Reclamation of Abandoned Natural Gas Wellsites with Organic Amendments: Effects on Soil Carbon, Nitrogen, and Phosphorus

Abstract

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 wellsites 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 five 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, final 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 reflects 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 extractable 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.