Sulphuric Acid Spray: A PracticalMeans for the Control of Weeds

Item Type text; Book

Authors Brown, J. G.; Streets, R. B.

Publisher College of Agriculture, University of Arizona (Tucson, AZ)

Download date 09/05/2018 05:28:23

Link to Item http://hdl.handle.net/10150/196755

Bulletin No. 128 July 1, 1928

College of Agriculture Agricultural Experiment Station

SULPHURIC ACID SPRAY: A PRACTICAL MEANS

FOR THE CONTROL OF WEEDS

By J. G. BROWN AND R. B. STREETS

PUBLISHED BY j!!tIif=oilg of ~

UNIVERSITY STATION TUCSON, ARIZONA

ORGANIZATION BOARD OF REGENt::.

Ex·Officio Memh('r!l His ExcoJlencl/'. GEORGE W. P. HUNT, Governor of Ari:;:ona._ .....•.... Phoenlx BON:. CHARLES O. CASE, State Supcrintcnd{'tlt of Publie

Instruction .................................. -...... -- .................... _ ....... Phoenix Appointed Members

HOr.:. ROBERT E. TALLY, Chl.ln~ellor ....... __ .......................... _ .............. Jel'ome HON. LOUIS R. KEMPF. LL.B., Secretary ...................................... _ ... Tucson HON. CLEVE W. VAN DyKE ... __ ............................................................... Miarni HON. CHARLES M. LA YTO:-J .......... ____ .................................................. Safford HON. GEORGE M. BRIDGE ...................................... _ ......................... Somerton HON. ROY KIRKPATRICK......................... . ....................... Globe HON. 1'1!EODORA MARSH, Treasurer .......................................... Nogales HON. FRANKLIN J. CRIDER, M.S .. Vice·Chnncellor ................ Superior - ----_.

HOMER L. SHANTZ, Ph.D., Se.D ......... __ .... __ .President of the University

AGRICULTURAL EXPERIMENT STATION JOHN J. THORNBER, A.M .... _ .... _ ............................ _ ......... Dean and Director JAMES G. BROWN, Ph.D ....................................................... _.Plant Pathologist WALKER E. BRYAN, M.S ............................................................. Plant Breeder PAUl. S. BURUESS, Ph.D ............................................... AI!Tj,:ultural Chemist WALTER S. CUNNINGHAM, M.S............. . ....... Dairy Husbandman HARny EMBLETON, M.S ................................................. Poul:ry Husbandman RALl'H :;. HAWKINS, M.S ............................................................ Agronomist ALLEN F. KINNISON, M.S .......................................... _ ............... Horticulturist GEORGE E. P. SMITH, C.E ..... _ ...................................... Agricultural Engineer ERNEST B. STANLEY, M.S .............................. _ .............. Animal Husbandman CHAHLES T. VORHIES, Ph.D ....................................................... Entomologist

"'JAMES F. BREAZEALE, B.S ......... __ ....... _ ........... _ ...................................... . ............. _ ............ _ ......... _._ ....... Research Specialist in Agru:ultural Chemistry

WILLIAM G. McGINNIES, B.S .............. _ ............... Grazinl!: Range Specialist MARGARET C. SMITH, Ph.D ......... Resenrch Specialist in Home Economics DAVID W. ALBERT, M.S ............................................ Associate Horticulturist RICHARD N. DAVIS, B.S ...................... _ ............ Assoriate Dairy Husbandman OSCAR C. MAGISTAD, Ph.D ......................... Associ~tc Agricultural Chemist ELIAS H. PRESSLEY, M.S ........................................ Associate Plant Breeder HAROLD C. SCHWALEN, M.S ................. Associate Agricultural Engineer RUBERT B. STREETS. Ph.D ............................... Associate Plant Pathologist IAN A. BRIGGS. M.s .................... _ ................................... Assistant Agronomist STANLEY P. CLARK, B.S ..... _ ........................................ Assistant Agronomist WILLIAM F. DICKSON, M.S .......................... _Assistant Animal Husbandman HUBERT B. HINDS, M.S ................................. Assistant Poultry Husbandman ANDREW A. NICHOL, B.S ....................................... _ ... Assistant Entomologist G. GORDON POHLMAN, M.S ......................... Assistant Agricultural Chemist HOWARD V. SMITH. M.S ............................... Assistant A{;l'icultural Chemist MALCOLM F. WHARTON, M.S ..... _ .......................... Assistant Horticulturist CARLTON L. ZINK, B.S_ .... _ ......................... Assistant Agricultural Engineer ARTHUR G. CARNS, B.S ....... Field Al>sistant in Irrigation and Hnttkulture

