Project title:
Tomatoes and cucumbers: Evaluation of
effective use of pipe-rail boom sprayers.
Reports:
First Annual Report (1997)
Second Annual Report (1999)
Final Report (tomatoes) (2000)
Project number:
PC 136
Project Leader & Agronomist
Andrew Lee
Horticulture Research International
Stockbridge House
Cawood, Selby, North Yorkshire YO8 3TZ
Project Engineer:
Professor Paul Miller
Silsoe Research Institute
Wrest Park, Silsoe, Bedford, MK45 4HS
Report Authors:
Professor Paul Miller and Andrew Lee
Location:
Horticulture Research International
Stockbridge House
Cawood, Selby, North Yorkshire YO8 3TZ
Tel 01757 268275. Fax 01757 268996.
Project co-ordinators:
Dr Nigel Dungey
Hazlewood VHB Ltd, Toddington Lane
Littlehampton, West Sussex, BN17 7PP
Mr Derek Hargreaves
111 Copandale Road, Molescroft
Beverley, East Yorkshire, HU17 7BN
Mr Philip Pearson
A Pearson & Sons, Wood House Nurseries
Fields Farm, Green Lane, Alderley Edge
Cheshire, SK9 7UW
Date project commenced:
December 1997
Date projected completed:
January 1999
Key words:
pipe-rail boom sprayer, volume application rate, nozzle
configuration, air-assistance, spray deposit, pesticide
application.
Whilst reports issued under the auspices of the HDC are prepared from the best available information,
neither the authors or the HDC can accept any responsibility for inaccuracy or liability for loss,
damage or injury from the application of any concept or procedure discussed.
©2000 Horticultural Development Council
No part of this publication may be reproduced in any form or by any means without prior
permission from the HDC
The results and conclusions in this report are based on a single series of experiments. The
conditions under which the experiment was carried out and the results have been reported with
detail and accuracy. However, because of the biological nature of the work it must be borne in
mind that different circumstances and conditions could produce different results. Therefore,
care must be taken with interpretation of the results especially if they are used as the basis for
commercial product recommendations.
CONTENTS
Page No.
PRACTICAL SECTION FOR GROWERS
Objectives and background
1
Summary of Results
1
Action points for growers
2
Practical and financial benefits from study
8
SCIENCE SECTION
Introduction
9
Materials and Methods
11
Results
17
Discussion
30
References
31
Appendices
32
PRACTICAL SECTION FOR GROWERS
Background and objectives
The commercial objective of the work is to determine the most effective spray practices for
long season tomato crops and provide growers with cost-effective and robust
recommendations. The guidelines reported here have been developed over a three year
period of detailed trialling.
Summary of Results
Year 3 (1999)
The results reported within this study confirm that high levels of deposits and deposit
uniformity (ratio between upper and lower leaf surfaces) can be obtained by operating at
volume application rates of around 2,200 l/ha to 2,500 l/ha. The highest levels of deposit
recorded on underside of leaf surfaces in the inner canopy were found at volume rates of
greater than 1,700 l/ha with the most uniform deposits at a volume rate of 2,340 l/ha.
The use of air assistance gave no substantial changes in deposit levels or the uniformity of
spray deposits when sprays (and air) were directed upwards into the canopy at an angle of
45o. When spraying horizontally, air assistance tended to increase deposition levels but
overall deposit distributions were less uniform particularly at volume rates in the order of
1,125 l/ha. It is recognised that the use of air assistance would involve a fundamental
redesign of the application machinery and the results reported here suggest that it would be
difficult to justify based on the performance obtained both in terms of total deposit levels and
the distribution of such deposits. It is possible that air assistance may be more important if
application rates of less than 1,000 l/ha were to be considered.
However this is not
considered practical because of the limitations to chemical concentrations and the high levels
of variability obtained in experiments at low application volumes. Work is on-going in
Germany and elsewhere on the use of air assistance and it may be worth investigating this
area again once further progress has been made.
