Hydraulic conductivity, bulk density, moisture content, and electrical conductivity of a new sandy loam feedlot surface
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abstract
Infiltration of nutrients and salts into earthen feedlot surfaces is of concern because of possible groundwater contamination. An experiment was conducted at a new feedlot to quantify changes in hydraulic conductivity and bulk density in the upper 15 cm of the feedlot surface. Moisture content and electrical conductivity were also monitored in the upper 210 cm of the soil profile. Soil samples were obtained immediately after construction of the feedlot (initial samples) and again nine months after introducing animals to the pens (nine-month samples). Soil samples were collected from three areas (apron, water trough, bottom) within each of four pens and also from a control plot located just outside the pens. Undisturbed soil cores front the upper 15 cm were tested for saturated hydraulic conductivity (KS) and bulk density. Soil samples were collected front 210-cm deep borings in 15-cm increments for moisture content and electrical conductivity. The geometric mean Ks of initial samples ranged from 9.3E-6 to 1.8E-5 cm/s, while nine-month samples ranged from 5.3E-7 to 1.9E-6 cm/s. Over the nine-month period, geometric mean Ks values decreased by 23 times for the apron area, 5 times for the water trough area, and 34 times for the bottom area. There were no significant differences observed in bulk density over the same time period. The amount of water stored in the upper 210 cm of the soil profile increased during the nine-month period within the pens and the control area, ranging from 14.2 to 20.3 cm. Electrical conductivity in the pen areas increased considerably in the surface 5 cm. This research shows that KS values of sandy loam surfaced beef cattle feedlots can be expected to decrease by one to two orders of magnitude during the first nine months of stocking, and that some infiltration of water and salts can be expected during this time period.
