By Dave Franzen, Soil Specialist

Joel Bell, Research Specialist

NDSU Extension Service

Soil testing is not used as regularly across North Dakota as it should be. It is the only number that represents a real portion of nitrogen (N) that growers can count on to factor into their N fertilizer rate decision. There are some growers who do not use soil testing because it is “too expensive.” But an analysis of soil testing, if the grower samples his/her field, reveals that sampling pays off.

However, we need to start with some assumptions:

• Anhydrous ammonia is $500 per ton (31 cents a pound of N)
• Urea is $370 per ton (41 cents per pound of N)
• Nitrate-N analysis is $4.50 per sample
• A full suite of soil nutrients is $14.50 per sample
• Field size per sample is 80 acres
• The price of wheat is $7.50 per bushel
• The price of corn is $3 per bushel

The soil test itself is almost negligible in cost. To pay for soil testing, the grower only requires 11 to 14.5 pounds of N savings for an entire 80-acre field to pay for it, or 0.6 bushel of wheat or 1.5 bushels of corn for the entire field.

However, most soil testing is conducted by a consultant. Let’s assume that the consultant will take a composite soil test with the suite of nutrients across the 80-acre field for $2 per acre. Our other assumptions will stay the same.

For 4.9 to 6.5 pounds of N per acre, or about 1/4 bushel of wheat or 2/3 bushel of corn per acre, a grower easily can hire a consultant to soil test an 80-acre field and provide a good guide to determining nitrogen and other nutrient rates for the field.

Soil testing always has paid, but this year it will pay more than ever.

NDSU Agriculture Communication