Release of Ammonia and Greenhouse Gases along Moisture Gradient from Manure and Urea Applied Fargo Silty Clay Soil

Abstract

Abstract. Greenhouse gas (GHG) [nitrous oxide (N2O), carbon dioxide (CO2), and methane (CH4)] emission and ammonia (NH3) volatilization from organic and commercial fertilizers are likely related to soil moisture levels. Effect of soil moisture [(30%, 60%, and 90% water-holding capacity (WHC)] on emissions from urea and manure treated (215 kg ha-1) Fargo-Ryan silty clay soil was studied under laboratory conditions. Soils (250 g) amended with solid beef manure (SM), straw-bedded solid beef manure (BM), urea (UR), and control (CT) were incubated for 28 days at 22±1°C, to determine GHGs (N2O, CO2, and CH4) emission and NH3 volatilization loss. The cumulative emission of N2O-N, CO2-C, and CH4-C ranged from 27 to 4402 µg N2O-N kg-1, 272 to 2030 mg CO2-C kg-1, and 10.1 to 1389 µg CH4-C kg-1 soil, respectively. The daily fluxes and cumulative emissions of N2O and CO2 generally followed the decreasing order of 30% < 90% < 60% of WHC. At 60% WHC, 1.01% of the total applied N was lost as N2O from urea treated soil. Carbon dioxide emission from manure treated soil (SM and BM) was up to two times the emission from UR treated soils. The Fargo clay soils showed higher CH4 emission at 90% WHC level. The cumulative NH3 volatilization loss from soil ranged from 29.4 to 1250.5 µg NH3-N kg-1, with the highest loss from UR amended soils at 30% WHC. These results suggest that gaseous emissions from manure and urea application under laboratory study are influenced by moisture levels of Fargo-Ryan silty clay soil. Keywords: Beef manure, Greenhouse gas, Soil water, Urea, Water holding capacity.