Choose Lubricants Carefully for Soil Testing

University and Industry researchers have evaluated many lubricants used to make soil sampling easier. This research has been done to make sure the lubricants do not contaminate the samples with nutrients such as nitrogen, zinc etc. What these researchers did not evaluate was the effect the lubricants had on nutrient levels if the soil samples were stored at room temperature for several days. This past spring and winter AGVISE conducted a preliminary study looking at WD-40 and PAM cooking spray. We wanted to look at the effect they had on nitrate levels if the samples were stored at room temperature for many days. What we found out is very important. If PAM or other vegetable sprays are used to collect the sample and the soil sample is stored at room temperature, the nitrate level drops to a very low level within 2 days. If WD-40 was used to collect the sample, the nitrate level began to drop after 4-5 days. If the samples were kept in a refrigerator or in a freezer, the nitrate level did not drop off. We are speculating that this is a biological process causing the problem. AGVISE will be doing another evaluation project this fall using both WD-40 and PAM cooking spray as sampling lubricants. At this time we recommend using WD-40 as a lubricant if necessary. Samples should be kept in a refrigerator or freezer if they will not be tested within 3-4 days. Later in the fall when temperatures cool off, this will not be a concern. Keeping samples cool or frozen is always recommended when sampling starts in August.