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Sample Soil, Save money

Wednesday, November 15, 2006
filed under: Fertility

Crop producers can save money by soil testing for nitrate nitrogen, says Jim Gerwing, South Dakota State University Extension Soil Fertility Specialist. Drought conditions in 2006 prevented crops in many parts of South Dakota and other areas from using much of the fertilizer that had been applied to fields.

“Really, this is a year when a person could make some serious money by soil-sampling for nitrate. The fertilizer that wasn’t used by the crop this year is still there as nitrate. In years now when we have so little rainfall, we know we didn’t lose it by leaching or denitrification,” Gerwing says.

Some soil samples from failed cropland indicate over 100 to 150 pounds of nitrate carryover in testing at SDSU.

“If we go back to our last kind of dry year, for example, in 2002, the average nitrate carryover after corn was like 107 pounds, where we normally find 50 or 55 pounds. The average, after corn, in 2002 was up 50 pounds an acre.”

Every pound of nitrate in the soil lets a producer cut the same amount when he calculates how much fertilizer his next crop needs. But Gerwing says other nutrients such as phosphorus, potassium, and micronutrients don’t change rapidly in the soil. That means producers can expect recommendations on those nutrients similar to this year.

Since sunflower is a deep rooted crop, a probe deeper into the soil would give a better idea about N in the soil that might be there for sunflower’s taking. “With sunflower, down to two feet is good, but testing down to four feet is better,” says Colorado State University extension agronomist Ron Meyer. Soil scientists generally recommend that you’ll need 50 pounds of soil N plus fertilizer N in the top 2 feet of soil for every 1,000 pounds of expected sunflower yield.

Soil Sampling Labs

A corrected address and addition to the list of soil sampling labs published in the last issue. The entire updated list can be found online at – click on ‘Sunflower Magazine’ then ‘view archives’ and ‘fertility.’ See the article Sept 06 article, “Fall Excellent Time for Soil Sampling.”

SDSU Soil Testing Lab

Ph: (605)688-4766

Fax: (605)688-4667



Samples can be sent to:

Soil Testing Laboratory

Box 2207A

South Dakota State University

Brookings SD 57007-1096

Samples can be delivered in person to:

Agricultural Hall (Use the north door)

Room 07

South Dakota State University

Brookings SD 57007-1096

Midwest Laboratories Inc

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