Soil water retention on gold mine surfaces in the Mojave Desert

An experimental analysis of soil water retention was conducted on three sub strates (an abandoned road, an overburden pile, and a heap leach) created b y gold mining activities in the Mojave Desert in southeastern California. W e mixed each substrate with straw, and the overburden pile and heap leach w ith growth medium, then applied surface rock mulch to half the plots in an attempt to increase soil water-holding capacity for revegetation efforts. F or each of the six treatments (controls included) we monitored soil water w ith time domain reflectometry following both a simulation of a rainfall eve nt and a natural rainfall that occurred immediately following the simulatio n. Both the simulation and the rainfall increased soil water between 3 and 8%, depending on the substrate. Water retention patterns in the two-week pe riods following each water addition were similar between the simulation and rainfall, and among all substrate types as values returned to background ( pre-water) conditions. The abandoned road substrate had higher background w ater content (16.5%) than the overburden pile (6%) and heap leach (5%). The road also had three times higher organic matter and five times higher soil nitrogen than the other two sites. Soil water retention was improved on th e overburden pile by the addition of just surface rock mulch or of straw-pl us-rock mulch. On the heap leach, increases were found with rock mulch only or with growth medium-plus-rock mulch. Rock mulches did not improve soil w ater retention and straw additions decreased soil water on the abandoned ro ad. Judicious use of soil amendments can improve soil water conditions and improve revegetation efforts on disturbed lands in desert environments.