Residual effects of topsoil replacement depths and onetime application of organic amendments in natural gas wellsite reclamation

Abstract

The success of reclamation on abandoned wellsites depends on their capacity to recover and sustain levels of soil quality similar to those existing prior to soil disturbance. A 1997-2000 study looked at four (0, 50, 100 and 150%) topsoil replacement depths (TRD) and five amendments [compost, manure, alfalfa (Medicago sativa L.) hay, wheat (Triticum aestivum L.) straw, check] in the reclamation of three natural gas wellsites in Alberta. In 2007 (10 yr after establishment) the wellsites were re-sampled to examine residual effects of reclamation treatments on soil properties. In 2007, there was no difference in SOC between the 50, 100 and 150% TRD treatments and all three were significantly higher than the 0% TRD by an average of 18%. Therefore adding half the amount of topsoil (50%) 10 yr previously caused long-term improvement in SOC (vs. 0% TRD), but adding more topsoil (100, 150%) did not produce further gains. Soil organic C (0- to 15-cm depth) on the compost and manure treatments (across all sites and TRD treatments) was significantly higher (+ 8%) than straw, alfalfa and check treatments some 10 yr later. Results show that initial investment in organic amendments for wellsite reclamation can have residual effects on soil quality.