soil testing and King County free soil samples testing

[Larry Fisher]

King County free soil samples testing

 

I (Larry) went to the site http://www.kingcd.org/pub_soil_soilsam.htm to check on King County free soil samples testing for Ruthann. The following paragraph bothered us:

 

We send our samples for a basic analysis that include phosphorus, and potassium, lime (pH), nitrate-nitrogen (fall only) and micronutrients. The lab report will include fertilizer and lime application recommendations for your desired crop yields.

 

Ruthann sent Jay an email on 03 March inquiring about why no Nitrogen level testing is done in the spring (when she needs to know it before she fertilizes).

 

His response:

 

The problem with taking Nitrogen (N) tests in the spring is that it is highly inaccurate.  The level on N will change based on the microbial activity in the soil at the time of testing.  So if you take your samples in the morning or afternoon on a cold day the results will be different than if you took the samples on a sunny day in the afternoon.  On the cold day, the bacteria and other critters in the soil that change N from one form to another are dominant <I suspect he meant “dormant”---Larry>.  As the soil warms, the activity speeds up.  In addition, since N is water soluble it tends to leach out of the soil during the winter.   So the reason we do the N in the fall it monitor the N levels after the growing season to prevent N leaching.

 

Most manures are low in N.  They are higher in phosphorous (P)and  potassium (K).  Those are the element you might want to consider over N when applying manures.  Since P & K don’t leach unless put in the soil in extreme levels (or if you have soil erosion), it is usually safe to apply.

 

Jay Mirro

Farm Planner

King Conservation District

 

So if you want a complete NPK, pH, and micronutrients soil test from King County, do it in the fall.

Larry