Zvomuya et al. 2007 - Reclamation of Abandoned Natural Gas Wellsites with Organic Amendments: Effects on Soil Carbon, Nitrogen, and Phosphorus

Organic amendments have been used to restore productivity to disturbed soils such as those on abandoned oil and natural gas wellsites. A study was conducted on three abandoned well- sites in southern Alberta, Canada to examine the effects of one-time applications of alfalfa (Medicago sativa L.) hay or beef cattle (Bos taurus) feedlot manure compost on soil properties under continuous wheat (Triticum aestivum L.). The base amendment rate (1×) [dry wt.] was 5.3 Mg ha−1 for compost and 3.1 Mg ha−1 for alfalfa. The fi ve amendment rates of 0, 1×, 2×, 4×, and 8× were soil-incorporated at the wellsites. Although approximately twice as much C was applied with alfalfa than with compost, fi nal SOC content was similar for the two amendment treatments, indicating the greater stability of compost-derived C. Nitrate N content in the 0- to 60-cm depth was not affected by compost rate (mean 213 kg ha−1) but increased by 7.78 kg ha−1 for each Mg ha−1 increase in alfalfa rate. This result refl ects the greater stability of compost-N compared with alfalfa-N and suggests a lower risk of NO3–N leaching with compost application. Compost rates >20 Mg ha−1 resulted in excessive extract- able P build-up in the topsoil (up to 95.7 mg kg−1), which may pose environmental risk to surface water. We recommend amending wellsites with up to 12 Mg ha−1 of alfalfa or <20 Mg ha−1 of compost during reclamation to improve C storage and nutrient cycling while minimizing nutrient loss to water systems.