aerial fertilization of wheat

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SMITHSONIAN MISCELLANEOUS COLLECTIONS

VOLUME

94, NUMBER15

AERIAL FERTILIZATION OF WHEAT

PLANTS WITH CARBON-DIOXIDE GAS

(With Six Plates)

BY

EARL

S.

JOHNSTON

DivisionofRadiationand Organisms, SmithsonianInstitution

(Publication 3346)

CITY OF

WASHINGTON

PUBLISHED BY

THE

SMITHSONIAN INSTITUTION

DECEMBER

20, 1935

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C6e£orbQ^alttmore(preset Baltimore,md.,o.s.a.

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AERIAL FERTILIZATION OF WHEAT PLANTS WITH CARBON-DIOXIDE GAS

By earl

S.

JOHNSTON

DiznsionofRadiationand Organisms, SmithsonianInstitution

(With

SixPlates)

INTRODUCTION

Experiments on the carbon-dioxide assimilation of

yomig

wheat plants reported by Hoover, Johnston, and Brackett (j)^{^} covered a wide range of light intensities and carbon-dioxide concentrations.

Under

the artificially controlled conditions used, it

was shown

that there

was

a linear variation of carbon-dioxide assimilation with carbon-dioxide concentration in the presence of excess light over a limitedrange.

With

the

maximum

lightintensity,approximatelyone- fourth that of sunlight on acloudless

summer

day in Washington, carbondioxide

became

alimiting factor ata concentration of about thatof nojmal air. Since sunlight intensity fora

number

of hours per clear day is

much

higherthanthe highest intensityemployed in these experiments,it

was

thoughtthat interestingand important data might beobtained

from

experiments conductedwith sunlight under

more

natural conditions out of doors

and

with the carbon-dioxide concentrationsurroundingthe plants

some

₃to4times that ofnormal

air.

It is not feasible here to

make

an extended review of the large

amount

of

work

covering the subject of aerial fertilization of plants with carbon dioxide.

Many

experimenters report beneficial effects.

Several sources ofcarbondioxidehave beenutilized,includingcarbon- dioxide generators,commercialtanks of thecompressedgas,scrubbed fiuegas,andthat arising

from

animal

and

plantmanures. Bothgreen- house

and

field experiments have been tried.

Carbon

dioxide

from

blast furnaces, after being freed of matter injurious to plants

and

piped tofields

where

it

was

allowed to spreadover extendedareas, caused

marked improvement

in cropyields. Because of thedifficulty ofconfining thegas oversuchlargeareasinopenfields,aerialfertili- zationwith carbon dioxideisbetteradaptedto greenhouse work.

Relativelylittle

work

onincreasing the products of photosynthesis by enriching the air with carbon dioxide has been done in this

Italicnumbersinparentheses refertolistof referencesatendofpaper.

Smithsonian Miscellaneous Collections, Vol. 94, No. 15

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SMITHSONIAN MISCELLANEOUS

COLLECTIONS VOL. 94

country as

compared

with such studies in England, France, and

Germany. Cummings

and Jones (2), using opencasesinthe greenhouse, hberated the carbon dioxide

from

sodium-bicarbonate sul- phuric-acid generators insucha

manner

that the plantswere bathed in an atmosphere rich in carbon dioxide for 8 hours aday. Closed cases were not satisfactory, since they subjected the plants to such abnormal conditions that consistent results werenot obtainable.

Ex-

periments with a rather wide ^variety ^of ^plants indicated a general increaseinplantproductionandthat plantscanusetogood advantage

more

carbon dioxide than occurs normally in air.

The optimum

quantity of carbon dioxide, as found by these authors, for plants

grown

in open boxes

(26x18

inches and 26 inches deep for the larger plants, and

52x28x12

inches for the smaller ones) varied with the plant.

For

lettuce this quantity

was

about 300 ^liters ^of carbon dioxide a day.

Cummings

and Jones further conclude that the continuity of supply is asimportant asthe totalamount.

Arthur,Guthrie,

and

Newell ⁽r),working-attheBoyce

Thompson

Institute for Plant Research, Inc., have studied the effects on ^plant growth andchemicalcompositionof increased carbon-dioxide concentrations ingreenhouses andinconstantlyconditionedrooms.

