Miller, James Ii. 1981. A comparison of cation sampling in forest soils by tension and tension-free

lysimeters. In: Barnett, J. P. ed. Proceedings, First Biennial Southern Silvicultural Research

Conference, 1980 November 6-7. Atlanta, GA. Gen. Tech. Rep. SO-34. New Orleans, LA: USDA Forest

Service: 317-322.

A COMPARISON OS? CATION SAME'LING IN FOREST SOILS

BY TENSION AND TENSION-FREE LYSINETER&

James H . Millerl!

Abstract .--Field tests conducted in two soils with ceramic

cup, ceramic plate, and tension-free lysimeters showed no concentration differences in collected cations (Ca, Mg, K, Na)

between cups and plates, except for the hydrogen ion. Mean pH

was 0.6 lower in cup collected samples for a sandy loam profile.

Tension-free lysimeters of the design tested had persistent

contamination from a glasswool component and yielded samples at

a 60 cm depth from a clay loam profile and not from a loamy

sand soil. Laboratory trails showed a marked response delay

with plate lysimeters when sampling changing cation concentrations.

INTRODUCTION

Tension and tension-free lysimeters are being

used more often to monitor natural processes in

soil profiles and nutrient-loss imppcts after

cultural treatments. These devices permit solution sampling within and beneath undisturbed soil

profiles. This cannot be done yet by other means.

Tension lysimeters with porous ceramic cups have

been used to monitor environmental contaminants

(Parizek and Lane 1970, Nutter et al. 1978, Neary

et al. 1979) and nutrient leaching processes

(Vitousek et al. 1979, &Co11 1978, Gosz and Dyck

1979). Tension plate techniques developed by Cole

(1968) have clarified leaching mechanisms (MeColl

and Cole 1968) and nutrient losses following

forest practices (Gessel and Cole 1965, Grier and

Cole 1971). Jordon (1968) refined techniques

using tension-free lysimeters and employed these

to investigate nutrient transfers in tropical

forest ecosystems (Kline and Jordon 1968; Stark

and Jordon 1978). The Investigative potential of

such sampling devices is great, but the validity

of cation sampling by the different lysimeters

has not been fully explored.

The objective of this study was to compare

tension-cup, tension-plate, and tension-free

L/Paper presented at Southern Silvicultural

Research Conference, Atlanta, Georgia,

Novimhp 6-7, 1980.

-The author is a Research Forester with the

Southern Forest Experiment Station, USDA-Forest

Service, at the George W. Andrews Forestry

Sciences Laboratory in Auburn, Alabama.

lysimeters for quantifying nutrient losses from

forest lands after vegetation management treatments. Each device was tested in the laboratory

for response variation while sampling known

concentrations of cations. 4. field study tested

differences iu concentrations from devices placed

in isolated profiles with vegetation uptake

eliminated. Sampling bias with the ceramic cup

has already been shown for phosphate (Hansen and

Rarris 1975) and ammonium (Wagner 1962) which

were not studied further here.

MATERIALS AND MRTRODS

Ceramic cup and plate samplers used In thie

investigation are the commercial models manufaetured by Soil Moisture Rquipnieat Corp., Santa

Barbara, California./ The ceramic cup has a

2-bar bubbling pressure (or air entry value) with

an outside diameter of 49.5 mm, an exposed length

of 61 mm and ceramic thickness of 2 to 3 mm.

Specified.lengths of polyvinyl chloride (PVC)

pipe are cemented to the cup permitting greater

sampling depth and differing ratios of sample

volume to vacuum-reservoir. The 60 cm length of

PVC was tested here.

Plates are constructed of 0.5 bar ceramic

with variable diameters of 265 to 275 mm and a

thickness of 9 mm. A rubber disk with outport

attached to one side of the ceramic plate by

peripheral wire and cement with a screen

is

/Use of trade, firm or corporation names in

this publication is for the information and convenience of the reader. Such use is not an official

endorsement or approval by the U.S. Department of

Agriculture of any product or service to the

exclusion of others that may be suitable.

- 317 -
interlayer to permit water flow. Connection

between outport and a combination vacuum-sample

bottle is by vacuum hose and copper tubing.

Solutions collected with the plate must travel

through 3 to 4 times more ceramic material than

with the cup samplers, which have absorptive

properties.

