Changes in soil properties reflect the success or failure of reclamation practices on abandoned wellsites. We examined the effect on soil properties of four (0, 50, 100 and 150%) topsoil replacement depths (TRD) and five amendment treatments [compost, manure, wheat (Triticum aestivum L.) straw, alfalfa (Medicago sativa L.) hay, check] aimed at reclaiming three wellsites (Strathmore, Hesketh and Rosedale) in southcentral Alberta. TRD treatment differences were consistent across all wellsites, with 30 to 32% higher soil organic carbon (SOC) on the 150% TRD compared to the 0% TRD. Initially, the alfalfa treatment showed higher levels of nitrate-nitrogen (e.g., 26 mg kg-1 vs. 3 to 7 mg kg-1 for the other amendment treatments in the 15- to 30-cm depth at Strathmore in fall 1998), which was related to its rapid breakdown and mineralization of organic N. After 40 mo (June 1997-October 2000), the average amounts (n = 3 wellsites) of added C conserved near the soil surface were: compost (65 ±10% SE) > manure (45 ±16% SE) > alfalfa (28 ±11% SE) > straw (23 ± 6% SE). Our results show that organic amendments play an important role in improving soil properties related to long-term productivity of reclaimed wellsites, especially where topsoil is scarce or absent. Key words: Wellsite reclamation, topsoil depth, organic amendments, soil quality
Long term changes in soil properties and enzyme activities after almond shell mulching in avocado organic production
