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November, 2018 Int J Agric & Biol Eng Open Access at https://www.ijabe.org Vol. 11 No.6 5
Drift and deposition of pesticide applied by UAV on pineapple plants
under different meteorological conditions
Juan Wang1,2, Yubin Lan1*, Huihui Zhang3, Yali Zhang1, Sheng Wen4, Weixiang Yao1,
Jiajian Deng5
(1. College of Engineering, South China Agricultural University/ National Center for International Collaboration Research on Precision
Agricultural Aviation Pesticides Spraying Technology (NPAAC), Guangzhou 510642, China; 2. Mechanical and Electrical Engineering
College, Hainan University, Haikou 570228, China; 3. USDA-Agricultural Research Service, Fort Collins, CO 80526, USA;
4. Engineering Fundamental Teaching and Training Center, South China Agricultural University, Guangzhou 510642, China;
5. Hainan NongFeiKe Agriculture and Technology Co. Ltd, Haikou 570100, China)
Abstract: Spray drift has always been a focus research area in the field of unmanned aerial vehicle (UAV) application. Under
the fixed premises of UAV operating parameters, such as height, speed and spraying liquid, the droplet drift is mainly affected
by meteorological conditions. In this research, the spray drift and deposition tests were conducted using a QuanFeng120 UAV
in a pineapple field under various different meteorological conditions. The experiment results showed that with the changes of
UAV operating height and wind speed, the start position of the in-swath deposition area had changed 4 m in the extreme
situation. The percentage of the total spray drift was from 15.42% to 55.76%. The position of cumulative spray drift that
accounted for 90% of the total spray drift was from 3.70 m to 46.50 m relative to the flight line. According to the downwind
spray drift curve, the nonlinear equations of the same type under the four operating conditions of the UAV were fitted. The
spray drift and the deposition of UAV application were significantly affected by different meteorological conditions and UAV
operating heights. The results could provide a theoretical basis for UAV spraying in pineapple plants and support for spray
drift control and prediction.
Keywords: UAV, spray drift, deposition, meteorological condition, pineapple
DOI: 10.25165/j.ijabe.20181106.4038
Citation: Wang J, Lan Y B, Zhang H H, Zhang Y L, Wen S, Yao W X, et al. Drift and deposition of pesticide applied by
UAV on pineapple plants under different meteorological conditions. Int J Agric & Biol Eng, 2018; 11(6): 5–12.
1 Introduction
Aerial spray has better mobility and pesticide application
efficacy than ground mechanical spray[1-3]. During pesticide
spraying, movement of pesticide particles or droplets toward
non-target areas driven by airflow is called drift[4]. Spray drift and
application safety has always been one of the key issues in the field
of unmanned aerial vehicle (UAV) spraying. Droplet drift not
only wastes pesticide and affects the prevention effect[5], but also
pollutes the environment[6-8].
Any substance released into the atmosphere (spray, smoke, etc.)
will be spread to other places. If spray drift loss contains high
amount of active ingredient drift sedimentation in any sensitive
Received date: 2018-03-12 Accepted date: 2018-10-30
Biographies: Juan Wang, PhD candidate, research interests: precision
agriculture technology and equipment, Email: 49792740@qq.com; Huihui
Zhang, PhD, Research Agricultural Engineer, research interests: airborne and
ground-based remote sensing, Email: huihui.zhang@ars.usda.gov; Yali Zhang,
PhD, Associate Professor, research interests: precision agricultural aviation
application, Email: ylzhang@scau.edu.cn; Sheng Wen, PhD, Associate
Professor, research interests: precision agricultural aviation application, Email:
58675023@qq.com; Weixiang Yao, PhD candidate, research interests: precision
agriculture technology and equipment, Email: 1913835329@qq.com; Jiajian
Deng, Agronomist, research interests: application of pesticides in agriculture
aerial, Email: 898549910@qq.com.
*Corresponding author: Yubin Lan, PhD, Distinguished Professor, research
interests: precision agricultural aviation application. National Center for
International Collaboration. Research on Precision Agricultural Aviation
Pesticide Spraying Technology, South China Agricultural University,
Guangzhou 510642, China. Tel: +86-20-85281421, Email: ylan@scau.edu.cn.
non-target area, it will cause damage to water, plant, human, animal,
etc. Pesticide drift refers to a physical movement in which
pesticide droplets or particles migrate from the target area to the
non-target area in the air during the course of the application or
after application for a period of time under uncontrolled conditions.