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The visualisation of dye deposit using the recommended boom arrangement illustrated in
Figure 1 and operating at 2,200 l/ha showed good levels of coverage throughout the canopy
and on upper and lower leaf surfaces (see Figures 2a and 2b). Similar observations of deposit
obtained with an air assisted application at a nominal volume application rate of 1,500 l/ha
also showed good coverage but with some areas of low deposit due to shadowing effects of
neighboring leaves.
Action Points for Growers [Recommendations based on three years work]
Defining the components for optimal boom configuration
Improving spray retention within the crop canopy
To define the volume rates that would optimise spray retention within the plant canopy
application rates in the range 700 to 4,200 l/ha were made. Spray retention by the canopy
increased with volume rates up to 2,500 l/ha. Increasing volume applications rates above this
level led to high levels of run-off recorded as an increase in ground deposits. For maximum
spray retention application volumes of 2,200 to 2,500 l/ha are recommended. At a nominal
walking speed of 1m/s this can be achieved with a nozzle flow rate of 1.2 l/min operating at a
pressure of 2.5 or 3.0 bar for 2,200 or 2,500 l/ha, respectively.
Improving spray penetration into the crop canopy
Mean droplet velocities from hollow cone nozzles are lower than those from flat fan designs.
As a consequence deposits on outer leaves of the tomato canopy were higher than on the
inner leaf samples when treated with hollow cone nozzles. Similarly nozzles with a narrower
spray angle, 80o compared to 110o, have higher droplet velocities. For improved penetration
into the crop canopy 80o flat fan nozzles are recommended.
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Improving deposit distribution between upper and lower leaf surfaces
Spray deposition was always found to be greater on upper leaf surfaces compared to lower
leaf surfaces. However, the majority of pesticide applications are made to control Red Spider
Mite populations which reside on the underside of the leaf. Spray deposition to this
important target site can be greatly improved by angling the nozzles upward at 45o compared
with the nozzles positioned horizontally on the boom. It is also important to remember that
Red Spider Mite migrate to the top of the plant canopy as the season progresses. Therefore in
order to target this site (upper plant canopy / lower leaf surface) it is important to match the
height of the boom / spray fan to the height of the crop. This should be achieved by layering
the crop prior to pesticide application.
Can air assistance improve spray deposition?
The use of air assistance gave no substantial changes in the level of deposits or uniformity of
deposits when spray (and air) were directed upwards into the canopy at an angle of 45o.
However, some improvements were noted when horizontal air flows were used. It was
recognised that the use of air would involve an increase in the costs of the application
machinery and the results from the work conducted suggest that such cost increases would be
difficult to justify.
Conclusions: The optimal spray boom configuration for long season tomato crops
With conventional vertical pipe-rail boom sprayers, application rates in the region 2,200 to
2,500 l/ha applied with 80o flat fan nozzles, spaced at 30 cm centres, operating at pressure of
2.5 to 3.0 bar respectively are the most effective way of attaining spray penetration into the
canopy. Application rates above 2,500 l/ha will lead to increased levels of run-off. At a
nominal walking speed of 1 m/s this can be achieved with nozzle flow rates of 1.2 l/min
operating at a pressure of 2.5 or 3.0 bar for 2,200 l/ha and 2,500 l/ha, respectively. The
international nomenclature for this nozzle type is referred to as “03F80” (03 = flow rate; F =
flat fan; 80 = 80o spray angle) and growers should quote this when ordering new nozzles. To
improve the deposit distribution to the all important lower leaf surface the nozzles should be
angled 45o upwards on the boom (Figure 1).
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The distribution of deposits is always more variable at the top of the plant canopy where the
variation between plants is greatest. In order to attain effective spray coverage for the control
of pests such as Red Spider Mite, which migrate to the top of the plant canopy, growers
should match the boom arrangement to the height of the crop. This will usually involve
lowering the heads of the plants prior to a spray application.
These recommendations are sufficiently robust so as not to require adjusting for different
spray formulations and will provide growers with spray coverage on upper and lower leaf
surfaces as illustrated by fluorescent tracer dyes in Figures 2a and 2b.