tKENNETH P. PICKRELL, B.S ... Field Investigator in Animal Husbandry CHARLES HOBART. M.S .......................... _ ......................... Research Assistant GEORt3-E H. SERVISS, M.S ......................... Field Assistant in Cotton Studies

EXPERIMENT STATION FOREMEN CAVE J. WOOD .......................................... _ .. _ .... Salt River Valley Farm, Mesa T. LESLIE STAPLEY .............. _ .. _ ............ Tempe Date~Palm Orchard, Tempe JAMES G. HAMILTON, B.S_ ............. Yulna Valley and Mesa Farms, Yuma GEORGE H. SEAMANS .. _ ..... _ .. _ ... _ ... _ .................................... __ .. _ .... _ .. __ .

.................. _ .... Assistant Foreman, Yuma Valley and Mesa Farms, Yuma CARL CLARK, B.S ............ ___ .... ____ .... ____ ...... .Prescott Dry-Farm, Prescott .J. RUSSEL REED ....... __ ....... _ ............. University of Arizona Farms, Tucson

'" In cooperation with United States Department of Agriculture, Bureau of Plant Industry.

t In cooperation with the New Mexico Agricultural Experiment Station and the United States Department of Agriculture, Bureau of Animal Industry.

CONTENTS

Introduction ........ -- ......... -.. ---...................... __ .............. ___ ............ 299 Some methods for controlling weeds .......... _____ ......................... 300 Sulphuric-acid spray as a weed killer ........ __ ............................. 302 Source of acid .......... __ .......... __ ..... _____ ...................... __ .. _ ................. __ 302 Preparation of the spray; precautions ....... ___ ....... __ ............. __ .. 304 Killing strength ...................... __ .... _._ .... _ ... _ ......................... _._ .. __ 305 Method of application. ___ .. ____ ...... __ ...................... ____ ... __ . ___ . __ ... __ .... 313 Cost of spraying ..... __ ................................................................... 314 Advantages of sulphuric-acid spray for killing weeds ............ 315 Summary ........................... _ .......................................... ~ ............ 315 Bibliography .............................................................................. 316

ILLUSTRATIONS

FIG. 1.- Fie!d mustarQ (Brassica sp.). A. Before spraying. B. Two hours after spraying with 5-percent 8:.11·

phuric acid .............................................................. 300 FIG. 2.- Ground cherry (Physalis angulata linkeana).

A. Before spraying. B. Twenty-two minutes after spraying with 2-

percent sulphuric acid .......................................... 301 FIG. 3.- Puncture weed (Tribulus terrestris).

A. Before spraying. B. After spraying with 2·percent sulphuric acid .... 303

FIG. 4.- Small hand-sprayer, capacity 3 gallons .................... 305 FIG. 5.- Wheelbarrow-type of sprayer, capacity 12 gallons .. 313 FIG. 6.- Power-sprayer, capacity 150 gallons ........................ 314

TABLES

TABLE 1.- Results of Spraying Weeds with Various Con-centrations of Sulphuric Acid ........................ 306-310

TABLE II.- Recommended Strengths for Spraying Weeds with Commercial Sulphuric Acid ........................ 311

TABLE IIL- Results of Spraying Puncture Weed (Tribulus terrestris) with Sulphuric Acid, Showing Ef­fect of Temperature, Humidity, and Method of Application .............................................................. 312

SULPHURIC ACID SPRAY: A PRACTICAL METHOD FOR THE CONTROL OF WEEDS

J. G. BROWN AND R. B. STREETS

INTRODUCTION

The problem of controlling weeds is important in combatmg plant diseases. Some weeds are alternate hosts of important plant-disease organisms. For example, the rust fungus, P /1,0-

cinia subnitens. lives on salt grass and several other weeds on which it produces spores which infect spinach. There are many similar cases. Weeds also hold over certain soil-inhabiting, dis­ease-producing fungi during the interval between crops. In this way they serve to keep alive Rkizoctonia which causes black scurf of potatoes and sore shin of cotton; also Phymatotri­chum, the fungus of the destructive. Texas root-rot disease. They harbor nematodes which cause root knot in many cultivated plants, and insect pests which attack a wide range of crops. According to recent discoveries by plant pathologists, weeds assist in wintering-over and spreading infectious mosaic.

