Transport of Residual Soluble Salts and Total Sulfur through Intact Soil Cores Amended with Fresh or Composted Beef Cattle Feedlot Manure for Nine Years

ABSTRACT

Composting of beef cattle (Bos Taurus) manure may increase the soluble salt (Ca, Mg, Na, K) and total sulfur (S) content and increase transport through the soil. Little research has been conducted on comparing transport of these chemicals through soil amended with composted (CM) manure versus fresh feedlot manure stockpiled for up to two months (FM). Our objective was to determine if the transport of these chemicals was greater for CM compared to FM when annually applied at 77 Mg ha⁻¹ dry wt. for nine years to a clay loam soil. Intact soil cores were taken from a field experiment in the spring of 2007. Deionized water was applied to the soil cores in the laboratory under steady-state (4.9 cm d⁻¹) and unsaturated conditions. Residual chemical concentrations in effluent were measured and breakthrough curves and cumulative mass loss curves obtained. The peak concentrations of K and total S; flow-weighted mean concentration (FWMC) and mass loss for Na, K, and total S; and recovery of Mg, Na, K, and total S were significantly (P ≤ 0.05) greater for CM compared to FM. However, peak concentrations, FWMCs, and mass loss of Ca and Mg were similar for both manure types. Treatment effects on these two soluble salts were likely masked by high natural Ca and Mg already in the soil. Analysis of co-variance also suggested greater cumulative mass loss of most chemicals (except Ca) for CM than FM at pore volumes between 0.25 and 2.5. However, our findings could not be explained by the differences in chemical content of the amendments or soil, or greater cation exchange capacity for CM than FM. The greater unsaturated hydraulic conductivity (at 7 mBar) of soil amended with CM compared to FM was the likely cause of greater transport of Na, K, and total S; and may be related to a physical effect of finer particles increasing water flow for composted manure.

ACKNOWLEDGMENTS

Chemical analysis was provided by Bonnie Tovell, and data analysis assistance was provided by Raygan Boyce.