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Figure 1.
The recommended boom configuration for the application of pesticide sprays to
P al n t cen tre lni e
P al n t su r af ce
9 no zz les
@ 0 .3m sp ac ni g
A ng le = 45 d eg rees upw a rd s
B oom cen tre lni e
high wire tomato crops. (All dimensions are in mm).
80 °
45 °
3000
2470
70
B a se el ve lo fp al n t
45 °
350
775
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Figure 2a. Typical coverage on upper (top photo) and lower (bottom photo) leaf surfaces of
top canopy leaves achieved with an application rate of 2,200 l/ha using the
recommended boom arrangement illustrated in Figure 1 for high wire tomatoes.
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Figure 2b. Typical coverage on upper (top photo) and lower (bottom photo) leaf surfaces of
bottom canopy leaves achieved with an application rate of 2,200 l/ha using the
recommended boom arrangement illustrated in Figure 1 for high wire tomatoes.
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Anticipated Practical and Financial Benefits
1. Annual crop yield and quality losses in protected horticulture due to pest and disease
attack are estimated to be in the region of 5%. This represents a financial loss of £2.6m
for tomatoes. Timely and effective pesticide application can potentially reduce these
losses. Frequently, the action of a pesticide is less effective than anticipated due to poor
application. With frequent ineffective application, resistant populations of pest and
disease pathogens can quickly develop. Therefore future control of pest and disease
could become increasingly difficult leading to greater crop losses.
2. Increasingly strict supermarket guidelines for the use of pesticides often restricts the
number of applications allowed to a crop, despite label recommendations. In order for
growers to supply these markets there will be an increased need to optimise the
effectiveness of each spray application. The final year of this project contributes to
information necessary for growers of tomatoes to achieve “Good Agricultural Practice” in
the use of pesticides.
3. The time involved in spray applications can be a significant increase in the labour
requirement for a crop. More importantly, time spent on spraying the crop may delay
other operations. It is therefore important to make sure that any pesticide applications are
as effective as possible.
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SCIENCE SECTION
INTRODUCTION
Pesticide applications in glasshouses are made using a wide range of techniques. Work to
examine the performance of pipe-rail systems for treating tomato crops was initiated
following a study that showed that growers were using a wide range of nozzle configurations
on such units (Fletcher, 1992) and that there were few guidelines relating to the effective
operation of this type of equipment.
Work at HRI Stockbridge House in the 1997 and 1998 growing seasons was aimed at:

determining nozzle positions and orientations on a vertical boom that would give high
levels of spray deposition and uniformity on the target tomato crop canopy grown at three
different crop densities;

establishing the degree to which deposition patterns could be modified by using different
types of spray nozzle, particularly hollow cone compared with flat fan designs;

defining volume application rates that would achieve good coverage with the minimum
run-off losses and associated risks of soil contamination.
Results from studies conducted in the first two years of the project showed that application
could be improved by using volume rates of up to 2,200 l/ha with 80o flat fan nozzles angled
at 45o upwards. There was also some evidence to suggest that the use of air-assistance at
volume rates in the range 1,000-2,000 l/ha could give good performance particularly with
regard to the ratio between upper and lower leaf surface deposits. A number of other
application parameters have been examined in these earlier studies (Miller and Power, 1998
and 1999; Hargrave, 1998; Lee 1999) but it is considered that practical advice to growers is
likely to be based on either the use of 80o flat fan nozzles directed upwards, an air-assisted
configuration or a combination of these. However, some issues needed to be resolved before
authoritative recommendations could be made to growers regarding sprayer configurations
and operational guidelines based on the previous work. These included:
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
confirmation of the volume application rate that, when applied with 80o flat fan nozzles
spaced at 300 mm centres and angled at 45o upwards, will give high levels of coverage
and the optimum distribution of deposits between upper and lower leaf surfaces: this
confirmation was considered to be important because the methods of sampling the
deposits on upper and lower leaf surfaces in earlier experiments (Miller and Power, 1999)
may have facilitated some re-distribution of deposits particularly at higher volume rates;

definition of the air-assisted spraying arrangements that would give optimum application
performance in terms of air volume flow rates, air speeds, directions and the interactions
between the airflow and the spray.