Pesticide drift includes vapor and airborne drift, which is caused by
the evaporation of the active ingredient of the pesticide. The wind
drift is due to the fact that the fine droplets in the spray are carried
by the airflow to the non-target area or disappearance. Dodge
pointed out that due to the growing concern about environmental
protection, the control of pesticide drift will drive the development
of new spray technology[9]. Therefore, droplet drift has become
an important issue in agricultural crop protection operation and
requires attention[10].
The physical transport of applied agrochemical sprays through
the air to any off-target site is considered spray drift. Many
factors affect drift including: (1) The effective composition and
type of liquid preparations, droplet size and volatility; (2) Spraying
equipment, use of technology, and aircraft operating parameters; (3)
Meteorological conditions, such as wind speed and direction,
temperature and humidity, atmospheric stability and terrain; (4)
The operator’s sense of responsibility and skill level[11-14]. To
control weeds, pests and diseases, it needs optimal pesticide dose,
the most suitable droplet size, and weather conditions, so that the
droplets in the target surface can be better coverage, attachment,
spread and absorption. Under the control of the same dosage, the
smaller the particle size, the better the coverage, however, there is a
risk of drift. Under the condition that the parameters of the UAV
are relatively stable, the influence of meteorological conditions on
6 November, 2018 Int J Agric & Biol Eng Open Access at https://www.ijabe.org Vol. 11 No.6
the deposition and spray drift of liquid pesticide is particularly
important. Applicators must understand weather conditions when
spraying pesticides, such as: wind speed, wind direction,
temperature, humidity and other effects of weather conditions[15].
One of the meteorological conditions that can occur to spray drift is
wind speed. At higher wind speeds, droplets dispersion and
dilution increase, ground deposition concentration decreases, and
the wind must blow the droplets or enough active ingredients in the
particles to the non-target area. The droplets cannot be obstructed
by obstructions or vegetation between the spray zone and the
non-target area. The droplet deposition behavior and drift
characteristics are the basic aspects of the spray effect[16,17].
According to the Chinese Civil Aviation Industry Standards,
measuring droplet drift materials are usually polyethylene wire,
glass, filter paper, water sensitive paper, chromatography and other
methods. Many domestic and foreign experts and scholars
researched on aerial spraying operation efficacy[18-21]. Some used
water sensitive paper and mylar card to analyze the deposition
parameters. Hoffmann and Hewitt concluded that although
USDA-ARS system, Swath Kitcamera-based system and Droplet
Scan scanner-based system have different test methods, the test
results were similar[22]. Franz applied fluorescence
spectrophotometers and light-sensitive paper on cotton leaves to
examine the effects of canopy characteristics and climatic
conditions on the deposition and drift of cotton droplets[23]. Lan
et al.[24]
. added adjuvants in the fixed-wing aircraft on the spraying
of cotton, and the effects of different adjuvants on the spray drift
were studied. Xue et al[25]. tested the spray and deposition of
UAV in a rice field under the condition of Z-3 UAV operating
parameters which could control 90% of the drift in 8 m. Fritz
suggested that the influence of wind speed in different
meteorological conditions is the most important. He also
indicated that wind speed was the dominant factor affecting the
transport and fate of aerially applied sprays[26].
China is the world’s fourth largest producer of pineapple.
Due to Hainan Island’s inherent advantages of natural environment,
pineapple production accounts for about 26% of the total in the
country. Pineapple is the third largest fruit in Hainan Island, only
below the production of banana and mango[27]. A survey found
that the main factors that harm Hainan pineapple production are
pests, diseases, fertilizer damage and phytotoxicity. Pests and
diseases include pineapple wilt disease, leaf spot, heart rot and
pineapple mealybug. Heart rot disease causes damage to new
plantation pineapple seedlings, wilt and leaf spot disease is mainly
harmful to pineapple plants covered with fruit, and pineapple
mealybug mainly damages pineapple plant in orchard. At present,
aerial spray test applied in pineapple plants has not been reported.