Although the case as set forth above is a strong one, weeds are undesirable for many other reasons. They take so much water and soil nutriment from the crop-plants about them as to reduce greatly their yields or cause their death. Weeds are unsightly and, therefore, lower the market value of property on whieh they grow. By clogging ditches and in other ways some weeds interfere with irrigation, cultivation, and other farming operations. Some weeds are poisonous to man, livestock, and other animals; some cause hay fever; others, like the puncture weed, inflict wounds, puncture rubber tires, and otherwise are annoying; a few, like dodder in nelds of alfalfa, ruin the sale of the seed.

The list of weeds which grow in Arizona is a large one and, as a result of improved facilities for transportation, it is inereas­ing rapidly. Not only are wild plants included among the offend­ers, but also certain volunteer crop-plants such as Johnson grass, Bermuda grass, various species of sweet clovers, and sour clov­ers. Many of these weeds rapidly invade fields in spite of hoe­ing and other forms of cultivation, especially during the period of the summer rains when conditions for growth in the irrigated districts of Arizona are almost tropical. To check their advance by the usual means is expensive. Obviously a practical method for their control is needed.

[299]

30{) f..!XPERIMEN7' STATION BULI,NT/tV NO. 128

B

FIG. 1.- Field mu~tard (B1'U8Sioo 8/).). A. BefOl'C spmyiug. B. Two houtls after sp!'uying with 5-percent sulphuric acid. The sponge-like texture of the soil in 8 is due to gases formed in the neutrnlization of the acid spray

b~' ulkaline constituents of the soil.

SOME METHODS FOR CONTROLLING WEEDS

In the attempted control of weeds numerous, widely different means have been tried. '1'0 be economically useful on cropped Jand the method employed must be reasonably inexpensive, effi­cient, easily applied, and nOD-injuriolls to the soil. Methods such as the application of heavy oils, burning with a gasoline torch. and scalding with steam injure the soil or are too slow and laborious for application to large areas. Some chemical weed­eradicators have been rejected for the same reasons. Sodium arsenite (1) has been found! to be toxic to nitrifying bacteria in

SULPHURIC ACID FOR CONTROI~ OF WEE!)." :WI

the soil, even in concentrations as low a.~ 1 part per million. Sodium arsenate (2) in low concentrations stimulates nitrifying bacteria, but high concentrations are necessary to kill certain we-eds so that the questions of cost of application and injury to

FIG. ing.

A

B

2.- Ground chl.>rrr (PhY!lfl/U. (,Illgll/ala Iil!kfana). A. Be10re spray~ B. Twenty-two minutes after IIpraying with 2-percent !lulphuric acid.

;)02 I \l'ft:lll)JE\'T , .... 'J'.!T10.V EI'L/,ETI.",· NO, 128

usdul soil organisms must be considered. COllper sulphate has b€.en used (3. 4) and found effective, Lut an accumulation of this chemical in the soil is injurious to crop-planis (;j). Ammonium chloride, calcium cyanamide (dry), corrosiyc St blimA.ie, and so(Hurn chloride h~ye been tried but haxE' not CI'lT.e- into gener.1] use on cropped land. Balacck (6) finds that sdphuric-acid and fE>rrous-sulphaie sprays are practicable, also kuinit and cyanide of lime in the form of dust, but all othel' methods me too expen­!:'live, A.slander (7, S) ,.Rabaie (n). Ridruejo (10), and Drioux (11) have studied sulphuric-acid spray as a wecd-eradi-cator and recommend it under favorable conditions.