There was also a need to define the volume
application rates that can be used with a configuration of an air-assisted sprayer that could
be shown to achieve high levels of uniformity within the treated crop.
It was also recognised that the ability to visualise spray deposition both on the target leaf
surfaces and throughout the target crop canopy would be an important aid to selecting
practical treatment options and in demonstrating the advantages of improved application to
growers and spray operators. It was therefore decided that techniques would be developed
for visualising such deposits based on the use of a fluorescent dye.
Since commencing the work to study spray deposition in glasshouse tomato crop canopies,
the authors of this report have become aware of some parallel studies being undertaken in
Germany (Wygoda, Rietz and Schäfertöns, 1999) which established that the highest levels of
underleaf coverage was obtained by using air-assistance with a high level of turbulence and
relatively fine sprays. The comparison was made at a volume rate of 1,200 l/ha and therefore
has some strong linkages with the results of work presented in this report.
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MATERIALS AND METHODS
Crop Details
A tomato crop cv Espero was sown on 11 December 1998 and planted on 20 January 1999
into a modern 400 m2 4.2 m high Venlo glasshouses at HRI Stockbridge House. The crop
was grown on the V-system at a final density of 14,000 heads per acre. Spray treatments
were not applied until a full crop canopy had developed. In all respects crop management
followed best commercial practice.
Sampling Procedure
Prior to spray application 10 mm x 50 mm chromatography paper strips were placed on four
plants in the centre of a 15 m crop row with sampling points on each of;
1. Top canopy leaves, upper and lower leaf surface in the inner and outer plant canopy.
2. Middle canopy leaves, upper and lower leaf surface in the inner and outer plant canopy.
3. Bottom canopy leaves, upper and lower leaf surface in the inner and outer plant canopy.
4. Stems (top, middle and bottom).
5. Ground deposits
In addition, whole leaflets from the inner and outer plant canopy were selected from the top,
middle and bottom of three plants within the treated area (Figure 3). The spray liquid
comprised water plus 0.2% tracer dye (‘Green S’, Merck Chemical Ltd) and 0.1% non-ionic
surfactant (Agral, Zeneca Agrochemicals). The sampling strategy was designed to enable
deposits on chromatography paper strips and plant leaflets in the top, middle and lower parts
of the plant canopy to be quantified separately.
Particular attention was directed at
quantifying the ratio between upper and lower leaf-surfaces.
Spray deposits on the
chromatography paper strips were quantified by recovering the dye into solution and
determining the volume of the original spray liquid on the target by spectrophotometry
calibrated against samples taken directly from the nozzles during the experiment.
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Figure 3
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The leaflets were weighed immediately after collection and the dye was recovered into
solution by washing with 50 ml de-ionised water such that deposits could be expressed as a
volume of spray liquid per unit leaf weight. Immediately prior to applications being made as
part of the experiment, the system was calibrated by measuring flow rates from the nozzles at
the set pressure and by recording the speed of the trolley system between rows by timing the
period to travel a measured distance. A nominal speed of 1.0 m/s was used for all treatments.
Checks on nozzle pressure and travel speed were also made during the experiment.
Some changes were made to the deposit sampling strategy employed in 1998 (Miller and
Power, 1999). The use of chromatography paper strips folded and attached to the edges of
leaves in different parts of the crop so as to sample upper and lower leaf deposits
simultaneously could have given errors due to spray liquid running between the upper and
lower leaf surfaces particularly at the higher volume application rates. Therefore separate
sampling papers were attached to the upper and lower surfaces of different leaves to minimise
the risk of re-distribution of deposits, with papers attached to lower leaf surfaces using a
double staple.
