SportsTurf provides current, practical and technical content on issues relevant to sports turf managers, including facilities managers. Most readers are athletic field managers from the professional level through parks and recreation, universities.
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FieldScience | Max Schlossberg, PhD, Joel Simmons SportsTurf's Point–Counterpoint: SLAN vs. BCSR Soil fertility interpretation: base saturation or sufficiency level? S OIL FERTILITY TESTING is a valuable agronomic tool composed of four steps; sampling, analysis, interpretation, and recommendation. Sampling practice is standard boilerplate stuff. Perhaps modified in regard to depth; e.g. by potential rooting depth of species or need for subsoil investigation, sampling accuracy improves with each additional sub-sample pooled from the area of interest. The next stage is analysis, and "routine" soil fertility analysis affords little artistic liberty. Submitted soils are dried and homogenized before an exact mass is mixed with an extrac- tion solution. Typically chosen on the basis of regional parent material or sample soil pH, extraction solutions include Mehlich-1, Bray P-1, Mor- gan, and Mehlich-3. Their purpose is to rapidly displace nutrients from soil and preserve them in their soluble forms, facilitating precise measure of solution nutrient concentrations by state-of-the-art analytical equipment. Since a known volume of extractant is added to a known soil mass, each >> Max Schlossberg, PhD resulting soil nutrient level (in parts per million, ppm) is derived pre- cisely from extractant concentration (mg/L). Success through the first half of the soil fertility testing process re- lies on consistency, and this is something I believe we can all agree upon. If only the second half were so easy. Interpretation is simple characterization of soil pH and nutrient levels by keywords like suboptimal, deficient, adequate, optimal, supra-optimal, and/or excessive. Dependable interpretation relates in- versely to the number of presumptions made in the process (fewer presumptions = better interpretation). The recommendation component communicates the rate and ap- plication frequency of the liming agent, amendment, and/or fertil- izer(s) required to achieve the turfgrass manager's expectation, and may be divided into pre-plant and annual maintenance sections. The value of the recommendation depends on the provider's interpretation of soil nutrient levels and familiarity with the growing environment and maintenance level imposed. The best consultants base their rec- ommendations on soil nutrient levels, resident turfgrass species/culti- var(s) adaptation, irrigation water quality/quantity, soil pH, seasonal climate patterns, and the client's cultural practice "schedule." Recom- mendations to engage in very specific fertilizer/amendment "pro- grams" composed of numerous products containing similar nutrients should be considered suspect. The base saturation tool in turf management T HE CONTROVERSY over the use of the base satura- tion ratio (BCSR) versus the sufficiency levels of avail- able nutrients method (SLAN) has perpetuated for many years now and with very little change in either side's thinking. The reality is that base saturation is one tool of many that most independent agronomists use to help their clients be- come more successful. The other important reality is that most of us using the BCSR method also look very closely at the sufficiency levels of nutrients studying both standard col- loidal soil test audits and water soluble paste extracts. For 25 years I have been a >> Joel Simmons strong advocate of the BCSR model and have heard every- thing from "it's wrong" to "he's going to ruin golf courses." A university agrono- mist recently said to me "We don't agree with the BCSR method but we know that most independent consultants use this tool." That spoke vol- umes, if it was in fact wrong or going to ruin golf courses we wouldn't be using it because our clients wouldn't pay us to come back. There are strengths and weaknesses to all models which is why using a broad spectrum approach to managing soil and building fertility programs is critical. Base saturation measures the percentage of the cations on the soil colloid. Based on the extensive works of many peo- ple, most notably Dr. William Albrecht from the University of Missouri, the ideal cation percentages are 68% calcium, 12% magnesium, 5% potassium, 3% trace nutrients, 2 % sodium and 10% hydrogen. These ideals are never found in practice and are simply a guideline to start from. This model is not a great tool in sand-based low CEC soils or calcareous soils as compared to clay/silt based soils so we compensate in these situations and lean much more on the sufficiency mod- els. However since most soils that we do evaluate are true soil profiles the BCSR model is a good tool to start with and pro- vides us with much information as to the nature of the soil. Perhaps the greatest value that those of us that lean on the base saturation tool gain is the one that tends to generate the most passionate debate. Base saturation helps us primarily with the physical properties of the soil, as we move a soil into 24 SportsTurf | January 2012 www.sportsturfonline.com By