Does long-term heavy cattle manure application increase salinity of a clay loam soil in semi-arid southern Alberta?

Livestock manure contains considerable salt and continued application to agricultural land may result in an accumulation of salt in soil. This study reports on the impact of 25 annual cattle feedlot manure applications on soil salinity and soluble salt content and composition of a clay loam soil in the semi-arid region of southern Alberta, Canada. Cattle manure has been applied at rates of 0, 30, 60 and 90 Mg ha(-1) per year under non-irrigated and at 0, 60, 120 and 180 Mg ha(-1) per year under irrigated conditions each fall since 1973. Soil salinity was assessed in the fall each year before manure application by examining the electrical conductivity (EC) using saturated paste extraction methods. The soluble ions, sodium adsorption ratio (SAR) and potassium adsorption ratio (PAR) were also determined each year. Soil EC values increased with the cumulative amount of manure used over the years and the increases were greater under non-irrigated than irrigated conditions. For every tonne of salt applied through the cattle manure, the average soil EC (0-150 cm) increased by 0.1108 dS m(-1) under non-irrigated conditions. The soluble Na+, K+, Mg2+ Cl-, HCO3-, SAR and PAR all increased with the cattle manure application and the increases were greater under non-irrigated than irrigated conditions. On the other hand, under both conditions, Ca2+ decreased in surface soil (0-15 cm) but increased at depths below 30 cut. The K+ ions became the dominant cation in manured surface soil. The increases in EC and soluble ions were lower under irrigation due to greater downward movement. High rates of manure application are not sustainable because they lead to soil salinization under non-irrigated conditions and leaching losses of soluble salts that could potentially pollute groundwater under irrigated conditions. Crown Copyright (C) 2002 Published by Elsevier Science B.V. All rights reserved.