Residual impact of topsoil removal and soil amendments on crop productivity over sixteen years
Soil erosion remains a threat to our global soil resource. This study was conducted to ascertain the effects of simulated erosion on soil productivity and methods for its amendment. Incremental depths (0, 5, 10, 15 and 20 cm) of surface soil or cuts were mechanically removed to simulate erosion at two sites (one dryland, one irrigated) in southern Alberta in 1990. Three amendment treatments (nitrogen + phosphorus fertilizer, 5 cm of topsoil, or 75 Mg ha-1 of feedlot manure) and a check were superimposed on each of the cuts. The sites were cropped annually until 2006. On average, sixteen year yield reductions were 10.0% for 5 cm, 19.5% for 10 cm, 29.0% for 15 cm and 38.5% for 20 cm of topsoil removal. Average grain yield loss was 50 kg ha-1 cm-1 yr-1 at the Dryland site and 59 kg ha-1 cm-1 yr-1 at the Irrigated site. Amendments ranked manure> topsoil > fertilizer in terms of restoring productivity to the desurfaced soils. The study reinforces the need to prevent erosion and indicates that application of livestock manure is an option for restoring soil productivity in the short term.
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