Effects of Coalbed Methane Co-produced Water for Irrigation in China’s Qinshui Basin: An Experimental Field Study

Abstract

The management of coalbed methane (CBM) co-produced waters (hereafter refer to as produced water) has broad effects on the native plants and soils in the Qinshui Basin of China and has become a high priority over the past decade. To investigate the short-term effects of produced water on crop production and soil health, a field study was conducted in the Shizhuang Block, which is one of the most active CBM-producing areas in the Qinshui Basin. Spring maize was grown during 2015 under the following flood irrigation treatments: freshwater (as a control), and three produced water sub-treatments with electrical conductivity (EC) values of 1.9 ± 0.9, 2.3 ± 0.5, and 3.4 ± 1.1 ds/m. The SAR concentration of the produced water ranged from 17.62 to 44.45 meq/L; the excessive SAR content makes the water unsuitable for direct irrigation without amendment. The pH, SAR, and constituent concentration of soil samples and crop yield were tested before planting and after harvest, while the soil moisture and plant height were measured monthly from June to October. The growth parameters indicated that salinity decreased total crop yield and individual plant height. The monitored soil indexes showed that the SAR content at a depth of 20 cm (top soil) exceeded that at 40 cm, and increased as the EC of the irrigation source increased at both depths. However, there were no obvious differences in pH or chemical composition of the soil samples, all being less than the Republic of China’s soil pollution standards. Soil moisture was determined more by the monsoon climate than by changes in the soils’ hydraulic properties.