Soil Water Depletion Under Crops on Reclaimed and Undisturbed Soils

Soil water depletion by profile depth increments and total water usage were measured yearly under either small grains or corn (Zea mays L.) over a 4-yr period on undisturbed Williams loam (fine-loamy, mixed Typic Argiborolls) and soil reclaimed following simulated stripmining. The reclaimed soil had topsoil thicknesses of either 0.23, 0.46, or 0.69 m respread over nonsaline, nonsodic spoil materials whose textures were gravelly loamy sand with and without a clay loam subsoil, clay loam, or silty clay loam. Total water usage and soil water depletion (for profile depths of 0 to 0.6 m and 0.6 to 1.5 m) were consistently greater, but essentially significant (P = 0.10) only in 1 yr, for the undisturbed compared to the reclaimed soil (averaged over topsoil thickness or spoil texture). Grain or biomass yields were significantly higher for the undisturbed compared with the reclaimed soil when growing-season precipitation was inadequate or poorly distributed. Shallower rooting depths and thus lesser soil water depletion even though the reclaimed soil had similar amounts of plant-available soil water at planting for 3 of the 4 yr resulted in water stress conditions and reduced potential productivity in inadequate precipitation years on the reclaimed soil. Similar water-use efficiency values were found for both the undisturbed and reclaimed soils for all 4 yr. If amounts of available soil water at planting and soil water depletion values had been more uniform between the undisturbed and reclaimed soils, the reclaimed soil most likely would have met the reclamation law requirement of “equal or better than” productivity present prior to mining (undisturbed soil productivity) for all 4 yr. Contribution from the North Dakota State Univ. Land Reclamation Res. Ctr., Mandan, ND 58554.