Name:- Guajarati dharmesh Enrollment no-130310105014 Subject – chemical process industries-1 SEM-3 Subject code-2130505.

Ammonia volatilization from urea

Overview Evolution of Urea consumption Definitions Urea Dissolution and Diffusion Urea Hydrolysis Ammonia Volatilization Research Results Summary

USA Evolution of N Fertilizers Consumption 21% Urea Ammonium nitrate 1973 / 74 Nitrogen solutions 2004 / 05 No abreviar Anhydrous ammonia Total compound N 1 2 3 4 5 Millions of tonnes www.fertilizer.org

Overview Evolution of Urea consumption Definitions Urea Dissolution and Diffusion Urea Hydrolysis Ammonia Volatilization Research Results Summary

Definitions Dissolution: urea absorbs water and converts from solid to liquid Hydrolysis: urea converts to ammonium (NH4+) Diffusion: movement due to motion of molecules Urea has no charge, diffuses easily NH4+ has charge, diffuses slowly

Overview Evolution of Urea consumption Definitions Urea Dissolution and Diffusion Urea Hydrolysis Ammonia Volatilization Research Results Summary

Urea Dissolution Urea has to be dissolved before it can be hydrolyzed

Urea Dissolution Urea has to be dissolved before it can be hydrolyzed Urea can absorb water from the atmosphere and from the soil/crop residue

Urea Dissolution Urea has to be dissolved before it can be hydrolyzed Urea can absorb water from the atmosphere and from the soil/crop residue Absorption of water from the atmosphere depends on relative humidity (RH)

Urea Dissolution Urea has to be dissolved before it can be hydrolyzed Urea can absorb water from the atmosphere and from the soil/crop residue Absorption of water from the atmosphere depends on relative humidity (RH) Critical relative humidity (CRH) is the RH at which urea dissolves

Effect of Temperature on CRH and Water Solubility of Urea

Urea dissolution and diffusion RH > CRH (80%) Dry Soil Crop residue www.agrium.com RH > CRH (80%) Crop residue Urea Urea Dry Soil

Urea dissolution and diffusion Wet Soil Crop residue Urea Urea www.agrium.com Crop residue Urea Urea Urea 1/2 inch Wet Soil

Crop residue Urea Urea Urea 2 inches

Urea Diffusion into Soil Depth Urea Determined by soil moisture

Urea Diffusion into Soil (after 10 days)

Overview Evolution of Urea consumption Definitions Urea Dissolution and Diffusion Urea Hydrolysis Ammonia Volatilization Research Results Summary

+ 2 2 Urea Hydrolysis Urea NH4+ Urease is derived from crop residues Urease enzyme Urease is derived from crop residues and soil microorganisms

Urease inhibitor Crop residue Urea Urea Urea

Overview Evolution of Urea consumption Definitions Urea Dissolution and Diffusion Urea Hydrolysis Ammonia Volatilization Research Results Summary

(gas) NH3 Volatilization Process (aq) (aq) Atmosphere NH4+ NH4+ Hydrolysis Urea + H+ NH4+ NH4+ (gas) Soil air (aq) Soil solution NH4+ Clay (aq) + Equilibrium H+ OM

Effect of soil pH on NH3 as % of Total N

(gas) NH3 Volatilization Process (aq) (aq) Atmosphere NH4+ NH4+ Hydrolysis Urea + H+ NH4+ NH4+ (gas) Soil air (aq) Soil solution NH4+ Clay (aq) + Equilibrium H+ OM

Increase in soil pH depends on soil H+ buffering capacity Higher clay and OM contents lead to higher soil H+ buffering capacity

Atmosphere ½ inch pH Urea hydrolyzes on the soil surface NH4+ NH4+ CEC pH 6 7 8 9

pH Urea hydrolyzes below the soil surface NH4+ NH4+ NH4+ NH4+ NH4+ 2 inches H+ H+ H+ H+ H+ H+ H+ H+ pH CEC 6 7

Effect of Temperature on NH3 Volatilization Soil ½ inch Urea NH4+ + H+

Effect of Temperature on Urea Hydrolysis

Effect of Temperature on NH3 Volatilization Soil ½ inch Urea NH4+ + H+

Effect of Temperature on % of NH3 pH = 8.5

Effect of Temperature on NH3 Volatilization Soil ½ inch Urea NH4+ + H+

Effect of Temperature on Conversion of Aqueous NH3 to Gaseous NH3

Effect of Temperature on NH3 Volatilization Soil ½ inch Urea NH4+ + H+

Effect of Wind Speed on NH3 Volatilization Atmosphere Wind speed Soil ½ inch Urea NH4+ + H+

