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 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 NO 3 –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.