MARDI Res. Bul l . (1986) l1(3), (2t t-217)

EVALUATION OF ULV SPRAYERS FOR WEED CONTROL INVEGETABLE PRODUCTION _ PART 1

K.C. YEOH*

Keywords: ULV sprayers, Laboratory tests.

RINGKASAN

Sebanyak l ima jenis penyembur 'u l t ra low volume'dan l3 saiz kepala penyembur te lah diu j i d imakmal untuk mengumpul data awal tentang s i fat-s i fat semburan alat tersebut. Peraturan penguj ian dimakmal te lah diselaraskan seberapa yang boleh.

Keputusan uj ian didapat i sama dengan spesi f ikasi yang diber i o leh pembuatnya. Berbagai-bagaikesimpulan te lah didapat i dar ipada k i raan kepadatan t i t isan semburan. Penyembur CP 15 MK I I te lahdianggap sebagai penyembur yang serba boleh kcrana penvembur in i boleh digunakan untukmenyembur segala jenis racun perosak termasuk racun rumpai .

INTRODUCTION

Weed dominance has become a majorproblem in vegetable production. In long-cultivated fields where ferti l izers had beenregularly added, the dominance of weeds ismenacing the vegetable crops. Weederadication by traditional manual meansusing the hoe is s low and tedious. Chemicalweed control method. therefore. must beresorted to.

In Peninsular Malaysia, importantweeds found in vegetable holdings areEleusine indica, Cleome rutidosperma,Cleome ciliata, Amaranthus blitum, Borrerialatifolia, Cyperus iria, Fimbristylis miliacea,Echinochloa colona, Digitaria longiflora,Asystasia intrusa, Ageratum conyzoides, etc.(Lee and CHoNG, pers comm.,1986). Asurvey of vegetable farming in PeninsularMalaysia indicated that the most widelyused weedicide was paraquat (ANoN.,1981). Its mode of action is essentially to kil lby contact action. Plant tissues are affectedvery rapidly and leaf discolouration occurswithin one or two hours after spraying withthe chemical.

Various types of weedicide applicatorsare being used in vegetable farming. These

with a 9-l itre or 18-litre metal tank, thetractor-mounted and power take-offoperated boom sprayer with a 600-800-litreplastic tank, and the engine-operated high-pressure power sprayer. However, thesetypes of sprayers have high discharge ratesand thus, use a large amount of water peruni t area. Much t ime is wasted in get t ingwater , mix ing the spray solut ion andrefi l l ing the tanks. The new trend is towardsthe use of lower volume appl icat ion,particularly the ultra low volume (ULV)sprays. The ULV sprayers have theadvantages of lower water requirement andhigher working output. These sprayers alsodemand less physical effort to operate andthus, are less tir ing to the operators. Takingthese advantages into consideration, thisexperiment was proposed to evaluate theuse of ULV sprayers for efficient weedcontrol in vegetable production.

The overall evaluation plan is, f irstly,to conduct laboratory tests on the sprayers.with various nozzle sizes to observe theirspray characteristics. Secondly, the sprayerswould be tested in a fallow field sprayingseveral weedicides to observe theireffectiveness of kil l . Thirdly, suitablesprayers and nozzles would be selected forapplying preemergence, postemergence and

include the hand-operated knapsack sprayer selective weedicides on plots planted with*Miscel laneous crops Research Div is ion, MARDI, Jalan Kebun. Kelang, Selangor, Malaysia.

2t r

vegetables. Finally, further studies may becarried out to adapt the sprayers for moreefficient use in vegetable cultivation. Thisreport deals only with the first stage oflaboratory tests.

The main objective of the laboratorytests was to obtain reliable data on thedischarge rate, spray swath width, spraydistribution, and droplet density of eachsprayer and nozzle size. These data providebasic information on their spraycharacteristics.

MATERIALS AND METHODS

Five ULV sprayers available locallywere selected for the laboratory tests. Theirspecifications are given in Appendix 1. Thesprayers and their nozzle sizes were asfollows:

Sprayer Nozzle s ize

Berthoud H2

Micron Herbi 77

Turbair Weeder

Birky Knapsack LV

C P I 5 M K I I

yel low, red, green

blue, yel low, red

1 . 2 m m , 2 . 0 m m

yel low, red

VLV 50, VLV IOO, VLV 2OO

Before each test, the revolution of thespinning disc atomizer of each sprayer,when not spraying any l iquid, was measuredusing the non-contact digital tachometer.The spinning disc was angled at 60 degreesfrom the horizontal and fixed at about 30 cmfrom the ground surface as indicated by astring tied to a weight (Plqte I ) .

