Healthy Soil - You Must First Measure It Before You Can Manage It. (Part One)
It does not matter what crops you grow, whether permanent or row crops, your soil health should be a high priority. When soil is healthy, it is productive. Productive soil grows healthy plants, with well-balanced vigor and precocity all without sacrificing crop quality. If you are being challenged by plant infections and fruit set and/or quality issues, you might need to take a closer look at the soil. The health of your soil is foundational to everything that grows out of it.
To gauge soil health you need to know its contents. A friend once described that concept this way, “You must be able to measure it, in order to manage it.” Begin with a soil test or tests which are representative of the block or treatment area needing to be addressed. A comprehensive soil audit will provide you with objective measurements of the nutrient inventory, nutrient release, soil texture and microbial levels.
Remember the data you get from your Ag lab is only as good as the sample gathered. This is why it’s important that the samples collected are representative of the conditions needing attention. In situations where there are problems, in the soil (or plants growing in these areas), be sure to sample such that the lab results can be used to build a corrective plan of action. In addition, the extraction method(s) used by the lab, also plays a key role in those results. That said, let’s discuss a few important details.
pH (soil):
When measuring the soil pH, the extraction method matters. The standard acidified (ammonium acetate) paste extraction is mixed in a 1:1 (soil:water) ratio; i.e. equal parts. By using an acidified medium for extraction, you get a rapid nutrient release and measurement of the soil nutrient inventory. With an acidified extraction medium there is a high level of cation release, this can be a higher release than what actually takes place in the soil. Cations are alkaline and they displace acidity. This can show the pH (soil) [see Table 1; red box] value to be higher than what is actual.
Table 1
pH (water):
In addition to an ammonium acetate paste extraction, a water pH extraction [see Table 1; red box] is also a useful measurement. Not all Ag labs offer this extraction, but the technology is here and it isn’t new, so it’s worth seeking out a lab that provides it. A water pH extraction gives additional information for more precise nutrient management and amendment planning.
Table 2
When calculating the soil water pH, the soil Cation Exchange Capacity (CEC) is calculated first. Then, based on the CEC, the soil sample is filled to Field Saturation Capacity with 68°F neutralized water and held for four hours. This simulates a good field irrigation. These are Dr. Albrecht’s research concepts that he discovered decades ago. By holding the soil sample at these controlled conditions (i.e. Field Saturation, temperature and time) allows for ideal conditions and a precise pH value calculation. If the process is rushed and shortened the results can be skewed. Nutrients like sulfur oxidize and release rapidly into sulfuric acid. This creates an acidified solution, but over time, as the solution is allowed to react, cations like calcium, magnesium, potassium, etc. can release. The presence of these cations buffers the acidity in the solution. [See Table 2] By controlling the variables, the resulting cation levels and final pH values represent a truer-to-real-life result; a value much more accurate as to what plant roots encounter and grow within.
With both extraction methods at work measuring the pH and nutrient release amounts provides useful information; this is what you have to work with in the soil. When you use only an acidified paste extraction you can have a problem. This extraction method is best suited for analyzing eastern soils. Dr. William Albrecht referred to these soils (east of the 97th meridian longitude) as old soils, “under destruction” because of the high annual precipitation and its extreme soil weathering effects. When precipitation is greater than 25 inches annually (see U.S. map Figure 1), soil cations (Ca++, Mg++, K+ and Na+) are displaced from soil particles, leached through the soil profile and away from plant roots. Over time, high carbonic acid levels from high precipitation, leaves behind an acidified clay and cation-deficient soil.
Western soils, on the other hand (west of the 97th meridian; see Figure 1), with the exception of the Pacific coastline, are referred to as “young soils”, by Dr. Albrecht. Because of lower annual rainfall amounts, these soils are slowly “under construction.” When there is less precipitation, there is less water (H2O). When there is less than 25’ of annual precipitation natural nutrient leaching does not occur. Less water means less hydrogen with which to form carbonic acid and the soil-acidifying and weathering effect is minimal. These soils tend to be calcareous and highly mineralized. When there is high cation content present it buffers what little acidity is present and soil-cation fixation happens. These minerals bond tightly to soil particles. This is “Nutrient Fixation 101” and while nutrient inventory levels are typically good, getting timely nutrient release can be a significant challenge.
Figure 1
When you are dealing with a soil-nutrient fixation issue, you could focus on acidifying the soil. Because the pH is a symptom of the soil cation balance, until they are in the proper proportions, you will be chasing soil pH indefinitely. Whereas, when you inoculate the soil with beneficial microbiology, it addresses the biological side of the Soil Health triangle and compliments the other two sides, being chemistry and physics. In the next SoilMatters issue, we will discuss Base Saturation and Soil Cation Exchange Capacity. These are also important details that help to measure soil health improvement and should be on your soil analysis and considered in your soil treatment plans.
You may not be working with beneficial soil microbes or putting much emphasis on your soil health. Maybe you aren’t soil sampling regularly. Perhaps, you don’t think it’s worth the investment or your advisor doesn’t see the point. Regardless, it’s your farm and the soil isn’t getting any younger. In order to produce high quality crops with consistent yields, you must start with the soil. I’d be happy to help you get better information and treatment options that will get you started improving your soil health and productivity. Start a conversation with me below, I have some additional information to share with you to help you get started.
Here’s to your crops’ success!
