Nitrate leaching in two irrigated soils with different rates of cattle manure
Received for publication December 15, 2008. Manure applied to irrigated land may potentially contaminate groundwater with NO3–N. An 8-yr field experiment was conducted in southern Alberta, Canada, to determine the effects of different rates of manure on NO3–N accumulation in two irrigated soil types and NO3–N leaching to shallow groundwater. An annual cereal silage was grown at each site and irrigation was based on soil moisture depletion. Treatments included a control, nitrogen fertilizer (NF) at 180 kg N ha–1 yr–1, and four rates of cattle (Bos taurus) manure (20, 40, 60, and 120 Mg ha–1 yr–1, wet-weight basis). Annual manure applications for 8 yr resulted in NO3–N accumulation in the soil profile at both sites. For every megagram of total N added from manure, NO3–N in the 0- to 1.5-m layer increased by about 50 kg ha–1 at the coarse-textured (CT) site and by about 100 kg ha–1 at the medium-textured (MT) site. Silage yield for all of the manure treatments was similar to yield for the NF treatment after the first 3 to 4 yr of annual manure applications. The greatest manure rate and NF treatments significantly increased NO3–N concentrations in groundwater at the CT site. Groundwater NO3–N concentrations were not adversely affected by manure or NF applications at the MT site. An annual cattle manure application rate of 20 Mg ha–1 provided sufficient N for irrigated cereal silage production and minimized NO3–N leaching in a medium-textured soil.