1. Experiments to confirm the volume rate effects 8th and 9th June 1999
A series of experiments were conducted using 80o flat fan nozzles angled 45o upwards and
spaced at 300 mm up the boom. Volume rates were varied by changing both nozzles and
pressures as shown in Table 1, based on a travelling speed of 1.0 m/s down the row.
Table 1. Nozzle selection and pressures for the volume rate treatments
Nozzle
type*
Pressure
(Bar)
8001
80015
8002
8003
8003**
3.0
3.0
3.0
2.5
3.0
*
**
Nominal
application rate
(l/ha)
750
1125
1500
2054
2250
Measured
application rate
(l/ha)
851
1276
1702
2340
2514
The first two digits represent spray fan angle (80); subsequent digits define
flow rate (1.0, 1.5, 2.0 and 3.0 l/min)
Conventional reference treatment.
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It was recognised that the changes in volume application rate indicated in Table 1 were
achieved at different spray qualities between fine and the centre of the medium spray quality
category (Doble, et al., 1985). This was considered to be acceptable because it could be
achieved by using the same number of nozzles on the boom (9) at a constant spacing,
illustrated in appendix I. Previous results (Miller and Power, 1998 and 1999) had also
suggested that the differences in spray quality associated with this nozzle selection would
have only small effects on the levels of deposition recorded. The reference treatment was
replicated three times to enable an estimate of the variability in the results of the experiments
to be assessed.
2. Experiments to examine air assisted spraying configurations.
Two sets of experiments were conducted to assess the performance of air-assisted
applications using different nozzle and air duct configurations. The first set of experiments
used the same basic configuration as for the 1998 experiments (Miller and Power, 1999) but
adapted such that the angle of the output air could be adjusted to be in a 45o upwards
direction. This was achieved by adding deflector plates in front of the outlets from the air
entrainment device. A single air entrainment section, 1.45 m long was used for this work by
mounting it on one of two alternative positions, applying treatment and then using it in the
other position to complete the application in the same way as in 1998. The position of the
spray nozzles mounted in the plastic air entrainment device was such that the nozzles were
closer to the crop canopy than in the case of the conventional arrangement and there was no
scope for adjusting the nozzle angle. It was therefore decided to modify the arrangement
incorporating the following changes:

building a unit with both upper and lower air entrainment devices mounted in a modified
frame and supplied with air simultaneously so that the need to make two passes to
complete each air-assisted treatment was eliminated;

a separate liquid supply line with nozzles mounted in the same way as for the
conventional system so that the same nozzle configurations could be used in the airassisted treatments including the angling of nozzles upwards.
©2000 Horticultural Development Council
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This modified arrangement also increased the distance from the nozzle positions to the crop
canopy enabling a more complete spray volume distribution pattern to be established before
the spray contacted the crop canopy.
Practical operation with this modified unit showed that it was very heavy and cumbersome to
use. A further unit was therefore designed based on the use of a single air tube mounted
close to the nozzles with the vertical air tube having a line of holes along its length and fed
with air from a separate compressor, illustrated in appendices IIa and IIb. This unit was used
in a final series of experiments in which spray deposits were visualised throughout the whole
of the canopy and at an individual leaf level using a fluorescent tracer dye (described in
Section 3). In these experiments, sprays were applied during the day, allowed to dry, and
detailed observations and photographs of the deposits were taken after dark using ultra-violet
illumination.
2.1 Air-assisted settings evaluated
In the first series of experiments, the addition of two levels of air-assistance to a spray
applied at 1,490 l/ha was compared with the reference treatment applied using conventional
80o flat fan nozzles directed upwards and applying 2,200 l/ha.
The runs with the air
assistance initially angled the air flow upwards at 45o using the added baffles but with two
treatments also applied with the air flow horizontal. The measured air velocities 300 mm
away from the air outlet determined with a vane anemometer (EDRA Ltd.) are shown in
Table 2.
Table 2. Air velocities for the first series of air-assisted experiments,
8th and 9th June 1999.
