Deep Plowing—An Engineering Appraisal

TROM early times man has had to-»• scratch the surface of the soil atplanting time to loosen it or change itsstructure so that rain could penetrateto the roots which need moisture togrow. Although years ago fanners ob-served that corn grew better when theyplowed deeper, "old Dobbin" could notpull a deeply buried plow. Also, largeplows were not available. Since thelimits on plow sizs and on. pullingability of tractors have increased great-ly in recent years, the research de-scribed in this report is a far cry from"old Dobbin" days. In addition, meas-urements of atomic radiation can beused to determine the location ofradioactive material applied to the sur-face before plowing. Computer proc-essing of these data indicates theamount of surface soil buried at anydepth and also plots the pattern of thesurface soil in the profile after plow-ing- This report covers: (a) the rea-sons for plowing deeply; (b) the limi-tations of deep plowing; (c) the powerrequirements to pull a large plow;(d) modifications of a large plowto obtain more complete and easierplowing, and (e) the soil burial pat-tern resulting from deep plowing.

REASONS FOR DEEP PLOWINGDeep plowing is not recommended

for all soils. Most soils which producehigh yields show little benefit fromdeep plowing; other soils may doubletheir yields. It was advantageous toplow soils which would not take upwater readily. Water tends to run offsuch soils rather than to soaic down tothe root zone. Deep plowing modifiesthe soil structure so that water may betransported more readily from the sur-face to the water table or Co drains.Impervious soil may extend down sev-eral feet or it may exist as layers. Al-though impervious soil layers may oc-

Pap«r No. 89-152 wu pres«nfd at the An-nul M*«hnc of eh« Amfiean Soci«tr of Aari-eulttml Eoainwra •e purdu* University. La-fylie. lad.. Juna 1969, on « precnm ananndby *• Power and MacfaiMry DivuiflB.

Tb» •uthon w. PAUL E. IA.MES and DALEE. WTLKINS. Azrieultml Eflttm—rt. AERO.ASS, USDA. Bciavill*. Md, aad laws. StateUniversity, Ami, Iowa. rMpwcUvly.

Tha reported, work u ooop«r»tiv« with ttrSoil aad Water Coiui-vtton Aoswch Oivuion.•ad. A* AzncuJiural Eafimcruifr R«i«nrch Di*VUMO. ASS. USOA.

Aithan' Nofi Mmtfea En thil piper or cnm-irwaaily manufactured equipnwnc and product*doc1) not imply endon«mcne OVT similar «quip-nwit and product* noe m«ntioa«d.

Adaiowtedcamn Th< auction wilh M thankDr. H. G. M«DUI, Soil SciJWuc. or SWORD. ARS,O'SDA for oil auutuw in oonduconx Ur rv-mfeh, Th* work reported tn tfau paper wupartially tupoorfd by food* from th« AtomicEawfy Comnuulua.

Paul E. JamiMZ&IBER ASA]

Furrowdwk. in. .

.1938M312416

• Intenutlonaf CatupiUKT.

es and Dale E.E MXMBEI

TABLE 1. POWEBTractor!

used•TD-18+TD-HtD-3tD-7+D-atD-TE+D-T.l-ArD-7E+D-7-I7A•D.TE+D-7-17A

1.

Wi!l ASHEO

lldns;AEUIRE.ME

ip—d.

I.I1..5132.3•1.U4.1

-IT:> rOR DEEP FLO

SufficeMil tVTM

Silly d»r loomSniidr 11"""Bocky nil IwmC-.-LY himCl«r 1mmClay loam

WING

Lucation

Bmhiand. TessaB*i0vtljtf. Md.Bfltsvilltf. Md.Tempi.. TexasTnnple. TcsaaTemple. Tcw

cur naturally, they are also formed bycompaction of farm machinery wheelsas Eney repeatedly pass over the soil.Such soil compaction by wheels is be-coming more of a problem as heavierfarm machinery is used. A layer ofimpervious soil may also be formed atthe depth of the plow furrow. Theseimpervious layers may be broken byplowing deeply, but will be formedagain by the wheels and plow. Moreresearch is needed to determine therequired frequency of deep plowingto satisfactorily reduce the effects ofthis compaction.

Another reason for plowing deeplyin some regions is to bury surface con-centrations of saline and alkali com-pounds so they will not stunt plantgrowth. Such chemicals lower the pro-ductivity and agricultural value of largeareas of land in the United States — anestimated one-fourth of the 29 millionacres of irrigated land in the UnitedStates and less extensive acreages ofnonirrigated land (Bower and Fire-man, 1957). An estimated 100,000acres of rangeland being considered forirrigation in new irrigation projects inIdaho are affected by areas of salinesodic (slick spot) soil. All slick spotsoils are not the same. There may beconsiderable variation in the structureand chemical composition of slick spotsin an area (Rasmussen, 1965).

In addition to changing the waterabsorption characteristics and buryingobjectionable chemicals, a third reasonto plow deeply is to bury disease-carry-ing roots where they are inaccessibleto new root growth. Roots of previ-ously harvested crops winter in theground and infect new spring rootgrowth which appears. VercEcilliumwilt of cotton, one of the root diseasescurrently causing crop losses, has beenfound to exist primarily in the top 8to 12 in. of soil (Wilhelm et al., 1967).For effective disease control, care mustbe exercised during plowing and scrap-ing to bury deeply all of the diseaseorganisms or a reinfescadon. will occur.Deep burial of the infected roots hasproven beneficial, but with existingequipment the benefits ;ire temporary.

Another reason for deep plowing isto bury objectionable deposits whichhave seeded of the surface of good soil.These deposits may be sand and debriscarried in by flood waters or radioac-tive particles from the air (fallout).The research of this report was initiatedby the Atomic Energy Commission tohelp determine how best to decontam-inate surface soil which has been con-taminated with radioactivity.

There are limitations to the valueof deep plowing, In many soil profilesthe subsoil contains little plant food.Plowing deeply in these areas may beobjectionable as it places the good soilwhere it is less accessible to the roots.

POWER REQUTBE-MENTSThe power required to pull the large

plow depends on the plowing depth;speed of plowing, and the character-istics of the soil being plowed. Whenplowing a 30-in. wide furrow, a draw-bar puTi of about 1,000 Ib is requiredfor each inch of furrow depth. A tight.dense soil requires much more powerthan a sandv, loose soil. One Cater-pillar D-3 tractor furnished enoughpower to plow sandy soil 31 in. deep.When Houston black clay at Temple.Texas was plowed to the same depth.two Caterpillar D-7 tractors in tandemhad just barely enough power. Table 1shows representative power require-ments with various plowing depthsalong with the soil type, location, andplowing speed.

COST or PLOWINGA local contractor in AmariIIo. Texas

supplied operators and two track typetractors for pulling the large plow dur-ing 1966. The tractors were Interna-tional Harvester models TD-18 andTD-24. The contractor was paid $43.00per hr for his tractors and operators.When plowing a furrow 30 in. wideand 30 in. deep and the plow was be-ing pulled 1'A mph by the tractors,about Vt of an acre per hr was plowed.--This means plowing would cost ap-proximately S57.0fl. per acre for thetractors and operators. To this must.—Ix added the cost involved when the ^

ii rBpnnttd from the TRAWACTTONa of the ASAE (Vol. 15. No. .3. pp. 420. 421 iuni 422, 1972)Publiihed by the American Society of Agricultural Engineers, St. Joseph, Michigan

This article is

80326

FIG. 1 Deep plowing in silty clay loamsoil. Blade is scraping surface soil intofurrow behind plow moldboard. Note re-tainer baffle behind moldboard to preventcollapse of soil into Furrow.

tractors were noC plowing, i.e., refuel-ing, m a n e u v e r i n g without plowing,loading and unloading tractors, and re-pairing the plow. Counting these lossesas 14 percent of the plowing dme. thedeep plowing cost was approximatelyS65.00 per acre. If an additional manis needed to operate the plow, hiswages must be included. To this musthe added the cost of amortizing the58,500.00 plow.

DESCRIPTION' OF PLOW

Large plows are available which willplow From 24 to 48 in. deep. The piowdescribed is Post Brothers Model FB-142. It is designed to plow a maximumdepth of 36 in. and width of 30 in.Without the scraper blade it weighs5,860 Ib; the scraper blade adds ap-proximntely 500 Ib. It has a right handmoldboard. The plowing depth is con-trolled by a hydraulic lift. A scrapingblade extends to the left opposite themoldboard. See FEg. 1.

FLOW MODIFICATIONS AND OPERATIONAs experience was gained using the

plow, we Found ways to change it inorder to make the operation easier andto plow better. Some of the modifica-tions were helpful and others were not.Other modifications were helpful insandy soil but unnecessary in clav soil.

Changes to Make Operationof Plow Easier

The plow, as received, had an ad-ditional scraper blade attached to thedrawbar. This was to scrape soil infront of the wheel riding in the furrow.Its adjustment required stopping theplow ;md relocating the blade; thi.swas slow and cumbersome. In orderto obtain faster, more accurate control

-lie i i i u ^ . Ji iuther l iMfi .mlK- 1.-'. liinlerwas added ^h ic l i L'(intr(]IIed the depthof the hiiTim" wheel. Sw Fi^ 2. Tliiagave fa.st adjustment re([iiired to keepthe plu\'." level while making die open-ing furruu" and during iE'i •siiii'teuiieiitOperaticn.

It w.i.s very awku.'.ird to move thelarge plo\\ frum one luL-atiun to -in-other a.-, die re.ir end drugged on theground. Not oiitv did the bottom orthe land-side we-ar rapidlv. but iC alsodamaged -i^phalt roads. Thi:> was elim-inated" bv constructing a c-xstor wheel.which \v.i:i mounted on the end of thelandside when the plow \va.s to bemoved.

Changes Co Get More Complete Burial(a) In sandv soil the landside ledge

collup-ied ,ind tell throu'^h LI slut in thelandside of the plow- Thi.s was ob-Jectionahle a;> the rurruvv wall tumbledin the buttcm of the furrow b&rore thetop soil could be sci-Liped into it. Tlii;*

FIC. 2 Top view of plow from rear.showinu hydraulic cylinders for adfustingwheel ^ett in^t .

was L-urrected bv adding .1 baffle CofiH the slot in the landside. See Fi^. 3.

