HOW TO DETERMINE PER-ACRE OUTPUT OF SPRAYERS 



1 . Power sprayers 



(a) Fill the spray tank with water. Make sure it is completely full. 



(b) Drive in a straight line for exactly 220 yards, operating the sprayer 

 at exactly the same pressure and tractor speed planned for use in 

 the field. It is a good practice to mark that notch on the throttle. (A 

 tractor travels slower in a soft field than on hard ground.) 



(c) Upon reaching the 220-yard mark, stop spraying. Then measure 

 carefully the amount of water needed to refill the tank (a quart jar 

 is satisfactory). 



(d) Convert the number of quarts of water used into gallons by dividing 

 by 4, and then multiply this figure by 66. Divide the result by the 

 width in feet of the strip sprayed. The answer obtained is the num- 

 ber of gallons the sprayer will put on 1 acre when it is operated at 

 the same settings. Example: Suppose the sprayer boom sprays a 

 strip 20 feet wide. After traveling 220 yards it takes 6 quarts to 

 refill the tank. Six quarts divided by 4 equals 1-1/2 gallons. Multiply 

 66 by 1-1/2, which equals 99. Then divide 99 by 20 feet (the width in 

 feet of the sprayed strip). The answer is just under 5, which is the 

 rate of application in gallons per acre. 



Comments and Precautions . --In some row crops only a narrow band 

 is sprayed, centered over the row, such as in pre-emergence treatments 

 in cotton and soybeans. When treatments are made in this manner the 

 rate of treatment is in terms of the area treated and not in terms of per- 

 acre of actual crop. For example, in cotton with 36-inch row spacing, if 

 a 12-inch band is treated at 1-1/2 pounds per acre (based on the area 

 actually treated ) the amount of chemical per acre of cotton would be 1/2 

 pound. 



2. Hand- Type Boom Sprayers 



Example: 3-gallon knapsack sprayer with a boom that sprays a 4-foot 

 swath. Fill sprayer and walk at a steady pace, maintaining a constant tank 

 pressure, for 110 yards. Refill tank, change number of quarts required to 

 refill sprayer into gallons, and multiply by 13 2. Divide this figure by the 

 width of the spray swath (4 feet). The answer is the number of gallons the 

 hand sprayer is delivering per acre at the pace walked and the tank pres- 

 sure maintained. 



If too much spray is being applied, walk faster or use less tank pressure. 

 For marked changes in rate of application, it may be necessary to obtain 

 different nozzle tips. 



3 . Single-Nozzle Hand Sprayers 



Example: 3-gallon hand sprayer with single nozzle. Mark off an area 5 by 

 20 feet (100 square feet). Fill sprayer with water to 3-gallon level and 

 spray 100-square-foot area using same speed and pressure that will be 

 used for spraying weeds. Refill sprayer, measuring accurately the amount 

 of water to refill to original level. The following tabulation gives the ratio 

 of weed killer to water required to apply 1 pint of weed killer per acre, 

 based on discharge of the nozzle: 



- 14 - 



