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.
Issue link: http://read.dmtmag.com/i/50965
The question of how soil nutrient levels are used to recommend fertilizer/amendment applications to a turfgrass-environment-cul- ture system is typically answered by one, or both, of the predomi- nant methodologies; the base cation saturation ratio(BCSR) or sufficiency level of available nutrients (SLAN). Brief and objective summaries of each method follow (in no particular order). The BCSR concept, developed by F.E. Bear and colleagues in 1945, supports maintenance of an "ideal" soil having: 65% of cation exchange sites occupied by calcium (Ca) charge, 10% by magne- sium (Mg) charge, 5% by potassium (K) charge, and 20% by hydro- gen (H) charge. Thirty years later, "The Albrecht Papers" defined the ideal BCSR as 10% H, 10–20% Mg, 2–5% K, 60–75% Ca, 0.5–5% Na, and 5% other cations. In support of plant productivity and health, BCSR embraces balanced availability of base-cation nu- trients in soil. The SLAN concept, introduced by Mitscherlich in 1909 and further-developed by Bray in 1945, supports comprehen- sive maintenance of nutrient levels (i.e., thresholds) on a soil mass basis. The SLAN method seeks to rectify nutrient deficiencies that would otherwise limit productivity and health (yield). Discussions relating each concept to justifiable attributes follow. SIMPLICITY Remember: the less presumed, the better the result. Interpreta- tion by BCSR requires conversion of soil nutrient mass to nutrient charge concentration, and presumes divalent cations of interest a range of "balance" we have repeatedly seen the soil open up physically allowing more water and air movement through the soil profile. We are not changing clay into sand, we are not mak- ing silt into clay, but are flocculating the soil just enough to relax the soil colloids to create the tiniest of pore spaces to allow air to flow through the soil a little more freely. The range that we are looking for from on a true base saturation test puts calcium into the 60-70 percentile, magnesium down to the 12-18 percentile, keeping potassium close to 5% and holding hydrogen levels to around 10%. On a true base saturation soil test when hydrogen is at 10%, the soil pH is always at 6.3 which is generally recog- nized as the point at which we have maximum potential nutrient mobility. Unfortunately, many laboratories do not run what we call true base saturation soil tests; they may show only the percentage of calcium, magnesium and potassium. Some very popular labs run reports that have pH readings in the low 6 range, which clearly suggests that there is close to 10% hydrogen on the soil colloid. Since pH measures the acidity of the soil, or in layman's terms the percentage of hydrogen, when the soil pH is below 7.0 we know that hydrogen is on the soil colloid. Too often the soil report does not show a hydrogen percentage or for that matter show the percentage of either the trace elements or sodium which in combination could add up to over 15% of the colloidal makeup when the soil pH is in the low 6 range. www.stma.org SportsTurf 25