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• to a liquid. The plastic limit is the moisture content at whnh the soil material ch;ut~*es from the semisolid to plastic; and the lirluid limit, from a plastic to n liquid. The pht~licitr index is the numerical diKecenc•c bet~~~een Lhe liquid limit ;uul the plastic limit. It indicates the rang, of nuiisltn'e content within which a soil material i, plastic Liquid IuniC and plasticih' index :u•e esti- niatal in table (i, but in table S the data nn liquid limit ;uul I~lastici(y index ;n~e based ou tests of snit samples. I'crnuahilil> is that qualil> ~f a soil that enables it In lrnn:mil ~t~ater nr air. it is estinutted on the basis of soil c'h;u;tctrrisLirs nhsrrced in the field, p:nticularly structure, porosity, and texture. 'I'hc estimates in fable G do not L,+I:r into acrnut+t lateral seepage rtr such transient ~.uil features as plowp:uts and surface crusts. AP:uI:11~Ic u'aLCI' CaI);ICIL\' Is Lhe ability of soils to hnlrl "alcr fur use b}• most plants. It is cnnnnnnly dc- I'uted as the difl'craue between the amount nl tt;t(cr in the soil al Ili ld capacil}~ and Lhc :uuount at Lhe Milling point of nu~sl imps. P.eactiun is the drgree of acirlilt• nr allatlinilc of n coil, exprr~;crl in p11 rnlues. The pi[ talue and lcrnts used Ln ~le~c rile soil reaction ;n'e explained in the Glnssar+. S;+linil~ rcfeis to the amount of soluble salts in the soils. IL i. exlu'esed as [he electrical ennrluclici(~ of the saturation extract, in millimhus per centimeter nt °.}'C. Salinity aficcts the suibtbililt of n soil Inr crop production, iLc sL;tbility when used as contraction material, sort the risk Of COCCDSImt to metals ;utd con- crete. $hrinl:-s~eell potential is the relative change in ~ol- lume to be expected of soil material t~ith changes in moisture content; that is. the extent to ~t'hich the soil shrinla when rlrc or sttells..'hen Bret. T:xtent of stn inh- inf; nnrl strolling i. influenced b>• the amount ;nut kind nl cl;+c in Lhc soil. Slu'inkin>,• and swelling oC soils c;ui.~es much d;unn~c to building foundations, roads. :uul other structures, ~, hifilr shrink-s+rell potential indicates a hazard to maintenance of structures built in, nn, nr trilh material hating this rating. l:isk of corrosion, as used in table G, pertains to potential so+l-induced chemical action that dissolves or u'ealcens uncoated .feel or concrete: The role of emro- .iun nn inn nnlerl steel is reLtted to such soil properties ;is rlr;tinagc, lr,xture, total acidih~, and rlectriral rou- rhu:titily ul' the soil material. The rate of rnrrosiun on cuni~r~4e is influenced mainly by the content ..I' soditnn nr nutgnesium sulfate, but also by texture and aridity. InsLill,ilions of unmated steel that intersect soil bnuurl- aries nr sail hori'r.ons are more susceptibly Lo corrosion than inslall;ilinns entirely in mte kind of soil nt• in one horizon. :\ Pa(Ing of Inx~ indicates a 1my prnhahlil)' of sail-inducrrl rnrrnsinn damage. A rating of hrplr inrli- r•ah•.e ;t high pruletbilih~ of rbimage. so that prntcclirc n~e;r<m'c Inr :;feel and mm'e resislaut concrete shnulrl be a<crl to at Dirt ur minimize rlanut~e. 1f)~ih~ul~~;*ic groupings are soil groups that are used in w;ilrrshrd phuming to estimate runoff frmtl rainfall. Soil pinprrlies are considered that.influynye the rate nl inliltr;ttinn obtained far a bare soil after prolonged netting. i:.xamples of these properties m'e depth to a srnsnn;il high w;tter table, water intake rate. permcahil- ilc ;il'Icr prolon~^yd trotting. sort depth In a eery slo~rly pcrntcablr Inter. 'the influence of present grntnul rnrrt' is ant. rnnsidyrerl in making the inrlicirlual hyrh~n- Ingir soil g~rnupings but is considered almte frith other tartars in lhr total hyrhningic evalu;ttion of a ttater- shrrl. '['he soils have been classified into four groups, A through 1). Group A coils Race Inn' t'tmnff ]totential. Thr-t• have