The

air

was

enriched withcarbondioxidetoabout_0.3percent, or 10 timesthat ofnormalair. In additiontosunlightoneof thegreenhousesreceived supplementaryartificial light,and oneof the

rooms

hadartificiallight only. Several types of plantswereused, the small grains being repre- sentedby^barley, ^wheat, andoats. Theirspring wheat (variety blue stem) data are

shown

intable i.

Table i.

—

Expcrhucntal Results on the Chemical Composition of the Aerial Portion of IJ'heat [from Arthur, GutJirie, and Nezvell (/)]

Carbohydrate (percent dry weight)

Treatment ^

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NO. 15 AERIAL FERTILIZATION OF

WHEAT JOHNSTON

₃

As

can be seen

from

thetable, the plants thatreceivedboth additional lightand carbondioxidewereheavier andcontained a greater quantity ofcarbohydrates thanthe controlplants.

No

signsofheading inthe control plants were notedat time of sampling, whereas those ingreenhousesiand2had beeninheadfor

some

time. Theseauthors conclude that

:

Small grains, such as barley and spring wheat, in contrastto potatoes, will

growandyieldwellata hightemperature (78° F.) ifgivenadditional lightand carbondioxide. Theproductionofthese grainsisnotfavoredby lowtemperature whendaylengthislongandcarbon dioxide supplyisabundant. Theweight per plant ofbarley increaseswith day length up to a 19-hour day. Total carbo- hydrates alsoincreaseandnitrogen decreases. Thefeedingofnitratewasfound tomake little ornodifferenceinthetotal percentageof nitrogeninthe barley plant, the percentage remaining high only when carbohydrate synthesis was restrictedbyshort days.

EXPERIMENTATION

In the laboratory experiments of Hoover, Johnston, andBrackett, in which growth

was

entirely under artificial conditions, the wheat plantswereconfinedtoa double-walledglasscylinderwiththeirroots extendedintoaflaskof nutrientsolution. In thefirsttype of experiments runoutside, Marquis wheat

was

plantedin six8-inch earthen- warepots (not glazed) containing agood gardensoil.

The

potswere buriedto theirrimsinwetpeat

moss

placedina^long,

narrow

cypress box. Cylinders30inches inlengthwith conical topswere

made from

clear celluloseacetate sheeting

and

so constructed thattheyfitted into the tops of the pots.

The

purpose of these cylinders

was

to confine airof a given carbon-dioxide concentrationabouttheplants. In order toinsure a fairly constant carbon-dioxide concentration, the desired air mixture

was

introducedthrougha glass tube emergingcentrally just abovethe surface ofthesoil. Holes cutin the cylinders atthe tops just beneath the aprons of the cones provided an exit for the air.

It

was

thought the flow of air through these cylinders

would

be sufficient tokeep the plantscool. It

was

soon realized, however,that additional cooling

would

havetobeemployed.

A means was

devised for flowing a thin sheet of water over the outer surfaces of the cylinders.

Near

the tops of the cylinders small jets of water

from

copper tubings wet short cloth curtains

wrapped

around the upper portions of the cylinders. This gave a fairly even distribution of water over the surfaces of the cylinders.

Even

withthis additional equipment,thetemperatureswithin the cylinderswerestillexcessively high oncleardays. This

was

in partdue tothehigh temperature of the tapwater usedforcooling,which frequentlyhadatemperatureof

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SMITHSONIAN MISCELLANEOUS

COLLECTIONS VOL. 94

25° to 28° C. as it

came from

thepipeline.

A

further reductionin temperature

was

brought about by placing a white cloth reflecting surfacebackof the plantsand byoperating amovable^"half-shade."

A

battery of these cylindersis

shown

inplatei.

They

wereplaced ona smallplatformabout6feetaboveground andinfront of a small framebuildingthat faced south.

The

flow of water

was

adjusted by the valves at the top.

The

waste pipe is

shown

below.

On

cloudy days,andat night, the^"half-shade^"

was

raisedby

means

of a rope andpulleys.

