DIVISION S-6—SOIL AND WATERMANAGEMENT AND CONSERVATION

Super Slurper Effects on Crust Strength, Water Retention, and Water Infiltration of Soils1

PARICHEHR HEMYARI AND D. L. NoFziGER2

ABSTRACTThe effect of hydrolyzed starch polyacrylonitrile graft co-

polymer, commonly called "super slurper," at rates of 0.0, 0.025,0.05, 0.1, 0.2, and 0.4% by weight on the crust strength, waterretention, and infiltration of selected soils was determined. Thestrengths of simulated crusts were measured for all the treat-ments. Infiltration rates were measured in the laboratory foruntreated soils and soils treated with 0.4% super slurper. Waterretentions were measured for all treatments by use of pressureplate and pressure membrane apparati.

Super slurper decreased crust strength and infiltration andincreased water retention. The crust strengths of a sandy loam,a loamy sand, and a clay loam soil were reduced 84, 75, and54%, respectively, by the addition of 0.4% super slurper. In-filtration rates were also reduced. Sorptivities for a sandy loam,clay loam, and loamy sand soil, treated with 0.4% super slurper,were reduced 38, 18, and 11%, respectively. Loamy sand andsandy loam soils treated with super slurper retained more wa-ter than the untreated soils. Super slurper had little effect onwater retention in the clay loam soil.

Additional Index Words: soil conditioner, soil crust, mo-dulus of rupture, H-SPAN.

Hemyari, P., and D. L. Nofziger. 1981. Super slurper effectson crust strength, water retention, and water infiltration ofsoils. Soil Sci. Soc. Am. J. 45:799-801.

IT is DIFFICULT to find a soil that is in perfect physicalcondition for all possible uses. In sandy soils, low

water holding capacities and high infiltration ratescan be major problems in establishing a successfulirrigation project. In clayey soils, crust formationssometimes cause problems for seedling emergence. In-terest exists in the use of soil conditions to overcomethese problems.

"Super slurper," chemically known as hydrolyzedstarch polyacrylonitrile graft copolymer, was devel-oped in the Northern Regional Laboratory of the Ag-ricultural Research Service, USD A, Peoria, 111. It hasbeen used for research since late 1975. It is insolublein water and, when wet, produces sheets of gel whichare similar to dry films but are approximately 30times larger in surface area (Weaver, et al., 1974).

A small amount of research has been done with su-per slurper as a soil conditioner. Super slurper has in-creased the water-holding capacity of sand. Shrader

1 Contribution from the Dep. of Agron., Oklahoma Agr. Exp.Stn., as part of project S-1718. Journal Manuscript no. 3810.Received 15 Aug. 1980. Approved 3 Mar. 1981.

1 Graduate Research Assistant and Associate Professor, respec-tively. Dep. of Agron., Oklahoma State Univ., Stillwater, OK74078.

800 SOIL SCI. SOC. AM. J., VOL. 45, 1981

Table 1—Modulus of rupture for different treatments of Tellersandy loam, Tillman-Hollister clay loam, and

Cobb loam sand.

Modulus of rupture (bars)

Treatments(% super simper)

0.00.0250.050.10.20.4

Tellersandy loam

0.875 a*0.817 a0.461 b0.343 c0.191 d0.142 d

Tillman-Hollisterclay loam

0.776 a0.614 b0.601 b0.548 b0.495 b0.341 c

Cobbloamy sand

0.441 a0.389 b0.374 b0.280 c0.176 d0.112 e

* Values followed by the same letter for each soil are not significantly dif-ferent at 0.05 level according to Duncan's multiple range test.

found that oats died 14 days after seeding in untreatedsand, but lived for 25 days in sand treated with superslurper (Kaniuka, 1975). Miller (1979) found thatsuper slurper increased swelling in soil and decreasedinfiltration. The purpose of this study was to inves-tigate the effect of super slurper on soil crust strength,soil water retention, and infiltration rate for three soiltextures.

MATERIALS AND METHODSMaterials studied were taken from the topsoil of Teller sandy

loam (a mixed, thermic Udic Argiustolls), Tillman-Hollister clayloam (a fine, mixed, thermic Typic Paleustolls and a fine,mixed, thermic Pachic Paleustolls), and Cobb loamy sand (afine-loamy, mixed, thermic Udic Haplustalfs). Teller sandyloam contains 12% clay, 24% silt, and 64% sand. Tillman-Hol-lister clay loam contains 33% clay, 42% silt, and 25% sand.Cobb loamy sand contains 8% clay, 6% silt, and 86% sand.Air-dried soil was ground to pass through a 2-mm sieve, mixed,and treated with six different rates of super slurper (0.0, 0.025,0.05, 0.1, 0.2, and 0.4% by weight) by mixing in a rotating, cy-lindrical mixer.