( b ) The soil throu'n out of the fur-row sometimes slipped back into thefurrow before the trailing bhide scranedthe surface soil in the furrow. Thiswas corrected by adding a retainer b.if-fle 5'-2 f t long and 2 ft bish mounted1% ft .ww from tlie laiKLiide. See Fig.1. This nruvided a -'ilot into which toscrape the surface soil.

(c) The trail ine scraper blade ex-tended .ilnmc 6 in. bevond tlie landsideover the Furrow-. Tlii^ resulted in car-rying the top soil along the blude be-yond the bottom of the Furrow. Thiswas corrected bv adding a retainer b;if-of tlie blade extending beyond thelandsldt-.

(d ) He.ivv sod draped irregularlyover the land-side led^e after plowing.Thi.s m.ide complete •'"d (.-iivera^e dif-ficult. ^\* ;ittriiiprt*<l lii ciitTfft tlii.sbv cut t ing '.lie ,sod w i t f i .1 I.trgc rollingcoulter 311 in. in diameter mounted in

front the landsida to cut the sodloose before plowing. This coulter wasuf little value.

Various width furrows ranging from42 to 24 in. were plowed. It was foundwide furrows resulted in poor coverageof the Cop soil and tilting of the plowduring operation. This resulted inshallow plowing, the plow operatedbest making a furrow about 30 in. wideand plowing to a depth of about 36in. With these dimensions the plowcut evenly and threw the soil aside.

Proper adjustment of furrow widthmay be made by observing the angleof the plow as it passes through thesoil. When the plow is set at the de-sired depth and the plow points downinstead of being level, it may be plow-ing too wide a furrow. When the fur-row width is narrowed, the plow willoperate smoother, require less drawbarpull, and will throw the soil aside fur-ther. This all results En more completeinversion of the soil.

Since the load of the plow was be-hind the right track of the tractor pull-ing the plow, this tractor was given aresulting torque which pulled the rearof it toward the furrow. When twotractors were pulling the plow, thistorque was overcome by having thelead tractor about one track width fur-ther away from the furrow than therear tractor. The rear tractor wasoperated about 1 ft from the furrowledge. Although a swinging drawbarwas unnecessary on the rear tractor, itwas helpful in eliminating the torqueon the tractor pulling the plow.

CORN YIELD INCREASEWhile no attempts were made to in-

clude a comprehensive report of in-creases in crop yield due to deep plow-ing, Table 2 gives representative in-creases in the yields that were ob-tained. The crops were grown in Pull-man siltv clav loam at the Southwest-ern Great Plains Research Center atfBushland, Texas during 1966 (Menzelet al., 1968). The soil is a slowlypermeable reddish chestnut soil on acaliche layer about 40 in. below thesurface.

FIG. 3 Landside view of plow ihowini;baffle added to prevent coJIapsa of furrowwall.

"ABLE ;. YIELD OF DRY MATTER WITH_____TREATMENT INDICATED_______

r—— RolotiU-i. 0m plowed.ta e«r h« t» l

TAr- - .1. aADIOACTIVITY BUH1ED AT VABIOU5 DEiTf IFTER NOBMAL CULTTVATICK

IKST bwc roou'dm«nua fodder'vbe»n strawybfn icedibb«ge ______

1.1023.STI2.388

518475932

2,3188.S494.60'!1.2" I

9BO1.338

!SS"S s"d•'"^^^'l"°'"'—'—• "- ndKitcnvity, swst

iSJO42.01S.T0.0

43.643.613.00.0

IT toil Silt lo«m. moidbomd pinw -(• ipikw-tonlh

hulowradioJcnvity, pcreent

4.6S2.440.02.8

ABLE 3. RACIOACTIVTTT BUBIED ATABIOUS DEPTHS AFTER DEEP PLOWING

mplint dttXh.

3d1121273333M

Htxb clarcontent

Pullmu wilradioactivity.

pTCTnt

"3\y-^6.2 i< :•

27.4 '--81.4 ^

1.0

Smdr loinElluon wil

PWLwie

I O.Sa\ °'S•r - 0.71»!'>4.2,19.,

-^^82.62.0

CONDITION OF SOIL AFTEB PLO'VING

The moldboard plow affected theJil in two respects. It fluffed up oriade the soil less dense. The density•as 25 percent less after plowing, ac-

cording to Menzel et aL (1968). Thiscondition changed as the soil graduallysettled down with time. Plowing andscraping placed the surface soil in thebottom of the furrow, and the subse-quent runow slice buried the surfacefoiL Results of tests conducted withand without the scraper blade indi-cated that the blade was necessary onlywhen complete burial of the surfacesoil was required.

To determine the actual degree ofburial of surface soil, a radioactivetracer was sprayed on the surface be-fore plowing. After plowing, 2-in. di-ameter, 2-in. thick samples containingradioactivity were removed throughoutthe profile. A comparison of the per-cent of radioactivity buried at each

depth using the large plow may beseen in Table 3 and Fig. 4. A com-parison of the percent of radioactivityburied at each depth by various tillagemethods is shown in Table 4 andFig. 3.

Beferences1 Bow. C. A. ud -Milton Firenm. l9i".

S>Uix >nd lOail will. Ycubook of AmculKm.p. 2S2-290.

2 MBB.l- 1L G., H. V. Eck. P. S. I«n»«. tnoi0. E. WilUu. IMS. Rrducooa of Strontlum-ASUpulw ia Fi«Id Croo« br 0««p Ptewtec •adSodium Cubonac Appliation. AitrowMnv Jour.oQ(3):499^02. Seoteinbtt-OctotMr.

3 Rumullf. W. W. 1S«5. Om plo-intfor improviBK llick ipot loill. C»p» •nd Soilx.ApnI-.M.y.

4 Wilhelm. Stephen. T. E. SftKen. H«t«« Tiecz.and Alan Gww. 1967. Vertical Diltlibution oiFtinguJ Suigmu . . . Hi^oltfn Plowinf for Con-tral of VerticLlIium Wilt m COKOQ. C.lUfomiaABricuitnre 21(3):2-4. May.

1C. 4 Soil profile! after deep plowing. The contour lints m-licale the distributioo of surfactt soil, and tho Bumbers on the•ontour Lines represent the magaitude oc radioactive tracer.

FIG. 5 Soil profiles after rototilliBg. Th« contour linea indicatethe dBtrihutioo of mrface soil, »nd the numberi on the contourlinel represent the magnitude o( radioactive tracer.

Rcorimed trom AGRONOMY JOURNAL' Vol. SO. SeOL-Qa. 19SS. p. ^99•3SS

U.U.C S^S^t^^^^9

for Official USB- fel7

Reduction of Stroaduni-SS Uptake in Field CropsBy Deep Plowing and Sodium Carbonate Application'

R- G. Menzei, H. V. £<A, P. E. James, and D. £7wi.U<uu2

ABSTRACT0<ep plowing reduced upeake of Sr" by four irrigated

crop* on Pullman filer clar loam ac n.««hiinA TOM*.Upalit wa» tether niinced »lien N»rf:0, »M plowainnda- widi the Sr". Tlic txladre coaoBicratiom o( Sr*m aamte lofbeaa (Clyem itwi), mfir bea CB«<aXFulfaru), xudansTau f5«rfhum Judanenf«>, and cabbage(fraoica almeea far cafilata\ piano fUKa •rich &"applied ia dUfereal Beacaeats were: roiarr tiJIed20 cm deep, l«r, plowed 90 OB dttp, 2MO; plowed 90an deep with 21,400 tg/ha <!(» IBM/acre) o{ Na O. i-7.la die plowing trcitnieou, W% of twd> the Sr* ind(he Na^Oi were baaded m the Eumw deeper »*^"73 cifl. Crop fields were lacreased br deep piowinfmd •were aHeezed Tery lictle by the applicatiou o£ NatCOi.Tliii eccieiimeac d<zadaiccacei chat a coxu: cheoiicai caabe plowed UBder deeply wich radioacuve coDUXBiaadonco reduce the upoke at the ladidacxire coacenal withSale effect oa yidd ttoni the dtemica}.

Jlddi&anai Zfy Wordss ndioactire wil coataaioa-doiir decoataniixmioa) soil caaaa^emenc,

CROPS grown on soill contaminated wich. radioac-tive fimon products take up small fractions o£

each eieaieat present (Trere ec aL, 1863). Radioactivestrontium nudidcs (5ironciunl-89 and itronriuia-90)usually predominate among the nucUdd taken up.Mea^urel for reducing the uptake at radionudides in-dude lime and fertilizer treatments (Reitemeier andMcnzel, 1960; Mybre ec al.. 1964), removal of con-

1 CoBtritluuon tzwa tbc Soil and 'Water Conservaooo Rc-tearch dmioa aad A^ricuJtural Za^aeenn; Raearch Divuioa.Agriculcural Researcb Service, USDA. ia cooaeraeioa wich theTexas A iculcurai experiment Sauoa. Tcus researdi wassupDorceci in part bv che UJ. Atomic loeryf Coaunuuion.Reteived Eeb. a. 1966-

'ILeaearcb Soil ScieauJU, UJ. SoQa Liboratory, BelaviIIe.Md. 20705. ind Soutbweiteni Creat Plaint Rstarch Caiter.Busfaland. Texai. and Ke&earch Agncukural EagiAeeri, Aericul-curaJ En ioeerio? Laboratory, -Beicrvilie. Afd. WU&un is nowa graduace Jiudenc u Iowa Siau Univemcy, Aaiea. Iowa.

499

500 AGRONOMY JOURNAL. VOL. 60. SEPTEMBER-OCTOBER 1968

Fig. 1. Plowing to a 36-inch depch on Pullman stiff clay loam.

taminated surface soil (Mcnzel. 1962), and deep plow-ing.

