Reclamation of forest soils with excavator tillage and organic amendments

In early 1994, a research project was initiated to evaluate the success of several techniques aimed at restoring productivity to degraded soils on landings near Vama Vama Creek, 44 km east of Prince George in Central British Columbia. Soils were developed from morainal parent materials, the usual surface soil texture was silt loam. Two organic amendments were used in this study, including freshly prepared wood chips and old sawdust. An excavator equipped with a site preparation rake was used to till the soils to a depth of 0.50 m. Organic amendments were subsequently added to the plots, and either left as a mulch or incorporated into the surface 0.20 m of the soil. Nitrogen was applied to all plots at a rate of 225 kg N ha(-1), which represents about one-third of thr 500-700 kg ha(-1) that was estimated to be required to compensate for N immobilization during decomposition of the woody residues. Survival was good for all treatments, but after 3 years, trees were growing best in areas that were treated with tillage alone. Trees growing on areas where old sawdust was used as an amendment had more volume than trees growing in areas where wood chips had been used. Control plots with no treatment had intermediate growth. Soil temperature and chemical properties were evaluated for their effect on growth. (C) 2000 Elsevier Science B.V. All rights reserved.