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49 <br />• 2-KEY 1U ABBREVIATIONS <br />a. Chemical Analysis: (Tables 3, 7 Appendix B) <br />pH - degree of acidity or alkalinity, 7=neutral, belay 7~cid, <br />above 7=alkaline; soils 5.5-8.5 are generally suitable for plant <br />growth, O.M.~rganic Matter, E.C.~7easure of salinity by electrical <br />ronductance; (NO.)= EC x 103 millimhos/an is scale used; Example: <br />9.0 is equivalent to about 2500 parts per million (ppn) of salts <br />and is a level that restricts growth of the more sensitive crop <br />and native plants. An EC x 103 value of 16 would be tolerated <br />only by the frost salt-resistent plants such as kochia or distichlis <br />(salt grass). <br />ESP - exchangeable sodium percentage. SAF.=Sodium absorption ratio- <br />a measure of tendency for sodium cations to be absorbed on clays <br />replacing other basic cations such as calcium. SAR values wer 15 <br />are considered unsuitable for most crop and pasture species. <br />• Elenents - Ca~alcium, Mg~nagnesium, Na=sodium, CaCO3~alcium <br />carbonate (pure lime), meq/l~nilliequivalents per liter, <br />SAT=Saturation percentage equals percent by weight of water held <br />by a soil at saturation. <br />b. Soil Surveys - SCS Form 232 Appendix A <br />Source: U.S. Dept. Agriculture Handbook 18 <br />Horizon - layers approximately parallel to surface with character- <br />istics produced by soil-forming processes. A simple key for the <br />Nucla soil survey is A1-Mineral horizons, formed or at the surface, <br />in which humified organic matter is intimately associated with <br />mineral fraction. <br />A2 - lighter colored layer associated with surface but lower in <br />organic matter, generally well-leached of minerals. <br />AP - surface layer disturbed by cultivation or pasturing; may <br />include sane of lower horizons by mixing. <br />B - (general) horizon or horizons underlying A horizon with some <br />evidence of mineral change such as accwnulation of calcium <br />• carbonates, higher clay contents, change in structural aggregates, <br />