With vanes 45o upwards
With vanes horizontal
Measured air speeds, m/s
Low air setting
High air setting
3.5 - 4.5
7.0 - 8.5
4.5 - 5.0
9.0 - 11.0
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The lower air velocities with the air angled at 45o upwards were due to the effect of the
resistance of the angled deflector blades. The second series of air-assisted applications used
direct comparisons between air-assisted and conventional applications at application volume
rates of 1,275, 1,700 and 2,200 l/ha with air and spray directed both horizontally and at 45o
upwards. All runs used a single air velocity of 3.0 m/s measured 150 mm from the air outlets
using a vane anemometer.
3. Visualisation of spray deposits
Photographic records of spray deposits were obtained by spraying a 1% suspension of a
fluorescent tracer dye (Saturn Yellow) with 0.1% of a non-ionic surfactant (Agral, Aeneca
Agrochemicals). Applications were made with the conventional reference treatment using
80o flat fan nozzles spraying 45o upwards at nominal volume rates in the range 1,000 – 2,200
l/ha and without air-assistance. Assessments were also made with the same configuration and
air-assistance directed horizontally from a modified design of air-assisted system as shown in
appendices IIa and IIb. This used a vertical air tube mounted beside the nozzle line with 2
mm diameter holes spaced at 20 mm centres. Air velocity measured at 500 mm from the
boom was 3 m/s.
4. Crop canopy characteristics
For all series of measurements, samples of crop leaves similar to those taken for the deposit
analysis were taken, weighed and the leaf area determined. This gave a relationship between
leaf weight and leaf area that can be used in the interpretation of the results obtained.
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RESULTS
1. Experiments to confirm the volume rate effects 8th and 9th June 1999.
Figures 4a and b shows the measured spray deposits, expressed as a mean for top middle and
bottom canopy layers on both papers (Figure 4a) and leaf surfaces (Figure 4b) for volume
application rates in the range 850 to 2,540 l/ha. As expected, there is a trend towards higher
deposits at the higher volume application rates which in the case of the leaf deposits reaches a
maximum value at the rate of 2,340 l/ha. It is likely that application volume rates above this
level result in high levels of run-off particularly from upper leaf surfaces. The absorbent
nature of the paper strip targets attached to the leaves meant that the effect due to possible
run-off were not seen with this target system.
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Figure 4
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Results from the paper targets used to assess the uniformity of the deposit distribution
showed that the lowest levels of deposit were consistently on the lower sides of inner leaves,
an important target site for pests such as red spider mite. Deposits on papers at this position
increased over the volume rate range examined.
The data plotted in Figure 5a and 5b is normalised to account for the effect of different
application rates to give data that relates to the dose retained on the target and is again shown
as a mean of top, middle and bottom canopy layers. These results show:

that the chemical deposits on leaves is approximately constant over the volume rate range
1,280 to 2,340 l/ha;

that chemical deposits on the underside of inner leaves increases with increasing volume
rate to 1,700 l/ha and then remains approximately constant;

that the highest level of uniformity of deposit both in volume and dose rate terms was at
the volume rate of 2,340 l/ha;

the highest deposit levels were always on the upper surfaces of leaves.
There were only small differences between leaf deposits in the inner and outer crop canopy
with the exception of the result obtained at 1,700 l/ha volume rate, which gave a relatively
low value for the outer canopy deposit. This is likely to be a function of the sampling
strategy used. The results from replicated runs of the reference treatment (Table 1) indicates a
standard deviation for paper deposits of 12 to 25% for inner canopy samples and higher
levels for outer canopy measurements, probably because these sample papers are closer to the
nozzles at the time of treatment.
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Figure 5
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2. Experiments to examine air assisted spraying configurations.
The results from the first series of experiments conducted on 8th and 9th June and comparing
the reference treatment (conventional 80o flat fan nozzles, angled 45o upwards applying 2,200
l/ha nominally) with a nominal volume rate of 1,500 l/ha and air directed upwards at 45o are
summarised in Figures 6a and 6b. Again the results are a mean of top, middle and bottom
canopy layers. The use of the low level of air assistance gave a high level of uniformity of
deposits. The results on the paper targets for the reference treatment, with the exception of
outer upper leaf deposits, are lower than recorded in the volume rate experiment (Figure 4a)
reflecting the variability in the sampling system. There is, however, good agreement with the
levels of leaf deposits recorded in the two sets of experiments (Figures 4b and 6b).