In the space beneaththeplatformwerelocated the airandcarbon- dioxide flow gauges, themixingflasks,andthe gas tanks. Theseare illustrated in plate 2. Commercial carbon dioxide of high purity, suppliedinheavysteelcylinders,

was

passed under₁₅poundspressure intoa cushion tank and then through a flow gauge into the mixing flaskfor the properdilution withair.

The

air

was

supplied

from

the high-pressure compressed-air line

from

the United States National

Museum.

It

was

reduced to 15 pounds pressure and passed into a cushion tankandthenintothemixingflask.

The

propermixtureofair and carbondioxide

was

thenpassedintothecelluloseacetatecylinders.

The

concentration of carbon dioxide in these growth cylinders

was

checked

from

timetotimebyanalyses.

Several preliminaryexperiments were run during the

summer

of 1933, but thewheat

grew

so poorlythatnodefiniteconclusionscould be

made

otherthanthatthe plants receiving the liigherconcentrations of carbon dioxide

grew

better than those receiving the lower concentrations. Becauseof thefactthatthe plantswere toocloselycon- fined in the cylinders, where the temperature

was

abnormally high, andbecause of the necessity for using a shadeand water filter,it

was

decidedtorepeat theexperimentthe following

summer

aftermodify- ing the conditions so asto

make them

alittle lessartificial.

On

April 14. 1934, Marquis wheat

was

plantedin the six 8-inch pots used the previous

summer

and in three plots of soil

2x2

^feet

laid off in the yard of the Astrophysical Observatory.

The

conical tops of the cylinders were

removed

to minimize the risein temperature of theairsurroundingtheplants. Neitherthe waterscreen nor the ^"half-shade^"

was

used.

At

thecorners of

two

of the 2

x

2-foot plotswereplacedslottedpostsintowhichsheetsofglass24

x

30inches in sizecouldbefitted.

A

plotwithglasswalls either30or60inches highcouldbebuilt

up

as circumstances warranted.

To

minimizethe removal of carbon dioxide

from

within these glass-walled plots by air currents, there

was

laid across the topa frame over which two layers of flynettingwere stretched.

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SMITHSONIAN MISCELLANEOUS

COLLECTIONS VOL. 94

the enclosed controls, the

number

and weight of grain were greater for the carbon-dioxide-treatedcultures.

The

^weightper grain

was somewhat

higher for the plants receiving the greater quantity of carbon dioxide.

One

other point of interest isthat these

same

plantsput outagreater

number

of tillersthan the ones treated with less carbon dioxide.

Those

in no. 6 appear to be an exception.

PLOT

EXPERIMENTS

Owing

to the poor stand in one of the 2x2-foot plots

from

the planting

made

onApril14,these threeplotswerereplantedon

May

9.

Becauseof thisdelay,seeds sproutedinthelaboratorywere usedfor thesecondplanting.

A

goodstand

was

obtainedby

May

14,atwhich time the carbon dioxide-air mixture at the approximate rate of 2 liters aminute

was

turned into theglass enclosure surrounding plot

A; B

servedastheenclosed controlplot,and

C

astheopenone.

On May

17 theglass sideswereincreasedinheight

from

30to60inches.

The

results of this experiment are

summarized

in table 3.

The

general appearanceand arrangement of these three plotsand of the 6-potexperimentdescribedaboveare

shown

inplate4.

The

wheatin the three plots, harvested July25, is illustrated in plate 5.

The

dry weightdata were determinedafter the plantswereairdried forabout 2months.

Table3.

—

Suimiiaryof1934Experimcnlimth WheatGrozvnin3x2-footPlots

PlotA PlotB

(inglass (inglass PlotC

Data enclosure) enclosure) (open)

.AverageCO2concentration(relative to

normalair) 3.8 i.i 0.9

Numberofseedsplanted 36 36 36

Numberofplantsharvested 34 33 31

Averagedata perplant:

Weight (grams) at harvest i4-52 6.39 3.47

Weightafterairdrying 8.02 5.00 3.02

Weightofwaterlostindrying... 6.50 1.39 0.45

Numberofheads 7.44 4.03 2.74

Weightofheads 2.88 2.51 1.26

Weight per head 0.39 0.62 0.46

Weightofstraw 5.14 2.49 1.75

Weightofgrain 0.85 1.70 0.77

Numberofgrains 26.08 57-70 37-52

Weightper grain 0.0326 0.0295 0.0205

Numberofgrains perhead 3.51 14-32 13-68

At

time of harvest thetotal weightper plant of those treated with carbon dioxide

was

over twice that of theenclosed control plot (B) andover four timesthatof theopen^controlplot (C). Thisgreatdif- ference

was

due largely tothe watercontent as is evidenced by the dry weights, which, however, still indicate a substantial increase of

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WHEAT JOHNSTON

₇

the carbon-dioxide-treated plants over both controls.