Field tests involving the use of deep plowing coreduce radiostrontium uptake have been reponed intwo articles (MUboume, Ellis, and Russell, 1959;Kachanova, 1962). In England. Milboume et aL (1959)Studied stroncium-89 uptake by several crops ai sixlocations on widely varying soil types. They com-pared (1) rotary cultivation to 8-10 cm, (2) plowingto 15-18 cm, and (3) plowing to 28-30 cm. Deep plow-ing significantly reduced stronuum-89 uptake in rye-grass ac three locations, with a maximum reductionof 78%. Reductions were smaller (about 50%) andless frequent with other crops (wheat, barley, kale,sugar beets, and potatoes). Deep cultivation appearedto be more effective on fine-texrured soils. Depth ofcultivation had liccle effect on crop'vields except atone location on a day silt soil where deep plowingmarkedly reduced yields. On a leached Chcmozemsoil in Russia (Kachanova, 1962), burying the surface10 cm of soil (containing surface-applied scroncium-90) ac the bouom oi che furrow when plowing 50 cmdeep reduced uotakc of scronuum-90 bv oats co 60%of the uptake after disking 10 cm deep.' Unfortunate-ly, the effecis of deep plowing on yields of plant ma-terial were not reponed.

Greater reductions in the plant uptake of radio-active scrontium could be expected from deep plowingif a larger fraction of the contaminated surface soilwere buried at the bottom of the furrow or if rooc de-velopment were minimized in the contaminated soiLOne approach to the latter possibility is to treat thezone of contaminated soil with a chemical that dis-courages roocing. Sodium carbonate was found (Men-zei, £ck, and Champion. 1967) co reduce the uptake ofStrontium-85 by soybeans and grain sorghum to a fewpercent of chac from che same depth when no chemicalwas added. The scronuum*o5 was placed in a layer50 cm below che soil surface, and sodium carbonaccwai spread ac the rate of 22.400 kg/ha driectiy on Actop of the stronuum-fl5. The addicion of sodium car-bonate lowered yields by about 10 and 2Q% with soy-

beans and sorghum, respectively, buc only the sor-ghum yield reduction was scaiisucaUy significant.

The experiment reported here was undertaken toccsi the effectiveness of deep plowing and sodium car-bonate application on the radio-scronuum upcake andyield of several crops.

METHODSThe experimental site was on Pullman silly dav loam ai ihe

Southwestern Greac Plains Research Center. This slowly per-meable reddish chestnut wil has developed on deeo aeoliandeposits under seouarid ciiraaic. The surface 1.2 m has a ca-tion exchange capacity of about 20 meq per 100 g. IE is about50% calcium-muraied with a pH of 6.3 to 23 on and 70%calcium-saturated with a pH of 7.5 below 23 cm. The soil isnoncalcareoul BE the surface, becoming- calcareous (3% CaCO,equivalent) at 30 COL with a layer of caliche (40% CaCQi eauiva-lent) at aoproximaielv 1-5 m. A more comDreheniive descriptionoi Pullman soil is available in the literature (Taylor et al, 1965).

The experimental design was a randomized block lolit plotwith four replications. All main plois received Sr" applications.Variables iiudied on main olois were: ( 1 ) roiocilled 2'0'cai deey,(2) plowed 90 cm deeo. and f3) application of 22,400 kg Na;C6,per ha and plowed 90 cm deep. Sugar beets. sudangrass. soy-beam, and cabbage were grown on tubplou- Main plots were9.1 x 18.3 m and subplots 9.1 x 4.6 m.

The experimental site was shallow plowed, disk harrowed, andirrigated 'in early March 1966- Main plot [Teacmenu were ap-plied between April 18 and April 25.

Strontium-85 was sprayed on the plot areas at the rate of110 ^c/sr. For immediate measurement of lurfaee radioactivitydistribution after plowing. 540 ^c/nr of gold-198 were apoiiedouuide the endi of four roioulled and four deep-plowed plots.After spraying the scroncium-85 and before deep plowing, com-mercial sodium carbonate (dense uh) was applied with. a 3-meter-wide fertilizer spreader on designated plots.

The plow (Tig. I), which cui x uniform furrow 90 cm deep,was drawn by two large crawler-type tractors. A scraper at-tached to the plow removed abouc 10 cm of contaminated sur-face soil and pushed it into the furrow behind the moldboard.la this way, a more or leu banded placement of surface »oil.radioisotope. and sodium carbonate wai achieved. Ic was be-lieved thaL. compared co a continuous layer, this discontinuousband placement of sodium carbonate znd contaminated surfacesoil might have less effect on yields vet continue to inhibituptake of icroniiuia-85. A more complete report of the en-gineering design and performance of the plow will be reponedby James et at (Manuscript in preparation).

The distribution of radioaciiviiv in the soil after ullage wasmeasured by determining the gold-198 concent of soil samplesremoved from the sides of bacxhoe'dug crencbes. Trenches wereperpendicular to the direction of tillage, approximately 30 cmdeeper than the depth of tillage, and spanned four completefurrows. Soil core samples 5 cm in diameter and depth wereremoved from the sides of the trenches at 15-cm intervals ana square grid pattern- Radioactivity was measured with a 7.6-x 7.6-cm sciauUauoD crystal and single<hannei gamma sprccro-metcr.

Broadcast applications of 200 kg N/ha and 50 kg P/ha weremade on all plou on April 21. N and P source) were ammonium.sulfale and concentrated superphosphate. The plou were beddedon 76-cni centers, and borders were constructed around themfor surface irrigation. Beds ran perpendicular to the directionof deep plowing.

The crops were planted on the beds in season and cared foraccording to conventional practices. Varieties and plantingdates were* 'KH-lO* nigar beeu. April 27: common sudangrasi,June 9; 'Clart' soybeans. June 9: and 'Round Dutch' cabbage,transplanted Auguu 31; and Seoiember I. Total amounts ofirrigidon waicr applied to the crops were: sugar beets. 96 cm:sudaograa and soybeans. 66 cm: and cabbage. 56 cm.

Samples were taken for Sr" analysis at three siages of growth:( I ) abouc half of full vegetative growth, (2) nearly full vezeca'tive growth, and (3) at the end of the growing' season. Ac finalharvest, sudangnss and soybeani were mature, lugar beecs badreached harvest suge for sugar production, and cabbage wasin heading iu;e. Cabbage wu laie because transplants wereused onlv after timely field iccdme failed. Sugar' beet roots

MEN2EL ET AL- REDUCTION OF SB.-B9 UPTAKE 501

and cops were sampled separately at all three stages of growth.AL macuricy. the grain of sudangrass and soybeans were sampledseparately bom che fodder. The samples were dried in a forceddraft oven ae 70 C and ground before analysis. Yields were de.termincd ac harvest excepc for sudangrass seed. which was par-tially shattered. After harvest, piu were dug in all plocs o(three reolicacions and depth. distribution. and proliferationo( roots were observed.

Radioactivity determinations were made on the ground plantmaterial, which was tint dry-ashed ac 150 C. Ash from 100 gof plant material. or less if the sample was smaller than 100 y,was pressed mio one or two 2-3- x 7.6-an polyethylene vials.The vials were counted on a 7.6. x 7£-cm well.cvpe scintillationcrystal for detecting gamma rays. A ^uO-channel pulse heightanaJyxer was used to record the gamma ray speccrum. AU countraces were correcxed for background, for the presence of varying'amounts of K-(0 in the samples. and for countinreffidency(which varies with the height of samole in the vial). The countswere made during' the periods December 1.7. 1966. and January9-12. 1967: but all count rates were calculated to the samereference date. December I. I960.

RESULTS^"'y.^ -w, Deep plowing placerfTnost oE the contaminated sur-

face soil' beneath 90 cin o£ soil. With the (our plotsexamined, the average and maximum amounts or"gold-198 found in the [op 30 cm of soil were 0.8 and1.6%, respectively, of the local amount found to adepth of 120 cm. The average and maximum amountsin the top 60 on were 3.8 and 6.2%, respectively,and in the cop 90 cm, 37-5 and 54.1%. The soil char-

__ acteriscics and operation of the plow were quite uni-' form. so it is lifcely that the same degree of burial was

achieved with scroncium-85. However, the bulk densityof the soil was about 25% less after plowing than be-fore. so chat a; settling occurred during the growingseason the depths co contaminated soil were some-what less than those observed. Measurements on theroiocilled areas indicated very uniform distribution ofgold-198 to a depth of 20 cm.

Although deep plowing allowed more complete ex-ploration of the soil by the roots, the maximum depthof rooting was similar wich rocary tillage and deepplowing. Sodium carbonate greatly reduced rootingin che buried topsoil but did not entirely prevent it.Some sugar beet roots passed directly through zonesof buried copsoil mixed with sodium carbonate. Inone observation, sudangrass roots found in the sodiumcarbonate zone had a burned appearance.

Dry matter yields of the crops ac harvest are givenin Table 1. The comparatively low soybean yieldsare attributed to a hail storm that occurred on August1. Although sugar beets and sudangrass were damagedextensively, they recovered more than the soybeans.One seeding of cabbage was destroyed by the hail.Lit; establishment caused the low cabbage yields. Theyields of sudangrass seed were not determined be-came of extensive shattering losses at harvest.

Least significant differences between [reacmentswere calculated for each crop because the yield vari-ance differed widely with different crops. In all case:,the yields were markedly higher with deep plowingthan with rococilling. However, with cabbage the largeyield differences; were not significant at the 5% level-Sodium carbonate application had no significant ef-fect on yielda of any crop. The "t" test comparingthese two treatments gave a value with sudangrass fod-der that would be exceeded by chance 10% of the rime.The similarly calculated value with soybean straw

Table 1. Yields of crootf (at hJrvat) grown wica differentpJowriar depths ana sodimQ carbonate treaitmesic, BusJUaud.Texas. 19S&

l.mi.m

Table Z. Relative Sr" concesicraooas in crops grown withdeep plowing- and lodinm carbonace treacoientt. Bushlaod,Texas, ISfi& (dncentratiODt wich Sr" roualled inta surface» cm 01 soU = 100.)

CM *u*Iff A^ U IT.bMI 0«4 IS.if H—U a

SW AWU IS.bMt On4 n.IMU K«w n 44.

SMducru*1— Ai« ir •-laoa So U 11.fBU«r On IS ».•Mrt On S3 iO.

S *«-nv» Au« 10 11.to9B S^ 11 IX.•m*' Oct U U.•Mrt 0«<iS ST.

CMf 0«tU L.H«r 1 LB— 1 B.