In the course of experiments on rhizoc.toniose of potatoes and cotton and on Texas rooi-rot the possibility of controlling the diseases by fallow or clean cultivation appeared to be depend_ ent upon a rapid and effective method of destroying weeds. At the suggestion of the senior author a series of experiments was conducted to test the effectiveness of variolls concentrations of commercial sulphuric acid on the more common weeds of agri­cultural and waste lands. It seemed particularly desirable to find a method applicable to fence corners and other places which could not be easily reached by the usual methods of cultivation. Naturally the results obtained, although sought primarily from thf' standpoint of the plant pathologist, are applicable to the destruction of weeds anywhere, whether it is desired to remove them from the roadside, garden, city lot, or field.

SULPHURIC ACID SPRAY AS A WEED KILLER

Sulphuric-acid spray has been used to destroy weeds in fields in the Scandinavian countries. Italy, France, and Spain for a number of years. The customary practice in growing small grains (9) is to spray the entire field before the weed-infested grain covers the ground, The acid kills the dicotyledonous weeds and also burns the grain more or less, but the latter recovers quickly and in 20 to 30 days is as vigorous as grain crops which have not been treated with the acid spray_ The rapid recovery giYes the grain a vegetative advantage over the weeds that attempt to come in later, so that a second crop of the latter doei not develop. In order that sulphuric-acid spray may be used profitably on large fields a satisfactory source of acid must be at hand and water must be easily obtainoo..

SOURCE OF ACID

The agricultural districts of Arizona are fortunate in having a satisfactory supply of sulphuric aCid available. The acid iii a

SI~f.PI1"RI(, A('/{J POR CONTROl. OF II'FJED.r;;, ;30;.1

by-product of the smelting industry and the output in Arizona can be greatly increased if the demand for acid should warrant it. Since the acid is produced locally, the transportation charges are less than they would be for shipment from out.':lide the State.

"

.;.... -', - .-... ~.' ~~-.

A

B

FIG. 3.- Puncture weed (TribulllX tIJ)·NJ8t'ris). A. Before spraying. B. After spraying with 2-percent sulphuric Ilcid.

304 E"s{PEHlMENT STATIO.\' flUI.LETl.\!.YO 1.:1>

PREPARATION OF THE SPRAY: PRECAUTIONS

Although the belief is not uncommon that sulphuric acid, like dynamite and nitroglycerine, is very dangerous to handle, it is not explosive. The acid can be handled quite safely by anyone who understands its properties and who will observe a few sim­iple precautions. Before preparing the spray the following paragraphs should be carefully read.

1. The mixing of acid and water generates a large amount of heat. When water is poured into the concentrated acid the generation of heat is so rapid that the mixture will boil and spatter hot acid on everything within reach. Therefore, always pOUT the acid slowly into the water with constant stirring so that no spattering will occur.

2. Contrary to popular belief, the concentrated acid is not actively corrosive to ordinary sheet metal or cast iron. The acid is shipped in lOO-gallon steel drums and may be kept in them for several years if they are sealed against moisture. Drums containing acid should be stored in the shade and the bung loos­ened enough to allow the escape of gases, since, if left out-of~ doors, the sun's rays may cause enough expansion to burst the drum.

3. The diluted acid is much more active chemically on iron and other metal than is the concentrated acid, and will corrode metals in contact with it for any considerable length of time. The zinc coating on galvanized metal is dissolved in a few min~ utes, so that vessels and spray tanks of this material should be avoided. Neither sheet metal (iroD, steel, or brass) nor east­ings (iron or brass) are appreciably corroded by 2- to lO-percent solutions of acid used in spraying, if the metal parts are first coated with cylinder oil or cup grease. Two or three gallons of used cylinder oil poured into the spray tank of a power sprayer and run through the pump and spray nozzles will protect aU internal parts from the acid. The agitator shaft and nozzles should be coated with cup grease. All metal containers and spraying machinery which have been used in connection with dilute acid should be thoroughly washed with clean water imme­ruately after use.

4. Either dilute or concentrated acid will eat holes in cloth­ing or shoes, or burn one's flesh, if allowed to remain in contact 'With it. One outfit of old clothes shoufd be kept for wear when acid spraying is carried on, since it is impossible to spray without occasionally getting a few drops of acid on one's clothing.

