Fertilization

Turfgrass fertilization is one of the most important cultural practices needed to maintain a healthy, dense stand of turf. Understanding the role each nutrient plays in turfgrass plants can help determine what is needed to maintain the health of the plants and to also eliminate excessive or unnecessary application of nutrients.

Before beginning a fertilization program, be sure to take soil and tissue tests to determine required nutrients for optimum soil and plant health.  Soil tests should be conducted on a routine basis - every one (for sand-based fields) to three (for native soil fields) years is recommended. 
Understanding Soil Tests

Turfgrass Nutrients
Macronutrients:
Primary Nutrients – Nitrogen (N), Phosphorus (P), and Potassium (K)
Secondary Nutrients – Calcium (Ca), Magnesium (Mg), Sulfur (S)

Micronutrients:
Iron (Fe), Manganese (Mn), Zinc (Zn), Copper (Cu), Boron (B), Molybdenum (Mb), Chlorine (Cl), Nickel (Ni)

Plant and Environmental Responses to the Essential Nutrients

Fertilizer Definitions:
Complete Fertilizer — contains nitrogen (N), phosphorus (P) and potassium (K)
Compound or Mixed Fertilizer — contains at least two primary nutrients
Homogenous Fertilizer — granular fertilizer that can have a variety of formulations, but is comprised of homogenized prills that are indistinguishable from each other
Blended Fertilizer — granular fertilizer that contains nitrogen, phosphorus and potassium, but is made up of separate components

Fertilizer Grade — the percentage of nitrogen (N), phosphate (P2O5), and water soluble potash (K2O) available
Fertilizer Ratio — relationship among percentages of nitrogen (N), available phosphate (P2O5) and water soluble potash (K2O)
For example: The ratio for a 10-5-5 fertilizer is 2-1-1.
Fertilizer Analysis — nutrient content by weight
For example: In a 20-5-15 fertilizer, 20 percent of the weight is nitrogen (N), 5 percent of the weight is phosphate (P2O5), and 15 percent of the weight is potash (K2O). In a 100 pound bag, 20 pounds would be nitrogen (N), 5 pounds would be phosphate (P2O5), and 15 pounds would be potash (K2O).

Calculations
To determine the amount of elemental phosphorus (P): P2O5 x .44 = P
To determine the amount of elemental potassium (K): K2O x .83 = K

Nitrogen Sources
The source of nitrogen determines turf growth rate, density and color. Nitrogen is broken down into two categories: quick release and slow release.

Fertilizer Programs
Cool Season Turfgrass



With active growth occuring in the spring and fall, the best time to fertilize cool season turfgrasses is from March to June and September to December. (This varies with geographic location.)
March - May: One to two applications may be necessary in the spring. This application assists with greening up the turf, but can be detrimental if there is a late frost.
June - August: Heavy fertilizer applications in the middle of summer should be avoided due to heat and drought stressing the plants. If fertilization is necessary, spoon feeding throughout the summer months will maintain turfgrass health.
September: The best time to fertilize is in the late summer. As plants begin actively growing again, fertilization promotes recovery from drought and heat related injury sustained during the summer months. Fertilization at this time also contributes to root and rhizome growth, disease and stress tolerance, and the storage of carbohydrates.
October - December: Fertilization in the late fall is advantageous because the majority of nutrients are used for root growth. There is not much vertical growth. Late fall fertilization can also be beneficial to early spring green up.

Warm Season Turfgrass



With active growth occuring throughout the summer, the best time to fertilize warm season turfgrasses is from May to September.
April - May: Early spring fertilization will assist with spring green up. One of the best times to fertilize is late spring because plants are actively growing and storing and manufacturing carbohydrates.
June - August: Fertilization can continue throughout the summer.
September: Late summer is also a good time to fertilize because plants are actively growing and storing and manufacturing carbohydrates.
October - March: If a field has not been overseeded, fertilization should not take place. 

Tips to Get the Most Out of Your Fertilizer
1. Soil test to determine the nutrients needed by the plants.
2. Depending on the turfgrass species, apply nitrogen in the amounts needed.
3. Apply nitrogen in multiple applications throughout the growing season.
4. Return clippings while mowing.
5. To avoid leaching, do not overwater.
6. Use a slow release fertilizer and apply less frequently.
7. If using a quick release nitrogen source, water it in to avoid foliar burn.


University Publications on Turfgrass Health:
Urban Nutrient Management - Virginia Tech
Developing a Turf Fertilization Plan - University of Tennessee
Essential Elements - University of Tennessee
Fertilizers - University of Tennessee
A Guide to Turfgrass Nutrient Recommendations - Based on Kansas State University Soil Test Results - Kansas State University
Nutrient Management Guidelines for State Property and Commercially Managed Turfgrass - University of Maryland
Late Fall Fertilization of Athletic Fields - Penn State University
Best Management Practices for Nutrient Management of Turf in New Jersey - Rutgers University
Managing Soil pH for Turfgrasses - Rutgers University
Understanding Fertilizer Labels - Rutgers University
Nutrient Management of Land Applied Grass Clippings - Rutgers University

Liming Turfgrass Areas - Penn State University
Agricultural Liming Materials - Rutgers University
Liming - University of Tennessee
Soil Acidity and Liming for Agricultural Soils - North Carolina State University

Using Gypsum in Southwestern Soils - University of Arizona
Applying Gypsum in Iowa - Iowa State University
Gypsum Use on Turfgrasses - University of Maryland

Evaluation of Spent Mushroom Substrate as a Topdressing to Established Turf - Penn State University

Understanding the Phosphonate Products - Penn State University

Soil Testing Information:
Soil Sampling and Analysis - University of Arizona
Directions for Soil Sample Collection - Cornell University
Soil Fertility Test Interpretation - Phosphorus, Potassium, Magnesium, and Calcium - Rutgers University