Subsoil Characteristics and Landscape Position Affect Productivity of Reconstructed Mine Soils

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Abstract
The placement of soil materials on minespoils during reclamation affects soil profile and landscape aspects of soil productivity. We hypothesized that the productivity of soil reconstructed by topsoil‐subsoil placement on sodic minespoil would be influenced by subsoil characteristics. A 1.4‐ha double wedge was constructed in west‐central North Dakota (annual precipitation 440 mm) from three subsoil materials (1.2‐m thickness at peak) placed in strips over smoothed minespoils so that north‐ and south‐facing slopes were 5 and 1.5%, respectively. Material mostly from B horizons of dominantly Argiboroll soils was used for subsoil treatments: (A) 50% clay; (B) 29% clay; and (C) 13% clay. Subsoils were covered with 0.2 m of mostly A horizon topsoil. Forage yields of crested wheatgrass [CWG, Agropyron desertorum (Fisch.) Schult.] were highest on C subsoil plots 4 yr out of 5 observed, and Russian wildrye [RWR, Psathyrostchys juncea (Fisch.) Nevshi] were highest on C subsoil plots 3 yr out of 4 observed. In contrast, 2 yr of spring wheat (Triticum aestivum L.) seed yields (824 kg ha−1 avg.) were 20 to 50% larger on A subsoil plots than on C subsoil, with B yields intermediate. Forage grass yields on north sideslopes of C subsoil plots averaged 1370 and 1040 kg ha−1 for CWG and RWR, about 20 to 60% greater than yields on other positions and subsoils. The largest spring wheat yields, 1068 kg ha−1, occurred on north sideslope positions of A subsoil plots. Sandy loam subsoils can enhance forage grass yields in rolling lands, while spring wheat yields can be increased by subsoils with greater water‐holding capacity.

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