PILOT EVAPOTRANSPIRATION STUDY:

Lysimeter Design

By

Paul C. Ekern

Technical Report .No. 130l-

August 1967

Project Completion Report

fur

PILOT EVAPOTRANSPIRATION STUDY

OWRR Project No. A-010-HI, Grant Agreement No. 14-01-0001-905

Principal Investigators: Paul C. Ekern and Jen-Hu Chang

Project Period: July 1, 1966 to June 30, 1967

The work upon which t his pUbl i cat i on is based was supported in partby funds provided by the United St at es Department of the Interioras author i zed under the Water Resources Act of 1964, Public Law 88-379 .

ABSTRACT.

The mari ne sub-tropic climate of Hawaii is particularly suited. to t he

use of semi-contained hydraulic l ysimeters. Field experiences in the use

of these l ys i met ers reveal a number of problems among which wer e f actors

r elat ed t o t he unusual tropical crops of pineapple and sugarcane. This

project inve s t igated the modification of the lysimeters to mi nimize some

of t hese probl ems .

Modular plant ing schemes in 1.52 meter rows or beds and tillage

depths of 0.3 to 0.6 meters dictated minimallysimeter size. The great

height and lodging of the cane required a large lysimeter area t o help in

the def i nit i on of the effective transpiring area. Polyester resin fiber­

glas s reinfo rced tanks.• 3 x 3 x: 1.52 m deep with paper honeycomb strength­

ened bot t oms were designed to meet the need for a large and r elati vely

deep container of minimal weight. The prevalence of high r elati ve humidi ­

ties nece ssitat ed the use of engi neer i ng graph paper to reduce di s t ortion

of r ecording traces from shrinkage and swelling of the paper. Des pite the

l imited diurnal and annual temperature variations, careful i nsulation of

the expos ed portions of the manometer was necessary. The regular diurna l

changes i n wind velocity impose d fluctuations on t he open-end manometer

used for r ecording the pressure changes i n the hydraulic load cells that

were off set by venting near ground level. Nylon reinforced buty l rubber

i r r igati on hose with the ends clamped was used to form the bolsters fo r

the l oad ce l l s . A silicone rubber sealant was used to ensure water t i ght. .

f ittings with standard copper tubing connectors to the bolsters. Stabi-

lity against rolling was achieved by placing some of the bolsters at right

angles to the ot her s . Large tensiometers of perforated polyvi nyl pipe

covered with porous Porvic membrane were designed to induce suction at the

base of the soil column. The water release curves for the Lat osols sug­

gested a 0.1 bar suction for an approximation of field capacity.

iii

CONTENTS

FIGURES ' " v

INTRODUCTION: LYSIMETER DESIGN REQUIREMENTS 1

OBJECTIVES AND SCOPE 2

INSTRUMENTATION 2

Extant Lys imeter Des igns ; 2Principles of the Hawaiian Design 3Specifications of the Standardized Hawaiian Design forPineapp1e Lys imeters .........•.................................... 8

Problems in the Lysimeter Operation 9Modifications of the Original Design 14

SUMMARY 16

REFERENCES 17

APPENDIX ; " " 21

FIGURES

Figure

1 Diagram of Hydraulic Lysimeter 4

2 Hydraulic Lysimeter Record, Low Humic Latosol, 0.36m. Layer .. 6

3 Loading and Unloading Response of Lysimeter Number 3 7

4 Wind Effect Upon Hydraulic Lysimeters 13

5 Water Release Curve - Waimea Soil (Site 1,0-15 cm) 23

6 Water Release Curves - Waimea Soil (Site 1,7-15 cm) 24

7 Water Release Curves - Waimea Soil (Site 1,15-20 cm) 25

8 Water Release Curves - Waimea Soil (Site 1, 23-30 cm) 26

v

INTRODUCTION: LYSIMETER DESIGN REQUIREMENTS

Hydraulic lysimeters were designed originally for the measurement of

water use by pineapple in Hawaii. Stringent limitations are imposed on

field lysimeters by the peculiar nature of pineapple physiology and the

agronomic practices in Hawaii. The consumptive use of water reported for

pineapple plantings was 0.75 to 1.25 rom per day, an amount little more than

that of dew (Krauss, 1930; Leopold, 1952; Monteith, 1957; Stone, 1963 and

Ekern, 1965). This is in striking contrast to the evapotranspiration of

more conventional plants such as sugarcane and Bermudagrass since their

water use is ten-fold that of dew (Campbell, et a~. 1959; Ekern, 1966a

and Campbell, 1967) . Meaningful measure of water use by pineapple requires

an instrument not only of great sensitivity, but one which records the

diurnal pattern as well as the amount of such use.

The extreme height of the cane crop (4.3 m) and the lodging during

its 24-month cycle impose equally stringent requirements on the lysimeter

design. For use with sugarcane, large lysimeters are required to minimize

the problem of defining the effective lysimeter boundary. The mi ni mum di­

mensions of the lysimeter are determined by the 1.52 m spacing of pineapple

beds and sugarcane furrow. Fortunately, the shallow rooting zone of the

pineapple makes a soil depth of 0.3 m acceptable (Bowers, 1929; Gwynne,

1962). However, the rooting depth of the cane is normally much greater,

and depends in large part on the depth of tillage (Trouse and Humbert, 1961).

The Latosols (oxisols) in which pineapple and cane are normally grown

in Hawaii have extremely high infiltration rates, release small amounts

of readily available water, and have unique thermal properties, thus, add­

ing further criteria to the lysimeter design (Ekern, 1966) .

The climatic provinces where pineapple and sugarcane are grown in

the islands and the microclimates produced by such agronomic practices

as mulching with polyethylene arid irrigation make a large number of such

instruments necessary for use at different sites; hence, low cost per

l ysimeter is imperative.

The remarkable seasonal uniformity of the sub-tropic marine climate

with temperatures always above freezing makes the Hawaiian Islands ideally

suited for water-filled load cells (Blumenstock, 1961). However, the fre­

quency of intense r ai nf a l l requires provision for the disposal of large

amounts of percolate through the lysimeters (Schwartz, 1963).

