Drift Potential Research Articles

An improved approach to estimate sand-driving winds

Wind resource assessment has important economic and ecological implications. Many developing countries in arid and semiarid areas are caught in a dilemma between the development of wind energy and the threat of sandy desertification. Sand-driving winds are momentous for both generating wind energy and aeolian research. The estimation for the probability of sand-driving winds has been rarely studied. The ability of the two-parameter Weibull distribution to estimate high wind velocities is questioned and parameters appear to have no practical significance. Drift potential (DP) is a way of evaluating potential sand transport volume by sand-driving winds, but the relationship between DP and the wind energy of sand-driving winds has been rarely studied. In this paper, a function was constructed from the expressions of DP and the two-parameter Weibull probability distribution to improve the estimation of sand-driving winds. This is simple and applicable to arid and semiarid areas worldwide. The mean wind velocity and the mean wind power density at a height of 10 m around the Badain Jaran Sand Sea in China, are in the range between 2.64 and 4.79 m·s−1, and 27.61–165.61 W·m−2, respectively. The mean wind power density of sand-driving winds accounted for half or more of the total mean wind power density. The relationship among DP, the wind power density of sand-driving winds and the probability of sand-driving winds, was proved theoretically. Gentle winds and strong winds are distinguished by the drift wind velocity at which potential sand transport activities (potential lost wind power density) reach their maximum. The scale parameter dominates the mean and median wind velocity, and represents the effect of convection. The shape parameter characterizes the atmospheric stability. These results provide a basis for the wind energy development, improve the understanding of aeolian activities, and have implications for sand control engineering.

Spray Backstop: A Method to Reduce Orchard Spray Drift Potential without Limiting the Spray and Air Delivery

Unmanaged spray drift from orchard pesticide application contributes to environmental contamination and causes significant danger to farmworkers, nearby residential areas, and neighbors’ crops. Most drift control approaches do not guarantee adequate and uniform canopy spray coverage. Our goal was to develop a spray backstop system that could block drifting from the top without any negative impact on spray coverage and on-target deposition. The design included a foldable mast and a shade structure that covered the trees from the top. We used a continuous loop sampling to assess and quantify the effectiveness of spray backstop on drift potential reduction. We also collected leaf samples from different sections of trees to compare on-target deposition and coverage. The results showed that the spray backstop system could significantly (p-Value < 0.01) reduce drift potential from the top (78% on average). While we did not find any statistical difference in overall canopy deposition with and without the backstop system, we observed some improvement in treetops deposition. This experiment’s output suggests that growers may be able to adjust their air-assist sprayers for a more uniform spray coverage without concern about the off-target movement of spray droplets when they employ the spray backstop system.

An improved model to estimate annual sand transport rate by sand-driving winds

Some of the surface on Earth, Mars, Venus, and Titan is covered by ripples, dunes, and other features formed by sand-driving winds. Many developing countries in arid and semiarid areas are caught in a dilemma between the threat of sandy desertification and the development of wind energy. The estimation for the probability of sand-driving winds has been rarely studied. The ability of two-parameter Weibull probability distribution to estimate sand-driving winds is questioned. Sand transport rate is used only for the evaluation of short-term aeolian activities. Drift potential (DP) is an accessible way of evaluating potential sand transport volume by sand-driving winds. However, the relationship among annual sand transport volume, DP and wind energy has been rarely studied. Sand-driving winds can be divided into gentle winds and strong winds, but it is hard to distinguish them and to quantify their effects on aeolian geomorphology. A function was constructed from expressions of sand transport rate and the two-parameter Weibull probability distribution to improve the estimation of sand-driving winds. On this basis, annual sand transport volume was accurately evaluated by sand-driving winds. This is applicable to arid and semiarid areas worldwide. The relationship among annual sand transport volume, DP and wind energy was analyzed from the perspective of dimensional analysis. Gentle winds and strong winds are distinguished by transport wind velocity at which aeolian activities on a sandy underlying surface reach the erosion–deposition balance, and which corresponds to annual maximum sand transport rate. On a sandy underlying surface strong winds control deposition, while gentle winds dominate wind erosion. The transport wind velocity is nearly constant, weakly related to the probability distribution of sand-driving winds. These results provide a basis for an improved understanding of aeolian activities as an important planetary surface process, sand control engineering, and wind energy development.