Ceramic cups are made from a non-vitreous

porcelain which contains more or less equal proportions of kaolin, alumina (A120 ),

3 3

ball clay,

and other feldspathic materials.- The Al203 is

essentially pure and 30% of the kaolin and ball

clay are composed of this compound. Plates are

90% Al2O3, 6% kaolin and 4% ball clay. Kaolin

and ball clay in both lysimeters are over 50% by

weight SiO2 and have potential contaminants of

iron, calcium (Ca), magnesium (Mg), potassium

(K), sodium OW, and titanium in amounts less

than 1.5% each. Initial treatments of ceramic

samplers are used to reduce the leachable or

exchangeable cation contaminants (Gover and

Lamborn 1970, Wolff 1967). I washed all ceramic

samplers first with distilled water (DW) to remove

ceramic dust, then 300 ml of 1N HCl was drawn

through each, and finally, 1.2 liters of DW was

tensioned through each lysimeter. This volume

of DW was required before cation contamination

reached zero.

Tension-free lysimeters were constructed of

a 285 mm diameter funnel made by cutting off the

upper portion of a PO-liter plastic carboy at the

shoulder and inverting it on the bottom as a base.

A drilled hole in the carboy cap with an epoxied

connector served as an outport permitting tubing

to be attached to a sample bottle. Glasswool

filled the funnel and facilitated water flow

(Stark and Jmxloo 197g). Xepcated acid treatment

(2% Xl) and DW washes of laboratory-grade glasswool was unsuccessful in eliminating cation

contaminants. Average contaminant concentrations

in a 300 ml DW wash were Ca 0.9 mg/l, Ng 0.5,

K 0.2, and Na 2.0. Polyester fiber was also

substituted for the glasswool and yielded

similar contaminant concentrations. Due to this

problem, tension-free data will be presented

separately in the laboratory and field results.

In the laboratory trails, 300 ml aliquots of

a premixed solution of four cations were

sequentially drawn (0.4 bar tension) or passed

(tension-free) through the samplers and analyzed

using standard atomic absorption techniques. The

solution concentrations were Ca 0.85 mgfl, Mg 0.45,

K 0.23 and Na 3.10. Finally a 300 ml DW was

then drawn or passed through each and analyzed.

This procedure was repeated on three devices of

each type to test the responsive capabilities of

the samplers.

Z'Personal communications with Mr. P. E.

Skaling. Soil Hoisture Equipment Corp.

In field comparisons, three lysimeters of

each type were installed In a randomized completeblock design with three blocks in a loamy sand and

three in a clay loam soil. The two installations

are about 150 m apart and both are located in

natural clearings under 53-year-old plantations

of loblolly (Pinus taeda) and shortleaf pine

(c. echinata),- An access trench 1.5 m wide, 3 m

long, and 1.5 m deep in the clearing centers was

provided with a wooden shelter, with open sides

for profile access. A sloping roof drained away

from the Installations. Tension plates and

tension-free samplere were Installed laterally

in the trench walls. Cups were installed by

auger holes using a 200-mesh silica sand interfacing material at the bottom of the hole, Lysimeters were emplaced at a 60 cm depth on the loamy

sand site and at 45 cm on the clay loam site,

below lateral rooting of the pines and equidistant from the access trench. A 30 cm wide

and 1.5 m deep root exclusion trench surrounded

the installation at a distance of 1.5 m from the

access trench. Polythene sheeting was backfilled

to the inside walls of the trenches to prevent

root encroachment. All vegetation within each

installation was carefully cleared and kept. clear

for the duration of the study. T!lus plant uptake

was eliminated as a variable.

A vacuum of 0.3 bars was maintained on

tension devices over a collection period only

during times of adequate soil moisture. At low

soil moisture, cups maintained tensions more

consistently than the plates, which required

reevacuation periodically. Although cups maiotained vacuum at lower soil moisture than plates,

very little sample was collected during these

periods. Tension-free lysimeters collected

samples only after intense storm events.

Soil solution was collected 3 days after

storm events or biweekly during extended rainy'

periods. Analyses included specific conductance

Ca, Fig, K, Na, and pH. Specific conductance was

measured with a conductivity meter with samples

placed in a 25°C bath. Cations were determined

by atomic absorption spectrophotometry. The pH

was measured potentimetrically.

RESULTS AND DISCUSSION

It is commonly thought that ceramic samplers

reach equilibrium with the soil solution after

installation. Thus, the process of adsorption,

diffusion, and screening which biased phosphate

sampling (Hansen and Harris 1975) merely delay

the actual changes in soil solution concentrations

when monitoring a profile. Tinis detection delay

can readily be seen in the laboratory results

with the plate samplers (Fig. 1). With Ca, 1.5

liters of a 0.85 mg/l solution were drawn through

the plates before the premixed sample concentrations were approached. Other cations reached

equilibrium within 600 ml.