Ammonia Loss (% of Applied N) Replication II Replication I 5 10 15 20 UAN UREA Nitamin 51mm Replication II Replication I Days After Application 40 60 80 100 120 Replication III

Optimum Conditions for Volatilization Small diffusion depth into soil RH > CRH High temperature High wind speed Low pH buffering capacity

Overview Evolution of Urea consumption Definitions Urea Dissolution and Diffusion Urea Hydrolysis Ammonia Volatilization Research Results Summary

Urea Applied to Pasture - Fall 2004 Nitamin® UAN Urea 50 40 Temp = 47oF NH3 loss (% of applied N) 30 20 10 Rainfall Soil water content 50 0.4 40 0.3 30 Rainfall (mm) Soil water content (g g-1) 0.2 20 10 0.1 20 40 60 80 100 120 Days after application

Urea Applied to Pasture – Spring 2005 Nitamin® UAN Urea 50 40 Temp = 63oF NH3 loss (% of applied N) 30 20 10 Rainfall Soil water content 50 0.4 40 0.3 30 Rainfall (mm) Soil water content (g g-1) 0.2 20 10 0.1 20 40 60 Days after application

(aq) Atmosphere H+ NH4+ NH4+ NH4+ Clay NH4+ OM Equilibrium Urea Urea

Urea Applied to Pasture - Fall 2005 Nitamin® UAN Urea 50 40 Temp = 62oF NH3 loss (% of applied N) 30 20 10 0.1 0.2 0.3 0.4 Soil water content (g g-1) Rainfall Soil water content 50 40 30 Rainfall (mm) 20 10 20 40 60 Days after application

Time of RH above CRH in the first 30 d Days after application 25 20 15 Time of RH > CRH (h) 10 5 5 10 15 20 25 30 Days after application Total: RH > CRH = 19 days 63 %

Soil water content (0.07 g g-1) Permanent wilting point (0.04 g g-1) Atmosphere RH > CRH (80%) Fescue thatch Urea Urea NH4+ Soil water content (0.07 g g-1) Permanent wilting point (0.04 g g-1)

Urea Applied to Pasture – Spring 2006 Days after application NH3 loss (% of applied N) 10 20 30 40 50 Nitamin® UAN Urea 0.1 0.2 0.3 0.4 Soil water content (g g-1) 80 Rainfall (mm) 60 Rainfall Soil water content Temp = 69oF

Soil water content (0.15 g g-1) Atmosphere Urea NH4+ Urea NH4+ NH4+ (aq) + Equilibrium NH4+ H+ Soil water content (0.15 g g-1) Field capacity (0.18 g g-1) CEC

Ammonia volatilization losses under field conditions Summary of Pasture Results Ammonia volatilization losses under field conditions Fertilizer Fall 2004 Spring 2005 Fall 2005 Spring 2006 --------------- Ammonia loss (% of applied N) ----------------- Urea 19 a* 6 b 12 a 13 a 14 a 46 a 33 b 34 b 24 a 18 a UAN Nitamin® Within a column, values followed by the same letter are not significantly different according to Fisher’s LSD at p=0.05

Summary for Pastures/No-Till Dry Soil, Dry Residue, RH < CRH: OK Dry Soil, Dry Residue, RH > CRH: not OK Wet Soil, Wet Residue: not OK Apply on dry soil, dry residue, expected low RH, and hope for 1 inch of rain whenever it rains. Apply on wet soil if 1 inch rain/irrigation is expected.

Summary for Clean-Till Crops Dry Soil: OK Wet Soil: not OK Apply on dry soil and hope for 1 inch of rain whenever it rains. Apply on wet soil if 1 inch of rain/irrigation is expected.

Summary for Pastures/Crops Knifed or disked in Dribbled Broadcast Knifed of disked in better than Dribbled Dribbled better than Broadcast

Urea Applied to Pine Plantations March 14 – April 12 (59oF) Rain

Urea Applied to Pine Plantations Rain 66oF

Laboratory Results (77oF, 90% RH)

Pine needle photo Urea Urea www.microscopyu.com NH4+ Organic Layer CEC

NH4+ Organic Layer NH4+ Pine needle photo Urea Urea CEC www.microscopyu.com CEC NH4+ Organic Layer

Summary for Pine Plantations Dry Forest Floor, RH < CRH: OK Dry Forest Floor, RH > CRH: not OK Wet Forest Floor: not OK Apply on dry forest floor, with expected low RH, and hope for 1 inch of rain whenever it rains. Apply on wet forest floor if 1 inch rain is expected.

Questions?