Soil Testing: Where Procrastination Can Pay Off


by Haylie Shipp


Harvest is behind us and, from crop insurance to crop management, there is a whole slate of choices ahead for farmers.  One decision that you may be facing is soil testing.  According to Clain Jones, Extension Soil Fertility Specialist at Montana State University, a soil sample costs somewhere between $25 and $40.  While it is an up-front cost, he told Northern Ag Network in a phone interview last week that the initial price is a small amount compared to how much can be gained or lost in over-applying or under-applying fertilizer.  

Fertilizer prices have stayed relatively steady in recent weeks.  However, in looking at DTN data, the cost is still substantial.  According to DTN’s latest estimates, on a price per pound of nitrogen basis, the average urea price was at $0.55/lb.N, anhydrous $0.43/lb.N, UAN28 $0.58/lb.N and UAN32 $0.58/lb.N.


The questions of “when” and “how” when it comes to soil testing can often be answered with “it depends.”  For nitrogen, Jones suggests an annual test.  With phosphorus and potassium, however, that can be held off until every two or five years.  

As for when, Jones highly suggests waiting if possible.  This is the case especially when it comes to nitrogen.  This is because nitrogen can be lost in the soil through leaching or gained in the soil due to organic matter decomposition.  In studies done by MSU, Jones has seen up to a 20 lb N/acre difference when comparing the fall and spring samples.  


To soil test a given field, Jones recommends taking 10 to 15 samples, mixing those together, and taking a subsample from that mixture to submit.  For more information on soil sampling, please visit the Montana State University Soil Fertility Extension Program website.



© Northern Ag Network 2014

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