Because Hainan Island belongs to the tropical monsoon climate, the
weather conditions are particularly important when a UAV is used
for pesticide application. At present, the domestic research on the
application of agricultural UAV has mainly focused on the effects
of operation parameters of aerial spraying on the characteristics of
droplet deposition distribution[28]. These main parameters
including air temperature, humidity, wind speed and direction and
UAV operating height, are all needed to be tested and evaluated.
At present, technical articles about aerial deposition and spray
drift on pineapple plants by a UAV has not been reported in China,
the experimental results can provide data and theoretical support
for the spraying of pineapples under different meteorological
conditions. Due to the lack of information on spray and
deposition of UAV application in pineapple pants, this article was
mainly to test the drift and deposition law of single-rotor oil-based
UAV in the different meteorological conditions in a pineapple field.
Test results can provide data support and theoretical basis for
pineapple spraying drift control and selection of suitable UAV
operation parameters.
2 Materials and methods
2.1 Test plan and meteorological conditions
The test place is located in, a 5 hm2 pineapple orchard in
Bolian town, Lingao County, Hainan Province (19°52'13"N,
109°38'39"W), China. Test meteorological data were recorded ,
in January 2-5, 2017 using a Kestrel Meterograph (Model NK-5500,
Nielsen-Kellerman Co., Boothwyn, PA, USA). The Meterograph
was placed in the upwind 5 m away from the flight line. The
distance from the ground was 105 cm, and data acquisition time
interval was 5 s. The meteorological data processing segment was
performed concurrently when UAV began to spray. The data
were averaged in 30 s for mylar cards deposition and in 60 s for
monofilament of drift testing devices. The wind direction refers
to the angle with the direction of the north (the direction north to 0°,
east to 90°, south to 180°, and west to 270°). The direction of the
flight was from north to south. In this paper, QF120 represents
QuanFeng120 UAV (Anyang QuanFeng Aviation Plant Protection
Technology Co., Ltd, Henan, China). Figure 1 shows a 3D
visualization. Sampling locations are shown in Figure 2. The
two sample lines with a distance of 40 m, were perpendicular to the
UAV flight line, and the sample line length was 60 m. According
to the spray characteristic of UAV, the in-swath deposition area
was preset to 8 m. Sampling stations were placed parallel to the
prevailing wind. There were two sampling lines (Line 1 and Line
2) for each replication. For each sampling line, in-swath
deposition samplers were directly under the UAV and were located
at 10 m, 8 m, 6 m, 4 m, 3 m, 2 m, 1 m, and 0 m upwind from the
downwind edge of the spray swath (designated as –10 m, –8 m,
–6 m, –4 m, –3 m, –2 m, –1 m, and 0 m). At each location, a
mylar card was placed. Downwind deposition samples were
placed at 1 m, 2 m, 3 m, 4 m, 6 m, 8 m, 10 m, 20 m, 30 m, 40 m,
and 50 m downwind from the edge of the spray swath. mylar card
size was 10 cm×8 cm. Nineteen sampling points were placed for
each sampling line. mylar card was located in the distance of 70
cm from the ground, and the average canopy height of pineapple
plants was 88 cm. Parallel to the flight line, 3 drift testing devices
were arranged in the middle of the two sample lines. The distance
of three devices from the flight line was 10 m, 25 m, and 50 m,
respectively. Each drift testing device consisted of two retractable
stainless steel tubes and three monofilament line (Ø=0.45 mm).
The height of the three monofilament lines was 1 m, 2 m, and 5 m,
respectively. Table 1 shows the parameters of the UAV and crop
characteristics. Figure 3 shows the UAV flight track collected by
Beidou system (an aerial Beidou positioning UB351 system
developed by the South China Agricultural University with the
RTB differential positioning function was equipped) [29].
Figure 1 UAV spray drift test collection and sampling location
3D visualization
November, 2018 Wang J, et al. Drift and deposition of pesticide applied by UAV on pineapple plants under different meteorological conditions Vol. 11 No.6 7
Figure 2 Test site layout showing flight line and sample locations
Figure 3 UAV flight track by Beidou and monofilament line
samples
Table 1 UAV specific parameters and crop characteristics.
