We know that healthy soils have certain components like NPK, and trace elements like boron and manganese. We know that under ideal conditions plants work with the soils to replenish them each year. When that fails we fertilize, either based on ‘best guesses’, habit, or professional recommendations. As we discussed last week, soil tests are vital and I have argued strongly for them. However, as our body of knowledge increases, one thing is becoming clear; standard soil tests may not be telling us everything that is going on in the soil profile. You may already be using soil tests, or you may begin this year, but what if the information was incomplete? If the information is incomplete, then the conclusions would be faulty.
Good Soil, Bad Test
Almost 90% of soil tests solicited by homeowners are standard tests and these are okay. Where they fail is their inability to tell you what is available for your plant to use. They will indicate how many units of a given mineral or nutrient are present. What they will not show you is how many of those units are actually in a useable form.
Think of it like this. I go to the ATM at my bank and insert my card then request an account balance. The reciept shows two balances: my balance and my actual balance (my stated balance plus or minus any deposits or charges I have. Now, if I act like my “Balance” is how much money I have in my account, I can end up with some serious problems. The information is not wrong, it is jsut incomplete because some items have posted but have not cleared. In a similar way, what you need to see in your soil is not just what you have, but what your plants have access to.
Standard soil tests are not, in the truest sense, bad tests. They just provide incomplete data. The benefit of these types of soil tests, though, is that they are affordable and most people are familiar with them. For a traditional soil tests expect to pay about $10-15.
If you are looking for more information, for an additional $10-25, a more in-depth test, known as a water soluble extraction can be conducted. According to Ken Pohlman, Agronomist and President of Midwest Labs, this test not only will indicate what minerals and nutrients are in your soil but what percentage of those elements can be readily utilized by the plants. “Water extraction is a more sensitive test. It can indicate elements present even at lower levels.” It is not enough to know what elements are in your soils at any given time, though, that is better than no knowledge at all. You need to know how much is available in relation to the other nutrients present. In corn for example, zinc is crucial. Without it, other essential elements will go underutilized, decreasing the yield and quality of your stand. Pohlman said. “Trace elements can be a limiting factor; without the proper balance, your yields can plateau. The key thing to remember is that fertility is a process not a destination.”
Paul Leeds, soil specialist and farmer adds that this test “only has value if you can interpret it;” you have to know what you are looking for. If you know how to read the tests, are working with a lawn and garden consultant or have a knowledgeable independent garden store rep then Leeds says the pay-off will be immediate. “It is the difference between buying a Cadillac and a Yugo; this test gives you more for your dollar. There are things that I will never catch on the basic test that I can catch utilizing the water soluble test.”
Even more highly specialized tests can be conducted for nominal fees. Among information you may want to test for, consider these: Texture Analysis, Cation Exchange Capacity, Micronutrients, and Organic Matter (OM). If you are seeding a brand new lawn, have not tested in several years, or are growing flowers or plants for competition then the additional costs can be justified.
While soil testing does present some variables, regular monitoring will give you comparative data you can use to make determinations about your needs. When determining the ‘value vs. expense’ question facing you in real-world applications, Paul Leeds related his experience on his own farm. “I spend a lot of money on fertilizer, but I can [save enough money to] pay for these tests by avoiding buying things I don’t need. We no longer put money into nutrients that we already have.”
Monty’s Plant Food Company President, Dennis Stephens, says, “You cannot make blanket statements. Some products, like Monty’s Liquid Fertilizer, may allow you to cut back on traditional fertilizer applications IF your soil is in basically good shape. We emphasize that you must start with a soil test. Once we know what is happening beneath the soil-line, we can adequately feed the plant and help balance the environment in which it is growing.” He added. “In many cases, slight adjustments to your amendments, either to the soil, or to the plant directly will allow you to maintain or increase your results for relatively little cost.”
Once you have determined to spend the extra money on these advanced tests you need to have a snap shot in your mind of what healthy soils look like so that you can make some comparisons and determine what is needed to create the ideal growing conditions for your particular crop. You also need to know what keys to look for in your soil test. We will spend time on that issue more in depth in our next installment. If you are looking for additional information check with your local county extension agent, extension soil specialist, or contact www.midwestlabs.com or Monty’s Plant Food Company.