Long-term measurements of aeolian transport directional variations over a zibar surface in the northern Kumtagh Sand Sea

Zibars are aeolian bedforms created by armoring of the surface by coarse grains. The existence and movement of these grains strongly influence zibar morphodynamics. Although aeolian sediment transport has been investigated for arid surface processes with a range of grain sizes, the measurement durations were short, making it difficult to establish the relationship between microscopic aeolian transport processes and macroscopic geomorphological processes. In the present study, we conducted field observations of aeolian sediment transport above a zibar in northern China's Kumtagh Sand Sea with a segmented sand trap. During six measurement periods throughout 2014, the sampler collected 314.76 kg of sediments within 1 m above the ground. The directional variation indicated that about 52.5% of the sediments came from the north, northeast, and northwest; the southeast provided the least sediments. The strongest aeolian transport occurred between August and October; the weakest was in winter. The aeolian sediment flux decreased with height, and 54% of particles were transported within 0.1 m above the ground. The transport profiles fit an exponential decay function. The flux's directional variation resulted from the combined effects of sediment availability and wind regime, so the calculated net transport differed from the drift potential. The seasonal and directional variations of aeolian transport significantly affect the morphodynamic process of zibars. The trend and the internal sedimentary structure of zibars were closely related to the aeolian transport process.

Effectiveness of coffee leaf miner control associated with spray deposition in coffee leaves

ABSTRACT Coffee production faces challenges due to the susceptibility of the crop to insects. Owing to the coffee leaf miner Leucoptera coffeella, which is one of the main insect pests, the technology for the application of phytosanitary measures becomes the main challenge for coffee growers. This study aimed to evaluate the effectiveness of coffee leaf miner control using different methods of application. The study was conducted in an experimental site in the municipality of Monte Carmelo - Minas Gerais. Spray depositions in different positions of the plant canopy and the effective control of coffee leaf miner were evaluated using the following application treatments: a hydropneumatic sprayer with varying spray volumes (200 and 400 L ha-1), two hollow-cone spray nozzles with the presence and absence of agricultural adjuvant, and electrostatic application using a spray volume of 200 L ha-1 with and without spray adjuvant. The addition of an adjuvant to the spray did not influence coffee leaf miner control; in contrast, a spray volume of 200 L ha-1 combined with the application of coarse droplets was efficient in the management of insect pest. The reduction in the rate of the application using coarse droplets increased the operational capacity and reduced spray drift potential.

Meeting droplet size specifications for aerial herbicide application to control wilding conifers

Large areas of New Zealand are being aerially sprayed with herbicides to manage ‘wilding’ conifer spread. The purpose of the study was to obtain and analyse droplet spectra produced by nozzles commonly used for wilding conifer spraying to determine whether or not operational recommendations for a target droplet size class (~350 µm) are being met. Droplet spectra were measured in a wind tunnel for 27 nozzle x 3 operating condition (nozzle angle, air speed and pressure) combinations tested for each of three spray mixes. AGDISP, an aerial spray application simulation model, was used to quantify the field performance implications of changes to droplet spectra parameters. Only one nozzle, the CP-09, 0.078, 30°, met the target droplet size specification when used at 45° but not at 0°. However, under these conditions, this nozzle produced a large driftable fraction. All but one of the other scenarios tested produced much larger droplet sizes. Operational spray mixes tended to slightly increase the potential for spray drift compared with the water control. The CP-09, 0.078, 30° nozzle used at 45° met the operational droplet size specification but is more sensitive to changes to nozzle angle (0° versus 45°) than the other nozzles tested. None of the three Accu-FloTM nozzles tested met the target droplet size specification. However, the Accu-FloTM nozzles produced very few fine droplets making them good choices for reducing spray drift potential.