QuanFeng120 Parameters
Power type oil driving single rotor
Nozzle Type 120-02
Droplet size/μm 268.6
Machine size/mm 2130×700×670
Flow rate (single)/mL·min-1 800
Number of nozzles 2
Tank capacity/L 12
Spray swath/m 5-8
Flight endurance/min ≥ 25
Driving speed /km·h-1 10.8
Crop density/hm-2 22 500
Crop type pineapple fruit tree
The average height of the crop/cm 88
2.2 Spraying method and pesticide type
In accordance with the design of test plan, place of mylar card,
assembly drift testing device and monofilament line, UAV
debugging was completed, equipped with Beidou system to capture
the UAV flight trajectory. The spraying pesticide was composed
of water, dinotefuran (Mitsui Chemicals AGRO Inc., Tokyo, Japan)
and rhodamine B (Sigma-Aldrich Inc., USA.) tracer. The
concentration of dinotefuran and rhodamine B tracer were 10 g/L
and 2 g/L, respectively. Each UAV operation was completed
when the sampling devices were completely dry. Disposable
gloves were worn to collect samples. mylar cards were sealed with
labeled plastic bag. Monofilament lines were rolled on a plastic
hollow shaft using a dedicated collection device and placed in
labeled plastic bag. All samples were numbered in order and put
into an ice box and brought back to the laboratory (China Tropical
Agricultural Sciences Institute Test Center) for analysis. mylar
cards and monofilament lines were eluted with 20 mL of ultrapure
water and the elution water was placed in a cuvette to measure the
fluorescence, and calculate the concentration of rhodamine B
contained in the sample Using the molecular fluorescence
spectrophotometer instrument (Model-F7000, HITACHI Inc.,
Tokyo, Japan). The fluorescence concentration curve was fitted
with the liquid sample, and the correlation was 99.9%. After the
sample concentration value is obtained, the deposition amount of
the sample was calculated according to Equations (1) and (2) as the
percentage of sample deposition rate:
()
s
mpl blk cal dii
dep
spray col
FV
A
−⋅⋅
=⋅
ρρ
βρ
(1)
%
10000
dep
dep
v
×
=
ρ
ββ
(2)
where, βdep is the spray drift deposit, μL/cm2; ρsmpl is the
fluorimeter reading of the sample; ρblk is the fluorimeter reading of
the blanks (collector+ ultrapure water); Fcal is the calibration factor;
Vdii is the volume of ultrapure water used to dilute tracer from
collector, L; ρspray is the spray concentration, or amount of tracer
solute in the spray liquid sampled at the nozzle, g/L; A
col is the
projected area of the collector for catching the spray drift, cm2;
βdep% is the spray drift percentage, %; βv is the spray volume, L/hm2.
3 Results and discussion
3.1 Samples –10 m to 50 m from in-swath and downwind edge
of swath-mylar tests under different meteorological conditions
UAV driving speed was kept at a fixed value of 3 m/s.
Although the environment was complex and changeable, the
temperature fluctuation value was within (26±2)°C and relative
humidity floats in (50±15)%. UAV operation parameters,
meteorological conditions, and simplified flight number
abbreviations (a and f curves) are shown in Table 2. UAV
operating height refers to the pineapple canopy.
Figure 4a shows the distribution curves of the mylar cards in
the sampling areas. It can be seen from Figure 4, when the QF120
was operated at the height of 2.5 m, the maximum deposition of
a-curve and b-curve occurred at 1 m and –1 m position. The
in-swath deposition area of b-curve moves backwards 2 m of the
a-curve. After 6 m and 4 m, respectively, spray drift in a-curve
and b-curve drastically reduced. Both of them had spray drift on
the upwind. As it can be seen from Figure 4b, when the QF120
operation height was 1.5 m, the d-curve with higher wind speed
had similar in-swath deposition area to the c-curve with low wind
speed. After 8 m and 6 m, respectively, spray drift in c-curve and
d-curve decreased sharply. Figure 4c shows that when the
operating height was 3.5 m, the e-curve of the higher wind speed
was significantly move backwards the in-swath deposition area of
f-curve, and the maximum deposition amount of the two was at
–1 m and 3 m, respectively. The amount of upwind deposition
was close to 0. The drift decreased after 20 m in e-curve and 3 m
in f-curve. The results verify the conclusion of Bird et al.[30]
And further stated that given similar stability conditions, increasing
wind speeds will tend to increase off-target deposition. Figure 5
shows the percentage of a-f curves in-swath deposition spray
8 November, 2018 Int J Agric & Biol Eng Open Access at https://www.ijabe.org Vol. 11 No.6
accounts for the total amount. The deposition bar of a-f curves
that under 1.5 m (c and d curves) and 2.5 m (a and b curves)
operation height, the wind speed effect on the deposition rate to the
total amount of spraying was less than 5%, but the in-swath
deposition decreased 22% by the wind speed varying by 1 m/s at
the height of 3.5 m (e and f curves).
