Nitrogen Sources and Turf Response Laurie Trenholm UF-IFAS Turf Specialist

Quick Release Nitrogen Soluble in water Provide fairly rapid response in turf Volatilize readily if not irrigated in Useful for repair of injured turf- athletic fields Provide for quicker turf establishment if growing plugs or sprigs in Response seen for days unless applied at excessive rate 2

Ammonium Sulfate 21% N (NH 4 ) 2 SO 4 Highly soluble and leachable Subject to volatilization Very acidifying – useful in high pH soils High salt index – must be watered in Deep green and longer response than many other soluble N sources

Urea 46% N Soluble Synthetic Organic Nonionic, highly leachable Subject to volatilization Low acidity - 1.8/kg N Low salt index

Urea Organic (but quick-release) N source Converted to ammonium-N form by enzyme urease in the soil after short time in the soil This happens within about 24 hours After this conversion, much less likely to leach if rainfall does occur

Ammonium Nitrate 33 – 34 % N Very soluble Subject to volatilization and leaching Low acidity –1.8kg acid/kg High salt index Can be explosive Short term response

Slow or Controlled Release Nitrogen Use various mechanisms to release N – Coating through which N diffuses – Chemical reaction used to create chemical bonds that ties the N up Release rates vary widely between products and due to temperature and microbial activity More expensive than QRN Less likely to leach than QRN if applied to bare soil, few differences in healthy turf that provides a ground cover 7

Sulfur Coated Urea 32-38% N Release depends upon –thickness of sulfur coating –microbial activity –soil environment temperature pH Cool season response-erratic Coating fragile- some spreaders may crack Response usually days

Polymer Coated Variable N N release varies, influenced by –coating thickness –soil temperature –not soil moisture –not influenced by soil moisture, pH, microbial activity Week 1: Moisture comes in through polymer coating, dissolves encapsulated N inside After week 1: Soil temperature causes N to diffuse through membrane

Polymer-Sulfur Coated Urea N release influenced by –coating thickness (vary by product) –diffusion rate –Less influenced by soil temperature and moisture Good for both warm and cool season application

Urea Formaldehyde Insoluble organic 38% N ; 65-71% WIN Biological N release –release by microbial activity –soil temperature Less effective in cool seasons Reaction of urea and formaldehyde gives chains of alternating C and N –Longer chains, slower release Nitroform, Blue Chip, Nutralene Can also be in solution

Methylene Urea 40% N - 36% WIN Microbial N release More rapidly available than UF Not as adversely influenced by cool temperatures Reaction of urea and formaldehyde gives chains of alternating C and N

Triazones 30% N Ring structured Triazones may contain methylene diurea N release by microbial action Response very similar to UF solutions

IBDU - Isobutylidene Diurea 31% N 90% slow release N released by hydrolysis as urea Release due to –pH (lower better) –Soil moisture –Granule size Good cool season response Less effective during heavy rain periods due to rapid release

Release Curves % N release over time Urea Formaldehydes – 1 mo: 20-40% – 2 mo: 23-45% – 4 mo: 31-53% – 6 mo: 38-58% IBDU – 1 mo: 21% – 2 mo: 32% – 4 mo: 50% – 6 mo: 63% Polyon (Polymer Coated Urea) – 1 mo: 49% – 2 mo: 75% – 4 mo: 90% – 6 mo: 94% Sulfur Coated Urea – 1 mo: 70% – 2 mo: 84% – 4 mo: 95% – 6 mo: 99%

UF Materials Comparison Nitroform GUARANTEED ANALYSIS Total Nitrogen (N) % 4.5% Urea Nitrogen 6.9% Slowly Available Water Soluble Nitrogen* 26.6% Water Insoluble Nitrogen Derived from: urea-formaldehyde *6.9% slowly available Nitrogen from methylenediurea and dimethylenetriurea. Nutralene GUARANTEED ANALYSIS Total Nitrogen (N)* % 6% Urea Nitrogen 20% Slowly Available Water Soluble Nitrogen* 14% Water Insoluble Nitrogen Derived from: methylene urea *20% slowly available Nitrogen from methylenediurea and dimethylenetriurea. 17

SRN Materials Label Comparison Polyon GUARANTEED ANALYSIS Total Nitrogen (N) % 1.5% Ammoniacal Nitrogen 28.5% Urea Nitrogen* 8.0% Soluble Potash 0.955% Water Soluble Magnesium % Water Soluble Iron Derived from: Muriate of potash, polymer coated urea, sulfate of ammonia, sulfate of potash-magnesia, iron sucrate *22.8% slow release Nitrogen from polymer coated urea. XCU (Polymer Sulfur Coated Urea) GUARANTEED ANALYSIS Total Nitrogen (N)* % Urea Nitrogen Derived from: polymer coated sulfur coated urea *38-39% slowly available Nitrogen from polymer sulfur coated urea. 18

22

Palm Beach County Nitrogen Demo Plots Treatments: 1.Control 2.Urea (soluble) at 0.5 lb N 1,000 ft -2 3.Urea (soluble) at 1.0 lb N 1,000 ft -2 4.Polyon at 1 lb N 1,000 ft -2 5.Polyon at 2 lb N 1,000 ft -2 6.Milorganite at 1 lb N 1,000 ft -2 7.Methylene urea 1 lb N 1,000 ft -2 Treatments applied Mar 12 Irrigated in with ~ ¼” water Irrigated 3 x week to apply ” each time 23

April 1 Control April 8 April 14

April 1 Soluble 0.5 lb N/1,000 April 8 April 14

April 1 Soluble 1.0 lb N/1,000 April 8 April 14

April lb N/1,000 April 8 April 14

April lb N/1,000 April 8 April 14

April lb/1,000 April 8 April 14

April 1 Methylene 1.0 lb N/1,000 April 8 April 14