Morphological characteristics and dynamic changes of seif dunes in the eastern margin of the Kumtagh Desert, China

The seif dune field over the gravel desert surface in the eastern margin of the Kumtagh Desert is a valuable experimental site for the observation of dune formation and dynamics. We used high-resolution remote sensing and station observation approaches, combined with wind and grain size data, to study the characteristics of the aeolian environment and the morphologies of and dynamic changes in seif dunes. We observed the ratio of the resultant drift potential (RDP) to the drift potential (DP), which was 0.37, associated with an obtuse bimodal wind regime. The drift potentials in the west-northwest (WNW) and east-northeast (ENE) directions were dominant, and the angle between the two primary DP directions was 135.00°. The dune orientations ranged from 168.75°–213.75°, which were parallel to the resultant drift direction (186.15°). The dune lengths ranged from 51.68 to 1932.11 m with a mean value of 344.91 m. The spacings of the dunes ranged from 32.34 to 319.77 m with a mean value of 93.39 m. The mean grain size of the sediments became finer, and the sorting became better from upwind tail to downwind tip, which indicated that the sediment of the seif dunes in the study region may be transported from northward to southward. The rate of increase in the length, the mean longitudinal migration rate of the dune tail, and the mean longitudinal extension rate of the dune tip (also called elongation rate) were 4.93, 4.63, and 9.55 m/a, respectively. The mean lateral migration vector of the seif dunes was approximately 0.11 m/a towards the west (–0.11 m/a), while the mean amplitude of lateral migration was 0.53 m/a, ignoring the direction of lateral migration. We found that the seif dune field formed first beside seasonal rivers, which can provide sediment, and then expanded downwind.

Measurement of exposure time with less than 10-ps in the framing camera

A pulse-dilation framing camera and its working principle are introduced. The exposure time with less than 10-ps is measured by an array of fiber bundle. The research results show that the shortest exposure time and maximum dilation factor of camera are approximately 5 ps and 16.4×, respectively. The exposure time with less than 10-ps can be achieved when the drift potential is less than 5 kV and the gradient of dilation pulse is greater than 6 V/ps, those are provide feasibility for the framing camera with exposure time less than 10-ps.

Wind Dynamic Environment and Wind Tunnel Simulation Experiment of Bridge Sand Damage in Xierong Section of Lhasa–Linzhi Railway

The Lhasa–Linzhi Railway is located in the sandy area of the South Tibet valley, with high elevation and cold temperature. The Xierong section is a bridge section where blown sand hazards are severe. However, the disaster-causing mechanism of blown sand hazards in this section is currently unclear, thereby hindering targeted sand prevention and control. To address this problem, the wind dynamic environment of and causes of sand damage in this section are investigated through the field observation of the locale and a wind tunnel simulation experiment. Results show that the dominant sand-moving wind direction in the Xierong section is SSE. The wind speed, frequency of sand-moving wind, sand drift potential (DP), and maximum possible sand transport quantity (Q) in this section are relatively high during spring (March to May) and low during other seasons. The yearly resultant sand transport direction (RDD, RA) is SW. The angle between the route trend of this section and the sand transportation direction is 30°–45°, and the sand source is located in the east side of the railway. During spring, sand materials are blown up by the wind, forming blown sand flow and movement from the NE to SW direction. Increased wind speed area is formed between the top of the slope shoulder of the windward side of the bridge and the downwind direction of 3H, causing blown sand erosion. Meanwhile, weakened wind speed areas are formed within the distance of -3H at the upwind direction and from the downwind direction of the 3H to 20H of the bridge. These areas accumulate sand materials at the upwind and downwind directions of the bridge, thereby resulting in blown sand hazards. This research provides a scientific basis for the prevention and control of sand damage in the locale.

The control of wind strength on the barchan to parabolic dune transition

AbstractThe evolution of barchan‐to‐parabolic dunes can be driven by vegetation establishment, which may be linked to climate change and/or human activity. However, little is known of the impact of changes in wind strength on vegetation development and the resulting impacts on the evolution of dune morphology and sedimentological characteristics. To address this issue, we studied the morphology and grain‐size characteristics of barchan, barchan‐to‐parabolic and parabolic dunes in the Mu Us Desert in north China, which was combined with an analysis of changes in normalized difference vegetation index (NDVI) and climatic variables during 1982–2018. The results reveal a trend of increasing growing‐season NDVI which was related to a significant decrease in drift potential (DP). Therefore, we suggest that the initiation of dune transformation was caused by the reduced wind strength which favored the establishment and development of vegetation. To reveal the response of sedimentological reorganization during the processes of dune transformation, grain‐size characteristics along the longitudinal profile of the three different types of dunes were examined. The decreasing wind strength led to the transport of fine sands on the upper part of the windward face of the dunes, resulting in a progressive coarsening of the grain‐size distribution (GSD) and a reduction in dune height at the crest area. No distinct trend in sorting and mean grain‐size was observed on the windward slope of the barchan‐to‐parabolic dune, indicating that the sand in transit had little influence on the GSD. Conversely, progressive sorting and coarsening of the sand occurred towards the crest of the parabolic dune. This indicates that vegetation development limited the transport of sand from upwind of the dune, and affected a shift in the dune source material to the underlying source deposits, or to reworked pre‐existing aeolian deposits, and resulted in the trapping of sand in the crest area. © 2020 John Wiley & Sons, Ltd.