2

Because of these unique qualifications, an inexpensive, extremely

sensitive, recording instrument was needed with a modular width of 1.52 m

and a depth ranging from 0.3 to 1.5 m.

OBJECTIVES AND SCOPE

It was proposed in this project to initiate an investigation of the

effect of water on crop yield and quality of sugarcane, pineapples, and

tropical truck crops, extending earlier research on the magnitude of con­

sumptive use in sugarcane and pineapple. Specifically in this pilot phase,

it was proposed to investigate necessary modifications of semi-contained

hydraulic lysimeters to make such lysimeters suitable for use with crops

in Hawaii, taking into account, for example, the great height of sugarcane

and the low level of transpiration in pineapple.

It was further proposed to review the currently available information

on the components of the hydrologic budget of suggested study sites since

the values reported for such meteorological variables as solar radiation,

wind velocity, and rainfall impose severe restrictions on the lysimeter

design. Among the variables rev iewed must also be the moisture storage

capacity of the Latosols and the effective rootipg depths of the crops

for these, too, are important determinants in the lysimeter design.*

INSTRUMENTATION

Extant Lysimeter Designs

The cost of extant continuously recording lysimeters presents a for­

midable barrier to their wide spread use in the field. Such major instal­

lations as the 6.1 m diameter lysimeter at Davis, California (Pruitt . and

Angus, 1960), the several lysimeters at Coshocton, Ohio, (Harrold and Drei­

belbis, 1945, 1967), the English installations (Morris, 1959), and their

counterparts in Australia (McIlroy and Sumner, 1961) were all elaborate

and expensive instruments based on mechanical scales.

Small mechanically weighted lysimeters are less expensive, but the

degree of sensitivity demanded (detection of changes of 0.02% of the total

*Comprehensive review of the extant literature on these subjects is inclu­ded in Climat e and agriculture: an ecological survey by Dr. Jen -Hu Chang,who is a project manager of this study. The book is in press.

3

mass) was difficult to obtain (England and Lesesne,1962).

The suggested use 6f electrical strain gages with a counterbalance

for increase sensitivity was limited by the expense of instrumentation

for continuous recording whether for the simple instruments at Tucson,

Arizona (Frost, 1962) or the elaborate installations at Tempe, 'Arizona ­

(Van Bave1 and Meyers, 1962) and in California (Libby and Nixon, 1963).

Floating 1ysimeters with buoyant air chambers are inexpensive, but

distort the root zones (King, et al.~ 1960 and Fulton and Findlay, 1966).

The use of zinc chloride solutions with specific gravities of 1.9 instead

of water eliminate the need for air chambers in these instruments (Mc­

Millan and Paul, 1961), but the solution's must be treated gingerly. The

modified floating instruments are still temperature sensitive (King, et

al. 1965). The underground moat in the lysimeter of Russian design is

a massive and costly installation (Popov, 1959). A Danish instrument

with a mechanical counterbalance of the major portion of the lysimeter

weight and a floating technique for measurement of the remnant weight re­

quires a precision beyond the intent of the 1ysimeters proposed for field

use (Aslyng, 1959).

Principles of the Hawaiian Design

The basic principles of the inexpensive instrument designed for

Hawaii have since been reported for instruments from Kenya (Forsgate,et

al.~ 1965 and Glover and F~rsgate, 1962), Canada (Holmes, 1963 and Natal,

Thompson and Boyce, 1967), Australia (Rose, et .al., 1966), the Netherlands

(Visser, 1965) and the United States (Hanks and Shawcroft, 1965; Middle­

ton, 1965; Tanner, 1967 and Tanner, et al., 1967). The weight of the

so i I-Ei.Lled lysimeter box rests on water-filled rubber tubes which act

as hydraulic load cells. The pressure generated by the weight on the

tubes was measured by a water-filled open-end manometer (Fig. 1), and

traced by a float-activated water stage recorder. The recorder was

first installed on this newly designed hydraulic lysimeter at the Pine­

apple Research Institute Experiment Station, Wahiawa, on August 20, 1958.

This initial instrument held soil in a square wooden box 25.4 ern deep

with a rigid yet permeable bottom through which excess percolate might

drain. The hydraulic cells were made from two water-filled automobile

inner tubes, and interconnected with rubber hose. A transparent riser

RECORDER

FIGURE I: DIAGRAM OF HYDRAULIC LYSIMETER (SCALE I CENTIMETER = 0 .3 METER).

.j::. •

5

from the tubes formed an open-end manometer. The two interconnected tubes

were laid flat on one side of the bottom of a 30.5-cm deep pit in the

coil. The walls on the pit were lined with: aluminum sheet to prevent col ­

lapse. There was a 2.54-cm clearance between the exterior of the lysi­

meter box and the outer guard frame holding back the soil at the edges

of the pit. A 1.22 m long piece of 10 cm x 10 cm angle iron was laid

along the extreme outer edge of the opposite side of the bottom of the

pit with the corner edge of the iron faced upward. When the lysimeter

box was placed in the pit, the edge of the angle iron formed a fulcrum

and the inner tubes supported the remaining weight.

Later models of the lysimeter omitted the leverage system of the an­

gle iron and rested the entire weight directly upon four tubes equispaced

on the bottom so that steady balance of the box was obtained. The hydrau­

lic head developed by the pressure of the weight upon the water in the

tubes was counterbalanced by the expansion of the tubes and the static

head formed in the manometer. The upper end of the manometer was trans­

formed into a 20 cmdiameter reservoir for automatic recording of the

water level. A simple float recorder made a continuous trace of the water

height in the reservoir and a levered linkage to the float magnified the.

level changes (Fig. 2).

Trial installations of lysimeter models with depths to as much as

1.5 m have been made. The greater pressures of the deeper lysimeters

caused the rubber tubes to stretch and greatly reduced the sensitivity

of the response. Later, non-stretching nylon reinforced irrigation hose

was used to form load cells which maintained sensitivity at these greater

pressures.

