Turfgrass Management: Determining How Much Nitrogen or Active Ingredient You Are Applying

Determining How Much Nitrogen You Are Applying

It is crucial to know how much nitrogen a managed turf stand is receiving, in order to properly maintain the turf, as well as manage growth, weeds, insects, and diseases.

Determining how much nitrogen being applied through granular fertilization does involve some simple math, but a chart has been created to save time to determine these calculations. This chart can be useful in determining how much nitrogen an application is putting down, as well as determining the total nitrogen rate for a season on a per 1,000 square foot basis.

• First, look to the y-axis (left), and determine your fertilizer's percent (%) nitrogen (the first number in a series of 3 on the bag. Ex. A 25-0-5 would have a nitrogen content of 25 %.)
• Then, move across the row to the right until you find the approximate amount of material you intend to put down per 1,000 square feet.
• Then move upwards to the x-axis (top) to determine what the rate of nitrogen per 1,000 square feet would be at that given rate.
• You can then determine what product to use in order to achieve the desired amount of nitrogen per 1,000 square feet. (Ex. If an applicator wanted to apply 1 pound of nitrogen per 1,000 square feet and apply it at a rate of 5 pounds per 1,000 square feet, a material with 20% nitrogen would need to be used.)
• The green boxes simply designate the low end of the material to be applied to get an even application of the material, and the yellow is just an indicator on the chart where a 5-pound application of material would be on this chart.

Image: Tanner Delvalle, Penn State

Determining How Much Active Ingredient You Are Applying

In order to effectively prevent a turf pest, a certain amount of pesticide may be applied to turf. Commonly, granular applications of a preventative pesticide are placed down prior to weed or insect emergence.

These materials are commonly referred to as "crabgrass preventers" or "grub preventers." Prevention of this pest will depend on several factors, one of which is the rate of the pesticide. This is essentially the dosage of pesticide being applied to the turf. If too little is placed down, control will likely be limited. If too much is put down, it is potentially a waste of material, an excessive expense, and could be detrimental to the turfgrass system.

Determining how much active ingredient is being applied, some simple math is involved, but a chart has been created to save time in determining these calculations.

• First, look to the y-axis (left), and determine the percent (%) of active ingredient in the material. This can be found on the label of the pesticide.
• Next, move across the row to the right to arrive at the proper rate of active ingredient per acre. Different pesticides recommend rates of pesticide per acre, which can be found on the label. (Ex. Season-long crabgrass control using prodiamine requires 0.75 pounds of active ingredient to be applied).
• Once you arrive at the proper rate per acre, move upwards to the x-axis (top) to determine the proper rate of that granular material in pounds per 1,000 square feet. (Ex. If an applicator wanted to apply a .43 granular prodiamine product at 0.75 lbs of prodiamine per acre, they would need to apply that material at a rate of 4 pounds per 1,000 square feet.)
• The colored boxes (yellow, green, gold, and orange) simply indicate a suggested range for the corresponding pesticides, shown to the right of each row.

Image: Tanner Delvalle, Penn State