D——«—«

<1.144>«.41. i«f • 4.ii.Jn*«.(Li-Hi*.(1-M1 *..d. Mil 11 a.

(0.Ill J 4(I*T3 ii 0(l.l«4 i a(I. "03 • 0

fl.WO(L, *** * fl-a.*4« •a(I.|T1 « O

(O.ITt.O(0. M7 J a(i.*u*a

« DM*••rtn 1.1iw»1.120»

Hfta.mI.U4)

amam

-uai

,14ftrim

.M».1U1

3«3>ri**>.mi

3M aUL •4M •

4U*10«lI.I.

UT •i111 •uo •m-Ul •u- •*XT ••OX •

—r oM •—— •

m.a^aa,•.•4T)•.a**ira.Ti)••M4ta.ae»ia.oul

a.aflla. 12-1a. 130.a-uil

4.as*.t.UB)f9, W>a.dT4i». ll»r<i.o«ma.ota

would be exceeded by chance 16% of the dme- Thus,the detrimental effect of sodium carbonate on yieldsappears to be very slight under these conditions. - .

The relative concentration of Sr" in the dry planematerial of crops grown with deep plowing and sodiumcarbonate was calculated for each sampling of eachcrop as a percentage of the cancencration in thematerial grown with rotocilling (Table 2). With deepplowing, the relative concentration was 20% or less inthe early samplings and increased to more than 20%in che lace sampling. With deep plowing and sodiumcarbonace application, the relative concentration wasgenerally about 2% in the early samplings and about5% ac harvest.

To estimate the standard error of the relative Sr"concentrations, it was; necessary to transform to thelogarithms of the concencracions. It was; not possibleto make chie usual analysu of variance because, evenafter transformation, che variances of Sr" concentra-tions: from different plane dssues and plowing treat-menu were not homogenous. The "c" test was, there-fore. used to evaluate the scatiincal significance of dif-ferences shown in Table 2.

The relative concencrauon of Sr" in every planetissue was less with deep plowing than with rocodU-ing, which wai always considered to be 100. Theseditterences were significant ac the 1% level exceptwith sudangrass; seed. which gave a value of "t" thatwould be exceeded by chance 4% of the time. Thereiadve concentration of Sr** in every plant tissuewai less wich the sodium carbonate application. Thesedifferences; were significant ac the 1% level with theexcepdon of the August 17 sudangrzss sampling, which

502 AGRONOMY JOURNAL. VOL. 60. SEPTEMBER-OCTOBER 1968

Table 3. VpcaJif of Sr" by mature erupt $rown with diftcteBlplowuu and lodiuzn earbooau treaonenu, Bushland, Texas,ises.

Cr—

iS;S;SLfa.UfiuJ Xxl.terSiww

KMACIII-I DM*JU - lu riTIB - 1.4U €74Ti3 • us u»UO* tU 4«1u- — «a

^a>-l &411*U17«ILJ

T»

««• M—— fit* N&CQ,a ^— HU 19» 491 1

was significant ac the 5% level. The increase in rela-dve concencracion with successive sampling of thesame tissue was not statistically significant with sugarbeet tops regardless of sodium carbonate treatment,with sugar beet roots or sudangrass when sodium car-bonate was applied, or with soybeans when sodiumcarbonate was not applied.

Differences between crops at comparable stages ofgrowth generally were not significantly different atthe 5% level. However, ac the first sampling, cab-bage and sudangrass had lower relative Sr" concen-trations than all Other crops when they were grownwithout sodium carbonate, and cabbage was lower thansugar beet tops or roocs when the crops were grownwith sodium carbonate. At the second sampling ofeach crop, cabbage was lower than sudangrass and soy-beans when the crops were grown without sodiumcarbonate, but there were no significant differencesbetween crops when sodium carbonate was applied.At harvest, there were no significant differences be-tween crops grown without sodium carbonate. How-ever, cabbage wai higher than sugar beet cops andsoybean straw when the crops were grown with sodiumcarbonate.

The total upcafce of Sr" by the various crops a;maturity is shown in Table 3. Since yields were in-creased by deep plowing, [bis treatment did notreduce focal uptake of Sr" as strikingly as it did therelative Sr" concentration. There was, however, amarked reduction in uptake of Sr" into crops whensodium carbonate was applied- The total uptake couldnot be calculated for sudangrass seed as no yield datawere obtained for this crop. The concentration ofSr" in sudangrass seed was about 1/4 that in the maturefodder.

DISCUSSION AND CONCLUSIONSIn fallout events requiring decontaminaiion of sur-

face soils, the advantages and disadvantages of deepplowing should be compared with those of other de-contamination methods, such as crop removal, vacuumsweeping and brushing of surface soil, and scrapingoff surface soiL Three methods have shown over 90%effectiveness in reducing radioscrondum uptake bysubsequently grown crops: deep plowing with sodiumcarbonate, as demonstrated in this study; repeatedmechanical sweeping of bare soil; and scraping off aclease 5 cm (2 inches) of surface soil (Meruel, 1S62).Machinery for scraping is more generally availablethan that for deep plowing or mechanical sweeping.Scraping requires less power and is cheaper than deepplowing; however, there is an added cosi for movingthe soil to a disposal area which must be considered(or each situation- Mechanical sweeping moves a

minimum amount of soil. but is slow because themachines are narrow and repeated sweeping is neccs»=—sary. Deep plowing could he done only once on a (given area because a second deep plowing would return (a long-lived radioactive contaminant and toxic chemi- Icat to the surface. Scraping and sweeping could be_1repeated if necessary.

The effect of deep plowing on crop yields muse alsobe considered. In some soils, deep plowing may in-crease yields by exposing more desirable surface tex-ture, burying a sale accumulation, or breaking upa zone of high soil strength in an otherwise ferulesoil (Bertrand, 1966). However, when newly exposedsurface soil has undesirable texture, is highly add orinfertile, or is otherwise unsuitable for tillage, deepullage may be detrimental to soil productivity.

On Pullman silcy dav loam at Bushland, Texas,deep plowing doubled the vieids of sugar beets andsoybeans and increased yields 60% with cabbage andsudangrass compared with rototilling of the surfacesoil. Plowing under sodium carbonate had little effecton yields.

Concentration of Sr" in mature planes grown ondeep-plowed plots ranged from 25 to 50% of that inplanes grown on rocotilled plots. In planes grown onplots with sodium carbonate plowed under, the con-centration of Sr" ranged from 3 to 7% of that inplants grown on rococilled plots- Because of the in-crease in yield with deep pfowing, the reductions incocal uptake of Sr" were somewhac less striking.

This meihod does not solve the problem of decon-caminacion of soils. On some soils, deep plowing maydecrease yields, rather than increase them. Sodium _carbonate may be coo readily leached to remain effec-rive for many years. However, die experiment dem-onscracel that a toxic chemical can be plowed under.with radioactive contamination to reduce the up-take of the radioactive material with little effect onyield from the chemical.

UTEXATLTRJ:; CITEDBenrand. A- R- 1966. Water conservation through improved

praaicct. /n W. H. Pierre. B. KiAham. J. Peaek. and R-Shaw fed.) Plant environment and efficient water use. Amer.Soc. Aeron, Madison. Wis.p. 207-223.

Frcre. M. H- R. G- .VIeniel. K. H- Lanon. B_ Ovenireet. andR. F. Reicemeier. 1943. The behavior of radioactive Ealloucia loils and plants. Nad. Acad. of ScL—NaiL Res. CoundL.Pub. 1092. Washington. D. C.

RacaaBova. G. F. 1962. Encry into planes of itrontium-90 Cromsoils in fidd experuBenu. Iivesuva limn-taier. Sel'ikoldloz.Akad. 4/47):105.110.

MoueL R. G. 1M2. DecoBiamiiiauoa of soils- Flanc food Rev.S(2):3-12.

—————, H. V. v^' and D. F. Qiamaioo. 1967. Zffea ofplacement depth and root-inhibiting chemicals on u?iake ofscronciua^S bv Geld croos- Agroa. J. 59:70-72.

MBboura*. G. M- F. B. H'", and S- S. R.mifll 1959. Tile ad-sorpuon of radioaccive suonciusx by planes under field coa-diuons m ihe United Kingdom- J. NlicL Enc^r pan A; Reac-tor So. 10:116-132.

MThre. D. I-. B- G. Menltl. H. Robcns. Jr, M. H. Frcre. M.AniemiTa. 0. W. Belie. D- R. -nmrnons. md E. H. Wood.I9fl4. Reducxion of scronduin.90 uptake by corn and aovbeanswith deep piaceineac. izTigaciou. and wd amfnfttnmts. Agnm.J. 56:«i-4<7,

Reiicmeier. E- ?- and R- G. MenzeL I960. Reiaiion of radio.acxive concaainauoa of croos co wil ferallcy. 7Ca lac. Coagr.Soil So- Trans. (Madison.'Wis.) m.U-U.

Taylor. H- M- C. E. Van DoreB. C. L. Godfrey, and J. R- •Goover. 1963. Soils of che SouchweKem Greu Plaias Fieldflatten. Texas Agr. £xpc. Sea. Misc. Pub. 669.

<- Qwy f^i-.Ci^-^- '"r•<^'•^ ^~ -^S n // /i'// / A , . /< 7 Tmbu' ->»t*- .

Deep Tillage and Soil - Plant -Water RelationshipEari Bumea and V. I- Hamer

-MIMMX ASA£

DEEP tillage to alleviate a specificsoil problem associated with crop

production has been the subject ofmany investigations in the UnitedStates and Canada for over 50 years.The transition in terminology over theyears is interesting. In early work,"deep tillage" meant plowing '8 to 16in. deep (5, 7, 10, 1;;, 16, 23, 37) •;however, it now means 16 to 36 in. ordeeper (2, 13, IS, 19, 29).

Deep-tillage trials have been con*ducted with many types of tillage toolson many different soils (4, 9, 13, 13,19, 25,'29, 34, 35, 36). Most of theearly investigators used some type ofsubsoiling equipment (20, 39) becausethe necessary power for inverting thesoil with large plows was not available.Since World War II, more powerfultractors have been built permittingdeeper tillage with plows.