In another set of lysimeters, the percolate was contained in a sump

on the lysimeter box. The sump was pumped periodically so that the amount

of percolate could be measured. This design was not pursued because rain­

fall amounts as great as 30.5 cm per day have been recorded for Wahiawa

and amounts of 7.5 to 15 cm per day are common. Such massive additions

of water area hundred times the expected evapotranspiration rate and it

was not feasible to design a recorder for such scale changes. The lysi­

meter bottom was left open· to vent the percolate as quickly as possible.

The extremely high infiltration rates and peculiar moisture properties

of the Low Humic Latosol used for most pineapple culture in Hawaii made

this soil. i dea l l y suited for such a procedure (Ekern, 1966b). The

6

3

E2E

2.25

-

0.500 .25

6T

8A.M. 8A.M. 8A.M. 8A.M.

'E5o-...J4w>w 3...J

ffi 2J- () NOON

~I • MIDNIGHT

00 2 3 4TIME IN DAYS

FIGURE 2: HYDRAULIC LYSIMETER RECORD, LOW HUMIC LATOSOL,O.36m. LAYER.

70

60

50-. til,:,e.-I-

~ 40lJJ3:

w>I- 30~....J:::>~:::>u 20

10

o

1117

1101

IOS7

10471042

IOU, 1000,0lMl4POLYETHYLENEEDt! REMOVED

7

o 10 20 30 40 50 60MANOMETER LEVEL (mm FROM INITIAL DATUM)

FIGURE 3: LOADING AND UNLOADING RESPONSE OF LYSIMETERNUMBER 3 WITH 4mm I.D. GLASS MANOMETERAND INITIAL STATIC HEAD IOOcm. ABOVEGROUND SURFACE. l

j

I· 1iI.1

~

8

thorough aggregation of this Latosol results in a water release curve

similar to that of gravel (Fig. 3). Generally twenty-four hours suf­

ficed to complete percolation from the shallow lysimeters.

Specifications of the Standardized Hawaiian Design

for Pineapple Lysimeters

Standard construction was used for eight lysimeters placed i n dif­

ferent locations on the islands of Oahu, Molokai, and Lanai. An outer

guard shell of 16~auge galvanized iron formed a I.S2-m square opening

with walls 0.78 m high. The upper and lower edges of the shell had a

2.S-cm section turned to form a right angle that reinforced these edges.

The inner box which contained the soil was made from 14-gauge galvanized

sheet. The box opening was 14.7 m square and 0.45 m deep. Again a rein­

forcing band was turned at the upper and lower edges. These particular

dimensions were imposed by the economical use of 1.2 x 3 m modular galvan­

ized sheets. The bottom of the box was made of 1.25 cm expanded steel

mesh supported by two cross pieces of channel iron. Since the bottom was

not rigid, the box was set on a platform of 2 x 12 planks that rested

directly on the tubes. A 5-cm layer of coarse gravel was placed directly

over t he mesh and soil filled to within 5 cm of the top of the lysimeter

box. This gave a 0.355-m depth of soil for plant roots.

The double-walled reservoir which formed the upper end of the mano­

meter had a 20-cm square inner and 25-cm square outer dimension. Panels

of styrofoam, 2.5-cm thick, were used as insulation between the walls.

The reservoir was 0.5 m deep and usually contained 0.38 m of water. In

the field, the reservoir was further insulated by a 15-cm jacket of dry

soil. The soil packed about the reservoir also served to stabilized the

system against wind vibrations.

The hydraulic cells were formed by four 750 x 16 heavy duty truck

i nner tubes. The inner tubes were interconnected by 6.34-mm polyethylene

tubing . The polyethylene tubing, which was connected to the reservoir

approximately 5 m from the lysimeter at the field edge, was buried 0.45 m

within the soil to minimize temperature changes .

Static hydraulic heads 0.6 to 0.9 m above the ground surface were

used i n most of the lysimeters. Since the depth of the pit for the stan­

dard lysimeter was 0.45 m, the usual water pressure was 0.155 bar.

9

Despite the potential friction losses in the plastic tubing and fit­

tings, operations at such low pressure heads gave a surprisingly rapid

response. When the response of the lysimeter was measured by manometers

3.95 to 6.3 mm in diameter, an approximate two-fold hydraulic magnifica­

tion was observed. Moreover, a satisfactory degree of linearity was pre­

sent over the range of change normally encountered (Fig. 3) in a week of

moisture used by the pineapple. A water stage recorder with a 10-cm dia­

meter Leopold Stevens float was mounted directly on top of the reservoir.

Change in water level was given an additional lever magnification and

traced on a chart renewed weekly.

When the reservoir with a 100-fold greater cross section was coupled

to the end of the manometer, the increased volume of water which had to

be displaced to change the pressure head reduced the hydraulic magnifica­

tion and introduced a time lag in the response of the instruments. The

advantage gained from the continuous trace of water level changes by a

float recorder more than offset the reduction in magnification and speed

of response. Even the~ 90 percent of the change in level produced by

the addit10n of a 11.32-kg weight was completed within 15 minutes.

The magnification of the standardized lysimeters installed ih 1959

was equivalent to a 3.08-fold magnification. The levers for these record­

ers had a 2.75 multiplication, hence, the hydraulic magnification must

have been 1.12-fold for the static hydraulic head used. Several of the

lysimeters at PRI Wahiawa had a more sensitive recording lever with a 5.9­

fold magnification. The total magnification of these more sensitive sys­

tems was 1 mm chart travel per 0.15 mm of water use of a 6.65-fold magni­

fication. This was again equivalent to a 1.12-fold hydraulic magnification,

though the static hydraulic head was slightly greater with a value of

1.52 m.

Problems in the Lysimeter Operation

Paper charts. One of the more exasperating problems arose from the shrink­

age and swelling of the chart paper on the recorders . The sensitivity

demanded from the record was such that 1 mm of chart travel represented

from 20 to 50 percent of the total day's water use for pineapple plants.