5. Goggles should be worn to protect the eyes. A solution of bicarbonate of soda (baking soda) will neutralize acid spots

.... n.PNcRIC ..lew FOil CO.VTRO/. OF Jrh'J-;f)S 305

on the flesh or clothing. This solution can be safely used to wash the eyes, if one should get acid in them. A half cupful of dry 1;00Ia in a gallon of water makes a satisfactory solution.

KILLING STRENGTH

Since the exact stl'ength necessary to kill the various species of weeds is dependent upon temperature and the size of the plants to be killed, the dilutions given below are only approxi­mate and may have to be varied for local conditions. The amount of acid actually adhering to the foliage of the plants sprayed determines the effectiveness of the spray. Low humidity and high temperatures are favorable to effective spraying. Humid­ity influences chiefly the rate of wilting and dying rather than the percentage of plant. "I event.ually killed.

FIG. 4.- Small hand-sprayer, capacity :1 gallOll!;.

305 EXPERIMENT STATION BULLETIN NO.It8

TABLE I.-RESULTS OF SPRAYING WEEDS WITH VARIOUS CONCENTRATIONS OF SULPHURIC ACID

I APP"Xo/ Stage or Percent Temp. pereent

W .. d growth Date acid Fahr. of Remarks I killing \

Careless 6-18 inches Sept. 18 1 96'1 80 ...... tall, in ". flower Sept. 18 2 9.

Sept. 18 31. "" 100

Sept. 18 5 95' 100

ea""'" 12-24 inches I , Some ..... tall, in May 28 5 99"2 90 I coarser

flower stems still '_no

S1=ng plants May 28 10

, 100 I

Fabo 4-12 inches - in diameter May 28 1 9'" 40

8--18 inches in diameter May 19 2 92'1 100

8-18 inches-in diameter May 19 5 92" 100

8-18 inches

I in il.iameter I May 19 10 92" 100

Lamb, 12-18 i.nehea' May 19 2 92" 98 - tall, in .. - May 19 • 92' 100

May 19 10 9'" 100 Badly collapsed.

Field 6-18 inches Oct. 27 1 .. "' 65 ,,-'" tall, yonng

Ct.'" Oct. 27 2 ... 90 ring

Oct. 27 ." .. " 100 Collapsed

Oct. 27 5 64' completely.

100 Collafesed comp etely.

"w I 12-18 inches Oct. 27 5 64" toO Thl"" I tau, in llower

14-18 inches May 19 2 92" 95 tall, in :!lower

Footnotes· , , • '. 20%, 16%, 21%.440%,1585%.622%. '" For botamcal names see Table III. Relative humidities.

S('I.PHl'RIC ACW p'OR CONTROL or n EF:nS 307

TABLE I.-(Continued)

I I Percent Approx.!

Stage of Temp. percent! Wood growth I Date acid Fahr. of I Remarks

I killing! 1 9S"!l

I 95

Ground 10·15 inches Sept. 20 Easily Cherry tall, in 2 OS" 100 killed.

flower I Wilted in , • "" 100 5 min.

SilverMleaf Berries Oct. 22 , 75°1S 100 Killed to Hone nearly ripe ground. Nettle

Oct. 22 10 7'" 100 Killed to ground.

4..g inches May 28 5 90" 100 Killed to tall, in ground. flower

I May 28 10 90" 100 Killed to

ground.

Croton 12-20 inches May 28 1 99" W Stems not tall, in killed. llower

May 2S 2 "" 90 Smaller

I May 28 'li< ,,.,., .. " toO killed.

Rayl ... Large and May 28 1 .. " " Small Goldenrod small leaves and

or tender tips Buno killed.

""'" 6--24 inches May 28 • ,," 90 Most of tall, green. leaves and Not lower-- tender tips ;"" killed.

May 28 'li< .. " 100 All leaves and tips killed.

May 25 , 92" 100 C,rtox probably killed •

May 1& to .. " too Cort", killed to ground.

May 19 , '2" toO Cort.. probably killed.

May 19 10 92" toO Cort.. killed.

308 EXPERIMENT STATION BULLETIN NO.U8

TABLE I (Contlnued) .-I , I A}:lprox.

I Stage of

I I Percent T""p percent

W,od I ""wth D.t. acid Fahr. I ,f Remarks i killIng

I --Alkali Various sizes Baa to 24 inches Flower tall, plants May 28 1 99· '0 Leaves

in flower and tender

100 tips killed.

