Ammonia Volatilization from Surface Applications of Ammonium Compounds to Calcareous Soils: VI. Effects of Initial Soil Water Content and Quantity of Applied Water

Abstract

AbstractAmmonia losses from (NH4)2SO4 (AS) and NH4NO3 (AN) applied to the surface of initially wet and initially dry soils, when followed by irrigation, were generally greater from the initially wet soils, especially when water application rates were < 2.5 cm. The greatest NH3 loss occurred at the lowest water addition and the least loss at the highest water addition. The addition of 20.3 cm of water to a Harkey silty clay loam did not reduce NH3 loss below that found with the addition of 5.1 cm of water. Ammonium was moved deeper into the soil by water in the initially wet soil than into the initially dry soil.Approximately a twofold increase in NH3 loss was observed following the application of AS and AN to the soil through irrigation water compared with NH3 loss following broadcast fertilizer application and subsequent irrigation. Again, initial soil water content influenced total NH3 loss with greater loss occurring from initially wet soil.A direct relationship was found between the loss of water and NH3 in sand. This relationship was not changed by placing a barrier to capillary water and N movement in the soil profile. The barrier greatly reduced absolute NH3 and H2O losses but did not influence the ratio of NH3 to H2O loss.