Deep tillage is not a panacea for allthe crop-production problems correctlyor incorrectly associated with physicalor chemical soil properties, as noted byDuley (10). However, where a spe-cific soil factor is limiting plant growth,deep plowing may be beneficial. Thisreview paper discusses some soil-plant-water relation problems that may becorrected by deep tillage. Generallythis discussion will be limited to fine-texcured soils or soils with a dense orcne-textured laver somewhere in theprofile.

Effect of Deep Tillage onPlane Growth and Water Use

Numerous soils have dense or fine-textured layers in the profile that re-strict water movement and plant rootdevelopment. If this laver is within

Ann*«d u a rial eaambuao« fraa (h« Sail udWita CaluamiM XMMU DcuitUL AAS. USCA.ud ih« TCUJ Ameuliuni Esaumm taw.

rb« audMft—e.UL BURNETT ud V. 1_ HAUStK—u raareb mi Kiacut md raarell IcneuJntfll a.

• Nuabtfl la puwAOa tttec n t0s Jppadad Hi-

TFaiaul ^•——————- (Sehaada. v'^ a il, udt«6i *aauJ rcoon. fcMilWten Gnat Pbio* k«cR&Coicr. luUuJ. 70-): tyu laaiuL repon <rf th« Bbeklud CauTW

Tawasss Sanaa, Tmplc. Te&

U«a ix uai •lu ud with • hica fuvaavs it w

. f. K. Sud—xl ud NocO-mr mal TO»T ter t9«.II »•

• Grai PIaiuHlUu. S-3.f Kabi««k. r. E. Ia9»*l TillT inuun dflw

•«Mk Aaaicu SMIIT tar CinL Eara—i. Irril*.rioa ud Druun IMUKT Coaunau. Lu Vc«u. M«r«N«r. 3 u4 ]. 1006.-tea.tuTm T«t=. [. L. E>«t W »1

b« uiMMirt U lh« «cft iRtcmaMal S«tl CanfrM.Ad«Jud& Ammlu. AWIM( ig6«. 11*4 p«MuJMd i* (««pfflCMrir a< !&• Caxinu.

ttCum. L L CJa«l« OeauauM of Ame^nm.S«jl b—fU 3«k—i—f TeKnnllfc AJb««. fgMiMt

the reach of tillage tools, it can bebroken up or mixed with other soil toimprove water penetration and plantroot development. In many instances,Planosols with characteristic daypanshave been improved by deep tillage..Vtiller et al (21) first reported attemptsto iniprove the claypaa soils of the cen-tral states by deep tillage, tile drainage,and deep placement of fertilizer. LaterSmith (37) presented additional datarrom subsoilmg experiments on thesesame soils.

The ciaypan in the Planosols of theCentral States is extremely plastic andunworicable when wet, but it is in astable granular condition when drv.This fact led Woodruff and Smith (40)to evaluate subsoil shattering alone andwith lime and fertilizer mixed with thesubsoil for improvement of the water-holding capacity and aeration of thesoil. They concluded that lack of limein the subsoil was of greater signifi-cance than was the poor physical con-dition of the soil, even though theyattributed increased corn yields to im-proved aeration in the subsoil Theyalso reported that root development orcorn and sweetclover was improvedby subsoil shattering and lime treat-ment.

Apparently, Woodruff and Smithwere concerned that mixing the claysubsoil with the surface soil would bede&imental to soil-plant-water rela-tions. But later, Fehrenbacher et al(13) mixed and fertilized Wier siltloam, a PIanosol in Illinois, to depths or9, 18, 27, and 36 in. Redistributing theclay in the mixed profile did not alterthe available soil moisture capacity norsignificantly change average soil watercontent below 24 in. (Fig. 1). Cornyields were not increased by fertilizerrate, deep tillage,. deep fertilizer, orhigh-rate fertilization. BfunfaH was nearoptimum in 1956 but was less favor-able in 1957. Tields for the two yearswere reported as a single average soinfluence of water availability on yieldscannot be evaluated. Boot developmentof corn was not innuenced by tillagealone in 1956 but was increased byfertilizer, particularly where the fertil-izer was placed throughout the entiretilled zone. Root development was notevalnated in 1957.

Mech et al (19) conducted profilemixing and deep-plowfag escperimenoon various soils ranging from a typicalPIanosol (leached A- horizon and adense B horizon with high clay content

. \

^'& 1 1 - 1 6u

z23.3« •

TILLED 3"TILLED 18"TILLED 2T"

SJ-ol TILLED 36" .17 18 1 9 20 21 22 23

PERCENT/ AVERAGE SOIL MOISTURE

FIG. I Relxooiuhip o£ avenge foil sc.coilienc duons the 193tf (rowing scuon tcof "ll'g- or mixing After Felirenbache:(13)

that restricted root development)loess (uniform silt loam A homein. deep). At high fertility levels,'yields were increased 20.1 bu o'.deep-plowed PIanosol but wereincreased on the deep-plowed IcsoiL Deep plowing resulted inwater depletion to greater depth.cause of increased root develop(Fig. 2).

In the Southern Great Plains, Hand Taylor (IS) deep-plowed Pusilty clav loam. a reddish chestnuthat has a dense, very slowly permclay layer extending approxin-from the 3-in. through the 20- to ;depth. Disk plowing to a depth 'in. increased the rate of soil wvcompared with normal plowingdepth of 4 in. During one year, '

-.w

i

12 ;* i« *»0«»fh To C««fr Of M««ur«in«Mf In I

FIG. 2 £.utr< wd iJEC euon wl mmrarsteat ia eawrmsaasi lad deep pJowed Fnlad (PIzBowl) a«ppeii to wuiier wbac.u« *vea«H of 1563 and 1964 pwnas sc-ktcct Moh a. ,1 (19)

supply was restricted only once; ho'-ever, in this instance grain sorghumvield was significantly higher on the24-in,. disk-plowed frearment. In ocheryears when water was never limiting.no yield differences were measured.

Recent deep-tillage research oaPullman silty clay loamf verified theresults of Hauser and Tavior, Grainsorghum yields were increased by deepplowing and profile mixing. However,yield differences due to plowing orprofile mixing were greater under lim-ited moisture conditions. The vield dif-ference was attributed to improved rootdevelopment and soil water use togreater depths with deep plowing.

Similarly, Burnett: has shown thatprofile mixing of Houston blacx dav, aGrumusol, which is dense and vervslowly permeable throughout the pro-file, resulted in increased cotton andgrain sorghura yields under limited soilmoisture conditions. The increasedyields were attributed to improved rootproliferation, which resulted in morecomplete water extraction from soillavers between 1 and 6 ft (Fies. 3and 4).

Others who have reported increasedroot development and sometimes in-creased crop vields by some form ofdeep-tillage include De Roo (8) on asandy loam soil with a compact layer,Rasmussen (29) and Cairns (4) onSolonetz soils, Saveson et al (34) andPatrick et al (25) on medium-texturedsoils with compact layers in Louisiana,and Raney et al (27) on alluvial soilsin Mississippi in dry years.

The studies cited show that plantgrowth can be increased bv deep plow-ing onlv where root development andperhaps water movement are restrictedby dense, compact, or fine-texturedlayers in the profile. Where water isnot limiting, plant growth is usuallynot increased even though root devel-opment is restricted (13, 13, 25, 27,30, 34).

4/22 5/28 6/30 V22. 8/30DATE, 1965

FIG. 4 Changes m mil water contest with tunem Housian black day valid conon. Chedt—conventional tiJbge of beddmf and rcbedaifl(.Roiorilled — treatment coiumcd of rotodllmg;and removing lueeesaivc 4-in. laycn of soil wa depth of 24 in. after which Ac mixed loQwaa replaced

Effect of Tillage on WaterIntake and Retendon

Water intake rates of soils withdense or fine-textured zones in the pro-file have been increased bv variousdeep-tillage methods. Hauser and Tay-lor (13) showed that disk plowing andvertical mulching to 24 in-, respectively,increased intake rates of Pullman silt)'clay loam 1.9 and 1.4 times that of4-in.-deep tillage in 19S9 (Table 1).Chiseling to 24 in. caused a small in-crease in intake rate in 1961 only.

Mech et al (19) plowed Freemansilt loam 36 in- deep to increase theeffective soil depth for water storage

ai—L plant growth bv breaking a por-tion of the dense B horizon. Oniv about20 in- of the profile were available forstorage of the 21-in. annual rainfall with-out deep plowing. Inflltration rates asmeasured with a double-ring infiltrome-ter were reduced by deep plowing(Fig. 5). Deep plowing raised sub-

FIG. S iBnInQ'on of waier into shallow- anddecp-piowcd Freeman nit loam viii. AfterMech el al (19)

soils with high clav content to thesurface which may explain the reducedintake rate in flooded rings. However,no soil-moisture differences were foundunder natural rainfall between conven-tional and deep plowing (Fig. 2). Thedata suggest that consideration begiven to the amount of inversion andmixing of the profile that is desirablewhen deep plowing is contemplated-

TABLE 1. TILLAGE E??SCTS ON WATERINTAKS OF PULLMAN SOIL—ADAPTED

FROM HAL'SER AND TAYLOR (15)

•rahp;depth, ill

Ditt195919601961

Total inc

Check4

1.421J61.17

life for 10

Chile!24

Inchex1.351.401-30

houriVernalmulch

34

1.982-201.79

Dilkslow

24

2.672.602.25

Rasmusseo (29) found that deepplowing saline-sodic soils in Idahomarkedly increased water intake rates(Fig. 6). These soils were medium tex-

FIG. 3 COQOB rooi frnemi (rowH ia Hounoa **i-"'r dar m 1965.(A) From aiaveaaoml alkfe tracmau(B) Proa ptoi racoaUcd 24 ia. deep m Aafw 1963(C; From plot with profile aodi&d 4 ft deep wnfa duchinc machine ia September 1564

FIG. 6 A.vaa(e quantity of wxicr absorbed* anddepdt at witer peaemaoiL, dnrinf 24'hr. irri-BIOOIU tumf dull farrowt. After ^•**iy"*w(2»

Cured at the surface but grad>- intofiller textured siitv clav load to clayloam below 8 in. In manv areas, anindurated or strongly cemented hard-pan oceured at depths of 20 to 40 in.Soil water available to planti; wasgreatly increased by increased effectiveplant root depth caused by deeo plow-ing.