May 19 2 92

May 19 ,,. 92 100 S-.

Ma}" 191 collapsed.

5 92· 100 S,""" collapsed

I and

I blackened. ,

May 19 10 92· , 100 S-. I collapsed

I I and

I blackened.

I

Dodder Plants in O{"t. 22 5 75· 100 Waxy flower (on surlace puncture penetrated. weed)

O{"t.22 10 75· I •• Wax;y surface

i penetrated.

-

Johnson I Seeds nearly gr." mature Oct. 22 5 75· 80 Blackened.

Oct. 22 10 75· 97 Killed to ground.

24 inches May 19 5 ". 70 Leaves high; DO killed ,aed wherever

spray touched. ,. 92· 9. S,= ,,,,= partly alive.

24 inches high; no seed May 20 1 99· ,.

Le .... spotted.

(Johnson grass continued to next page)

SULPHURIC ACID FOR CONTROL OF WEEDS 809

TABLE I -(Continued)

I I Pe:rcent Approx

I Stage of

I Temp. percent

W.od I ","'wth Date acid Fahr. of Remarks I killing

I I Johnson \

I 10 ,,' 90 Foliage

grass blackened

("ntinn'dl! and ;killed. I Some

I panicles

I emerged.

Bermuda Plants in I "' ... flowel" and

May 281 seed: some young plants 1 99' 10 Some

leaves killed.

May 28 5 99' SO Mostly killed to ground.

May 28 10 99' 100 Killed IIUld blaekened.

May 19 2 92' 50 Partly killod,

May 19 5 92' 90 KUled to ground.

May 19 10 92' 100 Killed. and blackened.

G~n Seedlinp to Foxtail plants in

Sower May 28 1 99' 60

May 19 2 92' SO Mal< .. prompt recovery.

May 19 8\, 92' 95 Makes prompt recovery.

May 19 5 92' 100 Makes prompt recovery.

I May 19 10 92' 100 A few

I plants

I recover.

310 EXPERIMENT STATION BU[,LETIN NO. us

TABLE I -(Continued)

Approx.' Stage of Percent Temp. percent t

Woe<! .",wth Date acid Fahr. of I Remarks killing

Stink Seedlings 2--5 I

gn .. inches tall in :!lower May 28 1 ". 50 L~~

partly killed.

May 28 , 99' 80

May 28 10 99' 100 Killed to ground.

Miasma Plants 12-24 .... inches tall, May 28 1 99' 40 ~v'" in dower and tende ,

tips killed. Ma.v 19 2 92' 95

Mav 19 3"> 92' 100 S ..... collapsed.

Md.v 19 5 92' 100 S ..... collapsed.

May 191 10 92' 100 S ..... I collapsed.

Yellow In seed May 19 , 92" 95

""'" "",." 10 92" 100

Bata Mata Plants 2 ft. Some

high May 28 1 99' 10 , .. "" killed.

May 28 3'" 99' " All leaves and tender tips killed.

Knotweed Plants 12-18 May 19 '''' 92" 100 inches tall

May 19 , 92' 100

Thistle ! Flower !May 19\ 10 ! 92· 100 I Blackened.

0.'" Plant 12-18 inches tall May Z8 10 9'" I Loa.,.

spotted.

:,( [.PH("RIC ACID FOR CONTROL OF WEEDS .311

In the case of Johnson grass, bindweed, and other weeds having extensive rootstocks on large taproots, the parts below ground are not killed by the first spraying, but this is also true of other treatments which do not permanently injure the soil. The number of sprayings necessary to eradicate such weeds will depend upon local conditions, but spraying should prove easier and cheaper than the methods usually employed to destroy them.

fABLE II.- RECOMMENDED STRENGTHS FOR SPRAYING WEEDS WITH COMMERCIAL SULPHURIC ACID.