The modulus of rupture of simulated crusts or briquets wasmeasured for each soil treatment using the technique of Reeve(1965). The force required to break each briquet was measuredon 10 briquets for each treatment. The water content of eachbriquet after breaking was determined on a dry mass basis.The bulk density of each briquet was determined by dividingthe mass of each dry briquet by the volume of the mold.

Pressure-membrane and pressure-plate apparati were used tomeasure the water content of soil samples at six suctions (0.2,0.5, 1.0, 4.9, 9.8, and 13.8 bars) using the technique of Richards(1965).

Water infiltration measurements were made using soil col-umns 50-cm long and 3.1 cm in diam. The column consisted of25 plexiglas rings, each 2-cm high. A perforated plastic platecovered with glass wool supported the bottom of the soil col-umn. It was opened to the atmosphere at all times. Waterwas applied through a plexiglas applicator with a perforatedbottom (Swartzendruber, et al., 1968). The applicator was con-nected to a calibrated burette containing a Mariotte bubblingtube to maintain a constant head of 0.4 cm at the inlet. Eachplexiglas ring was filled with the same amount of soil andpacked with a rubber-stoppered rod to obtain uniformly packedcolumns. The average bulk density of the soil column was cal-culated from the measured volume of the column and themass of soil inside the column. The bulk density of eachring was also calculated by sectioning the column after the in-filtration experiment was completed.

At the beginning of the infiltration experiment, the columnof soil was attached to the water applicator. The elapsed timewas measured for each 5 cm3 of water that moved into thesoil from the burette. Measurements were terminated whenthe wetting front reached a depth of 40 cm. Infiltration mea-surements were made on three soil columns for each untreatedsoil and each soil with 0.4% super slurper.

RESULTS AND DISCUSSIONThe modulus of rupture decreased significantly for

each soil as the rate of super slurper increased (Table

0.14

0.12

5> 0.10I-

K 0.08O£ 0.06LU

5 0.04

0.02

0.00

ACHECKD 0.2% SUPER SLURPERO0.4% SUPER SLURPER

4 6 8 10SUCTION (bar)

12 14

Fig. 1—Effect of super slurper on water retention in Cobb loamysand.

1). Duncan's multiple range test shows that the valuesfor the 0.05% treatment were significantly less thanthose for the untreated soils. The clay loam and loamysand soils showed decreases for the 0.025% treatment.The moduli of rupture for the sandy loam, loamy sand,and clay loam soils were reduced 84, 85, and 54%,respectively, by the addition of 0.4% super slurper.

Treatment differences in both bulk density and wa-ter content were not significant at the 0.05 level forany soil. The bulk density means among treatmentsfor a particular soil differed by < 0.025 g/cm3. Watercontent means among treatments for a particular soildiffered by < 0.003 g/g. Neither the bulk density northe water content changed monotonically as the rateof super slurper increased. This indicates that the re-duction in modulus of rupture was not due to eithera decrease in bulk density or to an increase in watercontent.

In the past, vinyl acetate-maleic acid copolymer(VAMA) and hydrolyzed polyacrylonitrile (HPAN)have been used for prevention of soil crusting. Addi-tion of 0.1% (by weight) VAMA or HPAN to San Luissandy loam (a mixed, frigid Aquic Natrargids) reducedmodulus of rupture from 0.53 to 0.0 bars; and additionof 0.1% (by weight) HPAN to Billings clay loam (amixed, mesic Typic Torrifluvents) reduced modulus ofrupture from 3.9 to 2.7 bars (Allison and Moore, 1956).Super slurper, like these two soil conditioners, showeda tendency to decrease crust strength.

Duncan's multiple range test was used to comparethe water contents of six different soil treatments ateach of six suctions for each soil. Super slurper ap-plied to Tillman-Hollister clay loam increased waterretention significantly (at the 0.05 level) only at arate of 0.4%. The difference in water content betweenthis treatment and the untreated soil was < 0.015 g/gat each suction. Super slurper at rates of 0.025, 0.5,and 0.1% did not increase water retention in Tellersandy loam or in Cobb loamy sand. Water retained ateach suction was significantly greater for the 0.2 and0.4% treatments than for the untreated soil. Watercontents for the 0.4%greater than those forsuction.

