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1637 (Projoct lands) -. depth ranging fr~ 10 to 18 inches. The subseil of the no.ture soil extends to dopths of fram 5 feot to as T.luch as 20 feot or noro. Tho onturo soils ho.ve developed principally on gentle slopes or nearly level areas where orosion has been ~nor. The line ef demo.rcation be- tween the topsoil and the subsoil is r.loro distinct in the hoavy soils where moisturo movement is moo h slower than in light soil. A gravol substratum is soldam found in oature soil profilos, consoquently natural drainage is restrieted. Iruno.ture seils oceur for tho most po.rt on the slopes where tho top- soil has been removed by wind or wo.tor erosion alnost as repidly as it was fo~ed. Sone of tho imr.Io.turo soils consist of duno sand, silty loess material, o.nd alluvio.l outwo.sh. Tho ia~aturo soils deriv~d frao largo stream dcposits usuo.lly h~vo 0. gro.vel substro.tum whioh provides oxcollent natural subdrainago, whoreas tho so soils dorived frcn smnll streo.n or wind doposits ho.ve no gravol substro.tun. . Soil toxturo vO-rios fre,n sho.now gro.velly soil to very heavy clo.y or adobo soil, end is dependont upon the parent natorinl from whieh tho soil is derived. The soils of the aroa ho.ve beon derivod froM. do.rk, elive-brown clay sho.le (Pierro shale); yoll~v, groy, or yollowish-brown, highly gypsiforous she.lo (Apisho.po. sho.lG~ Carlilo shale, c~d Graneros shale); li;:;ht grey Ghr-ly li.,,1.Cstono (Ti..~pr.s linestone); sandstono (Dako- ta sandstene); sundy stream or wind deposits; and old o.lluvial doposits on river bonehes or torraces. It is ostiouted that about two-thirds of the area which ho.s been survoyed consists of silty loun, clay loo.n, and clay soils and tho reIlUlindor consists of fino so.lOdy lel)JJl or sundy soils. Exhibit 2 shaws the goologico.l formo.tions of tho area. In nearly 0.11 soils of tho area there is an abundance of lime which is particulo.rly value.ble in maintaining go,od s)il structure and in mo.k- ing drainago and reclamo.tion from alkali easior o.nd more effective. On tho prosontly irrigatod lands it was originally beliovod tho.t, duo to the newnoss and =tural fortility of tho soils of this rogion, fortilizors were not noeded, i;Junure was not so.vod, straw o.nd stubblo fields Were burned ovor, and tho uso of com.."l6reial fertiliz ors WaS ridiculed. During more rocent yours, h~'ov8r, it ho.s been found that manuros, woll-rotted straw, corn stalks und groon mo.nuro creps plowed undor, and in "any eases tho use of comDllJrcial fortilizers rich in phospho.te prove beneficial. In this rospoct, tho neW knowlod:;o regard- ing tho need for and mnnner of consorving and maintaining soil fertiI. i ty on the new lands to ])0 initially irrigatod, will be particularly advantageous. Although tho nitrobon contont of tho soils is good and oo.sily rno.in~inod by the usa of logumo crops, the organic muttor eon- tent is low. This condition is cheractoristic of most somi-arid soils which ho.vo even 0.. low dogroo of alkalinity. --. 6