When the water use of grass sod or pan evaporation was measured, changes

in the paper size were insignificant in comparison to the much greater

10

evaporation trace change . . When the 1ysimeters were planted to pineapple,

a diurnal pattern was imposed on the trace as a result of the 2 percent

shrinkage of ·t he paper upon drying by day and the swelling upon wetting

in the evening. A dry 202-W Bendix Friez Thermograph chart expands 1.5

scale units (1.78 mm) when moistened by a damp sponge. The pattern of

shrinkage is centered on the midline of the chart so that the trace of a

fixed pen on the upper edge of the chart has an apparent rise as the pa­

per dries, while one in the center remains unchanged in position and one

near the bottom edge registers an apparent fall. This problem was parti­

cularly acute for Wahiawa as a result of the regularity of the humidity

pattern of saturation by night and 50 percent by midday since the major

gain in paper size occurred when the relative humidity changed from 80

percent to 85 percent.

Charts made of Keuffel and Esser Co. tracing paper 359-14elimina­

ted this problem of chart size and relative humidity . .

CabZe for fZoat connections. Bronze radio cable was first used for sus­

pension of the floats from the recording lever. The linear coefficient

of thermal expansion of the bronze introduced only minor error. Strands

of saran were later used, since its expansion coefficient is fortuitously

almost identical with the volumetric thermal coefficient of water. A

braided nylon cable was briefly used to replace a bronze cable. The ny­

lon responded to humidity much like hair and made an excellent hygrometer

but was useless as a recorder cable.

Reservoi r evaporation. Maximum daily evaporation rates from rain gages

and other small orifice devices have been reported to be 1.0 mm per day

(Gomm, 1941; Hamilton and Andrews, 1953, and Gill, 1961). Here too, be-.fore oil was added to the water surface, a deadweighted above-ground lysi-

meter installation had a daily loss of 0.5 mm. The oil layer eliminated

this net loss by direct evaporation from the reservoir.

Temperatupe changes. The changes in volume with change in temperature of

the several materials at critical points in the hydraulic system suggested

that only the expansion with temperature increase of the water in the re­

servoir would be important. If the entire installation were set above

ground for the maximum effect of temperature change with the rubber tubes

exposed directly to sunlight and the circulation of warm air, the apparent

- ,I

11

rise and fall of the reservoir level would correspond closely to the

changes in air temperature,as reported for Kenya by Wangati (196S). When

the tubes were installed in a soil pit 4S-cm deep, they were shielded

from sunlight and rested in a zone where the diurnal soil temperature

°range was less than 1/2 C.

The styrofoam insulation about the reservoir reduced the diurnal

water temperature range to SoC, a SO% reduction from the daily air tem­

perature range. An apparent 0.38-mm rise and fall of the water level

would be caused by this SoC temperature change . Addition of dry soil for

further insulation about the reservoir reduced the water temperature

change to less than 2.SoC, which would induce an apparent gain and loss

of only 0.19mm/day. When the daily rate of water use of transpiring

vegetation was measured, the near constancy of the average daily tem­

peraturesin Hawaii made the change in reservoir level from temperature

negligible. The slight rise of the water level by expansion during the

day was overwhelmed by the fall from the actual water use rate of rap­

idly evaporating soil or transpiring grass.

Although seasonal and diurnal flux of temperatures is a problem

in other geographical regions, the variation within Hawaiian Latosols is

so small that no attempt has been made to control temperatures within

the lysimeter. The buoyancy effect noted by Morris (19S9) in an above

ground lysimeter in a glass house would be equivalent to only 0.02S mm

of water for a 10°C rise in air temperature, and would be negligible

for the near constant temperatures within the soil pit in the field.

Temperature gradients within the lysimeter can cause rapid soil moisture

transfer in Latosols (Ekern, 1966). However, even with the very great

seasonal temperature changes reported at Davis, California and Tempe,

Arizona, only minor differences in soil temperatures within the lysi­

meters have been reported (Pruitt &McMillan, 1961, 1962; Van Savel &Reginato, 1962). The large air space beneath the Davis lysimeter forms

an insulative barrier and subsoil temperatures have risen as much as

3.SoC above the undisturbed soil nearby. The seasonal and diurnal flux

of temperatures within Latosols in Hawaii is so small that no attempt

will be made to control temperatures within the lysimeter unless mea­

sured temperature show marked departures from those in the undisturbed

surroundings.

12

The annular gap about the edge of the lysimeter and the outer re­

taining wall has produced peculiar imbalances of temperature and moisture

transfer in several lysimeters. A vapor barrier across this gap pro­

duced an apparent diurnal cycle of distillation and condensation in

Australian lysimeters which was reduced to a tolerable level if the gap

was left open (McIlroy &Sumner, 1961). The most spectacular resultant

of closure of the gap was found in the Coshocton lysimeters where expan~

sion and shrinkage of the grease seal caused an apparent diurnal rise

and fall of the lysimeter long interpreted as dewfall. Removal of the

grease seal stopped this distortion (Harrold, 1962; Harrold &Dreibelbis,

1967). The annular gap of the Hawaiian lysimeters was partially closed

with polyethylene film to prevent soil and other debris from washing into

the pit. No diurnal pattern was found on these lysimeters with the

partial closure of the annular gap.

Wind ef fe ct s . The strong diurnal wind pattern at Wahiawa (Leopold, 1948)

from nightime calm to coupling of the trades and 4.5 m/s wind at the

1.8-m level by day during the summer introduces an effect on the open-end

manometer.

The suction would be 1.25 mm of water for a 4.5-m/s wind across the

manometer calculated after Dines' suggestion (Middleton, 1942). The

actual change would depend upon the exact geometery of the openings. The

measured effect over the Hawaiian lysimeters was equivalent to 1.0 mm,

but was quite noticeable (Fig. 4). An apparent change of 0.75 to 1.25 mm

has been reported from the floating lysimeters at Davis (Pruitt &McMillan, 1961). When the California lysimeter was vented at ground

height considerable reduction in this wind-induced pressure drop occurred.