The forward walking speed of theoperator was measured using a stop-watchwhile the wind speed was measured usingthe hand-held Dwyer anemometer.

For the d ischarge test . a measur ingcylinder was used to measure between 200ml and 400 ml of water which was thenpoured into the solution tank. The timetaken to completely discharge the wholevolume of water was measured using a stop-watch. An average of five readings wastaken to indicate the discharse rate for eachnozzle.

*: .

Plate 1. Spinning disc atomizer ofBirky sprayer positioned at 30 cm

above ground surface as indicated bya string tied to a weight.

The spray distribution of each nozzlewas monitored using the water-sensitivepaper. The paper could also be used forchecking the droplet density. Each strip is2.5 cm wide and 50 cm long. A total of sixstrips of the paper were laid out in acontinuous l ine and a single pass of eachnozzle was made across them at the centre( Plate 2) . The density of droplets per squarecentimetre was then counted with the aid ofa piece of paper with a one-centimetresquare window. An average of three counts,one at the centre and the other two at eachend. was taken to indicate the dropletnumber.

Plate 2. Single pass made at the centre of thewater-sens itive paper for monitoring

the spray distribution and droplet density.

2t2

The effective spray swath width wasmeasured from the distribution of spraydroplets on the water-sensitive paper. Afterstudying the concentration of the dropletson the paper, arbitrary demarcation l ineswere drawn to indicate the boundaries ofthe swath and the width measured.

RESULTS AND DISCUSSION

The results obtained from thelaboratory tests are sumrnarized in Table I.The average forward walking speed of theoperator was 0.5-0.7 m/second. This speedwas slower than that (1.0 m/s) normallyquoted by the manufacturers in calculatingthe spray volume. However, a walkingspeed of 0.5-0.7 m/s is considered morenormal for the Asians.

The discharge rates obtained from thesprayers with different nozzle sizes weregenerally slightly higher than those given bythe manufacturers. Water was used in thetests. The discharge rate would decreaseslightly if the spray solution had a higherviscosity.

Knowing the walking speed, sprayswath width and the discharge rate, thespray volume could be calculated in terms ofl itres per hectare. In the application ofweedicides, the spray volumes are normallyclassified as follows (MerrHews, 1979):

Ultra low volume (ULV) : < 50 l itres/haVery low volume (VLV) : 50-200litresihaLow volume (LV) : 200-500 litres/ha

As can be seen from the figuresobtained, the Berthoud H2, Micron Herbi77 with blue and yellow nozzles, TurbairWeeder and Birky Knapsack LV fell underthe ULV classification. The Micron Herbi77 with the red nozzle and the CP 15 MK IIwith its three nozzle sizes were classifiedunder VLV while the conventionalknapsack was not even under the LV sprays.

The droplet density is crit ical inpesticide application. The following provides

a guide on the minimum droplet densityrequirement in the target area for thevarious types of sprays to be effective(Crea -Ggrcy , 1981 ) ;

Droplet density(min. no. /cm2)

Type of spray

2 0 - 3 02 0 - 3 03 0 - 4 0

5 0 - 7 0

Insecticides

Preemergence weedicides

Postemergence, contactwcedic ides

Fungicides

In this study, the droplets as shown onthe water-sensitive papers indicated theuniformity of the distribution of the spraysover the whole swath. From the dataobtained, the droplet densities fo'r the threenozzle sizes of Berthoud H2 and the bluenozzle of Micron Herbi 77 were below theminimum requirement of 20 droplets persquare centimetre. The effectiveness ofthese sprayers, even for applyingpreemergence weedicides, is thus suspected.In addition, the droplet densities for theyelfow and red nozzles of Birky KnapsackLV and the yellow nozzle of Micron Herbi77 hovered around the lower l imit of thedroplet number requirement. Field testswould have to be carried out to gauge theeffectiveness of their sprays. The red nozzleof Micron Herbi 77 could be used forapplying preemergence weedicides whilethe two nozzle sizes of Turbair Weedercould be used for applying insecticides,preemergence and postemergence weedicides.The CP 15 MK I I , wi th the improvedhydraulic nozzles, could be used for apply-ing all the pesticides including fungicides. Inaddi t ion, i ts spray volumes of 57.1-165.5litres/ha, when compared with the sprayvolume of 694.7 l itres/ha of the conventionalknapsack, gave a saving of 4.2-12.2 t imesin water requirement.

The spray distributions and dropletdensities for VLV 50, VLV 100 and VLV200 nozzles are shown in Plates 3-5.