Table 2 Meteorological conditions and operating parameters
Parameters a-curve b-curve c-curve d-curve e-curve f-curve
Real time wind speed/m·s-1 4.7 1.8 0.7 2.2 3.7 1.78
Mean speed/m·s-1 (30 s) 3.18 2.17 1.17 1.37 3.93 1.71
Mean speed/m·s-1 (60 s) 2.82 2.0 1.14 1.25 3.59 2.02
SD/m·s-1 (60 s) 0.76 0.60 0.49 0.60 0.73 0.46
CV/% (60 s) 27 29 43 48 20 23
Real time wind direction/(°) 63 100 160 120 55 56
Mean wind direction/(°) (30 s) 69.7 92.5 169 128 65.5 63
UAV operating height/m 2.5 2.5 1.5 1.5 3.5 3.5
UAV driving speed/m·s-1 3 3 3 3 3 3
Mean temperature/°C (30s) 27.2 26.1 27.8 25.9 24.9 26.5
Mean relative humidity/% (30 s) 50.8 60.55 60.8 57.6 67.6 57.6
Note: SD- standard deviation, CV- coefficient of variation.
a. a and b curves b. c and d curves c. e and f curves
Figure 4 a-f curves in-swath and downwind from edge of swath deposit as measured on horizontal mylar cards
Figure 5 a-f curves deposition in-swath account for the total
amount of spray (%) as measured on horizontal mylar cards
3.2 Samples from downwind edge of mylar card tests under
different meteorological conditions
Figures 6 and 7 show a and b curves in the downwind of spray
drift percentage and the cumulative drift percentage of total
measured drift at each sampling point. At the operating height of
2.5 m, real time wind speeds were 4.7 m/s and 1.8 m/s, and wind
direction difference was 37°. The a-curve shows that the
cumulative drift percentage of 90% of total measured drift occurred
at about 10.05 m, and the spray drift percentage at the 10 m
position was 1.52%. The a-curve total spray drift accounted for
26.44% of the total spraying. The b-curve shows that the
cumulative drift percentage of 90% of total measured drift occurred
at about 3.70 m, and the spray drift percentage at the 4 m position
was 2.22%. After 6 m, the drift was nearly zero. The b-curve
total spray drift accounted for 23.20% of the total spraying. The
average wind speed of a-curve and b-curve in 30 s were 3.18 m/s
and 2.17 m/s, respectively. The change of wind speed at (–3 m to
3 m) had significant effect on the deposition of a-curve and b-curve
(p<0.05). a-curve (R2=0.995, p<0.001) and b-curve (R2=0.996,
p<0.0001) were obtained by a nonlinear fitting. The fitting curves
of the drift deposit and the downwind distance were obtained as
shown in Equation (3) and the fitting parameters are shown in
Table 3.
2
02
(ln( / ))
exp( )
2
2π
c
Axx
yY w
wx
=+ ⋅ −
⋅⋅
(3)
where, y is the drift deposit; x is the downwind distance; Y0, A, w,
xc are all coefficients.
