Calculating the Amount of Nutrient Being Applied
Liquid Fertilizer Nutrients Per Gallon
Multiply the weight of one gallon by the percentage nutrient to obtain the weight of that nutrient per gallon liquid.
11.0 x 3% phosphorus = 0.32 lb phosphorus per gallon 26-3-4
11.0 x 4% potassium = 0.43 lb potassium per gallon 26-3-4
__lbs per gallon x __% Nutrient = __lbs Nutrient per gallon
Calibrating Your Granular Spreader
Example: 25-2-4 fertilizer, need 0.80 lb Nitrogen per thousand
__lbs N / __% N = __lbs per 1,000 fertilizing material to apply
Estimate the amount of 25-2-4 you will need for the test and place this in the spreader.
Set the spreader at the setting suggested for the bag for your spreader. This is a suggested setting only. The condition of your spreader (age and specific variations in your model) will cause differences in the actual setting and this suggested one.
Spread the material along the open area you have chosen. Walk at the pace you normally will during actual applications in yards. Many spreaders are dependent on walking speed along with spreader settings. Start your walk before your measured start point to ensure accurate calculations.
Weigh the amount of material left in the spreader.
Measure the length and width of the area covered. Calculate this into square feet (Length x Width).
Calculate the amount applied per 1,000 sq ft
__lbs x (1,000 sq ft / __sq ft) = __lbs applied per 1,000 sq ft
Factors that affect spreader settings include walking speed, differences in granular size, moisture content of granulars, coatings (such as Team Pro), age and condition of spreader, amount of overlap and other similar conditions.
Calibrating Boom Sprayer Gallons Per Minute
Distance = 200 ft, Time = 34 seconds
(3,600 x __ft) / (5,280 x __seconds) = __miles per hour
Spray speed: miles per hour...................4 mph
Nozzle spacing: inches...........................20 inches
(__gallons per acre x __mph x __inches nozzle spacing) / 5,980 = __gpm
(__gallons per 1,000 sq ft x __mph x __inches nozzle spacing) / 136 = __gpm
Check for target flow. Collect water from one new nozzle for 1 minute. Compare this volume with the target flow rate calculated in Step 3. Recheck any rates over or under by 10% of the recommended rate. Fine tune your rate with pressure adjustments. If two or more nozzles are found to be worn, replace all nozzles to ensure consistent, accurate spraying.
Calibrating Backpack Sprayer Gal Per 1,000 sq ft
Spray an area measuring exactly 1,000 square feet. Walk at a constant speed as you would during normal operations, holding your nozzle at your normal height.
Measure the amount of water left in the sprayer. Subtract this from what you started with. The amount used is the amount sprayed per thousand square feet.
Increase rates by walking more slowly or using a larger tip. Decrease rates by walking faster or using a smaller tip.
For more uniform spray coverage, cover the area twice at half rate, the second pass being at right angle to your first.
3 - 1 = 2 gallons per 1,000 sq ft being applied
__gallons start - __gallons end = __gallons per 1,000 sq ft (if use 1,000 sq ft as your area)
(__gallons start - __gallons end) x 1,000 / __sq ft covered = __gallons per 1,000 sq ft.
Calibrating Spray Gun Gallons Per Minute
Measure the amount of time needed to walk through 1,000 square feet.
Time needed to cover 1,000 square feet times the amount collected during spraying one minute equals the application rate per 1,000 square feet.
Adjust application rates by changing pressure, application speed or tip size.
__gallons per minute x 1,000 / __sq ft covered = __gallons per 1,000 sq ft applied.
Calculating the Size of An Area
Square or Rectangle
Example: 40 ft x 30 ft = 1200 sq ft
pi x r x r = Area pi = 3.1412 r = radius
3.1412 x __ft radius x __ft radius = __sq ft Area
0.8 x D x D = Area
D = Diameter
0.8 x __ft Diameter x __ft Diameter = __sq ft Area
Ovals Or Egg Shapes
(within 5% accuracy)
0.8 L x W = Area
L = Length
W = Width
0.8 x __ft L x __ft W = __sq ft Area
B = Base of Triangle
H = Height of Triangle
0.5 x __ft B x __ft H = __sq ft
A = One Parallel Side
B = Second Parallel Side
H = Height Perpendicular to Parallel Sides
0.5 (__ft A + __ft B) x __ft H = __sq ft Area
Divide area into sections of shapes you can calculate then add these for total area. Dividing the irregular shape into smaller divisions will result in more accurate calculations than using large areas. Another method is to average lengths and widths to make a calculable shape, being as accurate as possible with these averages to lessen error.