The effect of wind speed averaging time on the calculation of sand drift potential: New scaling laws

Drift potential (DP) is a key factor used to quantify aeolian sand transport, and it is often used for predicting wind erosion and dune mobility under climate change scenarios. It is proportional to the mean of the cube of the wind speed at a 10-m height when that wind speed is above 6.2 m/s (12 knots), a speed threshold above which sand can be transported by the wind. DP depends on the temporal resolution and the averaging time of the wind velocity measurements. Usually, either a 10-min or 1-h mean wind speed is used to calculate the DP, although different studies have used different averaging periods for calculating the mean wind speed and, consequently, the DP. Here, we perform a comprehensive analysis of an extensive, long-term wind speed database from different locations around the world and from reanalysis data sources, and show that DP decreases with the averaging time of the wind speed. The decrease of DP versus the averaging time interval can be approximated by a stretched exponential function. In addition, the relative decrease of DP, as a function of the maximum DP, is smaller for high wind speed sites. This result is a consequence of the fact that high DP sites are characterized by longer clusters of successive wind speed events above the threshold velocity; they are thus less affected by the time averaging process. Interestingly, the clusters' lengths decay exponentially with wind speed and faster for low DP sites. Our new results have important implications for calculating the effective DP and for better estimating the biases that result from using wind data with different averaging times, which is a common problem in aeolian research. We also found an approximate linear relation between DP and the wind power that is close to the analytic approximation for the relation between the two. This new finding has many important applications since it will allow one to calculate DP from wind power data and vice versa. In addition, it implies that the same scaling laws found for DP also exist for the wind power.

Spray drift characteristics test of unmanned aerial vehicle spray unit under wind tunnel conditions

Since the 2010s, unmanned aerial vehicle (UAV) sprayer was applied more and more widely for low-volume aerial pesticides spraying operations in China. However, droplets from the UAV sprayer have a higher drift risk due to more fine droplets sprayed and a higher flight height than ground sprayers. Study on UAV spray drift has been a new hot spot within the field of pesticide application technology. Most of previous studies used direct field methods for spray drift, but the meteorological conditions in field were unstable and uncontrollable, and drift research under an actual operation state in wind tunnel has not been reported. Therefore, 25 treatments of wind tunnel measurements and droplets spectrum tests of 10 models of nozzles were conducted to explore the influence factor on spray drift characteristics of UAV chemicals application in this study. A spray unit with a rotor of UAV was innovatively installed in wind tunnel, and the airstream from the wind tunnel was regarded as the relative moving natural wind to simulate the flight status. The airborne and the sediment spray drift was measured to study the effects of the nozzle type and size (flat fan, hollow cone and air-inclusion nozzles), flight speed, adjuvant (DRS-60, Y-20079, MF and G-611) and meteorological parameters (20°C & 40%, 20°C & 80%, 30°C & 40% and 30°C & 60%). The drift potential (DP) and the drift potential reduction percentage (DPRP) in vertical and horizontal directions were obtained for each test. Both nozzle type and size had an impact on the spray drift potential obviously by affecting the droplet size and the ratio of fine droplets, and the regression linear models between DPRPV/DPRPH and DV50, V75 were established (R2=0.934/0.925). Flight speed also had a significant effect on the spray drift characteristics, and reducing the flight speed could increase the DP effectively. Adding spray adjuvants could affect the DP under experimental meteorological parameters, and the anti-drift performance ranked in the order of DRS-60>MF>Y-20079>G-611. Recommendations were proposed in order to reduce the spray drift for UAV sprayer’s operation. These findings can contribute to provide guidelines and technical support for the wind tunnel spray drift tests of UAV and the field operation regulation of unmanned aerial PPP application. Keywords: unmanned aerial vehicle (UAV) sprayer, wind tunnel, spray drift potential, nozzle, adjuvant DOI: 10.25165/j.ijabe.20201303.5716 Citation: Wang C L, Zeng A J, He X K, Song J L, Herbst A, et al. Spray drift characteristics test of unmanned aerial vehicle spray unit under wind tunnel conditions. Int J Agric & Biol Eng, 2020; 13(3): 13–21.