Figure 6 a-curve in-swath and downwind from edge of swath
deposit as measured on horizontal mylar cards
November, 2018 Wang J, et al. Drift and deposition of pesticide applied by UAV on pineapple plants under different meteorological conditions Vol. 11 No.6 9
Figure 7 b-curve in-swath and downwind from edge of swath
deposit as measured on horizontal mylar cards
Table 3 a and b curves drift nonlinear fitting curve coefficients
Y0 A w Xc
c 0.000089037 0.05867 0.3605 6.38598
b 3.31313E-5 0.00797 0.1787 3.67159
Figures 8 and 9 show c and d-curves in the downwind of spray
drift percentage and the cumulative drift percentage of total
measured drift at each sampling point. At the UAV operating
height of 1.5 m, real-time wind speed were 0.7 m/s and 2.2 m/s,
and wind direction difference was 40°. The c curve shows that
the cumulative drift percentage of 90% total measured drift
occurred at about 6.90 m, and the spray drift percentage in c-curve
at the 6 m and 8 m were 14.43% and 1.87%, respectively. After
10 m, it was nearly zero. The c-curve total spray drift accounted
for 15.42% of the total spraying. The d-curve shows that the
cumulative drift percentage of 90% total measured drift occurred at
about 3.91 m. The spray drift percentage in d-curve at the 4 m
position was 5.328%. After 6 m position, drift was nearly zero.
The total amount of drift accounted for 18.74% of the total amount
of spraying. Since the wind direction in c and d –curves changed
from 160° to 120°, the d-curve cumulative drift percentage of 90%
of the total measured drift position moved forward 3 m than
c-curve, but the d-curve total amount drift was still slightly higher
than the c-curve. Both of c and d curves had drift at –3 m, –4 m,
and -6 m position in the upwind. The upwind cumulative drift
percentage in c-curve and d-curve accounts for 38.38% and
56.20% of the total drift. The change of wind speed at the whole
sample line had no significant effect on the deposition of c-curve
and d-curve (p<0.66). c-curve (R2=0.999, p<0.0001) and d-curve
(R2 = 0.997, p <0.0001) were obtained by a nonlinear fitting. The
fitting curves of the drift deposit and the downwind distance were
obtained as shown in Equation (4) and the fitting parameters are
shown in Table 4.
2
02
(ln( / ))
exp( )
2
π
c
Axx
yY w
wx
=+ ⋅ −
⋅⋅
(4)
Figure 8 c-curve In-swath and downwind from edge of swath
deposit as measured on horizontal mylar cards
Figure 9 d-curve in-swath and downwind from edge of swath
deposit as measured on horizontal mylar cards
Table 4 c and d Curves drift nonlinear fitting curve coefficients
Y0 A w Xc
c 4.75863E-5 0.11813 0.22748 5.0522
b 1.89224E-4 0.04995 0.31746 3.14676
Figures 10 and 11 show e and f-curves in the downwind of
spray drift percentage and the cumulative drift percentage of total
measuring drift at each sampling point. At the UAV operating
height of 3.5 m, real-time wind speeds were 3.7 m/s and 1.78 m/s
with same wind direction. The e-curve shows the cumulative drift
percentage of 90% total measuring drift occurred at about 46.50 m,
and the spray drift percentage was 17.80% at the 10 m, 0.08% at
20 m, and 3.71% at 30 m, drift spray percentage increased to
29.53% at the 40 m position, decreased to 0.25% at 50 m, and
decreased to zero in upwind. The e-curve in-swath area moved to
2-8 m. The e-curve total spray drift accounted for 55.76% of the
total spraying. The e-curve shows that the cumulative drift
percentage of 90% total measuring drift occurred at about 33.54 m.
After 3 m, drift was almost stable, and no more than 3%, except for
at the 10 m position with spray drift percentage of 4.29%. The
f-curve shows that the total amount of drift accounted for 33.33%
of the total amount of spraying. The change of wind speed at the
(2-8) m position had significant effect on the deposition of e and f
(p<0.05) –curves. The drift curves need to be segmented and the
data were not sufficient enough for fitting.
Figure 12 shows a-e curves in the whole sample line of spray
drift percentage. Table 5 shows the a-e curves spray drift
percentage parameters. As it can be seen from Figure 12 and
Table 5, the 90% of the total measured spray drift position varied
from 3.91 m to 46.50 m. When the UAV operation height was
lower than 2.5 m, the mean speed (SD<0.76, CV<0.27) was less
than 2.82 m/s, we could control the 90% of the total measured
spray drift position within 10 m. At the UAV operation height of
3.5 m, the mean speed (SD<0.73, CV<0.20) was less than 3.93 m/s,
and the position of 90% of the total measured spray drift can up to
46.50 m. The droplets drift distribution was chaotic that should
be paid much more attention in UAV spray application.
