Start Your Year With Solid Information
Posted in General by Curtis Williams
BY DALE MILLER, AMERITURF CORPORATE AGRONOMIST:
Spring is almost upon us and it’s time to put together fertility programs based on experience and confirmed with science.
There is no exception for the experience of years of applications against climate, traffic and assessment of where the plant is going into spring, but confirming programs based on tools such as soil chemical extraction, soil paste extraction and water analysis will provide an excellent scientific method to improving your chances of appropriate fertility programs.
Using a POGO to evaluate moisture and EC, Salinity Index in real time will solidify programs to a level never reached in the past.
As water is the single biggest input annually on almost all courses understanding monthly use in low rain periods and annual use for total nutrient input is where a fertility program should start each year.
Water analysis should be performed once annually unless you have water that changes, sources that change or are getting treated water which will change.
Do not accept the monthly report from treatment labs as the gospel and definitely not the annual report. Do not assume that your water is what it was last year or a few years ago. Water quality changes and should not be left to an assumption.
When using a good water analysis that provides total soluble elements at acre inch increments you will be able to calculate the amount of each element applied annually.
To calculate this, simply take the amount of an element/compound per pound per acre inch of irrigation, and then multiply that times the total annual water used and divide that by the water in an acre inch (27,154 gallons).
For example: 15 lbs. Ca x 75,000,000 gallons water used annually/27,154gal/ac in = 41,430 lbs. of Calcium applied to the area irrigated per year.
Do the same math for all the elements/compounds and you now have the total input from your irrigation system annually. This by far exceeds any fertility input annually and most people never consider these numbers.
Look at both the good and the bad, as this will help you understand what is going on in your soils as the oldest agriculture rule is, “As your water is, your soil will be.”
When looking at the soil analysis, use of a chemically extracted soil analysis next to a water extracted “Paste” analysis will provide a far better assessment than either on their own.
Most labs now use Mehlich III analysis, which is a strong acid that strips the nutrients from the mineral rock itself, as well as solubilizes any applied fertility in the soil at that time and any compounds tied up in the soil but not necessarily attached to the soil. This is a very consistent analysis method though not all agree on its benefit. It is still however the most accepted analysis method for chemical extraction of elements from soil.
Remember though, none of the elements attached to the soil, tied up as compounds or still in granular input form, are available to the plant. The plant can only take up nutrients in “ionic” singular elemental form; the plant can’t take up inorganic compounds.
So, the soil analysis is worth looking at as it is the bank of elements and compounds that you are hoping will find their way to available and usable by the plant.
The additional method of looking at soils we subscribe to is “Paste” extraction. This involves the same soil sample, but uses either de-ionized water or your water to solubilize elements that are readily water soluble. This gets some criticism as it is not accepted by all and it’s not clear how you make a paste from sandy soil, as well as the fact that you do not generally have saturated soils in turf.
It is however a valuable method to understanding what is solubilized in water which is the input used in turf to solubilize elements from the soil.
Some labs are working very hard to use weaker organic acids to solubilize elements in an attempt to mimic how the plant and the biology work together to solubilize elements naturally.
As the soil contains/holds these elements, the application of irrigation and rainfall solubilize some of these and the natural processes of the plant and the biology solubilize some of the elements. A combination of as many of the testing tools available today are the best method of a scientific approach to fertility building which as stated earlier, needs to have the key factor of experience.
Last, I encourage you to consider the best time to sample soil analysis and the depth to sample.
The best time is as far away from nutrient inputs as possible. Early spring before spring applications are started will be a much better base line than summer or fall sampling periods for understanding the base line characteristics of soils and nutrient availability. As applied fertility has a wide range of solubility, it should be as far away from the soil analysis as possible.
The depth of samples from a representative area is about 4 inches in turf.
Though we may get rooting deeper than 4 inches, the majority of uptake and effective root systems is in the upper 2 inches with 4 inches being on the outside of effectiveness. This is important as labs use a common Ag standard of measurement unless otherwise specified.
Labs use an Acre 6 inches as the standard soil capture area. This equates to 2,000,000 lbs. of soil and is used in the calculation of total nutrients in the soil.
As we in Turf have a 2-4 inch effective root system as opposed to most Agricultural plants in far better soils, it is important to sample to a depth of no more than 4 inches and specify this on the sample bag and documents sent to ensure that the lab does all calculations on 4 inches, which represents 1.33 million pounds as opposed to the acre 6 inch standard of 2 million pounds.
For accuracy sake, a difference in that much weight should be considerably different and of concern.
I can’t stress how important it is to start the year off with a greater understanding of what is going on in the soil and water, and how all this should affect and influence your fertility plan.
Use the combination of water analysis, soil chemical extraction and soil paste extraction to provide a comprehensive analysis and basis to building the annual fertility program with much more confidence and accuracy.