Mapping the temporal and spatial changes in crescent dunes using an interferometric synthetic aperture radar temporal decorrelation model

Abstract The interferometric synthetic aperture radar temporal decorrelation model is a powerful tool for describing surface changes over time. Recently, this model has been used in several dune stability studies. However, so far, the combined effects of spatial and thermal decorrelation on the estimation of temporal decorrelation in dune regions have not been studied. In this paper, we propose a temporal decorrelation model for a dune area based on the consideration of the effects of spatial and thermal decorrelation, and we validate the model using the sand drift potential (DP) and precipitation, by which the potential of this model to describe surface changes in crescent dune area is evaluated. Furthermore, we test the proposed model by mapping changes of stability in crescent dunes on both sides of road in the Taklamakan Desert between May 22, 2017, and May 29, 2018. The results show that, first, spatial decorrelation in the dune area can be ignored, but thermal decorrelation cannot. Second, the temporal decorrelation gradually decreases with increasing synthetic sand drift potential (RDP, a vector synthesis of DP), but its sensitivity to different levels of RDP is different. When the RDP is at a relatively low level (between 0 and 50), even small changes in it can be identified. However, when the RDP is at a relatively high level (greater than 50), even relatively large changes in it are difficult to distinguish. Third, when the RDP is low, this model can clearly distinguish the intrusion of dunes of different scales into a highway protection system.

Field evaluation of spray drift and environmental impact using an agricultural unmanned aerial vehicle (UAV) sprayer

Unmanned Aerial Vehicle (UAV) applications at low-volume using fine and very fine size droplets have been adopted in several commercial spray scenarios allowing water-saving and high-efficiency operation in delivery of pesticides. However, spray drift associated with UAV applications, especially for fine droplets generated from spinning disk nozzles, has not been fully understood, raising environmental and regulatory concerns. The objectives of this study were to compare the drift potential of three different volume median diameter (VMD, or Dv0.5) of 100, 150 and 200 μm from a commercial quadcopter equipped with centrifugal nozzles exposed to different wind speeds under field conditions. Prior to field test, the droplet size of the centrifugal nozzle was measured by a laser-diffraction particle-size analyzer. The results showed that the relationship between rotation speed and Dv0.5 agrees with the negative power function. Field tests found that the deposition at 12 m downwind direction decreased by an order of magnitude compared with the average deposition within the in-swath zone. The deposition of almost all the treatments at 50 m downwind is lower than the detection limits of 0.0002 μL/cm2. Based on the results from this study, the drift distance of this specific very popular UAV model is much less than that of manned aerial applicators. Based on the predicted equation (R2 = 0.83), the detected drift amount increased with increasing wind speed and decreasing Dv0.5. This work provides basic information to quantify the effect of wind speeds and droplet sizes on UAV spray drift potential which supports on-going regulatory guideline development for spray buffer zone and drift risk assessment protocols.

Application of a new wind driving force model in soil wind erosion area of northern China

The shear stress generated by the wind on the land surface is the driving force that results in the wind erosion of the soil. It is an independent factor influencing soil wind erosion. The factors related to wind erosivity, known as submodels, mainly include the weather factor (WF) in revised wind erosion equation (RWEQ), the erosion submodel (ES) in wind erosion prediction system (WEPS), as well as the drift potential (DP) in wind energy environmental assessment. However, the essential factors of WF and ES contain wind, soil characteristics and surface coverings, which therefore results in the interdependence between WF or ES and other factors (e.g., soil erodible factor) in soil erosion models. Considering that DP is a relative indicator of the wind energy environment and does not have the value of expressing wind to induce shear stress on the surface. Therefore, a new factor is needed to express accurately wind erosivity. Based on the theoretical basis that the soil loss by wind erosion (Q) is proportional to the shear stress of the wind on the soil surface, a new model of wind driving force (WDF) was established, which expresses the potential capacity of wind to drive soil mass in per unit area and a period of time. Through the calculations in the typical area, the WDF, WF and DP are compared and analyzed from the theoretical basis, construction goal, problem-solving ability and typical area application; the spatial distribution of soil wind erosion intensity was concurrently compared with the spatial distributions of the WDF, WF and DP values in the typical area. The results indicate that the WDF is better to reflect the potential capacity of wind erosivity than WF and DP, and that the WDF model is a good model with universal applicability and can be logically incorporated into the soil wind erosion models.