The flow of wind past the recorder housing produce complex pressure

pumping as well as a net pressure differential. Barography and open-end

sYmmetry has recorded these pumping effects as great as 32 mm of water

for a 22.35-m/s wind (Middleton, 1942). The size, shape, and location of

openings in any building can have a marked effect upon the pressure pat­

tern produced (Theakston, 1962). This effect was noted to be marked on

the housing for the recorders for the lysimeters at Copenhagen (Ekern,

personal observation, Oct. 1960). Opening the access hatch to the area

beneath the 6.l-m diameter lysimeter at Davis, California, created an

open-end manometer and the pressure drop caused was recorded as an ap-

13

NOTE APPARENT GAIN IN MOISTUREIN MORNING AND lOSS IN EVEN­IN~, BUT NET LOSS DURING THEOAT.

/----I "f \\ I\ I

'- /-- .-'

..--, ./ \I I\ I

'--"---LNOTE APPARENT GAIN IN MOISTURE,

MORNING, AND EQUIVALENT LOSSIN EVENING.

/'/I\\ /

'-.: ./........ -

LEGEND

• POLYETHYLENEMULCH

() POLYETHYLENEPLUS TRASH MULCH

08 12 24 8 12 24 8 12 24

8 .... z ....~

....0:I: 0 :I: :I:

Z (!) Z (!) !:2z z zc c c~ ~ ~

-8/6/62-1-8/7/62-1-8/8/62 .1DATE AND TIME

FIGURE 4 : WIND EFFECT UPON HYDRAULIC LYSIMETERS.

3.125

3.750

0.625

eneno....J

~ 1.250zwa::~a..<{

~ 1.875=>~eno::E

-E~ 2.500

14

parent gain in the weight of the lysimeter. The pumping effect of wind

across the lysimeters at Tempe has been reported to limit their sensi­

tivity and imposed a need for smoothing of the record on windy days

(Van Bavel and Meyers, 1962).

Durat ion of tubes. The rubber tubes in the underground installations

were protected from sunlight and were at a nearly constant temperature

of 24°C. Deterioration of the material was not a problem, for several

of the lysimeters remained operative over a 4-year period. In dry

locations on Molokai, rats, apparently in search of water, destroyed

both the polyethylene tubing and the rubber automobile inner tubes in

the underground installations.

I nstrument calibration. Periodic addition of known weights was used

to calibrate the instruments. The time of response with the reservoir

was greater than that for the manometer alone, but even then an hour

sufficed to complete the response. Attempts to calibrate the 1ysimeters

in the field from rainfall was limited by the precision of the rainfall

measurements. The outer rim of the 1ysimeter enclosed an area of 2.32 m2

and a weight change of 4.47 kg was considered to be equivalent to 1.94 mm

of evaporation.

Modifications of the Original Design

Use of nylon reinforced, butyl i rrigation hose. The rubber inner tubes

stretched under the weight of soil depths greater than 0.75 m, and a more

substantial hydraulic load cell was designed with nylon reinforced

20.3-cm butyl rubber irrigation hose . Bolsters were constructed from

the tubing by sealing the ends. The original scheme of vulcanization

proved too expensive, and strap iron clamps, 5 em wide, were bolted di-

. rectly through the hose with 3 bolts to ensure closure. A length of

1.59-mm welding rod caught between two iron straps close the tube end.

The bolts on one end could readily be loosened to allow air escape

when the tubes were filled with water .

Tube interconnections. Standard bulkhead connectors for copper tubing

had to be modified to ensure a water tight seal to the hose. Brass

washers and nuts were devised to make the seal and silicone rubber was

15

added prior to tightening to further secure the waterproof seal. Copper

tubing interconnections were felt necessary to preclude rat attack.

Bolster pat t ern . Two long bolsters were placed parallel the outer edges

of the lysimeter box, and a series of shorter bolsters placed between

them, but at right angle to the longer bolsters. This pattern gave sta­

bility against rolling of the cells with side pressures on the lysimeter

box.

Lysimeter box desi gn. Fiberglass reinforced polyester boxes, 3.05 m2 x

1.52 m were designed for sugarcane lysimeters. The walls were 4 mID

thick, with 4 parallel reinforcing ribs of wooden 2 x 4's encased in the

plastic for flexural strength of each wall. The lysimeter bottom was

a sandwich of two 4 mID fiberglass polyester sheets enclosing a resin

impregnated paper honeycomb 12 mm thick. This gave a box of great

strength, but one which only weighed approximately 447 kg.

Drainage t ensiometers. Larger tensiometers were made from 5 cm dia­

meter polyvinyl pipe, perforated, with an intervening layer of nylon

screen, and an outer Porvic membrane (Sedgley &Millington, 1957). Re­

moval of soil percolate for the analysis of leachates and the establish­

ment of soil drainage to suctions near field capacity at the lysimeter

base were sought. The M grade Porvic is purported to have a bubbling

pressure of 0.57 bar and the S grade pressure of 0.24 bar. Prelimi­

nary trials indicate soil moisture suctions as great as these cannot

be developed with the membranes, but that drainage to suctions of 0.1

bar can be made. This approaches the 0.1 to 0.15 bar suction desired

for Latosols (Ekern, 1966b).

Soi l moi s ture release values. Soil moisture variables were determined

for the soils at Kamuela, Hawaii, proposed site for lysimeters. This

is an ash derived soil and differs from the moisture release charac­

teristics of the Low Humic Latosols (Figs . 5 to 8 and Table 1 in Appen­

dix).