Figure 10 e-curve in-swath and downwind from edge of swath
deposit as measured on horizontal mylar cards
10 November, 2018 Int J Agric & Biol Eng Open Access at https://www.ijabe.org Vol. 11 No.6
Figure 11 f-curve in-swath and downwind from edge of swath
deposit as measured on horizontal mylar cards
Figure 12 a-e curves in-swath and downwind from edge of swath
spray drift percentage as measured on horizontal mylar cards
Table 5 a-e curves spray drift percentage parameters
Parameter a b c d e f
90% Drift/m 10.05 3.70 6.90 3.91 46.50 33.54
Total drift/% 26.44 23.20 15.42 18.82 55.70 33.33
These results were similar to that from Fritz[26], it indicated
increased downwind ground deposition resulting from increased
wind speed, the results indicated that wind speed was the most
dominant meteorological factor in the transport and fate of aerially
applied sprays.
3.3 Monofilament lines samplers at 10 m, 25 m, and 50 m
vertical string tests under different meteorological conditions
Drift testing devices were arranged at 10 m, 25 m, and 50 m
paralleled to the flight line. Each drift testing device had 3
monofilament lines at the heights of 5 m, 2 m, and 1 m. The
meteorological chart records the average meteorological data for
UAV within 60 s from the start of the operation. Table 6 shows
the a-e curves spray drift meteorological data in 60 s. It shows the
standard deviation and coefficient of variation for each curve in
60 s with the wind speed and wind direction. As shown in Figure
13, at the UAV operating height of 2.5 m, b-curve monofilament
lines deposition was relative to a-curve at 10 m position. The
deposition rates of single monofilament decreased 90.70%, 97.16%
and 97.67% at the testing device height of 5 m, 2 m, and 1 m,
respectively. At 5 m, 2 m and 1 m height of the drift testing
device, the b-curve drift deposition was almost 0 at the 25 m
position. At the 50 m position, both a and b-curves were nearly 0.
The a-curve had a wind speed of 4.7 m/s at the moment of spraying,
and the drift deposit and drift distance were significantly increased
than b-curve.
In Figure 14, c-curve and d-curve had the similar meteorological
condition. At the height of 1.5 m of UAV operating, c-curve drift
deposition was almost 0 at all the drift testing devices located at
10 m, 25 m and 50 m. At 10 m position, the d-curve
monofilament lines deposition was very low and no more than
0.00046 μL/cm2 at the heights of 5 m, 2 m and 1 m. The d-curve
spray drift were almost 0 at 25 m and 50 m locations. Although
c-curve had a lower wind speed than b-curve at the moment of
spraying, the mean speed was not much difference. The d-curve
spray drift deposit and distance were not significantly increased
compare to c-curve. In Figure 15, e-curve and f-curve were
measured at the height of 1.5 m of UAV operating. The f-curve
drift testing devices located at 5 m, 25 m and 50 m. At the 25 m
position, the mean speed was 2.02 m/s for f-curve and 3.59 m/s for
e-curve. The deposition rate of f-curve decreased 75.77%,
85.47% and 70.18%, relative to the e-curve at the monofilament
lines height of 5 m, 2 m and 1 m, respectively. The drift deposition
of e-curve was considerably high at 25 m, up to 0.0149 μL/cm2.
Figure 13 a and b curves deposition by treatment on monofilament lines placed 10 m, 25 m, and 50 m downwind from the
swath edge at three testing device heights (1 m, 2 m, and 5 m)
November, 2018 Wang J, et al. Drift and deposition of pesticide applied by UAV on pineapple plants under different meteorological conditions Vol. 11 No.6 11
Figure 14 c and d curves deposition by treatment on monofilament lines placed 10 m, 25 m, and 50 m downwind from the
swath edge at three heights (1 m, 2 m, and 5 m)
Figure 15 e and f curves deposition by treatment on monofilament lines placed 10 m, 25 m, 50 m downwind from the
swath edge at three heights (1 m, 2 m, and 5 m)
At 50 m, both e and f curves had spray drift deposition. At
5 m and 2 m monofilament line heights, f-curve deposition was
three times of those in the e-curve. At 1 m height, the amount of
deposition was similar. When the operating height of the UAV
increased to 3.5 m, the wind speed ranged at 2.1-4.1 m/s, and wind
direction was 55°. The droplets were likely to drift more than
50 m. The spray deposition of the lower mean wind speed can
drift more seriously at some location because of the unstable wind
speed during the UAV operation. Again, it showed that increased
airborne concentrations resulting from smaller droplet sprays and
increased wind speed. Airborne concentration data demonstrated
that increased atmospheric stability increased the time that smaller
droplets remained suspended in the air, which could lead to
increased downwind transport[26].
