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• Pratucal Approac~or Effective E ~ S Control • 91 <br />' YLTL Biomass <br />' The measuremrnt 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 biomass can be as simple as 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 as 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. The <br />vegetation is the dried or asked under uniform conditions and the resulting <br />' residue weighed for comparison. <br />' PO Penetration or Openness <br />This parameter measures indirectly the ability of plant roots and/or shoots 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 gttandtadvely the beneficial or detrimental <br />affects of surface cover. <br /> Field Notes: It is extremely imporrant to remember that a high aerial densiry <br /> might result in increased erosion control e,•~iciency in the shorn rerm. but unless <br /> the surface mulch or geotextile has a 'balanced openness' which allows <br />' vegetaton to become established, thereby producing permanenr erosion control, <br /> the long term erosion control benefit is marginal, even wink 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 least concentration is the one which limits: In the case of plants, 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 as a form of nitrogen, or N, <br />' necessary to cause decomposition. Where the amount of carbon in a material is <br /> O t995 [ECA <br />' <br />