风洞环境下喷头及助剂对植保无人飞机 喷雾飘移性的影响 = Effects of nozzle types, adjuvants and environmental conditions on spray drift potential of unmanned aerial vehicles in a wind tunnel

In order to investigate and reduce spray drift during the use of plant protection unmanned aerial vehicles (UAV), a spray unit consisting of a single rotor and a nozzle was simulated under the controlled wind tunnel conditions (wind speed 5 m/s, spray pressure 0.3 MPa and rotor speed 2 300 r/min). The effects of 11 kinds of nozzles and 4 different adjuvants on droplet drift were investigated. The drift potential index (DIX) and drift potential reduction percentage (DPRP) were also evaluated and compared. The results show that under the condition of 20℃/RH 80%, the drift distribution of different nozzle types in vertical plane and horizontal distance showed a regular change trend. Compared with the reference nozzle F110-03, the order of the drift potential of nozzles from large to small was TR80-0067 > ST110-0067 > XR110-01 > ST110-015 > TR80-01 > ST110-02 > XR110-03 > F110-03 > IDK series. The effect of IDK120-01and IDK120-015 was similar and they were the best ones. Under the wind tunnel condition of 30℃/RH 40% and wind speed of 5 m/s, compared to the control group without adjuvants, the mean drift reduction rates of spray nozzle XR 110-01 with adjuvant of 0.5% Silwet DRS- 60, 1.0% Maifei (MF) and 1.0% Y-20079 were 43.3%, 15.6% and 5.2%, respectively. The selection of drift reducing adjuvants needs to consider the type of adjuvants and their effects. At the wind tunnel conditions of 20℃/RH 40%, 20℃/RH 80%, 30℃/RH 40% and 30℃/RH 60%, the spray nozzle XR110-01 added with 1.0% MF adjuvant was beneficial to the reduction of airborn drift. Especially, under high temperature and low humidity conditions, it had better drift reduction effect. This study has provided reference and guidance for nozzles selection, adjuvants selection and the field application of UAV for plant protection, and also data basis for the further study of the drift reduction technology of nozzle and adjuvants.

Aeolian sediment fingerprinting in the Cuona Lake Section along the Qinghai-Tibetan Railway

Quantitative analyses of aeolian sediment provenance are necessary to elucidate aeolian sand pathways and define objective targets for control measures. In the present study, annual wind data and remote sensing information were utilized to ascertain the source of aeolian sediments along the Cuona Lake Section of the Qinghai-Tibetan Railway (QTR). Fingerprinting approach with different tracer selection strategies was used to assess contributions of each source types. The results indicated that (1) wind erosion behaviours that contribute to sand sediment occur mainly on the west side of sandy areas during October to April. The resultant drift potential of this period reached 1086.18 VU, indicating a high energy level. (2) The aeolian desertified land within the source area expanded by 8.05 km2 from 2001 to 2017. The degraded alpine meadow, bare hilly land and river courses were identified as potential sources of aeolian sediments. (3) The contributions from degraded alpine meadow, bare hilly land and river courses were estimated as 4%, 58% and 38%, respectively. Synthesising these results, appropriate control measures for the bare hilly land and river courses on the west side of Cuona Lake should be able to greatly restrict sand transport and alleviate the railway sand hazard. This study will provide a firm basis for sand hazard control in the Cuona Lake section and can be utilized as references for other regions encountering threats from aeolian sand.

Particle drift potential of glyphosate plus 2,4-D choline pre-mixture formulation in a low-speed wind tunnel