16

SUMMARY

Review of extant lysimeter designs and field experiments suggested

that some form of the semi-contained hydraulic lysimeter based on a water­

fill,ed load cell was best suited to evapotranspiration measurements un­

der Hawaiian conditions. The extremely low water use by non-transpiring

pineapple plants required the development of a recording lysimeter of

great sensitivity, achieved by direct measurement of load cell pressures

with an open-end water manometer with a float recorder. The great

height, lodging, and potentially deep-rooting habit of sugarcane required

a large, deep lysimeter, but one of less sensitivity since the water

use rate was ten-fold that of pineapple. The large, deep lysimeter was

constructed of polyester resin fiber-glass reinforced for durability

and light weight. Reinforcing wooden ribs supplied flexural strength

to the sides against the later pressures of the Latosol. Paper honey­

comb strengthened the bottom of the lysimeter but little additional

we ight was added.

Large drainage tensiometers of Porvic were designed to develop

suction at the base of the soil column and allow the removal of percolate

waters for analysis. The sub-tropic marine climate of the Hawaiian Is­

lands eliminated the hazards of freezing, and reduced the problems from

temperature changes within the hydraulic system. Diurnal wind varia­

tion posed a distinct problem in measurement with an open-end manometer,

solved in part by venting the housing near the surface. Even then, the

total weight of the large lysimeters was great. It was offset by using

nylon-reinforced irrigation hose for the bolsters which form the load

cells. Arrangement of the bolsters in a geometric pattern with several

of the bolsters at right angles to the others minimized the tendency of

the lysimeter to shift in place under the burden of the very tall cane.

The water release properties of the well aggregated Latosols were mea­

sured, s ince they produce drainage, evaporation, and thermal properties

strikingly different from those of temperate latitude soils.

17

REFERENCES

As1yng, H. C. 1959. Evaporation and radiation heat balanae at the soilsurfaae. Archiv fur Meteoro1ogie, Geophysik, and Biok1imato1ogie.Sec. B. 10:359-375.

Blumenstock, D. J. 1961. CZimates of the states: Hawaii.Bur. No . 60-51. 20 pp .

U.S. Weather

Bowers, F. A. I. 1929. The root systems of pineapple plants. Experi­ment Station of the Association o'f Hawaiian Pineapple Canners,Univ. of Hawaii. PPCA BuI1. 12. 35 pp.

Campbell, R. B. 1967. Sugaraane, in Hagan, et aZ., Irrigation of Agri­cultural Land. Amer. Soc. Agron. Monograph II. pp. 649-653.

Campbell, R. B., J. Chang, and D. C. Cox. 1959. Evapotranspiration ofsugaraane in Hawaii as measure by in-field Zysimeters in relationto alimate. Proceeding 10th Congress IntI. Sugarcane Technologists:637-649.

Ekern, P. C. 1959. Evapotranspiration patterns under trade wind weatherregime on aentraZ Oahu, Hawaii. (Abstract) Agron. Abstr. 1959:4.

Ekern, P. C. 1965. Evapotranspiration of pineapple in Hawaii. PlantPhysio1. 40(4):736-739.

Ekern, P. C. 1966a. Evapotranspiration by Be~udagrass sod, Cynodondacty1on, L. Pers., in Hawaii. Agron. J. 58(4):387-390.

Ekern, P. C. 1966b. Evaporation from bare Low Humia Latosol in Hawaii.J. of App1 . Meteor. 5(4):431-435.

England, C. B. and E. H. Lesesne. 1962. Evapotranspiration researah inWestern North CaroZina. Agr. Eng. 43(9):526-528.

Forsgate, J. A., P. H. Hosegood, and J. S. G. McCulloch. , 1965 . Designand installation of semi-enalosed hydrauZia lysimeters. Agr. Meteor.2(1):43-52.

Frost, K. R. 1962. A weighing eoapobranepi-romebe», Agr. Eng. 43(3):160.

Fulton, J. M. and W. I. Findlay . 1966. Reproduaibility of evapotrans­piration measurements from fZoating Zysimeter. Can. J. of PlantSci. 46(6):685-686.

Gill, H. E. 1961. Evaporative losses from smaZl orifiae rain gages.J. of Geophys. Res. 65(9):2877-2881.

Glover, J . and J. A. Forsgate.from Larqe tanks of soil.

1962. Measurement of evapotranspirationNature. 195(4848):1330.

Gomm, F. B. 1961. A modifiaation of the standard Weather Bureau rain

18

gage for summer and winter us e. Bull. Amer. Meteor. Soc. 42(5):311­313.

Gwynne, M. D. 1962. Root sys t ems of pineapple plant s . East AfricanAgr . and Forest . J. 27 (4) :204 -2 06 .

Hamilton, E. L. and L. A. Andrews. 1953. Control of evaporation f romrain gages by oil . Bull. Amer. Meteor. Soc. 34:202-204.

Hanks, R. J . and R. W. Shawcroft . 1965 . An economical lysimeter forevaporat i on studies . Soil Sci. Soc. Amer. Proc. 57 (6):634-635.

Harrold , L. L. 1962. Errors i n the evaluation of dew amounts by t heCoshocton lysi met ers. Bull. IntI. Assn . Sci. Hydro1. 7(3):73-74 .

Harrold , L. L. and F. R. Dreibe l bi s . 1945. An accounting of the dai lyaccretion, depletion, and storage of soil water as determined byweighi ng monolith l ysimet er s. Tr ans. Amer. Geophys . Union 26( 11) :283-2 98.

Harrol d, L. L. and F. R. Dreibelbis. 1967. Evaluati on of agriculturalhydrology by monol ith l ysimeters. 1956-62. USDA TB1367. 123 pp.

Holmes , R. M. 1963. Note on hot water bot t l e lysimeter . Can. J. ofSoil Sci. 43(1 ):186-1 88.

King, K. M. , E. I. Makamma1, and V. Turner. 1965. Errors invo lved inusing zinc chloride so lut i on in floating l ysimet ers. Water ResourceResear ch 1 (2): 207-217.

Ki ng, K. M., C. B. Tanner , and V. E. Suomi . 1956 . A floating lysimeterand i t s evaporation recorder . Trans. Amer. Geophys. Union 37: 738­743 .

Krauss, B. H. 1930.Un i v. of Hawaii.

Evapotranspi rat i on of pineapple .131 pp.