- 318 -
SEQUENTIAL VOLUME (LITERS)

Fl~urc? 1. Wan concrntrntfonn nf sqtmplrs

drown from u known ~olutlon (ronrentrntlons

indlcatod by horlmnlnl dnnhtd llncrs) and

the nwpl6? Htandurd dcvfutionn (vorttcnl

1 IflW). The dotted Ilnc?w lndlcntc? u ftnal

dfstfl I(*d water wunh (0.3 lltcrri) und the

suhricquc*n L wash con~n 1 ral 1. on.

- 319 -
Concentrations higher than the test solutions were found in samples for Mg and K. This

phenomenon and the variable concentrations in the

DW, evident by the large standard deviations,

must result from desorption of bound ions. The

large standard deviation also shows this desorption response to vary greatly from plate to

plate. The plate with the slowest concentration

response had the slowest average flow rate.

No percolating water reached the tension-free

sample containers at the sandy site.

Using sample concentrations from the 12 storms

as observations, a two-factor analysis of variance

tested differences (1%) between soils and between

cup and plate lysimeters. An additional analysis

of variance and Duncan's multilple range tests were

performed on the three lysimeter types using the

tension-free collections in the clay loam soil.

Table 1. Mean cation concentration in solution washes of known

concentration and a final wash of DW through tensionfree lysimeters.

Solution Ca Mg K Na

Premixed

Concentration 0.85 0.45 0.23 3.1

1 7.52 1.c5 .72 15.8

2 3.44 1.83 .G7 15.1

3 2.21 1.09 .38 7.4

4 1.60 .80 .26 4.8

5 1.42 .71 .23 4.2

DW wash 2.82 1.32 .73 8.1

Cup lysimeters showed a more rapid response

to drastic concentration changes. Although deviatione from teat resolution concentrations of + 1%

are apparent, the accuracy of analysis approximates 2 1% ,at these concentrations. Potassium

deaorption or leaching in the DW wash of cups

points to a source of sampling bias with decreasing concentrations.

Persistent contamination was in the solution

washes and DW washes passed through the tensionfree devices (Table 1). Sodium was most concentrated. These devices had been previously washed

with over 20 liters of DW in an attempt to eliminate the glasswool contaminants. The premixed

concentration of K was finally reached after 1.5

liters, but absorbed or bound ions of all cations

were leached in the DW wash.

Twelve storm periods were sampled at the field

sites between July and November 1979. The longest

storm was two weeks and the shortest 3 days. All

devices had been previously installed and samples

collected for at least 2 months before the July

sampling commenced. This waiting period allowed

for ample equilibration time. If equilibration

of the ceramics does take place, then solution

concentrations collected from both devices in the

uniformized soil profiles should be the same.

Collection from tension-free lysimeters were only

made at the clay site during the sampling period.

Mean values for the 12 collections pre&nted

in Table 2, show no significant differences

(IX level) between cups and plates for specific

conductance, snd Ca, Mg, K, and Na concentrations.

The two samplers in loamy sand and clay loam soils,

showed that total ionic concentrations were less

in the clay soils as evident by significantly

lower mean specific conductance. Significantly

lower Ca concentrations appear responsible for the

lower specific conductance in the clay profile.

Two of the plate lysimeters in the sandy profile

consistently gave higher concentrations for Mg

and Na and corresponingly lower values for Ca and

K . This appears to be endemic profile variation

and was not found to be significantly different.

Thus, monitoring of the most concentrated cations

does not differ between lysimeter types at the

concentration levels tested with an in vivo - -

situation.

The only significant difference was pH.

Plate lysimeters consistently collected samples

that were .2 to ,6 pH units higher. Due to the

logarithmic nature of the pH scale, hydrogen ion

activity was 1.5 to 4 times greater with the cup

samplers. It would appear that selective

absorption or screening or hydrogen ions was

occurring with the plates and an equilibrium

between the soil solution, ceramic plate, and

sample solution had not been reached.

- 320 -
Sample contamination is evident in the mean

concentrations from tension-free devices presented

in Table 2. Magnesium concentrations were the

only cations sampled that were not different

from cup and plate samples. The inability to

sample below rooting-zone depths in loamy sand

soils plus the,contaminatlon problems with the

glasswool polyester fiber will preclude the use of

this sampler type in future forest nutrient-loss

research.