4 Conclusions
With the increase of the mean wind speed and UAV operating
height, spray drift distance and the total spray drift percentage also
increased rapidly. When the average wind speed is less than
3 m/s, the flying height of the UAV is preferably controlled to be
less than 2.5 m, which can effectively control the spray drift. The
influence of the UAV operation height on the total spray drift
percentage was significant. When the operation height was less
than 2.5 m and the mean speed varied in 1.14-2.82 m/s, the total
spray drift percentage just floated 11% and was less than 26.44%.
As the UAV operation height was up to 3.5 m, the mean speed
varied in 2.02-3.59 m/s, and the total spray drift percentage reached
55.76%. The influence of the UAV operation height and wind
speed on the position of cumulative spray drift percentage of 90%
of the total measured spray drift were significant. The position
varied in 3.91-46.50 m. When the operation height was less than
2.5 m, the mean speed varied in 1.14-2.82 m/s, and the 90% spray
drift distance can control in 10 m. As the operation height was up
to 3.5 m, the mean speed varied in 2.02-3.59 m/s, and the 90%
12 November, 2018 Int J Agric & Biol Eng Open Access at https://www.ijabe.org Vol. 11 No.6
spray drift distance can be up to 33.54-46.50 m.
With the increase of the real time wind speed and UAV
operating height, the in-swath area and spray deposition changed
obviously. The influence of the wind speed on the distribution of
the in-swath area was obvious when the UAV operating height was
not lower than 2.5 m. The in-swath area start position moved 3-
4 m as the wind speed changed, especially when the real time wind
speed changed greatly. The wind speed had a statistically
significant (p<0.05) effect on the in-swath area deposition.
With the increase of the wind speed and UAV operating height,
the influences of the wind speed and UAV operating height on the
monofilament lines deposition of drift testing devices were
significant. At the 1.5 m UAV operating height, the wind speed
varied in 0.5-2.2 m/s, and all the monofilament lines deposition
were nearly 0. At the 2.5 m UAV operating height, the wind
speed varied in 1.0-4.7 m/s, and the monofilament lines deposition
had obviously changes as the wind speed changed. At the 3.5 m
UAV operating height, the wind speed varied in 1.0-5.1 m/s, and
the monofilament lines deposition were considerably high.
In actual operation, UAV operating height should below 2.5 m
when spraying in pineapple plants and the wind speed should be
5 m/s or less. If UAV needs a higher height, we should choose a
smaller wind speed and stable weather condition and set enough
buffer zone.
In this research, pesticide applied by UAV test was carried out
based on real-time meteorology. The experiment proved that the
wind speed had a significant effect on the spraying efficacy. The
UAV operation parameters should be reasonably selected
according to the meteorological conditions. When in-swath area
offset occurs due to meteorological conditions, remedial measures
should be taken to prevent reinjection and leakage.
Acknowledgments
We acknowledge that this work was financially supported by
the National Key Technologies Research and Development
Program (2016YFD0200700), Guangdong Leading Talent Project
(2016LJ06G689), 111 Project (D18019), Educational Commission
of Guangdong Province of China for Platform Construction
(2015KGJHZ007), and Science and Technology Planning Project
of Guangdong (2017B010117010). Thanks to the National Center
for International Collaboration Research on Precision Agricultural
Aviation Pesticides Spraying Technology for the full participation
persons of the experiment (Weixiang Yao, Pengchao Chen,
Changquan Yue, Xiaoyu Huang, Jinli Lin, Linlin Wang, Changwei
Zhu, Yusen Deng, Cong Huang, Yulong Fu). Thanks to Hainan
NongFeiKe Agriculture and Technology Co., Ltd. for their fully
support.
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