M. S. Thes is,

Leopo ld , L. B. 1948. Diurnal weather pat t erns on Oahu and Lanai , Hawaii.Pac. Sci. 2(2 ): 81- 95 .

Leopol d, L. B. 1952. Dew as a source of plan t moisture . Pac. Sci. 6 (3 ):259- 261 .

Libby , F. J . and P. R. Nixon . 1963 .a wide range of site si t uat i ons.62:153-158.

A portab le lysimeter adaptable toIntI. Assn . of Sci. Hydro1. Pub .

McIlroy, I. C. and C. J . Sumner. 1961. A sensi t i ve high-capacity balancef or continous automatic weighing in the f i e ld. J. Agr. Eng. Res.6( 11):252-2 58 .

McMil lan , W. B. and H. A. Paul . 1961. Floating lysimeter us es heavyl i qui d for buoyancy . Agr. Eng. 42(9) :498-4 99 .

Middleton, P.Agr. Eng.

1965. HydrauLic weighing Lysimeters.Personal communication.

Wash. State Univ .

19

Middleton, W. E. K. 1942. Met eoroLogi caL instruments. Univ. of TorontoPress. pp. 13-14, 134-139.

Monteith, J. L. 1957. Dew. Quart. J. Roy. Meteor. Soc. 83(357):322­341.

Mor r i s . L. G. 1959. A recording weighing machine for the measurement .of evapotranspiration and dew fan. J. Agr. Eng. Res . 4(2) :161-173.

Popov. O. V. 1959. Lysimeters and hydrauLic soiL evaporimeters. IntI.Assn. Sci. Hydro1. Hannover Symposium. pp. 26-37.

Pruitt, W. O. and D. E. Angus.suring evapotranspiration.

1960. Large weighing lysimeters fo!, mea­Trans. Amer. Soc. Agr. Eng. 3(2):13-18.

Pruitt, W. O. and W. D. McMillan. 1961. Some aspects of the lysimetermethod of measuring evapotranspiration. (Abstract) Symposium Papers.10th Pac. Sci. Congr., Honolulu, Hawaii. pp.324-325.

Pruitt, W. O. and W. D. McMillan. 1962. Some observations of the down­wind variation of evaporative heat fLux at the surface. 2nd AnnualRept .• Chap. 5. U.S. Army Electronics Proving Grounds;Univ. ofCalif .• Davis, Calif. Tech. Program Contract IDA-36-039-SC-80334.pp. 77-97.

Rose, C. W., G. F. Byrne, and V. F. Begg. 1966. An accurate hydrauLicLysimeter with remote weight recording. CSIRO Div. Land &WaterRes. Tech. Paper 27. 31 pp.

Schwartz, F. K. 1963. ~obable maximum precipitation in the HawaiianIslands. U.S. Dept; of Commerce. Weather Bureau. Hydrometeor. Rept ~39. 98 pp.

Sedgley, R. H. and R. J. Millington. 1957. A rapidly equilibrating eoi/l ,moisture tensiometer. Soil Sci . 84:215-217.

Stone, E. P. 1963. The eco Loqica L importance of dew. Quart. Rev. ofBioI. 38(4):328-341 .

Tanner, C. B., M. Fuchs, and T. A. Black. 1967. Energy transfer measure­ments at the earth's surface. Terminal Report NSF Section in Atmos-phere Sciences. Grant GP-2404. pp. 24-32. .

Tanner, C. B. 1967. Measurement of evapotranspirations, in Hagan. 'etaL., Irrigation of AgriauLtUraL Land. Amer. :Soc . Agron. Monograph ·II. pp. 534-555.

Theakston, F. H. 1962. Snow accumuZation about f~ structures• . Agr.Eng. 43(3):139~141, 161.

Ii

20

Thompson, C;. D. and ,J . P. Boyce. 1967. Dai l y measur ements of potent ia Levapo t ransp i rat i on from f ully canopied sugarcane . Agr. Meteor . 4(4) :267-279 .

Trous e , A. C., Jr. and R. P. Humbert. 1961. Some ef fec t s of soi l com­paction on sugarcane r oots . Soil Sci. 91: 211- 217.

U.S. Dept . of Interior, Bureau of Reclamation. 1956.Territory of Hawai i . Vol. 2 , Hydrology Append ix.

Mol okai Project~

pp.1- 15.

Van Bavel, C. A. M. and L. E. Myer s . 1962. An aut omat i c weighing l ysi ­meter . Agr . Eng . 43 (10):586-5 88 .

Van Bavel , C. A. M. and R. J. Reginato. 1965. Precision l ysimetry fo rdi rec t measuremen t of evapor at i ve f lux . Proceedings of the Sym­posium on the Met hodol ogy of plant eco-phys iology, 1962 . (Mont­pe l ier , France ). UNESCO. pp. 129-135.

Vis s er , W. C. 1965. A method of determining evapot ransp irat ion in soi lmonoli ths . Proceedings of the Symposium on the Met hodol ogy of plantec o-p hys i ol ogy , 1962. (Montpelier , France). UNESCO . pp .453-460 .

Wanga ti , F. J . 1965.l ysi meter system.

A note in t emperat ure variation in the MugugaAgr . Met eor . 2(1) :53- 54 .

