Nitrogen Sources and Turf Response

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

2. 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 30-45 days unless applied at excessive rate

3. Ammonium Sulfate • 21% N (NH4)2SO4 • Highly soluble and leachable • Subject to volatilization • Very acidifying – useful in high pH soils • High salt index - 3.25 – must be watered in • Deep green and longer response than many other soluble N sources

4. Urea • 46% N • Soluble Synthetic Organic • Nonionic, highly leachable • Subject to volatilization • Low acidity - 1.8/kg N • Low salt index - 1.62

5. 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

6. Ammonium Nitrate • 33 – 34 % N • Very soluble • Subject to volatilization and leaching • Low acidity • 1.8kg acid/kg • High salt index -2.99 • Can be explosive • Short term response

7. 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

8. 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 60-90 days

9. 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

10. 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

11. 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

12. 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

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

14. 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

16. 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%

17. UF Materials Comparison Nitroform GUARANTEED ANALYSIS Total Nitrogen (N)........................................ 38% 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)*.......................................40% 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.

18. SRN Materials Label Comparison Polyon GUARANTEED ANALYSIS Total Nitrogen (N)........................................ 30% 1.5% Ammoniacal Nitrogen 28.5% Urea Nitrogen* 8.0% Soluble Potash 0.955% Water Soluble Magnesium 0.2175% 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)*....................................38-39% Urea Nitrogen Derived from: polymer coated sulfur coated urea *38-39% slowly available Nitrogen from polymer sulfur coated urea.

23. Palm Beach County Nitrogen Demo Plots Treatments: • Control • Urea (soluble) at 0.5 lb N 1,000 ft-2 • Urea (soluble) at 1.0 lb N 1,000 ft-2 • Polyonat 1 lb N 1,000 ft-2 • Polyon at 2 lb N 1,000 ft-2 • Milorganite at 1 lb N 1,000 ft-2 • Methylene urea 1 lb N 1,000 ft-2 • Treatments applied Mar 12 • Irrigated in with ~ ¼” water • Irrigated 3 x week to apply 0.08-0.3” each time

24. Control April 1 April 8 April 14

25. Soluble Urea @ 0.5 lb N/1,000 April 1 April 8 April 14

26. Soluble Urea @ 1.0 lb N/1,000 April 1 April 8 April 14

27. Polyon @ 1.0 lb N/1,000 April 1 April 8 April 14

28. Polyon @ 2.0 lb N/1,000 April 1 April 8 April 14

29. Milorganite @ 1.0 lb/1,000 April 1 April 8 April 14

30. Methylene Urea @ 1.0 lb N/1,000 April 1 April 8 April 14