The data in Figure 6 shows that in volume terms, the leaf deposits from the conventional
reference treatment were higher but, that when normalised to account for different application
rates to represent the situation of a constant applied dose deposits, the air-assisted treatments
were higher (Figures 7a and 7b). The results from both the paper and leaf targets suggested
that the greatest uniformity of deposits between upper and lower leaf surfaces was achieved
with the lower level of air assistance.
Results obtained with the same air-assistance configuration as shown in Figures 6 and 7, but
directed horizontally are summarised in Table 3. Deposit levels tended to be greater than
those with the 45o upward lower velocity air-assisted treatment (Figures 6a and 6b) but with a
much higher level of variability particularly at the low air velocity setting.
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Figure 6
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Figure 7
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Table 3. Measured deposits (μl/paper or μl/g of leaf weight) for air-assisted treatments
applying 1,500 l/ha with air directed horizontally.
Sample position
Inner upper - paper
Inner lower - paper
Outer upper - paper
Outer lower - paper
Inner – leaf
Outer – leaf
Measured deposit
Low air assistance
High air assistance
42.1
77.9
24.0
21.6
178.1
116.2
35.0
40.6
109.3
61.7
139.9
113.7
The results of experiments examining the effect of air assistance with air and spray applied
both horizontally and directed 45o upwards at nominal volume application rates of between
1,000 and 2,200 l/ha are summarised in Figures 8 to 10 respectively. Since each treatment
comparison was made with the same nozzle conditions and hence the same volume
application rate, data for this set of experiments have not been normalised.
At the higher volume application rate of 2,200 l/ha (Figure 8) there was some variation
between the two replicated measurements made with no air assistance and with the spray
angled upwards at 45o. There was no substantial differences between the non air-assisted and
the air-assisted application either in terms of deposit distribution (as assessed by the deposits
on papers) or total leaf deposits. The use of air assistance substantially increased deposition
when air and spray were directed at the canopy horizontally but it is noticeable that the level
of uniformity was less good when applications were made horizontally. This again supports
the results obtained in earlier studies (Miller and Power, 1999).
Similar results were obtained at a nominal volume application rate of 1,500 l/ha (Figure 9)
although assessments were only made in this case with the air and spray directed 45o
upwards. Again no substantial advantage can be attributed to the use of air assistance.
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Figure 8
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Figure 9
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Figure 10
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There was more variability in deposition levels at the lowest volume application rate,
nominally 1,125 l/ha (Figure 10) particularly when air and spray were directed at the crop
canopy horizontally. When spraying horizontally, deposits were again increased by the use
of air assistance and at 45o the air dramatically increased the under-leaf coverage at the outer
parts of the canopy.
In some of the experiments using air-assistance, the level of under-leaf coverage was
increased and this may be important when treating insect pests that are mainly resident on the
underside of leaves.
3. Visualisation of spray deposits
Typical results for the upper and lower leaf deposit distributions for top and bottom leaves in
the canopy applied using the conventional, reference nozzle system operating at 2,200 l/ha
are shown in Figures 2a and 2b respectively. At this volume rate, good levels of coverage
were achieved on upper and lower leaf surfaces throughout the canopy.
At volume
application rates lower than 2,200 l/ha there was evidence of areas of low deposit due to the
shadowing effects of leaves particularly on the inner parts of the canopy supporting the
measurements of deposit distribution made with the paper samples. Similarly, no large
changes in distribution pattern when using air-assisted applications were noted at any of the
three volume rates used for these assessments (1,125 l/ha, 1,500 l/ha and 2,200 l/ha)..
Sample photographs and video footage of the coverage obtained for all treatments have been
archived at Silsoe Research Institute and are available for the Horticultural Development
Council to use, as required for grower workshops, publications etc.
