Spray volume

The types of sprayer and nozzle and number of nozzles are selected depending on the required spray volume and the shape of the crop canopy. Application method, maximum spray volume, application frequency and interval must be as stated in the protocol. 

Spray volume should be based on the stage of growth of the plant. Spray volume is calculated based on plot size shape and stage of growth of the crop. 

Values of the spray volume and amount of test substance are rounded off to one decimal place. 

Application of the test substance to the test system is without doubt the most critical step of the residue field trial. Under-application may be corrected, if possible and if approved by the Study Director, by making a follow-up application if the error becomes known shortly after the application has been made. Over-application errors can usually only be corrected by starting the trial again. The Study Director must be contacted as soon as an error of this nature is detected. Immediate communication allows for the most feasible options to be considered in resolving the error. If application errors are not detected at the time of the application, the samples from such a trial can easily become the source of undesirable variability when the final analysis results are known. Because the application is critical, the PI must calculate and verify the data that will constitute the application information for the trial. If the test substance weight, the spray volume, the delivery rate, the size of the plot, and the travel speed for the application are carefully determined and then validated prior to the application, problems will seldom arise. With the advent of new tools such as computers and hand-held calculators, the errors traditionally associated with applications to small plot trials should be minimized in the future. The following paragraphs outline some of the important considerations for each of the phases of the application. 

A combination of techniques is typically used to verify the accuracy and precision of agrochemical applications to soil. For example, the catch-back method or passtime method is typically used in conjunction with analytical results from application verification monitors to confirm proper application. The catch-back method involves measuring the spray solution volume before and after application to double check that the desired volume of test solution was actually applied to the test plots. Experienced applicators are often able to apply within 2% of the targeted spray volume. 

The actual application rate should be calculated based on output, the active ingredient concentration, and the application time or land area covered. Once the plot has been treated, the amount of product or spray volume remaining should be checked as verification of the application rate. 

Target the minimum recommended spray volume per acre. The nozzle configuration should be adjusted to fit the canopy at the time of application, which is normal agricultural practice. The application sprayer should be calibrated prior to treatment. Calibration records should be maintained and submitted as raw data. Applications should be made within 1 h of mixing and applied at a time with little or no wind. The applications should be made when leaves are dry. All application parameters must be recorded. The following list gives example data collection from application ... 

Vertical surfaces collect spray primarily by impaction. Plants and other entities with a vertical component will collect some material by impaction, and typically also by deposition, as discussed in the previous section. While horizontal collectors will tend to collect all or most material that falls out on to them, vertical collectors will have collection efficiencies that are more closely related to their physical characteristics, especially collector diameter. The SDTF used a-cellulose cards oriented perpendicular to the ground and strings made of cotton or Teflon in its field studies to assess spray volumes at locations above the ground. Many other researchers have used strings for assessing airborne spray volumes in drift studies. ... 

Tank-mix samples were taken prior to each application to determine actual spray concentration. For high-volume applications, the remaining spray liquid was estimated. After completing the low-volume application, the volume of the remaining spray solution was measured and another tank sample was taken. Application rates were calculated from the spray volume, acreage, and concentration of the active ingredient in the tank sample. 

To assess the reproducibility of spray volume delivery, a series of preweighed weigh boats were placed on the instrument s carousel, and the instrument was programmed to spray a single time into each. After spray delivery, the boats were reweighed, and the volume of liquid calculated. The maximum amount of fluid dispensed was 105.1 pL, and the minimum was 65.7 pL The average of 20 separate determinations was 88.8 pL, yielding an error of 11.2%. 

Singh, M. and D.P.H. Tucker (1983b). Effect of reduced glyphosate rates, spray volumes and delivery systems on bermudagrass control in Florida citrus groves. Proc. Fla. State Hort. Soc., 96 34—37. 

The central issue seems to be whether it is better to keep the deposit near the bark surface or have it penetrate. More spray volume is required to gain good penetration, and this raises the cost. Low volume sprays that do not penetrate significantly would be cheaper and would involve a lesser risk of phytotoxicity, where green trees are sprayed for protection. 

Compound Molecular Weight Solubility in H2O (- 25 °C) Spray Volume for 1 lb al in Solution... 

When BALAN/Emulsifiable Concentrate D tank mix was tested at a rate of 5 gal/acre, the system was unsuitable for application (Table VII). However, when the spray volume was increased to 10 gal/acre, the tank mix was compatible. As a result, the the BALAN Dry Flowable label recommends that tank mixes be applied at a minimum of 10 gallons/acre. 

To assess the reproducibility of spray volume delivery, a series of preweighed weigh boats were placed on the instrument s carousel, and the instrument was programmed to spray a single time into each. After... 

Although wide drop-size distributions can sometimes be an advantage (Hislop, 1983) the large numbers of small drops produced in hydraulic nozzle sprays can result in spray drift and inadequate targeting (Miller, 1993). Rotary atomisers (Bals, 1975) can reduce the breadth of drop-size distributions and provide a more targeted size distribution. They have not been widely adopted in broad-acre ground crops, because their spray volumes and drop trajectories often cause control difficulties, but they have found some acceptance in orchard sprayers. 

Advanced nozzle designs, such as twin-fluid, pre-orifice and air-inclusion nozzles, can also be used. Most are designed to reduce spray drift. Atomisation in twin-fluid nozzles occurs because the interaction of air and liquid. Different spray qualities can be produced by changing both liquid and air pressures. Low spray volume rates (75-1501/ha) and high work rates (ha/hour) are possible. 

Large drops, with their greater kinetic energy, can cause problems as they impact on crops. Drops greater than 200 im diameter (Brunskill, 1956) have the potential to cause spray runoff and contamination of the soil. With the lowering of spray volume rates, and the use of more fine nozzles, this problem has reduced in importance in recent years, but the trend towards the use of coarse sprays for drift reduction may reintroduce the problem in the near future. 

The most commonly used application systems in arable crops are boom sprayers equipped with equally spaced hydraulic nozzles (Robinson, 1993). The quality of the spray influences the quantity deposited on the crop and spray-drift. The combination of forward speed, nozzle type and pressure defines the sprayed volume. Volume rates have been reducing for several decades. While in the 1950s it was common to spray 10001/ha, nowadays 100-3001/ha is more common. 

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