Deep Tillage and SoilFertility Relationships

In many areas of higher rainfall orwhere irrigation water was available,plant response to deep tillage alonewas sometimes unfavorable or incon-sistent. Under such conditions, fertil-izer incorporated throughout the loos-ened soil unproved plant growth in anumber of experiments (2, 7, 11. 13.17, 23, 30, 40).

Differential fertility with soil depth. may affect the results of tillage experi-

ments; e.g., Hauser and Taylor (15)noted phosphorus deficiency svmptomson grain sorghum grown on deep-plowed Pullman silty clay loam. Studiesby Ecfc et al (11)' on" the same soilshowed that available phosohorus wasover four times higher in the Ai, hori-zon (0 to 5 in.) than in the lowerhorizons (Table 2) which partially ex-plained the deficiency symptoms inthe deep-plowing experiment.

Subsoils generally contain less avail-able plant nutrients than topsoils,therefore, careful planning is reauiredto avoid nutrient deficiencies after deepplowing. The chemical properties ofthe profile should determine whethercomplete inversion of the soil or mix-ing would be better. Lyies et al (IS)studied the soil-mixing characteristicsof two disk plows and one moldboardplow and concluded that there wasconsiderable mixing of the plow layerby all plows, but the disk plows placedmore of the 0 to 4-in. depth incrementin the bottom of the furrow slice thandid the moldboard plow. In the caseof the Pullman soil with most of theavailable phosphorus in the 0 to 5-in.increment, muting would be more de-sirable than inversion (11, 13).

The fertility status can also be modi-fied by broadcasting fertilizer beforedeep plowing. The mixing effect of

the plowing operation will place thefertilizer at greater depths and perhapsmore uniformly through the profile thansurface application after deep plowing.

Deep Plowing for ReclamationOf Sodic and Saline Soils

Sodic or saline soils have been im-proved by deep plowing in several ex-periments (1, 4, 22, 29). The most dra-matic results were achieved on slickspot (solodized-Solonetz^) soils withsubsoils high in lime and with adequate

i—water available for leaching. Basnus-sen (29) found that soluble salts andexchangeable sodium were reducedsubstantiaJIy in the upper 18 in. of theprofile within one year after freatment,and were reduced Co noncritical levelsto a depth of 36 in. in three crop yearsby deep plowing (Fig. 7 and 8). He

i1" attributed the changes to improvedinfiltration rates and increased water

FIG. 7 Elecsial cooduerivtty of Ac ttrnra-don eniact (EC,) at che Sebree K>il profile be-fore m-tmieac arLd 3 yexn mer ffeamienz. AfterR^xmuucn (29)

FIG. S EJdungable lodium pereeaafe at dieSebice nil profile before BeaaneBX and 3 Jaxss&uz oeamieac. .adapted from Binrmwn (2S)

TABLE 2. SOME CHEMCAL PROPERTIES OF A PULLMAN SILTY CLAY LOA.M PROFILE—_________________AOATTED FROM WS. ET AL (11) ____

Depth10.

0- 55- 8a-i3

13-19[9-2321-3838-565o-o5

HORZOB

Alp321BEB22iB2uB2hlB2b2Cab

NiHCO,exoact-ibleP

. "0°S3.92.01.02.04j

ToolP

ppm450374328344322327

ToolN

perceni0.1060.1050.0820.0620.0530.0490.0350.021

pH

(J6.!7S737.613

Oryxasetrusteepercent

1J81330340.94O.f90-i30-COJS

Exehugc-abicK

ppfn475440425450475425420210

penetration from deep plowing, whcaused soluble salts to be ieaehed frthe plant root zone. Similar resiwere reported on another Soionsoil by Cairns (4) with significantdistribution of calcium and sodiumthe profile.

Sandoval and Reichmani] have <tained benefits from deep piawiBhoades silt loam (solodized-Solone-soil in North Dakota, even though tsoil has a dense sodic claypan near tsurface and has low and earemely v;able calcium supplies in the subsoilcontrasted with the high lime subscin the experiments of Rasmussen (2*The annual rainfall in North Dakotaonly about 13 in.. and irrigation wais not available in the area where tresearch was conducted. Soil amerments of manure and .gvpsum wdeep plowing (8 and io in.) wimore effective in increasing pisgrowth and infiltration rate than ploing alone.

Deep plowing for reclamationsodic soils is successful onlv if a SLply of calcium is available to be mixwith the high sodium soil Innltratirate is increased by mechanical mixirwhich permits more water Co percokthrough the profile. Sodium is replacby calcium on the exchange compitand the percolating water leaches tdissolved sodium below the plant rezone. Thus reclamation of saline screquires both high calcium soil lavewhich can be brought to the surfaby plowing, or gypsum amendmerand adeauate water supolies for ^eacing.

Saline soils have been plowed 50 :deep for reclamation in the Imper-Valley of Ciliforoiasi. In some eastlong periods of periodic leaching werequired after deep plowing to redu'the salinity of subsoils turned up ideep plowing, la 1963, a modificatixof the subsoiler, called a "slip plowcame into use in the Imperial ValleIt consists of a single chisel shankwhich is attached a reinforced flat pla8 to 14 in. wide and 10 to 12 ft IonThe place is attached to the rnj^point and mounted with the S- to 14-idimension horizontal and the 10-12-ft dimension extending upward arbackward at 60 to 70 deg. from ttvertical plane. The upper end of ti-plate rides even with the surface of trground when operating. The slip plovoperating at depths up to 6 ft, breaiup dense layers by lifting, rolling anmixing. The advantages claimed for ttslip plow include (f l ) reieveling is uinecessary, (b) very little saline soilturned up, and (c) greater economy-S14 to S18 per acre as compared witS40 to S60 per acre for deep plowiniUttle research data are available othis techniaue. but it should be mor

]

Saildepth, m

0- 88-16

16-21)20.2328-3333-3939-4545-5151.5757-o3

••TAB

FreemanChKI5 in.

1J31JI1-481.651.66

1.65

1-6 3. SI

silt loam"Plow36m.

1.151.451.421J» .1J81.40

TECT OF

Miud48m.

1.471.421.451.461.461.441J81.46Ui1.66

DEEP TBulk (

WSoildcach. ia

0-101(1.1816-31)30-4545-55

GE ONiemicyer "it loam1

Check. 9ia-

—— l / x1J41.481.461.541.52

SOIL ai

hMixed27 in,

L38USIJO

JLK DENS

Pullma)Soildepth, ia

3- 99-15

15-21

!TY

a lilf clay iaCheck

. 4u.——sia.i.401.401.46

iam^Plow24 ia.

1.44IJ41.30

(li. and Fehrenbacher ec al (13)iljurtrate the textural changes that mayoccur bv plowing or profile mixing(Fig. .10').

" Compiled from Mcch et al (19). Measurements for values reported were made 3 yean afterplowuf lad profile mixing;.

+ Compiled flora Fehreaiacher cr al (13); Compiled from Hauler and Taylor (15). MeuuremeBO for values reported -were made 4 veari

after plowing 24 in. deep.

applicable to saline soils where littleor no inversion of the subsoil is desiredthan to Solonetz soils with high limesubsoils that need to be brought to thesurface so the sodium on the exchangecomplex can be replaced with calcium.

Effect of Deep TillageOn Soil Physical Properties

Changes in sou physical propertieshave "been associated with various till-age treatments. BusseB (33) states thatdeep plowing improves soil aerationand the data of Bumett and Taekett"'confirm this statement Fig. 9 illustratesthe uniform concenttation of oxygen inHouston black clav that had been me-

chanically mixed to 4 ft compared with.ex&eme variations found in nonloos-ened profiles. Bulk density was re-duced and pore space increased inthese studies, which accounts for thehigher and more uniform oxygen con-centrations found in soils with modifiedprofiles.

Lower bulk densities are usuallyfound in soils that have been deeptilled (13, 13, 19). Some representa-tive data are shown in Table 3.

Tillage implements that invert ormix soil horizons may affect soil parti-cle size distribution if textural differ-ences are present in the natural profile.The data of Carv et al (6), Lyies et al

t^ieATIQM t - - COMWIUTtoNJ^ TILLJUlltfMWIon I ."" WLtO >*" 17. TUS•tW.I(ATIO« 3——l»(»t,tC*T101 •—— ......a,.-:—/—

PIG. 9 OxT«n amtcasiHw ia Roimaa bbdt di? u aieeied br preffle modification. Preale modi-fcadoo—profile mixed with tnauhJai "'- '•'f" ia 4 h. CoavenlioiuJ dIlJfe—beddinf and rebedcuAfwith Imtr. Prank BoJi&aiioa earm ue ncastt of faur tcia. Avenfe 0, oir« »"h con'en-tiaoal dl]«cc oat lhawa ia order to uliixaale mruibulcy often touad in thi< «ail

FIG- 10 Chanid ia profile day coaieat re-iulaa( from pionic mixing. Adapted irom (a)Cair e: al (6), (o) rehrenhaciicr a al (13),and (c) Lyici et al (H).

Data relative Co changes in aggrega-tion or aggregate stability caused bydeep tillage are meager. Some of theeffects of conventional tillage on aggre-gation of surface soils should have appli-cation to aggregation of deep-tilledsoils. Harris et al (14) state that theeffect of tillage on aggregation is afunction of soil moisture content at thetime of tillage and that the optimumcondition lies within a narrow moisturerange. They quote Russell's (32) defi-nition of optimum moisture content asthat content "sufficient to fill all thesoil pores with water." Russell con-cluded that the more intensive the till-age, the lower is the optimum moisturecontent needed to produce stable ag-gregates. Rogowsia and Kirxham (31)minimized the importance of tillage inaggregate stabilization because theirresearch revealed that little water-stableaggregation results from physical pres-sures.

Unpublished data and observationsbv Burnett on Houston Black clayshow that rigorous profile mixingcaused pronounced changes in soilstructure bv creating coarse aggregatesor clods. These artidficial aggregateswere quite stable and were visuallyevident three years after profile mixing(Fig. 11).

