Making the Switch-Fall to Spring Soil Sampling

For most of the Midwest, drought conditions continue into the fall and winter months.  Field fires, low grain moisture, and tillage practices are proving to be difficult hurdles, but dry soil conditions make soil sampling especially difficult. Not only are soil sampling conditions challenged by dry soil, but lab results take more interpretations than seasons with adequate circumstances.

Fall soil sampling has, historically, been the peak timing for sending in numerous bags of soil to the lab.  This is due to many factors.  Once the grain is harvested, it leaves an open canvas to sample exactly where the client or sampler would like to.  This keeps the process as efficient as possible and leads to the most reliable data.  The lab reports the soil analysis for further review, and then the correct fertility program can be implemented. 

Testing when the crop is harvested not only allows for quicker/more precise sampling, but also applications can then be made without crop damage.  As most fertility programs apply in tons, or several hundreds of pounds, rather than small in-season amounts.  All this is possible because there seems to be more time at the end of the season to achieve applications.

Where this used to be the case, now many growers are hiring sampling and applications to be done.  Whereas before, growers needed that extra time in the fall to do it themselves.  Because of this, most research and response data has been for fall applied nutrients.  Now with new studies, technology and contracting sampling/applications there has been a movement to spring soil sampling. 

Spring offers many benefits to sampling compared to the traditional fall sampling.  There is more uniform moisture, and certain nutrients like potassium have been released from the previous crop residue.  It can be more ideal for a soil sample since dry conditions are not often experienced.  Growers may experience slightly higher pH values in the spring and potassium levels.  Nutrients like nitrogen and sulfur, anions, may leach and decline over winter months depending on precipitation, temperature and soil type.

Now that there are multiple windows of opportunity for sampling, some precautions must be taken into consideration.  If soil sampling and application are conducted the same season as seeding, it may delay some planting applications due to relying on samplers and applicators.  Depending on the product being applied, some salt injury could occur, or the nutrients will not be available in time for the new plants.  This in mind, many spring samples are for fall applications of fertilizer.  Especially if pH and maintenance programs are being utilized.

If you have any questions about how spring soil sampling may benefit your operation, please reach out to your ALGL agronomist.