Herbicides which are in liquid and wettable powder formulations are applied with the help of knapsack sprayer by using flat-fan nozzle or impact nozzles otherwise known as deflected nozzles or floodzet nozzles. The application is usually made at low pressures ranging 15-25 PSI to avoid drift. To be more careful for avoiding drift to the plant portions, a protective shield may also be fixed over the nozzle. The herbicides with granular formulations are usually broadcasted by mixing with sand for obtaining even distribution. Sometimes when the sprayers are not readily available the liquid formulations at the rate of 1 lit is mixed with 20-25 Kgs of sand and broadcasted uniformly by maintaining 2 cm layer of water. Equipment used Hand sprayers The following procedure may be used to calibrate a sprayer having a relatively small spray tank capacity, such as the 2 to 5 gallons size commonly carried by hand, on the shoulder, or as a backpack. To properly calibrate such sprayer, they must be equipped with a pressure regulation valve located between the spray tank and the nozzle outlet so that a constant sprayer out put maintained. Pour a known volume of water into the spray tank. Close spray tank and pump up pressure. At constant pressure and uniform speed, spray a known area. Determine the sprayer out put for the area by substracting the amount of water remaining in the spray tank from the amount originally poured in the tank. Sprayer out put for a given area may be adjusted by changing the pace or the nozzle orifice size or both. Generally the spray pressure remains set at about 25 Psi. If necessary, the sprayer out put can be expressed as gal/A by dividing the area A (43,560ft2) by the area spayed (ft2), multiply this value by the volume of  water applied / area and conversion of gallons. (1gal = 128 fl oz = 3,785 ml) 1 fl oz = 29.57ml. The following procedure may be used to calibrates sprayer equipped with any type of spray nozzle designed to cover uniformly a given area with the spray mixture, at constant speed and spray pressure. Fill the spray tank completely with water. Select a safe speed (use bet 2 and 5 mph) for the terrain to be sprayed and use this speed during calibrations. Make off any convenient distance. Generally, the greater the distance the greater is the accuracy in determine sprayer out put. Make one or more passes with the spray over the measured distance at the selected speed operation the sprayer only over measured distance. Determine the volume of water applied to the area by refilling the spray tank to its original water level and carefully note the no. of fluid ounces required. Calculate the area sprayed by multiplying the width of the area sprayed by the distance travelled measured in feet. Divide the no. of square feet in / A (43,560) by the no. of square feet in the area sprayed to obtain the no. of such plots / area. Multiply the no. of plots / area by the no. of fluid ounces applied / area. Divide the total no. of fluid ounces of water applied / area by the no. of fluid ounces in 1 gal (128fl oz) to obtain the sprayer out put expressed in gallons of water / area. Machine (power ) sprayer calibration Proper sprayer calibration is essential to the application of the correct mount of herbicide. The volume of carrier applied by sprayer is governed by a 5 factors Speed of the sprayer and the area to be sprayed. Spray pressure used. Number of nozzles used. Size of the nozzle orifice opening. Viscosity of the liquid. Increasing the speed of the sprayer over the area sprayed (other factors remaining constant) results in less carrier applied to the area. Slower speed results in the application of a greater volume of carrier. The more commonly used speeds of ground equipment are between 2 and 5 miles/hr depends on lands. With other factors remaining constant, increasing the spray pressure results in a greater volume. of carrier being applied to a given area. Conversely, a lower spray pressure results in less carrier applied. On general spray pressure of 15 to 40 ponds / square inch are used when applying weedicides. With the other factors remaining constant, any increase in the no. of nozzles used with the sprayer results in increased sprayer out put. Added nozzles, however do not necessarily increase the volume / area applied. They may be spaced nearly to increase the area covered during each of the sprayer. Similarly a decrease in the no of nozzles used usually results in a smaller area sprayed, rather than a change in a vol / area. With the other factors remaining constant, the use of larger-size orifice nozzle tips results in a greater vol. of carrier being applied to a given area. Smaller size orifice tips will deliver a smaller vol. of carrier. With the other factor remaining constant, the lower the viscosity of the liquid carrier the greater the volume of carrier (or spray mixture) applied to a given area.The greater the viscosity the less applied. The most practical mean of changing sprayer out put during calibration is to change the speed ornozzle orifice size or both. When adjusting sprayer out put during calibration , it has been in mind that spray droplets become smaller as the spray pressure is increased or nozzle orifice size is decreased. The smaller the spray droplets, the greater is their tendency to drift from the target area with air movement. For uniform spray covers, proper nozzle tips must be used and the nozzle spacing must be adjusted properly for the land involved. Nozzle tips of the same orifice size must be used in all nozzles of the spray boom, otherwise sprayer out put will not be uniform. Herbicide dosage calculations In general, the first steps in the procedure for calculation herbicide dosage are to be known. Which herbicide(s) to use for best results under your particular set of conditions. What the recommended dosage is for the herbicide How much herbicide(s) present in a given quantity of the commercial product to be used. The following general formulas may be used for solving most herbicide dosages. For liquid Formulations (Soluble, emulsifiable , flowable (slurry)) Pounds of active gradient / gallon of formula For dry formulate (wettable powder, granular pellets) Significance of symbols on the herbicides label Toxicity category Actual-oral toxicity LD50 mg/kg Color of Triangle Signal-word required on label Warnings symbol on the label Extremely toxicity 0 - 50 Red Poison Skull and cross bones Highly toxicity 51 - 500 Yellow Poison - Moderately toxicity 501 - 5000 Blue Danger - Slightly toxicity 5000 Green Caution -

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