutrients, too. University research emphasizes the need for sulfur on low organic matter soils...sands usually. Rates range up to 15 to 20 pounds per acre. Chloride is the newcomer in nutrient needs and research continues to show that applications of 20 to 40 pounds per acre as either potassium chloride or magnesium chloride can boost yields four to eight bushels per acre...sometimes more. Tolerance to moisture stress and plant diseases are also benefits from chloride application. Returns have been about $4 for each $1 invested.

Don’t let outstanding profit potential get away from you in 1997 because of factors you can do something about. Soil fertility is one of things you can manage for higher yields...and higher profits.


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