The number

and weightofheadsper plant are alsogreater.

However,

theweight perhead and the

number

of grains per plant areless inthe carbon- dioxide-treatedplot.

The

^largeincrease in total weightis due to the weight of straw. Althoughtheweight pergrain of the plants on the carbon-dioxide-treated plot

was somewhat

greater thanthose of the

two

controlplots,the

number

of grains perhead

was much

less. This experimentlikewiseindicatesthe acceleratingefifectof carbon-dioxide aerial fertilization on vegetative growth and an apparent depressing- effect on grain production.

During the following

summer

the plot experiment was repeated withoneadditional treatment. It

was

thoughtthat ifphosphorusand potassium fertilizerswere addedtooneof thecarbon-dioxide-treated plots attime of heading, these plantsmightbeimproved with^respect totheir grain production.

The

general procedurein thisexperiment

was

similar to that of the previous year.

However,

the rate of air fiow

was

increasedtoabout₅litersa minute,

and

theenclosed control plot

was

changedtotheeastendof the row.

The

appearanceof the plants

when

harvested is

shown

in plate 6, and the data are

sum-

marizedintable4.

Table4.

—

Smninaryof1033Experimentwith J}'heatGrownin2x2-footPlots

Data

Average CO2 concentration (relativeto normalair)....

Numberof stalksharvested...

Totalweight (grams)atharvest Totalweightafter airdrying..

Weightofwaterlostindrying.

Number of heads Dry weight of heads Dryweight per head Dryweight ofstraw Dry weightofgrain Number of grains Dry weightper grain Numberofgrains perhead...

Each

plot

was

plantedto'/2grains ofwheat,

two

tothehill,during thefirst

week

of April.

By

April 26 the plants

showed

a fair start.

The

glass sides,60inches high,wereplacedaroundplotsi, 2,

and

3,

and

the carbon-dioxidemixture turnedintoplots2and3onApril29.

The

averagecarbon-dioxide analyses

showed

theconcentrationin plot 2tobe

somewhat

greaterthanthat ofplot3,the onetowhichphos- phorusand potassium fertilizerswereadded. Thisfertilizercombina-

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SMITHSONIAN MISCELLANEOUS

COLLECTIONS VOL. 94

tion

was

applied in a solution of

KH2PO4

at four dififerent times after the plants started to head out.

The

total quantity added

was

about 10grams.

When

the plants wereharvested, the

number

tothe hillcould not be determined.

For

thisreason the datahave been expressedastotal foreachplotratherthantheaverageperplant,asintable 3.

On May

10 the leaves of the plantsinplots2

and

3

showed

aslight yellowing. Thisyellowing of the carbon-dioxide-treated plantsduring their early growth

was

also observed in the previous year's experiments. Later the plants overcamethis initial handicap and outgrew the plants of the controlplots.

By

June7 plants^{in plots} ⁱ and 4 had startedtoheadout,butnosigns ofheadingwereinevidence in plots 2 and₃ (those receiving extra carbon dioxide) until a day or

two

later. This

was

also in keeping withobservations

made

the previous year.

By

June 27vegetative growthhad practically ceased, andthe carbon-dioxide treatmentswerediscontinued.

So

far as vegetative growth and the

amount

of tillering are con- cerned, this experiment

showed

a beneficial effect of the carbon- dioxide treatment.

The

weight of straw

was

increased, as

was

also the

number

of heads produced. Although the weight of grain

was

greater on the carbon-dioxide-treated plots, the greater

number

of grainsproduced reduced the average dry weight per grain of these plots to practicallythe

same

value as the enclosed control, approxi- mately0.03grams.

The number

of grainstothehead

was

butslightly greater in the enclosed control plot, whereas in the previous year's experiment it

was

considerably greater.