Persistence of ChangesBrought About by Deep Tfflagc

The literature is replete with con-clusions that changes brought about bydeep tillage are transitory. Baney andEdminrter (26) stated, "Whenever soilis loosened in the course of seedbedpreparation, the reduced soil denatv isquite transient It tends to recocaolidatewith the first rain and may approachthe same density that it bad before

FIG. II Sirucnmi cbangei ia HQIUIOB bladeelar rauldaf fiom pronie mixinc. Plwiosrapa.o{ reinnani at 5' by 0.111. loil core abained threeywv after rotoaUJaf, lateriace b<cwtefl iKre-zated and llnicnueleii loll u ipproxiinateJr 30m. below che foil surrace.

plowing." Numerous other investigatorshave reached similar conclusions (3,10, 12, 16, 20, 23, 23, 30, 38). Severalfactors are common to maav or thereported experiments in which deeptillage effects were transitory and areworth noting: (a) most experimentalsoils were medium- to coarse-texturedsilt loams or coarser, (6) the compactedlaver was Often "induced" bv farm ma-eninery rather than being genetic, and(c) die deep-tillage implement usuallywas a subsoiler or "chisel."

Recently numerous deep-tillage ex-periments have been reported wherechanges in soil properties remainednearly constant for several years.Caimsff found small but consistentyield increases in wheat and hay cropsfor 6 years on SoloneQ soil plowed 22in. deep in 1939. Soluble salts werereduced to a depth of 5 ft. The avail-able phosphorus content was greaterthan before deep tillage. Hauser andTaylor (15) concluded that four veaisof cultivation and irrigation, had notrepacked the 9 to 21-in. depth of Pull-man siltv clav loam disk plowed to 24in. deep because the bulls density ofthis layer was significantly lower andthe water incaice rates remained higherthan for shallow-plowed plots. Ras-mussen (29) reported that the im-proved chemical and physical conditionof deep-plowed Solonetz soils per-sisted for four vears and that cropyields continued to be higher for thisperiod of study. Burnett* observed thatthe lower densities of Houston bladeclay resulting from pronie modificationpersisted for at least four years. Mechet al (19) noted that changes in bullc

density, water extraction, and ; de-size distribution of a deep-^wedFlanosol were still evident after threeyears lad chat hay and wheat yieldswere increased.

Certain related factors in the experi-ments dted are noteworthy; (a) theexperimental soils were either fine tex-cured throughout the profile or therewas a fine-textured, dense layer withinthe profiie; (b) the tillage operationwas drastic ia each case, ranging fromlarge disk and moldboard plows toback-hoes and frenching machines.which resulted m thorough mechanicaldisruption and nu-ong, (c) a subsoileror "chisel" it used produced limitedeffects as compared with the othertillage implements; and (d) the decsezones were essentially genetic in na-.cure, although probably aggravatedsomewhat by cropping with an attend-ant reduction in organic matter.

DocmsionThe data reviewed indicate that suf-

ficient experimental evidence is nowavailable to predict whether dee? till-age mav alleviate soil-plant-water re-lations problems associated with densesoils or soils with dense lavers in thepronie. -Knowledge of the physical andchemical properties of the soil in ques-tion is required for a reasonable pre-diction. for example, consider the twosoils—Pullman silcv clav loam m theTexas Panhandle "and 'Bichfield siltyclav loam m southwest Kansas. Bothare classed as reddish chestnut soilsand developed from medium to fine-teaured calcareous eolian sediments ina semiarid climate with average rain-fall of 17 to IS in. Principal cropsgrown on both soils are wheat andgrain sorghum. A compact clay loamplow layer mav be present in the Rich-field soil, whereas the Pullman has adense clay layer from about the 8 to20-io. depth-' Mechanical compositionand textural classification of the twnsoils are given in Fig. 12. bulk densityand soil water retention data in Table4, and water intaJce rates in Fig. 13(24). These data, along with soilmoisture depletion data. indicate thatroot development is not restricted onthe Bichfield soil but is severely re-stricted on Pullman soil. Toereiorc,deep tillage should be more effectiveon the Pullman than on the Richfieidsoil. No deep-tillage research has beenconducted on the Richfieid soil, butHauser and Taylor (13) and Ecic et althave experimentally verifad the bene-ficial effects of deep tillage on PullmansoiL

Even though desirable changes maybe made in root development, waterretention, density, pore-size distribu-tion, fertilitv, salinity, and permeabil-ity by deep tillage, the changes may

FIG. 12 XeebaaicaJ compoiidon andclauuicadon at Pullman aad RiduieiciftCT Mmick ud Slema (24)

TIME - HOURS

HG. 13 Avenfe balta iauke raux for i«axtnicanou of (iaia lor^hma oa Ridifieid?ullmm uili, ism Miiiidc tnd SIfttn (24;

not be reflected in increased e.yields. Water supply to the crop seeto be paramount in importance inabsence of other overriding considedons suca as a fertility or salinity prclem. Crop yields have been increasmost by deep tillage, as compared wnormal tillage when moisture waslimiting factor. Hence, the pnmabenefit of deep tillage seeas tothrough either one or a coabinacionthe following mechanisnu: (d) increain root proliferation which enables cJplant to extract water from a larg'volume of soil, (6) increase in storewater due to improved water entry, <(c) increase in stored water due tchange m particle arrangenieaL

SUMKART AfTO CONCI.USIONS

Deep tillage if not a panacea for a.the crop production problesu asxoaared with physical or chemical soiproperties. However, where ccmm soi

51

TASLS'4. BULK. DENSITY AND 500.MOla-TURE RETENTION OATA.

RICHFIELD AND PUI—MAN SOILSfrom Muuci; and Skucn (21)

Pernianeflt AvailableBuJJc wilanff Field wU

Oeplh deOJtcr pomc capfdty moiicure

1& S/CCRichfldd0-12 US

12-24 US2-Mf 1-3237-72 (loca) 1.26PuJInua0-12 1J3

U-24 1-5224-36 1.52J6-48 1.5018-60 1.406fl.?2 1JO

in-pcrrt

1.962.112.051.96

2.092.462-^72.432.492.68

in. pern

19s4.U4.114.00

4.0 S4.133.S23.673.683.58

ULperfl

1572.02

"2.062.04

1.991.67l.-i;1.241.190.90

factors can be identified that limitplant growth, deep tillage may be bene-fidaL

Fine-textured or dense soil laversoften restrict root growth and watermovement. Soil serves as a reservoir tostore water for plant use between ramsOr between irrigations- D&ep plowingor intensive soil profile mixing mav in-crease the depth of soil that can beutilized as a soil moisture reservoir byplants. Plant growth and crop yieldshave been increased by plowing orprofile modification where moisture islimiting, but where water is not limit-ing crop vields are usually not in-creased-

It is sometimes impossible to fill thesoil water reservoir on soils with vervlow intake rates. 'VVacer intake may beincreased by plowing or other Beeptillage, if the low water intake is dueto dense or fine-textured' lavers in thesoil profile. Care must be exercised toavoid placing slowlv permeable soilson the surface where thev mav resfricEthe intake rate. Best results are ob-tained by mixing slowly permeable ma-terials throughout the profile.

Subsoils generally contain less avail-able plant nutrients thafl topsoils; there-fore, careful planning is required toavoid nufaient deficiencies after deepplowing. The chemical properties ofthe profile should determine whethercomplete soil inversion or mixing wouldbe better. Where fertilizers must be ap-plied to the land, they may be mixedthroughout the soil ir applied to thesoil before plowing.

'"—• Deep plowing may greatly assist inreclaiming saline soils. Successful recla-mation of saline soils requires bothhigh caldum soil layers, which can be

brought to the surface by plowing, andadequate water supplies lor leaching.

Deep plowing of clay soils improvessoil aeration, reduces bulk density, andincreases pore space. Deep tillage im-plements, which invert or mrt' the soil,create changes m particle size distri-bution with depth in the profile. Soilprofile mixing of day soils has causedpronounced improvement in aggregatestability.

The persistence of soil changes cre-ated bv deep tillage varies with soiltyptf. Physical changes in the soil pro-file created by deep tillage are longlasting if: (a) the soils are fine tex-tured throughout the profile, (b) thetillage operation is drastic, such astillage with large plows, and (c) thedense- or fine-texturcd zones are essen-tially genetic. FhvsicaJ changes in soilsinduced by deep tillage are more tran-sitory if one or more of the followingconditions apply: (a) the soils aremedium to coarse te-vtured, (b) thecompacted lavers were induced byfarm machinery, or (c) the deep-tillageimplement used was a subsoiler orchiseL

Deep tillage to correct physical soilproblems will increase crop yield wheremoisture available for crop growth islimited. Generally, deep tillage to cor-rect physical problems does not Im-prove crop yields in the presence ofample water supplies.

The data reviewed in this paper indi-cate that sufficient experimencal evi-dence is now available to predict withsome accuracy whether deep tillagewill alleviate some problems in soil-plant-water relations. Knowledge of thephysical and chemical properties of thesoil in question is required for a rea-sonable prediction-

ReferencesI Aaupov-kJrJue1', I. N- Tht iaipro*'anefl1 of Sola-

n«z (ail* under uyit-itri iad noA-irfi(i)«d eoadiuoMin cinwciiaa 'oith Uw iiiiliuuoa »t fifiia and waneludf. Akxd. Nauh, S.SJJL. Lcainpid. i*»cnm,Scriu BiolofU^oJuia. No. u }'i8. |;S4-l B«nrvoifty. S. A. Suauiil plowine oi mri-podxol

toilf Ud tan/ eultivitiu. Zanlcd(ii« h: ^-49. Rricral-Zliar, Biai. io;6, Na. IIJI, iyn.

3 Berc. C. «M den. BOK&. 0. via oe*>- Saa« daoW fAc root d«««la«m*ai of »cncultwal cropt in »n<iriJTcn oceufruic i* rodr ela? milt. 'wil. Ltfldh.Oaderf'J Gr>T. &i.rs 100.111, IB?I.

4 C*'"". H. K. Soa< efl«cu at deep wu»t w Sote-ocn Mil. Cuud. I. Soil Sei. -a; 173-rrs. 1't^'

y C*rda«. P. U. Tiltifr *ftd WtMUt apvwwa atNcaai. UaL USOA fuJL if. 1911.

