Fertilizers: Form & Function

Fertilizers – Basic Definition Has a guaranteed analysis. This is the minimum level of fertilizer nutrients expressed as a percentage. Also tells us the source of the fertilizer nutrients. Contains fertilizer nutrients. Not a growth amendment or stimulant.

Classes of Fertilizers Soluble Slow Release Chemically Slow Release Physically Slow Release ‘Stabilized’ N Sources Those that are Slow-Release via Mineralization (Organic) Other fertilizers – bioenhanced, microbially mediated, etc. Those derived from proteins?

Soluble Fertilizers Immediate nutrient release Rapid turfgrass response Possibility of turf burn Tend to be inexpensive Examples: urea, (NH4)2SO4 Most often our foliar sources, too.

Other Soluble N Sources Ammonium sulfate (21-0-0) Calcium nitrate Potassium nitrate (13-0-44) Sodium nitrate (16-0-0)

Establishment of Hybrid Bermudagrass as Affected by N Source Day/Month/Year 7-9-02 7-29-02 8-13-02 shoots per cup cutter Ca(NO3)2 76 a 127 b 147 a NH4NO3 74 a 137 a 145 a 7-6-04 7-21-04 8-19-04 88 a 96 a 98 a 90 a 109 a 100 a

Slow-Release Fertilizers Physically slow-release Slow release via a physical coating around a soluble prill Technologies have been around since the 1950s, others newer (80s and 90s) SCU PCU, resin-coat, multi-coat Chemically slow-release Slow release by their manufacturing method (homogeneous) – 1950s Ureaformaldehyde/Methylene urea IBDU

Chemically Slow-Release Slow release due to a chemical reaction. Nitrogen must be made plant available by bonds being broken. Methylene ureas (urea formaldehyde). Isobutlyidene diurea (IBDU). Slower, more consistent N release. Higher cost than soluble.

(7.8 g N m-2)

Physically Slow Release Coated with wax, sulfur or plastic to make slow-release. Typically urea, but also may be K2SO4. Consistent, slow N release. Length of release varies with coating thickness and other coating characteristics.

6.8 g N m-2 2x 6.8 g N 2 x 4.9 g N 4 x

6.8 g N m-2 2x 6.8 g N 2 x 4.9 g N 4 x

There are MANY different types: Penn G-2 color as affected by slow-release N source, Farmlinks GC, 2007

2016 Prill damage study, Auburn. Estimated Days for N Release days after application 1 Percent Nitrogen Release Traffic None P-value 45 7.0 2.6 0.04 90 13.0 6.7 0.09 120 6.3 1.9 0.24 180 3.2 0.3 0.97 Estimated Days for N Release %N release Traffic None P-value 45 13 7.8 0.15 90 11 7.5 0.34 120 6.3 4.8 0.44 180 5.0 4.4 0.71 2016 Prill damage study, Auburn.

Total Percent N Volatilized by Source 5 10 15 20 25 30 35 40 45 50 Urea SCU Polyon Methx AN Milorganite N Source % N Volatilized

‘Stabilized’ Nitrogen Fertilizers Urea with the addition or either a nitrification inhibitor (dicyandiamide), urease inhibitor (N-(n-butyl) thiophosporic triamide), or both. Inhibits the enzymes urease and ammonium mono-oxygenase.

Volatilization (Urease) Inhibitors Maleic itaconic co-polymer – Nutrisphere-N® Ca-Heteropolysacharides Cl and Ca-Aminoethylpiperazine Cl – NStay®, Stay-N® Calcium polymer blend – NZone N-(n-butyl) thiophosporic triamid- UMaxx, Uflexx, Hydrexx

Volatilization Lab Method Loss of N to atmosphere as ammonia gas. Big issue in manure application. Common with urea or urea-based products. Irrigation lowers N loss. Lab Method

Passive Micrometerological Technique – Field Study 10 foot aluminum mast Wind vane Oxalic acid-coated tubes inserted perpendicular to mast at 5 heights

How to prevent volatilization losses? Don’t use urea (still an issue on high pH soils, however) Water in Slow-release sources Foliar Volatilization inhibitors

3.2 mm 6.4 mm 12.7 mm 25.4 mm

Nitrification Inhibitors In agriculture, we try to slow this ammonium to nitrate conversion using nitrification inhibitors. Have been around for 40 years, but are coming back into the market again with new products.

Nitrification – Conversion of ammonium into nitrate, done by nitrifying bacteria. Incubation study. Effect of addition of dicyandiamide. + inhibitor urea urea + inhibitor control control Extractable soil ammonium Extractable soil nitrate

Fertilizer

Urea versus Urea + additive 1 lb N/M 0.8 lb N/M Never a significant difference between the two treatments.

Organic Fertilizers and Biofertilizers

Organic – at its simplest, it means that the product contains carbon. Organic Fertilizer - a material that is derived from plant or animal-based materials.

Let’s take a closer look at that…. Dissolved organic N (ppm) Microbial biomass N (ppm) Soil organic matter (%) Control 6.49 + 3.83 104 c 4.51 b Organic (216) 3.78 + 1.20 134 a 4.95 a Organic (216) + post-herb 1.67 + 0.03 128 ab 4.55 b Mineral (219) 7.07 + 2.03 106 c 4.44 b Mineral (98) + pre/post herb 4.36 + 1.77 100 c 4.37 b Mineral (245) + pre/post herb + fung 4.30 + 1.44 110 c 4.63 b Mineral (171) + pre/post herb + insect 4.84 + 1.32 107 c October, 2004 data collection Long term application of organic fertilizers resulted in a significantly higher soil microbial biomass. Cheng et al., 2008

Penn G-2 bentgrass putting green N at 4.9 g N m-2 (1 lb N/M)

Crystal Green Crystal Green is sustainably produced by Ostara using nutrient recovery technology that combines phosphorus, nitrogen, and magnesium into pure crystalline granules. Crystal Green is virtually water insoluble and releases only in response to organic acids produced by growing roots. Phosphorus content in wastewater can be reduced by recovering a portion of the phosphorous as a crystalline product called struvite. Struvite is relatively easy to dry and handle and shows potential as a slow-release fertilizer. Struvite is the common name for magnesium ammonium phosphate hexahydrate (MgNH4PO4 · 6(H2O)).

Percent establishment of Tifway hybrid bermudagrass as affected by P source. Auburn, AL, 2014. Bermudagrass was sprigged on June 25th 2014. All P applied at 2 pounds P2O5 per 1,000 ft-2 (9.8 g P2O5 m-2) 1 wk prior to sprigging.

(9.8 g P2O5 m-2)

(9.8 g P2O5 m-2)

guertea@auburn.edu