The droplet size was not measured dueto lack of facil i t ies. However. some infor-

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Plate 3. Spray distribution anddroplet density for VLV 50 nozzle.

Plate 4. Spray distribution anddroplet density for VLV 100 nozzle.

Plate 5. Spray distribution anddroplet density for VLV 200 nozzle.

mation on droplet size for Micron Herbi 77 ,CP 15 MK II and the conventional knapsacksprayers could be obtained from Nc (1985).

His data showed that more than 60Vo ofdroplet size from the three sprayers fell inthe range of 100-300 microns. Droplet sizeis highly important if pesticides are to beapplied efficiently with the minimumcontamination of the environment. Whendrift must be minimized, a medium (20I-400 microns) or coarse (> 400 microns)spray is required, irrespective of sprayvolume appl ied.

The Berthoud H2, Micron Herbi 71and the Turbair Weeder are controlleddroplet application (CDA) sprayers.Controlled droplet application refers to theapplication of spray solution at correct sizeof droplets for a given target, e.g., insect :70-100 microns and weed 200-300microns. As a result of the uniformity ofdroplet size produced, there is optimizationin the use of minimum spray volume toachieve effective control.

The revolutions of the spinning discatomizer measured, when no spray wasdischarged, were within the range given bythe manufacturers. When spray solution isapplied, the number of revolutions of thisdisc would drop slightly. As an example, thedisc revolution of red nozzle of BerthoudH2 was 2 500 rpm when not spraying. Itdropped to2 240 rpm when spraying (manu-facturer's information).

CONCLUSIONS

The results of laboratory tests were inaccordance with the specifications given bythe manufacturers.

The actual walking speed of theoperator was between 0.5 m/s and 0.7 m/s ascompared with 1.0 m/s frequently quoted bymanufacturers. As a result, the sprayvolumes applied were higher than thosestated by them. The discharge rates obtainedwere also generally slightly higher thanthose given by the manufacturers.

From the droplet densities obtained,the red nozzle of the Micron Herbi 77 could

215

be used for applying preemergence weedi-

cides while the 1.2 mm and 2.0 mm nozzle

sizes of Turbair Weeder could be used for

applying insecticides, preemergence andpostemergence weedicides. The CP 15 MK

II, with the improved hydraulic nozzles was

the most versatile as it could be used for

applying insecticides, weedicides and fungi-

cides. In addition, the CP 15 MK II gave a

saving of 4.2-12.2 times in spray volume

requirement as compared with the conven-tional knapsack sprayer.

Generally, the soundness of construc-tion, ease of handling, operation and main-

tenance of the sprayers were satisfactory.

ANoN. (1981). An Agro-Economic Survey of Vegetable

Farming in Peninsular Malaysia (ed. DtNc,

T.H., Vtul t - .1, P. and YusoH, S.) , p. t t6.

Serdang: MARDI Press.

CrBn-Gelcv (19t31). Watcr-scnsi t ivc papcr for

monitoring the spray distribution. Ciba-Geigy

Agricultural Division, February 1981.

ACKNOWLEDGEMENTS

The author wishes to express his

thanks to Dr Ramli Mohd. Noor for his

support and encouragement on the

proceeding of this experiment, Dr Lee Soo

Ann for his valuable discussion, suggestion,

proofreading and loan of the various ULV

sprayers, Mr Nuruddin Hasnan for helping

in carrying out the tests and taking slides

and photographs. The author is also grateful

to Mr Fadzerun Ahmad and Mr Misrohim

for their help in conducting the tests.Thanks are also due to Ms Siti MurniSastero for typing the manuscript.

Nc, P.H. (1985). Nozzles, f low-rates, droplet s izes and

controlled droplet applicators. Paper presented

at Workshop on Recent Trends in Pesticide

Application Technology with Emphasis on Weed

Control, Kluang, Incorporated Society of

Planters, Johore, 19t35, Appcndix I -VI I .

MA'rrHFrws. G.A. (1979). Pesticide Application Method

333 pp. Ncw York: Longmans Inc.

ABSTRACT

. A total of five ultra low volume sprayers with a total of 13 nozzle sizes were tested in the

laboratory to gather background data on their spray characteristics. Laboratory test procedures were

standardized as far as possible.

The results obtained from the tests correspond with specifications given by the manufacturers.

Various inferences were made from the droplet density count. The CP 15 MK II was considered the

most versatile sprayer as it can be used for spraying insecticides, fungicides and weedicides.

REFERENCES

Accepted for publication on 27 August 1986

276

Dicetak oleh Unit Percetakan MARDI, Serdang, Selangor.Kementerian Pertanian Malaysia.