2_percent Acid - Puncture weed Careless weed

Field Mustard

Sow Thistle Careless weed Bata Mata

percent Acid-Johnson grass Nut grass

terrestris ) palmeri) (young

(Andropogon ha/'p('1UJe) (C1lper-us ellculentus)

( AplopappJU

TABLE lIT.-RESULTS OF SPRAYING PUNCTURE WEED (TRIBULUS TERRESTR18) WITH SULPHURIC ::1 ACID, SHOWING EFFECT OF TEMPERATURE, HUMIDITY, AND METHOD OF APPLICATION. t:I -

State of growth Date Percent 'r~P-eratlll"e Percent

acid Fahr. humidity

Mature plants AUg. 18 1 98· .0 Aug. 1& • 98· .0 Aug. 18 ." 98· 20 Aug. 18 6 98· 20

-Seedlings and young Sept. 18 1 96· 26

plants Sept. 18 • 96· 26 Sept. 18 8" 90· 26 Sept. 18 , 90· .,

Mature stems 10-30 Oct. 22 , 7'· " inches long Oct 22 10 76· " Rapidly growing May 28 1 ". 16

young plants 4-12 May 19 • 92· ., mches tall and May 19 '" 9.· ., some mature stems May 19 , ... 21

May 19 10 92· 21

Time required Method of to wilt or

application discolor

Sprinkle 15 minutes Sprinkle 12 minutes Sprinkle 10 minutes Sprinkle 7 minutes

Spray 16 minutes Spray 11 minutes Spray 9 minutes Spray 8 minutes

Spray 15 minutes Spray 10 minutes

Spray 22 'minutes Spray 14 mmutes Spray 12 minutes Spray 9 mmutes Spray 7 minutes

Approx. percent of

killing

.0 7' 90 96

'0 90

100 100

100 100

., 100 100 100 100

Remarks

Uneven Uneven

Uneven

Blackened

Uneven

Blackened Blackened

~ ~ >: .. '" :< ~ '" 5 ~ ~ ~

~

SUl~PHURIC ACID FOR CONTROL OF IflHW$ 313

Flc. 5.- Wheelbarrow-type of sprayer, capacity 12 gallons.

METHOD OF APPLICATION

A bucket or barrel sprayer is satisfactory for small areas, but a power sprayer is neces;;;ary for large areas. The ordinary hand or power sprayers used for control of plant diseases or inRed pests can be used for spraying the acid, if the sprayers are wMhed thoroughly with clean water immediately after using. Metal parts protected by lubricating oil or cup grease are not corroded by the acid. Sprinkling or applying the acid without pressure has been found to be much less effective than spraying (see Table III); besides, it requires more than double the quan­tity of solution for the same area than does spraying. A pres­sure of 150 pounds or more is more effective than lower pres­sures. because under high pressure the leaf surfaces are thor­oughly wetted in spite of their hairy or waxy coating .

. Just enough spray should be applied to wet thoroughly the lt'af surface of the weeds. Two hundred gallons should be ample

;!l.j /':XPBR1JIS;"'7' STATION BULLET/X .VO. 128

for acre. Five hundred gallons will spray a strip 20 feet wide along 1 mile of ditch or fence row.

In Scandinavian countries 100 gallons per acre are used in ::;prayin~ grain fields to eradicate we~ds, but thiS'. is done when the plan~ are not over G inches high. Spraying while the weeds arc small is recommended since the young plant.s nre more easily killed and it is difficult to wet thoroughly a tangle of lanre plants.

Spraying with sulphuric acid is intended to supplement il'ri­!ration and cultivation of the field before planting, and also cutti­\'ation or hoeing while plants are small. Weeds can be pre\"ented [tom seeding by plowing or spra~Ting as soon as the crop is harvested. Ditches, fence rows, and idle or waste land should be sprayed in time to pre\·ent the weeds from maturing seeds.

PIG. 0.- POW{·I"-spru),el", cupacity 150 gallons.

COST OF SPRAYING

The following estimates are based on the prices quoted by the Apache Powder Company, f.o.b. Curtiss (near Benson), Arizona .

$20.00 per ton in single 100-gallon steel drums $]9.00 per ton in car-lois (about 24 drums) $17.50 per ton in tank cars

Twenty dollars per ton is equh·alent to 15 cents per gallon, since 1. gallon of acid weighs about 15 pounds. The quotations given are 1'01' the strongest grade of commercial acid (92%). Since

SULPHURIC ACID FOR CONTROL OF WEEDS 315

the- price is based on the strength of the acid, the 92-pereent acid is the cheapest to buy because no transportation charges are paid on water.