The water content of Cobb loamy sand is shown as a

treatment were significantlythe 0.2% treatment at each

HEMYARI & NOFZIGER: SUPER SLURPER EFFECTS ON SOIL 801

Table 2—Parameters S and A of infiltration Eq. / = Sf"2 + At

Check 0.4% super slurper

Soil

Teller sandy loam

Tillman-Hollister clay loam

Cobb loamy sand

Replication

123123123

S(cm/min"2)

0.9861.0300.9900.6150.6450.6313.1733.2743.125

A(cm/min)

0.0041-0.0002

0.00380.00120.00130.00140.04070.03850.0163

Correlationindex

0.9990.9990.9990.9990.9990.9990.9990.9980.999

S(cm/min"1)

0.5870.6370.6350.5130.5110.5312.7272.9092.843

A(cm/min)

0.00270.00070.00130.00190.00250.00200.0365

-0.01640.0171

Correlationindex

0.9990.9990.9990.9990.9990.9990.9990.9970.999

function of suction in Fig. 1. Super slurper at 0.2 and0.4% rates increased the water content at a suctionof 0.2 bars by 0.03 and 0.10 g/g, respectively. At highsuctions, the increases were only 0.01 and 0.04 g/g.The 0.2 and 0.4% treatments for Teller sandy loam in-creased water contents by 0.01 and 0.05 g/g, respec-tively, at a suction of 0.2 bars and by < 0.01 g/g atsuctions > 4 bars. In both soils, the increase in watercontent was greater at lower suctions than at highersuctions. This suggests that super slurper may in-crease the ability of these soils to store water for plantuse.

Super slurper appears to be somewhat effective inincreasing water retention like some other condition-ers. Allison (1956) studied the effect of HPAN andVAMA on water retention of Pachappa loam (a mixed,thermic Mollic Haploxeralfs), Billings clay loam, Pa-chappa loam (alkali), and Umapine loam (a mixed,mesic Aquic Torriorthents). HPAN and VAMA wereused at the rate of 0.1% by weight. Water retentionwas measured at 0.1, 0.33, 1, and 15 atm suctions. Itwas observed that water retention was increased in thetreated alkali Pachappa soil at 0.33, 1, and 15 atmby both HPAN and VAMA, but water retention wasnot increased in the nonalkali Pachappa soil. Waterretention increased for treated Umapine soil only at0.1 and 15 atm and for treated Billings soil, at 0.33 and15 atm. Peters et al. (1953) investigated the effectof calcium carboxylate polymer (CRD-186) and so-dium salt of hydrolized polyacrylonitrile (CRD-189)on water content of soil. Addition of CRD-186 andCRD-189 at a rate of 0.4% (by weight) increased thewater content of a coarse-textured soil very little.

Super slurper was found to decrease the rate of wa-ter entry into all three soils. At small-to-moderatetimes, Philip (1957) found that the cumulative infil-tration / could be represented by the relationship

7 = St» + At,where t is time, S is the sorptivity, and A is a parameterwhich depends upon the ability of the soil to transmitwater. Values of S and A were obtained for each soiland each treatment by fitting Philip's equation to theexperimental data by the least-squares method. Thesevalues, along with values of the correlation index, areshown in Table 2. In each case, Philip's equation fitsthe data very well. Sorptivities of soils treated withsuper slurper were 38, 18, and 11% less than the

sorptivities of the untreated sandy loam, clay loam,and loamy sand, respectively. Variations within aspecific treatment were much less than variations be-tween treatments. The average bulk density and thevariation in bulk density were nearly the same fortreated and untreated soils. The average bulk densi-ties for the treatments for a particular soil differed by< 0.015 g/cm3. This suggests that the reduction ininfiltration rate and sorptivity was not due to in-creased compaction of the treated soil.

These infiltration results are in general agreementwith those of Miller (1979) who also found that superslurper decreased infiltration. This is in contrast tothe results for VAMA and HPAN which increased theinfiltration rate of Pachappa loam 5 to 10 times (Alli-son, 1956).

These results indicate that super slurper has poten-tial for modifying soil properties. Additional researchis needed to determine the longevity of the treatmenteffects under field conditions.