APPENDIX

21

TABLE 1. WATER RELEASE VALUES FOR WAIMEA SOIL SAMPLESvolumetric water content

Ntv

SUCTl~ ! SITE I SITE II SITE II I SI TE IV SI TE v SITE VIem HQH o - 15 em 7.5 - 15 em 15 - 23 c. 23 - 30 ClI o - 15 ClI 30 - ~5 em o - 15 em 15 - 23 ClI 15 - l O em o - 15 COl 16 ca sc C:I

10 61. 70 6l. 90 6l .0" 55 . 0" 6l .2" 6~.8:: 6~.20 6l . 0" 66.2" 7l .I " 62 .9" 7~ . I ~. 7" 58.9" 50.i" 59. 70 7~ .1 0 83. lIO 62.20 61. 0" 65.0" 57. 0" 6l . ~0 - 98.6"" 70 .2=

eo . 70 . 77 . 71 . 7~ .83 . 77 . 67 . 72 . 70 .6 7 . 90 .80 . 95 .8 9 1.02 .92 . 67 .66 . 81 . 86 . 92 . 95 .71 - . 71 . 73

13 - - - - - - - - - - - - - - - - - - - - - - - - - 60. 00

eo - - - - - - - - - - - - - - - - - - - - - - - - - -~7 . l - - 5~ . 1 50.0 56.2 57 .~ 51.00 55 . 00 58. 5 67 .6 56.9 57 .0 ~ . 60 50 . ~ ..... 50 - - - - 57. 00 63 .00 52.00 - - - . 78

50 57.10 56 .20 - - - - - - - - - - - _. - ~7 . 60 66 . 20 69. 00 50.5 0 - - - 58.80 55 . 60 77. 60 65 .7 0

75 5 0 .~0 52.20 - - - - - - - - - - - - - - - - 57 .5 0 - - - - - 62. l0 -9l - - 50 . 1 ~~ .O 53.2 5 3 . ~ ~5 .20 50.00 53.0 61.9 51.9 - - - - - - - - 53. 00 60 .00 "9.00 - - - -

100 ~~ .90 '+8. 60 - - - - '+2.80 - - - - '+8 .~ ..... 00 '+7.3 0 '+2. 30 ~.80 ~ . 90 - 5 5 .~ - - - - '10.9 0 - -105 - - - - - - - - - - - - - - - - - - - - - - ~.9O - - 59. 10

115 - - - - - - - - - - - - - - - - - 58.2 0 - - - - - - - -l l 5 - - - - - - - - - - - - - - - - - - - - - - .....~ - - 56 .7 0

136 '+0.80 '+~ .80 - - - - - - - - - - - - - - - - - - - - - - - -1'+6 - - '+7.2 '+1. 0 51.5 50. 8 37 . 90 ~ .OO 50.l 58.6 50 .6 - - - - - - - - ~9. 00 56 .00 ~7 . 00 - - - -1'+8 - - - - - - - - - - - - - - - - - 50 .90 - - - - - - 55.90 -150 - - - - - - - - - - - -r.e '+1.90 ~5. 00 ~ .~ 37.10 ~.OO - - - - - - 39 .9 0 . -200 30 .10 ll.80 - - - - l1. 30 - - - - - - - - 32.60 29 .8 0 - l O.3 0 - - - 30. l0 28 . 50 - 35. 30

eo . 56 . 59 - - - - . 56 - - - - - - - - . 71 ..... - .6 0 - - - . 51 .58 - . ~ 7

500 25 .80 28.90 - - - - 28 .8 0 - - - - - - - - 27 .2 0 25. 70 - 26. 30 - - - 30. 70 23.70 - 37. 90

eo . 55 . 6l - - - - . 56 - - - - - - - - .6 7 . ~ - . 59 - - - . 52 . 59 - . 52

1, 000 25 .20 26 .10 37.5 2~.'+ l~ .l - 28.0 0 23 .20 2'+ .~ 23 .1 26 .6 - 26 . '+0 25 . 90 lO.IO 28 .1 0 23 . 60 - 22 . 50 27.~ 32.20 30 .80 32.20 2~ . 60 - 29.2 0

eo - - - - - - - - - - - - .95 . 8~ 1.09 - - - - - - - - - - -~.OOO 20 . 80 21. 6 l2 .'+ 23 .2 31.3 - 2'+.9 0 21.20 22. 1 20.8 25.2 - 2~.20 23.2 0 26. ~ 25 .1 0 19.90 - 21. 30 23.00 27.20 25. " 29. 00 19.80 - 23 .~

8,000 17.90 19 . '+0 ll.8 22 .9 l l. l - 25.2 0 21.30 21. l 20 .1 2'+.3 - 23.20 22.10 25.00 23.60 17. 90 - 18.80 22.00 27.10 25.20 23. 10 18.60 - 20.80

15,000 17.60 17. 90 - - 29 . 1 - 22 .8 0 - - - - - - - - 20 .5 0 1~.70 - 16 .20 - - - 19.70 - - 17 . 10

eo = BULK DENS ITYx = CORE So'I'f'LES

:= = ASH POCKETS

0.100.08

0.06

0 .04

0.02

0.000 10 50

10.08.0

6.0

4.0

2.0

1.0~ 0.8

~ 0.6

Iz 0.4o~U::l(f) 0.2

20 30 40

VOLUMETRIC WATER- PERCENT

FIGUR E 5: WATER RELEASE CURVE - WAIMEA SOIL.SITE I, 0-15 em.

23

70

24

100.00

0.10 () CORE SAMPLES

• BULK SAMPLES

L-- l- ..L- -'-- --I..- --L -.L.._ (Jr.-----l

700.01

o 1020 30 40 50 60VOLUMETRIC WATER - PERCENT

FIGURE 6 : WATER RELEASE CURVES- WAIMEA SOIL.SITE I, 7-15 em.

10.00

CJ)0::<{(II

Iz 100O 'l-t)

:::lCJ)

25

100.00

() CORE SAMPLES

• SULI< SAMPLES

10 20 30 ~O 50

VOLUMETRIC WATER - PERCENT

FIGURE 7 : WATER RELEASE CURVES -WAIMEA SOIL.SITE I, 15-20 em .

0.01 L- L..- L..- L..- L..-__---'L..-__---'~CI

o

0.10

10.00

(f)

~mI

~ 1.00r-o:::>(f)

26

loono .

1000

ena::«enIz:o 100t-U:J(f)

010

() CORE SAMPLES

• BULK SAMPLES

001 '--- --'-- --L. ----' J-- {

o 10 20 30 40 50 60VOLUMETRIC WATER- PERCENT

FIGURE 8 : WATER RELEASE CURVES- WAIMEA SOIL.SITE I, 23- 30 em