Impact of soil reconstruction method on yield, nutritive value and botanical composition of a mixed grass-legume stand

Mineral sands mining has disturbed over 400 ha of prime farmland in Dinwiddie County, VA. This land is being reclaimed to a hay and pasture post mining land use. In 2005, an experiment was initiated that compared three soil construction methods. The treatments were 1) Control: rip, lime, P, and routine fertilization per crop management protocols, 2) Biosolids: rip, lime stabilized biosolids at 78 dry Mg per ha, and routine fertilization per crop management protocols, and 3) Topsoil: rip, lime, P to subsoil, 15 cm of topsoil return, and routine fertilization per crop management protocols. The objective of this experiment was to compare the effect of soil reconstruction treatment on the yield, nutritive value and botanical composition of mixed cool-season grass-legume sward. Total seasonal dry matter (DM) yield ranged from 8,500 to 9,500 kg DM per ha and 4,200 to 5,800 kg DM per ha for 2006 and 2007, respectively and was not affected by soil reconstruction treatment or N fertilization in either year (P > 0.05). Crude protein (CP) concentration in the forage tissue was higher for the biosolids treatment for the first and second harvest in 2006, but did not differ in 2007. Crude protein was high enough to meet the requirements of a brood cow at all stages of the production cycle. In 2007, total digestible nutrients (TDN) were higher for the biosolids treatment for the first harvest only. In 2007, TDN was greater for the control and topsoil treatments and was likely influenced by greater quantities of legumes found in these treatments. Depending on year and harvest, legumes contributed between 20 and 35% to the total dry matter for the topsoil and control treatments and were not detectable in the biosolid treatment. Initial results indicate that properly amended mine soils generated from the mineral sands mining and reclamation process can support the production of high quality forage crops.