4. Crop canopy characteristics
The relationship between leaf weight and leaf area for samples taken from different parts of
the crop canopy are plotted in Figure 11. This data provides the basis for interpreting the
measured deposits into a leaf area measure.
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Figure 11
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DISCUSSION
The overall results from the results presented in this report strongly complement the data
collected in the 1997 and 1998 cropping seasons. In particular, the results confirm that there
is no advantage to be gained by operating at volume application rates of above 2,500 l/ha
either in terms of the total deposits on leaves or in terms of increasing the chemical deposits
on the undersides of leaf surfaces. The photographic records obtained also indicate that when
applications are made using conventional 80o flat fan nozzles directed upwards at an angle of
45o, high levels of deposition are achieved with good distribution on upper and lower leaf
surfaces and throughout the canopy.
It is recognised that limitations relating to the allowable maximum concentrations of some
pesticide products may limit the extent to which volume application rates can be reduced.
However, the results from the whole of this HDC funded study consistently indicate that
good levels of deposition can be obtained at volume application rates in the range 2,000 –
2,500 l/ha.
Using conventional nozzles directed upwards at the volume rates indicated above, results
from this study show no substantial advantages from using air-assistance. Given that airassistance is very likely to involve an increase in the capital costs of application equipment
and added complexity in terms of operation in the glasshouse, results from the study
conducted here make no case for the use of such techniques. However, studies elsewhere
with tomato and cucumber crops (e.g. Wygoda, et al., 1999) suggest that high levels of
deposit and uniformity of deposit can be achieved at volume application rates of less than 100
l/ha and under such conditions, the performance of application systems may be enhanced by
using air-assisted applications. It would be advisable to await the results from these studies
(Wygoda et al., 1999) before investigating the potential of air assistance again.
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REFERENCES
Doble, S.J.; Matthews, G.A.; Rutherford, I.; Southcombe, E.S.E. (1985)
A system for
classifying hydraulic nozzles and other atomisers into categories of spray quality.
Proceedings of British Crop Protection Conference - Weeds, 1125 - 33
Fletcher, J.T. (1992) Tomatoes - An examination of the efficiency of spray application to
commercial crops. HDC Research Report PC 54
Hardgrave, M. (1998) Tomatoes and cucumbers - evaluation of effective use of pipe-rail
boom sprayers. PC 136. Annual Report, 1997. Horticultural Research International
Lee, A.W.; Miller, P.C.H.; Power, J.D. (2000) The application of pesticide sprays to tomato
crops. Aspects of Applied Biology, 57, Pesticide Application, 383 - 390
Miller, P.C.H.; Power, J.D. (1998) Tomatoes and cucumbers - evaluation of effective use of
pipe-rail boom sprayers - the contribution from Silsoe Research Institute to HDC Project PC
136 led by HRI Stockbridge House. Contract Report CR/823/97/1618 Silsoe Research
Institute
Miller, P.C.H.; Power, J.D. (1999) Tomatoes and cucumbers - evaluation of effective use of
pipe-rail boom sprayers - the contribution from Silsoe Research Institute to HDC Project PC
136 led by HRI Stockbridge House - work in the 1998 growing season. Contract Report
CR/938/99/2079 Silsoe Research Institute
Wygoda, H.-J.; Reitz, S.; Schäfertöns, J.-H. (1999)
A new application technique in
greenhouse row crops. Poster presentation at XIVth International Plant Protection Congress,
Jerusalem, Israel.
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APPENDIX I
Nozzle arrangement used for the conventional reference treatment within the experimental
programme and now recommended boom configuration for the application of pesticide
P al n t cen tre lni e
P al n t su r af ce
9 no zz les
@ 0 .3m sp ac ni g
A ng le = 45 d eg rees upw a rd s
B oom cen tre lni e
sprays to high wire tomato crops. (All dimensions in mm).
80 °
45 °
3000
2470
70
B a se el ve lo fp al n t
45 °
350
775
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APPENDIX IIa
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APPENDIX IIb
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