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Pra~vel Approach Effective E & S Control - 91 <br />B21 Biomass <br />The measurement of biomass is simply the amount of plant material produced <br />over a period of time. In general, the greater amount of biomass, the greater <br />amount of surface cover and effective erosion control. <br />Assessment of biomazs can be az simple az visually determining which BMP <br />promotes the most vigorous growth of plant material over a set period of time. <br />It can however be taken to many extremes, such az comparing crown growth to <br />root growth and initial growth versus long term cover. <br />Field Notes: In general, biomass comparisons are usually made by clipping the <br />vegetation above ground from similarly-sized, randomly selected plots. 711e <br />vegetation is the dried or asked under uniform conditlortr and the resulring <br />residue weighed for comparison. <br />PO Penetration or Openness <br />This parameter measures indirectly the ability of plant roots and/or shuocc to <br />penetrate a BMP, usually a surface applied mulch. In most cases it is directly <br />related to aerial density although it can be combined with the factor B21 <br />(biomass production) to derive quantitatively the beneficial or detrimental <br />affects of surface cover. <br />Field Notes: !t is extremely important ro remember that a high aerial densiry <br />might result in increased erosion control efficiency in the shoe term. but unless <br />the surface mulch or geotextile has a 'balanced openness' which allows <br />vegetation to become established, thereby producing permanent erosion control, <br />the long term erosion control benefrr is marginal, even with long-lived, <br />synthetic mulches, which eventual break down from exposure to ultraviolet rays. <br />CN Nutrient Uptake <br />Some BMPs have the physical or chemical ability to adsorb, absorb or <br />otherwise draw nitrogen, phosphorous or potassium from the soil, leaving less <br />nutrients available for plants. By scientific principle, the nutrient which is in <br />the leazt concentration is the one which limits: In the case of plane, that <br />nutrients is usually nitrogen. <br />Organic, biodegradable materials are sometimes described by their carbon to <br />nitrogen ratio, or C:N. This term describes the amount of carbon in a material <br />relative to the amount of energy, usually expressed az a form of nitrogen, or N, <br />necessary to cause decomposition. Where the amount of carbon in a material is <br />O 1995 IECA <br />