SUMMARY AND CONCLUSIONS

Three dift'erentexperimentswerecarried outwith Marquis wheat to study the effects in sunlight of increased carbon-dioxide concentration (inmost casesabout four timesthatof normalair) of theair surrounding the plants during their growth. In one experiment 8- inch potswereused,

and

inthe

two

otherexperimentsplots

2x2

feet were employed. Commercial carbondioxide ofhighpurity

was mixed

withtheairsurroundingtheplants.

The

carbon dioxide

was

confined to the spaceaboutthe plantsbycylindersof clear celluloseacetatein one experiment

and

bysquare glass sides intheothers.

The main

conclusions to be

drawn from

these experiments are that airenrichedwithcarbondioxide (i) increased thetilleringof the wheat, (2) greatly increased the weight of straw, increased (3) the

number and

₍₄₎ weightof heads, (5) increased the

number

ofgrains

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WHEAT JOHNSTON

₉

produced, and (6) slightly delayed the time of heading.

The

^weight

per grain

was

practicallythe

same

as that of the controlsevenin the experiment in which phosphorous and potassium fertilizers were added attime of heading.

Greatdifferencesin growth wereobtainedin theplotexperiments between the enclosed plants and those

grown

inthe open.

The

enclosed plantswerelarger,heavier,and

more

succulent,andtheweight per grain

was somewhat

greater. In the potexperimentthe plantsin theopenculture (no. 5)

grew

betterthanthose of thecorresponding control (no. 4). There appears tobe

some

evidence, since thispot experiment, of a toxic effect of cellulose acetate. If this is true, it

may

account for the poorer growth of the plants enclosed in the celluloseacetatecylinders. It

would

appear thatthe higherhumidity within the enclosedplots

was

beneficial totheseplants.

The

evidence, however, is not conclusive, since the temperature

was

also higher withinthan withoutthe enclosures.

The

aerial fertilizationof plantswithcarbon dioxideraisesa

num-

ber of interesting questions.

Many

of thesecanbe answered,however, bylaboratoryexperiments undercontrolled conditions.

The

practical application of this type of fertilization in field experiments

and

the supply of carbon dioxide in sufficient

amounts

for practical field

work

arestillunsolved problems,in spiteof the

work

that hasbeen done.

Even

its application togreenhouseculturerequires theutmost precaution.

The

escape of the gas mixture into agreenhouseis not sufficient in itself, but a recirculating system, as notedby

Owen

_{4)

aids materiallytoward obtaininguniform distribution.

While

experiments in which carbon dioxideis usedasan aerial fertilizerare of important scientific value, the practical application of this type of fertilizerincommercial

work

isfar

from

beingsatisfactory,although itsapplication togreenhousecultureappearsto bemostpromising.

REFERENCES

(i) Arthur, JohnM.,Guthrie,John^D.,andNewell,John M.

1930. Someeffectsofartificialclimateson thegrowth andchemical composi- tionofplants. Amer.Journ.Bot., vol._17, pp.416-482.

(2) CuMMiNGs, M.B.,andJones, C.H.

1918. The aerial fertilization of plants with carbondioxide. Vermont Agr.

Exp.Stat. Bull. 211, pp. 1-56.

(3) Hoover,

W.

H.,Johnston,EarlS.,andBrackett,F.S.

1933- Carbondioxide assimilationina higherplant. Smithsonian Misc. Coll., vol. 87, no. 16,pp. 1-19.

(4) Owen, Owen.

1923. Carbondioxideinvestigations. Exp. andRes. Sta.,Nursery and Market GardenIndustries'Development Soc,Ltd.,9thAnn.Rep.,pp. 82-94.

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SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL.94,NO. 15,PL

WHEAT Cultures Enclosed

in

Transparent

Cylinders

of

Cellulose Acetate

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Q Si

2 ~

< ?

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SMITHSONIAN MISCELLANEOUS COLLECTIONS _{VOL. 94,} NO.15, PL.5

c

Appearance of Wheat Harvested from the

1934Plot

experiments

Averagecarbon-dioxide concentration relativetonormal air was: A,3.I

B, I.I;C,0.9. (Seetable3.)

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rt

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D.

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