Based upon an average of 200 gallons of spray per acre the all''ount of acid used and the cost per acre are as follows:

2% 3%% 5% 8% 10%

4 gal. acid at 15 cents ..................... . 7 gal. acid at 15 cents .................... .

10 gal. acid at 15 cents ................. _ .. . 16 gal. acid at 15 cents ....................... . 20 gal. acid at 15 cents ....................... .

$ .60 per ac~ 1.05 per acre 1.50 per acre 2.40 per acre 3.00 per acre

Expenses for freight and labor have not been included since they are likely to vary with the locality.

ADVANTAGES OF SULPHURIC-ACID SPRAY

1. The sulphuric-acid spray is the quickest and cheapest method of weed-control when acid and water are easily avail­able, especially in places difficult to reach with farm machinery.

2. It kills rapidly - in 10 to 30 minutes, depending upon temperatures.

3. It does not injure the soil as do oil and arsenic sprays the effects of which are cumulative. Since most soils in Arizona are alkaline, excess sulphuric-acid spray reaching the soil is quickly neutralized.

4. Sulphuric-acid spray applied under pressure is more effec­tive as a killing agent than when sprinkled on weeds.

5. Apparatus used in spraying sulphuric acid should be pro­tected by applying grease or heavy oil to the metal parts likely to be attacked by the acid. It should be carefully washed after use.

SUMMARY

1. Weeds are favorable to the existence of plant diseases for they harbor disease-producing organisms and viruses, nema­todes, and insect carriers; they also rob crop-plants of water and soil nutriment, interfere with farming operations, poison stock and adulterate the seed of some crops. Weeds are increas­ing in numbers and their control is becoming increasingly im· portant. For controlling weeds sulphuric-acid spray is recom­mended.

2. Sulphuric acid is a by-product of the smelting industry and a large supply is easily available to the various agricultural di.!ltricts of Arizona.

316 EXPERIMENT STATIO.V B{'I.,LETIN NO. 1:.:8

. 3. Directions are given for preparing the spray and also precautions to be observed in its use.

4. The killing strength of sulphuric-acid spray is given for many weeds common in Arizona.

5. Apparatus for applying the spray is suggested, the approximate cost of spraying is discussed, and advantages a:re enumerated.

BIBLIOGRAPHY 1. Greaves, J. R, and Carter, E. G.- Influencp of sodium

arsenite on the microflora of soiL Bot. Gaz. 77:63~72. 1924. 2. Brun, David L.- The destruction of the star thistle by arsell~

ate of soda. W. Australia Dept. Agr. Jour. 5:512. 1925. 3. Millara, W. A.- Dry spraying for the destruction of char_

lock. Jour. Min. Agr. Gt. Brit. 28:134-142. 1921. 4. Robson, R.- Control of the weeds whitlow, pepperwort, and

black mustard. Jour. Bd. Agric. London. 26:56-63. 1919. 5. Forbes, R. H.- Certain effects under irrigation of copper

compounds upon crops. Ariz. Expt. Sta. Bu!. 80. 6. Baiaeek, B.-Prostredky k hubeni ohnice a horcice polni.

casove spisky ces odborn zemedE'Hske radv pro <5echy 42. 1921.

'1". Aslander, A.- Utspadd svavelsyre sam besprutningsmedeJ mot ogras. Nordisk Jordbrugsforskning 126-146. 1925.

8. Sulphuric acid a~ a weed spray. Jour. Agr. Res. 34:1065-1091. June 1, 1927.

9. Rabat€, E.- Emploi de l'acide sulfurique pour 1a destruction et pour la lutte conire divers parasites. Rev. Path. Veg. et Entomol. Agric. 11 :288-298. 1924.

10. Ridruejo, L.- La destruccion de ma1as hierbas can el acido sulfurico en los campos de cereaiel:! (4. ana de experienciaR). Boletin de la Estacion de Patologia Vegetal. (Madrid) 1;81~ 94. 1926.

11. Brioux, Ch.- Saturation dans Ie sol de i'acide sulfurique utilise por 1& destruction des mauvaises herbes. Compt. Rend. Acad. Sci. Paris. 179 :74-77. 1924.