Phosphorus and Potassium Soil Tests Over 8 Years

By Randy Simonson, Ph.D.
Technical Services Manager

This is last year's presentation showing what the soil tests have done over several years at the TSM_® Research Farm at Catlin.  The charts below show that the phosphorus and potassium levels can change from year to year.  This is why we recommend taking soil samples every year and not using a soil sample taken three or four years ago.

Both the phosphorus and potassium levels start out rather high, then moves up or down from year to year.  There are four different treatments in this field, yet the P and K levels on each of these fertilizer treatments tend to move in the same direction.  This is especially true for the potassium levels.

We used to believe that if you produced a very good crop yield, the soil test would move down because the crop took more out of the soil than we expected.  Conversely, if a poor crop yield were produced, the soil test levels would move up because of the unused fertilizer.

On the top of each chart are numbers showing whether that year produced more or less than average.  The numbers are the percent more or less (-) than the average yield.  This allows us to see if the soil tests are moving according to the yield.  The charts show that the first year produced crops that were 14% greater than normal and the soil tests went down.  The second year produced yields that were 20% less than normal and the soil tests went up.  So, in the first two years, this theory seems to hold water.   However, if you look at the next years, there is no correlation to yield and soil test movements.  Thus, there are obviously other factors that affect the up and down movement of phosphorus and potassium.  One of these factors may be the mineralization of soil organic matter.  Many different weather and environmental conditions affect mineralization.

Taking soil samples every year is a very important part of the TSM_® Fertility Program.  TSM_® strives to produce the best recommendation for each field and soil sampling every year is one of the tools we use to more accurately feed the crop.

Problem Fields

By Randy Simonson, Ph.D.
Technical Services Manager

Problems will start showing up in fields soon, if they haven't already.  Is there an area that is shorter than the rest of field, or is off color?  Every year we have whole fields or areas in the field that are not growing, as they should.  Many times it has to due with weather.  Sometimes it is fertility, although using the TSM program will lessen this possibility.

If you have an area in a field that does not look right and you suspect it has a nutrient deficiency, take tissue samples and soil samples from the bad and good areas of the field.  Some deficiencies increase with extreme weather conditions.

Compaction, low micro levels, a pH too high or too low, can all cause crop stress.

The pH of a soil also can be an important factor in the availability of a nutrient.  For example, zinc like most other micronutrients are much more available at low pHs than high pHs.  The table below illustrates how the availability of zinc decreases by 100 times for every one pH unit increase.

Trimble AgGPS Autopilot

By Gary Grimm
Agri-Data Management Manager

With advances in technology, new things keep coming.  Trimble has introduced an auto pilot system for agriculture that will steer a tractor or an applicator, eliminating overlap and reducing inputs.  This unit gives farmers and dealers the capability to establish a straight line much like a parallel swathing system and then follow that line without touching the steering wheel.

For the price of $54,900, the system includes a GPS base station, antenna and TrimComm 900 radio transmitter on two tripods.  The system transmits Real Time Kinetic (RTK) signals to identical equipment that is mounted on the vehicle, which is capable of centimeter accuracy.  The base station is capable of providing coverage of up to 6 miles or one can take the base station from farm to farm.

There are many benefits that come from using the autopilot system.  Skips and overlaps will ultimately be eliminated.  Tom Niewohner, a farmer using the system, states that on a 2500 acre farm, a person could have as much as 150 acres of overlap.  By reducing this to near zero, it will save time, fuel, labor or chemical costs.

RTK GPS can also produce topographic maps accurate to within an inch.  Generating this type of map will aid in the analysis of site-specific agriculture.  A grower will know the lay of the land and will be able to pinpoint areas of concern as well as good areas by overlaying a yield map with this data.

Compaction reduction is another benefit that can be realized.  By traveling the same track time after time, the compaction zone is confined to one area.  The system will also allow a farmer to plant without markers around the clock.

With a list of benefits that can save money the drawback still is the hefty price tag.  The autopilot system may not be for everyone but warrants being watched for future developments.

Puzzle of the Month: "Squares"

The famous mathematician Dr. Square Root had two sons, exactly a year apart.  One day shortly after they had both turned a year older, he noticed that if you squared their ages and then added the squares the total would be 1105.  How old are his sons?

To find out if you have solved the puzzle correctly, send your answers to:

TSM Services, Inc.
Attn.: Kim Vallery
FAX: (800)626-3807
E-Mail: 

The Answer to May's Puzzle!