EFFECTS OF COALBED METHANE-PRODUCED WATER ON SORGHUM-SUDANGRASS GROWTH AND SOIL CHEMICAL-PROPERTIES

Production of methane gas from coal seams generates well water that is slightly to moderately saline. Since land application is a potential method of disposal for this water, a greenhouse study was conducted to evaluate plant response and changes in soil chemical properties resul ting from irrigation with coalbed methane-produced water. The soil was a Montevallo (Typic Dystrochrepts)-Nauvoo (Typic Hapludults) associat ion located in northern Alabama. Two irrigation methods used in the in itial greenhouse test were 1) continuous, irrigation 24 h d(-1) and 2) intermittent, irrigation for 12 h and off for 24 h. In a second green house test, three irrigation methods were used: 1) continuous, irrigat ion for 24 h d(-1), 2) intermittent, irrigation for 12 h and off for 4 8 h, and 3) irrigation to maintain field capacity, by daily additions of the respective irrigation water. The flow rate for continuous and i ntermittent irrigation treatments was 3.75 mm h(-1). In each greenhous e test, 5 levels of salinity were generated by mixing well-produced wa ter with deionized water to give solutions containing 0, 10, 20, 40, a nd 100% well-produced water (specific conductance (second greenhouse t est) of 0.2, 1.4, 2.2, 4.4, and 9.3 dS m(-1), respectively). Correspon ding sodium adsorption ratios were 0.1, 27, 36, 55, and 81, respective ly. Sorghum-sudangrass [Sorghum bicolor (L.) Monech] was harvested for forage yields and chemical analysis at 14-30 days after initiation of irrigation treatments. Results from these preliminary short term, gre enhouse studies show that coalbed methane produced water that is typic al for Alabama (total dissolved solids less than or equal to 2000 mg L -1) can be applied to highly weathered soils. The results indicate tha t plant growth of summer annual grasses will be optimized if an irriga tion system is used to apply produced water at a rate to maintain soil moisture at or near field capacity.