» C*/T. E- £-. Hone-. C. M- wd Meeh. S. I. Rfbtiaaiiup yf iLllan ud lauluanoa la ine T'ttd oflifalfa oa Freaau till lua. APBB- I- IV i^tU. 196".- Cbitewt- £- C-. *Bd Cat*. [. S. Sufcta.luit. d««f>

tillulf ud iail drnaffidnc IB the G/eic Ptiin*. A»r.to. w 4*ciat. !;ii.I EX Xaa. rtwr C. »»K ftwnh u« Cwwtwu te-

bKea MiU. COA*. ACT. £xa. Su. B"'l. No. M. 199-.9 Oo«««a. L 0., ud Hdtdmon. D. W. CompMiwa

of inirud toil* 1*» tneion. Apicultttfal Eatincwt3*i<a) ?4-»S. '«• Frt>"*"T '«3.

ia Duier. F, L. Subwilmc la ibc Giat Plaint. I.Swi lod WUCT Cinu. i±: i . IOT-.

it Ecfc. H. V., Hiu*«. V. L_. ind Ford. R- H.Feruhw B««u lof reuarine prBflucli»i*T °1* Pull««"Mirr CUT la-UB Uier vinou* decr«a ot wU raaaral.Sail Sci. &oc- Ama. Prac- 39: W9-ui. iW-

12 FurcJI. F- 0. KJOIJI KunJ Inuuuiiaa: I. Th*Fan Hayi iinaeJi EzperuBeu Suu«o. l ak Ap. £m>.Su. dr. 311. i(Mt.I; FehreflDBcaer. 1. B-. Vi.-ra, ;. P.. aad LJRC. A. L-

D«p tUbct *nd dew ica tti»aito« cnXTtaieau on acuvpu Mil- Sod Su. Sac. Ainc. Proc- SS-- Mi-)37.

U Hami, 1L. F- Oiotffi. G.. *ad AUen. 0. N.DTomuct at ml iccrecluan. /• Adifaeo so Acn*"-WT, Vol. tB. £dtlrt ItT A. C. .Snniw*. Acadwifc P»c*».Nf Ywk in*: Laaooa. p. nff-iog. 19*6.

H Hautcf. V- L.. Md Tartof. H. AI. £'ilwo»B o(4—9'utlJf B«na»tBB an » *iwtr pm«cai>i» KiLTruu«iou ri th« ASAE •:lll i -ild, UJ. IO&J-

l6 Kuiu. 1. B, ud ilaiflw, 0. »• Ur-taai erop-rfltauoa aad ulli;e exitoiaeau 11 IB( CaVV (KJOJIJHrwca £x9Cfia*At Suiiaft. C;50A Cir. »-». 1946-

IT t-.n, |. G. plowLA( dfBUu aad fcrulao'i *o«ctUtCar beet crop. Micfc. ACT. izp. Su. Qm". ***U. 13:133-H7 Iflll.

(J Lyici. Lmk. Halrua, U. 0-, ud T&MDU- I. LSini'auxiac eUnciffiRwi af tbre* dcn^uilacc p-0**-I. Sail JU \V»er Cam. if: 1^.111. t«61.

19 tUea, Sic9m« ;.. Horaa. G- U-. Cox. L. M..*ad Carr. £- L ^<H1 profilf modiAcluoa W todL&iw&IXIAC md d«ep picwiac. Tmuu(iu>i oi cl>* AiA£lB:t6> T7I-779. I9W.» MiddltiBO, H. E. Soil u * phwl *'»*»». II-

M®diivi&i tAc pti?.«=»l ffropCTtit* »t wl. '* SoU ?BT*-nai Caadiuaal and Plant GfOTfl, £4. SyTM T. Sly.AculcniK Prctt. IM.. .'•'cw Tork. N.V. p. l4-*t. l91»-

ai Mtllef. i-L ?.. HucehitBii. C. 9- Dmiil-m. '?- K-.and Hudciian. 9.. R- Ornoate ui»aue»uo«u aa thenonhcm .Mluoun prairn. ilo. A^r. EJP. Su. Bull.

"ss,%'^>aJ^."P. .\I., ind Staicit. H. V- Sua«oiltilllS* u in lid ia ihe recbtsaneitt at th* Wll ul IQeCiM. Ctind iciti >a Amoaa. |. of Soil *'*W Cd".Iftd" 4: =3-30, ig;;.

31 MOIK.', J. G and Cidiuiina. A. ?. Sail Bneinmtud liUale lor eorn. 111. ACT- ^P. s"- Bu11- 1!11: 3-3'

3* Mmxh. I. T.. *ad Slc«<n. W. H. Griia wr-ehwB irricicion.--iier auoipEmcnc 1)0 fLiehneld ladPuUmia Mill. TtimaeuBtti w M ASAE; 9:13) 36»-i;i.3-3 tQ66

33 PttMk. W. H.. Jr.. Slo»a<. L. W., *fld Phillip*,S A, Reipaale oi eotlofl *ttd tBro IB detp pbceB»entat (ertilirer ind Otfl> tiltate- Soil fci. Soe. Acoct. P/BC-

'3I<^2fllt".' •»" ., >ad Edsunitcr. T. W. Appro»hwID iaU co«paeiiBB rforch. T"iuaaiB(ii a( me ASA£4;(s) y&-s<i. 1961- . ,

3- fiJIOCT. w. A-> Gtt**M. P. H" ^OO*"- 0- ——loflo. T. N-, md ffiiliimnitt. B. F- E3ecti at dtcpt)fc*kn»e umiirt; incftaied T"1^ " oBtaiflrt u> drylean. Miuiiuppi F»ra, Xa. i7i i. I. 199J-' l* AantT. w- A.. Sa»t»oa. I. 1-. lad OiU. W. R.SludT a( Kill eoBiB»ction oa Miuiui pi n»o delta Kill*.V[ Cantf. Ini. Sail Sci. 9^90- ?: f^-W, '»*-^ ILJunuu«B. W. W.. Lc»-», G- C.. aM ?wbfft.

M, A, laprovmtnc of iftc C&iieoti-Softt (*olo1i*ed-Solueix) llicfc ipot *oil* ia iiiuifawttloa Idiba. USOA.ARS 49-91, 19 P9. "A- -

}0 Rabcn>oa. W. K.. Fukdi. !. C. A.. Hittion. C. E-.ThOBpiw. L. G., Lipttoroo. R. W.. itid Landy. V . H.Rciulu tioca iuai«iiia( ind dcca ferutitaitOB ot earafor s ?em. Snil S<i. Soe. ABirf- ProC- 11: no-34fi, t9I7.

11 Hopwrnti. A, S., ind Kifktum. Don. MaiKUf.Brcttwc. iad fonwuoB of «-»icr-t"ble MU aey-^tt*. Soil Sci. Soe, A(a«f. Pfos. 16; tn-St*. iflfa.I» ELuuell. E- W. la>». B«tf- Soil Sci. (Han>endca.

EncLiod). Ttcli. Cflmniif. J-: '•'<>• l»<&•3] Huu«U & WJlicr. Soil fOfidiiioRi ind pH"t

raih. flib editiDft. 1<AB Wile? k Son> Ltd« y*wyork. N-.y. diS B- i?<*- ,, . ,,.y S*»w*n. K. L.. Luad, A. P. ml Sl«nM, L. •a .

De«P tillaic IB ton (11. 1 oa e«repu(cd will 'a itotCMIU irn of LouiMBi. USDA.AR5 41-^1. i0t.

1; toith, D. D. Sutnoil caadiiiaamc oa "TP*11*for «a<«r conicn-luaa. Apwiliuni Easmwrifll 121 (i)

*~3A Smith, 0. D.. Wwtn*(l. C. M^ and Whin, D. M.Iwildiac J Mil dcepa. Acrxuliuni £acineerinr ilid)»<7-i<l. 31$. AuptK 1»47-

l? Smith. K. S. Eipcnaiw* »ith **.a*<Hl)BC. d-o(iUJCc. iaa iui(HOtl d)ra*B)iuaC. W- ACT- £xp- 'u-

"ll Sptia, IiiBti W- »"d McCuflc. D. L. S<M>«b'<>Barw in lUfoiiiae. Arron. 1- JB: lOJ-in. W*-

30 Voli., N. ). Praaleai* wonccted wilh wowl placc-01011 af ItftilHtn. PMC. aird Anatwl Mwiat a< theNatiaoal |oiai Oi*»mt«« "• Ecfiiliif AppticauM.

'Wflodruy'C. M^ «iid Smith. 0. S,' Sabwil .h»t.tctWt »»d nteail limmt tw "W prtdiet'wt " cl'TP1'1—b. Sail Sd. &K. ABM». yrBe. 11; 339^43. W-

52

SOIL INVERSIONPLAN VIEW

DIRECTION OF MOVEMENT

CUTTER WHEEL

1. SOIL CONFIGURATION PRIOR TO INVERSION.

LOW LEVEL CONTAMINATEDSURFACE SOIL

GROUND SURFACE

•!.•;i^•••.~\~\.'\:: '•:.. \\.\ \.\\'t^~\\:\ \^\\

.... \W. \\ ^UNCONTAM"^El' T501^,^ ^A^V;..'^^^"''.'• • • • . \ \^\ \' • - v\ ^ - ' • " ' : . ••••'-; "v.';. •^•;\ Vv^tV

2. MAIN BOTTOM PLOW ROLLS SOIL TO CREATE A FURROW.

3. SOIL CONFIGURATION AFTER PASS OF MAIN BOTTOM PLOW.

4. CUTTER WHEEL SLICES THROUGH SURFACE VEGETATION.

5. SKIMMER PLOW REMOVES TOP LAYER AND DISCHARGESMATERIAL TO ADJACENT FURROW.

6. SOIL CONFIGURATION AFTER PASS OF SKIMMER PLOW.

7. NEXT MAIN BOTTOM PLOW FOLLOWS SKIMMER PLOW ANDROLLS SUBSOIL OVER SURFACE SOIL.

8. SOIL CONFIGURATION AFTER PASS OF MAIN BOTTOM PLOW.

9. SOIL CONFIGURATION FOLLOWING INVERSION AND RECOMPACTION.