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<br />-. <br /> <br />lG.1 i <br /> <br />(Projecrliilids) <br /> <br />~ore definite conclusions can be ~de from n detailed survey in whioh <br />not only the depth and texture of the soil would beoome known to <br />greater depths, but also the amount of permeability or rate of soil <br />moisture movement would be studied. <br /> <br />It was realized at tho start of the land classification studies <br />conducted in the area that beoause much of the soil is derived fran <br />shale, the dro.inago factor was of special importance in the finnl <br />detormino.tion of the various land classes; consequently, only those <br />ureas believed to hc.ve good natural drainago and arcus which oould be <br />artificially dro.inud ct 0. Imv cost, providing it becamo necessary, Were <br />olass~d as irrigo.ble. <br /> <br />Supplomonto.l wator <br />need for moro extensive <br />C(l,soS _so.tiSfo.e"t_~ry:.-=-._:: _ <br /> <br />for the Illnd presently irrigated may create the <br />drainage systoms whioh at present are in most <br /> <br />--- --- <br />-------- <br />- - - - <br /> <br />. ____ _ d_____ _ ___ <br />- - -------- <br /> <br />--------- <br />.._-~--- --- <br /> <br />~--- .-- <br />,- <br />-- --...- <br /> <br />" ~.:-:-':_~so:r~r~=O:!~~i~~ty-~:---:- :c.~--'- __:"-~o::- -c.o".~ <br /> <br />. <br /> <br />In numorous spots tho shales underlying parts of tho o.roo. on the <br />Eastorn Slope and outoropping on tho hill slopes are hco.vily impreg- <br />nated with soluble salts. These consist largely of sodium sulfate, <br />co.lcium sulfo.te, magnesium sulle.to, and smallor amounts of sodium chlo- <br />ride. The soluble so.lts aro dissolvod by tho surfllce wator which flows <br />into tho Arkanso.s River and its tri buU,ries and by drcinago water whic h <br />peroolctes through tho subsoil and shaly substr~tum. River wator ~s it <br />comes from tho mounto.ins is noarly puro, but o.ftor ontering tho regions <br />where soopago cocurs it beoomes contaminatod with salts. Tho ooncon- <br />tration incroaso s downstrcr_m. <br /> <br />In addition to o.lko.li salts somo of the sho.le bods contribute so- <br />lenium to the soil which rosults in livostook losses whon o.nimAls oon- <br />sumo cortain native plc,nts or ro.ngo woeds. Howover, thoso plants dis- <br />appour under irrigo.tion farming as demonstrated by tho fe.ot thc.t little <br />or no livestock poisoning ho.s ocourrod on the prosontly irrigo.ted"land, <br /> <br />Alkali in sufficient o.nounts to bo seriously toxic ooours only in <br />canpuro.tivoly small areas. The degroo of alkalinity end amount of sol_ <br />ublo salts present in the" soil are closoly o.ssocio.ted with the o.mount <br />of lCQ,ching and druinege tlr.t occurs with irrigation. The prosenco of <br />"bleck c.lko.li" which is o.ssooieted with a high pH was not observed in <br />tho prosontly irrigatod croo.s. This is probc.bly tho rosult of npply- <br />ing irrigation water oontaining large quantities of calcium sulfate- <br />which eh(".ng~H. +'ho j.nsol~bl~ ~odi1D'n &f.J.l+.s; ....Q f\. sc.lup] f? f'Jnn. '!lhir.h i.n <br />---e--~------ <br /> <br />10 <br />