AbstractThe introduction of 2,4-D–resistant soybean and cotton provided growers a new POST active ingredient to include in weed management programs. The technology raises concerns regarding potential 2,4-D off-target movement to sensitive vegetation, and spray droplet size is the primary management factor focused on to reduce spray particle drift. The objective of this study was to investigate the droplet size distribution, droplet velocity, and particle drift potential of glyphosate plus 2,4-D choline pre-mixture (Enlist Duo®) applications with two commonly used venturi nozzles in a low-speed wind tunnel. Applications with the TDXL11004 nozzle had larger DV0.1 (291 µm), DV0.5 (544 µm), and DV0.9 (825 µm) values compared with the AIXR11004 nozzle (250, 464, and 709 µm, respectively), and slower average droplet velocity (8.1 m s−1) compared with the AIXR11004 nozzle (9.1 m s−1). Nozzle type had no influence on drift deposition (P = 0.65), drift coverage (P = 0.84), and soybean biomass reduction (P = 0.76). Although the TDXL11004 nozzle had larger spray droplet size, the slower spray droplet velocity could have influenced the nozzle particle drift potential. As a result, both TDXL11004 and AIXR11004 nozzles had similar spray drift potential. Further studies are necessary to understand the impact of droplet velocity on drift potential at field scale and test how different tank solutions, sprayer configurations, and environmental conditions could influence the droplet size and velocity dynamics and consequent drift potential in pesticide applications.

INFLUENCE OF GLYPHOSATE CONCENTRATIONS ON SPRAY SOLUTION PHYSICOCHEMICAL CHARACTERISTICS AND DRIFT POTENTIAL

ABSTRACT The herbicide glyphosate is sprayed with varying application volumes that result in different concentrations used in the spray solutions. Thus, this study aimed to evaluate the effect of glyphosate concentrations on the potential risk of droplet drift, surface tension of spray solution, and contact angle of droplets on surfaces. Three experiments were conducted in a completely randomized design. Drift potential was evaluated by median volumetric diameter (MVD), percentage volume of droplets with diameter smaller than 100 μm (%V<100 μm), and coefficient of uniformity (Span), with 12 replications. The surface tension of spray solutions and contact angle of droplets were evaluated on Urochloa ruziziensis leaves, paraffin film, and glass, with four replications. Changing glyphosate concentrations in the spray solution changes the droplet spectrum and contact angle on different surfaces due to changes in spray solution physicochemical characteristics, such as surface tension. The increased glyphosate concentrations in the spray solution lead to increased drift potential of droplets, reducing the surface tension and contact angle of droplets on surfaces.

Drift Potential from Glyphosate and 2,4-D Applications as Influenced by Nozzle Type, Adjuvant, and Airspeed

<b>Highlights</b> <list list-type=bullet><list-item> The AIXR nozzle and modified vegetable oil reduce drift potential. </list-item><list-item> Downwind spray deposition increases non-linearly as airspeed increases. </list-item><list-item> Nozzle selection is more important than adjuvant to mitigate spray drift. </list-item></list> <b>Abstract</b>. Spray drift is a critical concern for pesticide applications and the largest focus for its reduction has been placed on increasing droplet size. The objectives of this research were to evaluate the influence of nozzle type, adjuvant, and airspeed on the droplet spectrum and spray drift deposits from applications of glyphosate plus 2,4-D in a wind tunnel. Two studies were conducted using three 11002 nozzles types (XR, DG, and AIXR) individually attached to a one-tip boom. The working pressure was 207 kPa. The first study evaluated drift from the potassium salt of glyphosate (1260 g ae ha-1) plus 2,4-D amine (450 g ae ha-1) tank-mixed with four adjuvants (individually) sprayed at 2.2 m s-1 airspeed. A glyphosate plus 2,4-D solution with no tank-mixed adjuvants was also evaluated. The second study evaluated drift from glyphosate plus 2,4-D applications in four airspeeds (0.9, 2.2, 3.6, and 4.9 m s-1). Drift potential was determined using 2 mm monofilament line collectors and a 1,3,6,8-pyrenetetrasulfonic acid tetra sodium salt (PTSA) fluorescent tracer added to solutions, quantified by fluorometry. Nozzles and adjuvants influenced droplet size distribution of glyphosate plus 2,4-D solutions. Among the nozzles, the AIXR produced the coarsest droplets and the lowest tracer deposits (12 ηg cm-2) at 12 m downwind regardless of solution type. When nozzles were pooled, the modified vegetable oil (MVO) reduced the spray deposition by 36% at 12 m compared to the solution without adjuvant. At 4.9 m s-1 airspeed, tracer deposit at 12 m downwind was 2-fold lower when applications were made through low-drift nozzles (DG and AIXR) compared to the XR nozzle. Results suggest that drift-reducing adjuvants tested in this study may not reduce drift and nozzle selection should be considered as a more important factor than adjuvants in order to mitigate spray drift.