Fertigation Calculator

Calculate fertilizer injection rates, stock solution concentration, and nutrient ppm for fertigation systems.

System flow (GPM)

Target rate (lb N/acre)

Field area (acres)

Nutrient content (%)

Injection ratio (%)

Irrigation run time (min)

Product density (lb/gal)

Tab to move between fields

Product needed (lbs)

217.4

Target concentration (ppm)

1,997.1

Product needed (gal)20.02

Stock injection rate (GPH)30

Product rate (GPH)10.01

Stock concentration (lb/gal)3.62

Est. EC increase (mS/cm)2.85

How to Use This Calculator

Enter your irrigation system flow rate in GPM and field area in acres.
Set the target nutrient application rate in lbs per acre (e.g., lbs of nitrogen).
Enter fertilizer nutrient content percentage (e.g., urea = 46% N) and product density in lb/gal.
Set the injector ratio (%) and total irrigation run time in minutes.
Read Product needed (gallons), Target concentration (ppm), and Injection rate (GPH) to configure your injector.

How the result changes with Nutrient content (%)

System flow (GPM): Irrigation system flow rate in gallons per minute.
Target rate (lb N/acre): Desired nutrient application rate per acre (e.g., lbs of nitrogen).
Field area (acres): Total irrigated area receiving fertigation.
Nutrient content (%): Percent nutrient in fertilizer product. Urea=46% N, UAN-32=32% N.
Injection ratio (%): Injector ratio (stock solution ÷ system flow). Typical: 0.5-2%.
Irrigation run time (min): Total irrigation set duration in minutes.
Product density (lb/gal): Liquid fertilizer density. UAN-32=11.06, UAN-28=10.65, water=8.34.

Product needed (lbs): Total liquid fertilizer product needed.
Product needed (gal): Total product volume in gallons.
Target concentration (ppm): Nutrient concentration in irrigation water.
Stock injection rate (GPH): Gallons per hour of stock solution injected.
Product rate (GPH): Gallons per hour of undiluted product to inject.
Stock concentration (lb/gal): Lbs of product per gallon of stock solution.
Est. EC increase (mS/cm): Rough estimate of electrical conductivity increase.

Identify Input Parameters
4 parameters
System flow (GPM) = 50, Target rate (lb N/acre) = 20, Field area (acres) = 5, Nutrient content (%) = 46 = 7 input(s) provided
Calculate Product needed
Product needed = totalNutrientLbs / nutrientFraction
217.4 = 217.4
Calculate Target concentration
Target concentration = (totalNutrientLbs * 453592) / (totalWaterGallons * 3.7854)
1997.1 = 1997.1
Calculate Product needed
Product needed = totalProductLbs / productDensityLbPerGal
20.02 = 20.02
Calculate Stock injection rate
Stock injection rate = systemFlowGPM * 60 * injectorRatio
30 = 30