NITROGEN CYCLE Department of Plant and Soil Sciences Oklahoma State University Stillwater, OK Tel: (405) Department of Plant and Soil Sciences Oklahoma State University Stillwater, OK Tel: (405)

Loss from the System Ammonia Volatilization (urea) Surface Volatilization (anhydrous ammonia) Immobilization Leaching Plant N Loss Denitrification

Fertilizer NH 4, NO 3 Organic Matter Pool InorganicNitrogenInorganicNitrogen

NO 3 - -N, kg ha -1 Udic Argiustoll, cm, #502 N Rate kg ha N Rate kg ha NO 3 - -N, kg ha -1 Udic Argiustoll, cm, #505 Depth, cm

photosynthesis carbohydrates respiration carbon skeletons amino acids NH 3 reducing power nitrite reductase nitrate reductase ferredoxin siroheme NO 2 3 NADH or NADPH Bidwell (1979), Plant Physiology, 2nd Ed. Metabolism associated with nitrate reduction

Industrial view of the Nitrogen Cycle Nutrient Overload: Unbalancing the Global Nitrogen Cycle Simple N Cycle NITROGEN Cyle Links

Urea 1.Urea is the most important solid fertilizer in the world today. 2.In the early 1960's, ammonium sulfate was the primary N product in world trade (Bock and Kissel, 1988). 3.The majority of all urea production in the U.S. takes place in Louisiana, Alaska and Oklahoma. 4.Since 1968, direct application of anhydrous ammonia has ranged from 37 to 40% of total N use (Bock and Kissel, 1988) 5.Urea: high analysis, safety, economy of production, transport and distribution make it a leader in world N trade. 6.In 1978, developed countries accounted for 44% of the world N market (Bock and Kissel, 1988). 7.By 1987, developed countries accounted for less than 33%

Share of world N consumption by product group Ammonium sulfate85 Ammonium nitrate2715 Urea937 Ammonium phosphates15 Other N products (NH 3 )3629 Other complex N products168 Urea Hydrolysis increase pH (less H + ions in soil solution) CO(NH 2 ) 2 + H + + 2H 2 O > 2NH HCO 3 - pH 6.5 to 8 HCO H + ---> CO 2 + H 2 O (added H lost from soil solution) CO(NH 2 ) 2 + 2H + + 2H 2 O > 2NH H 2 CO 3 (carbonic acid) pH <6.3 H 2 CO 3  CO 2 + H 2 O

Computation/commodityProduction, mT World consumption of fertilizer-N82,906,340 Fert-N used in cereals (60% of total applied) 0.60 * 82,906,340 = 49,743,804 World Cereal Production, mT Sorghum 3% Rye 1% Oats 2% Millet 1% Barley 8% Rice 28% Corn 29% Wheat 28% NEED for INCREASED NUE

World grain N removal, 2002%NmT Wheat2.1312,502,267 Corn1.267,439,266 Rice1.237,007,101 Barley2.023,154,192 Sorghum1.921,356,807 Millet ,032 Oats ,012 Rye ,788 Total N removed in cereals33,144,465 N removed in cereals (from soil & rain, 50% of total)16,572,232 NUE = ((N removed - N soil&rain)/total N applied)33%

____________________________________ l World cereal grain NUE33% l Developed nation cereal NUE42% l Developing nation cereal NUE29% ____________________________________

Flowchart for NUE