Gessel, S. P., and D. W. Cole

1965. Influence of removal of forest cover on

movement of water and associated elements

through soil. J. Am. Water Works Assoc.

57:1301-1310.

GOSZ, J. R., and W. J. Dyck

1979. Monitoring the effects of clearfelling

on soil. nutrient loss. Uhat'e New in Forest

Research No. 70. For. Res. Inst., Rotorua,

New Zealand, 4 p.

Table 2. Specific conductance, pH, and cation concentrations

collected from two soils using three lysimeter types.

Soil Lysimeter

Spec.

Cond. Ca Hg K Na PR

Loamy Sand Cup

Plate

pnhoslcm --_I--- ---mg/l----

1022 5.8a 2.la 0.9a 1.6a 5.8a

117a 4.7.a 3.4a .4a 1.9a 6.4b

-------_-__-_________--____

Clay Loai Clip 60b 1.m 2.0a .9a 1.53 5.9a

Tens~~~~~re~'

d5b l.Ob 1.9a l-la 1.4a 6.lb

2ooc 4.lc 2.7a 2.3b 24.3b 7.sc

i/Weans in a column followed by the same letter are not significant1

5

different at the 1% level.

Tension-free data compared to the cup and plate collections in

the clay loam soils only.

CONCLUSIONS Crier. C. C., and D. U. Cole

The cup lysimeter is the most reliable device

for sampling cations, although a bias in phosphate

and ammonium sampling has been demonstrated for

these samplers (Hansen and Harris 1975; Wagner

1962). If the type of plate lysimeter studied in

this investigation is used, then initial samples

may not reflect actual soil solution concentrations

due to plate adsorption. Plate-collected samples

will not reflect accurate concentrations when

drastic seasonal changes in soil solution concentrations occur. Cups are easier to install but

plates have the distinct advantage of quantifying

nutrient loss on an area basis due to the flat

shape. The use of both cups and plates is needed

to accurately sample cations and given an arealloss estimate.

197i. Influence of slash burning on ion transport in a forest soil. NW Sci. 45:100-106.

Grover, B. L., and R. E. Lamborn

1970. Preparation of porous ceramic CUPS to be

used for extraction of soil water having low

solute concentrations. soil Scl. sot. Am.

Proc. 34~706-708.

Hansen, E. A., and A. R. Harris

1975. Validity of soil-water samples collected

with porous ceramic cups. Soil sci.. sot. Am.

Proc. 39:528-536.

Jordon, D. F.

1968. A simple, tension-free lysimeter. Soil

sci. 105:81-86.

Kline, J. R., and C. F. Jordon

1968. Tritium mwement in soil of tropical rain

forest. Science 160:550-551.

HcColl, J. G.

1978. Ionic composition of forest solutions

and effects of clearcutting. Soil. sci. sot.

Am. J. 42:358-363.

LITERATURE CITED

Cole, D. W.

1968. A system for measuring conductivity and

rate of flow in a forest soil. Water Resources

Research 4~1127-1136.

McCall, J. G., and D. W. Cole

1968. A mechanism of cation transport in a

forest soil. NW Sci. 42:134-140.

- 321 -
Neary, D. G., J. E. Douglass, and W. pox

1979. Low piclorsm concentrations In streamflow resulting from forest application of

Tordon 1OK. Proc. South. Weed Sci. Sot.

32:182-197.

Nutter, W., R. C. Schultz, and G. H. Brister

1978. Land treatment of municipal wastewater

on steep forest slopes In the humid southeastern United States. In: Int'l Symp. on

State of Knowledge in las Treatment of

Wastewater (Hanover, N. H.) p. 265-274.

Parlzek, Richard R., and Burke E. Lane

1970. Soil water sampling using pan and deep

pressure vacuum lysimeters. J. Hvdrology

ll:l-21.

Stark, N. M., and C. P. Jordon

1978. Nutrient retention by the root mat of an

Amazonian rain forest. Ecology 59:434-437.

Vitousek, P. M., J. R. Gosz, C. C. Grier, J. M.

Melillo, W. A. Reiners, and R. L. Todd.

1979. Nitrate losses from disturbed ecosystems.

Science 204:469-474.

Wagner, George H.

1962. Use of porous ceramic cups to sample soil

water within the profile. Soil Sci. 94:379-386.

Wolff, R. G.

1967. Weathering wood stock granite, near

Baltimore, Maryland. hm. 3. Sci. 265:106-117.

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