SOIL PROPERTY CHANGES FOLLOWING IRRIGATION WITH COALBED NATURAL GAS WATER: ROLE OF WATER TREATMENTS, SOIL AMENDMENTS AND LAND SUITABILITY

摘要

Saline-sodic water is a by-product of coalbed natural gas (CBNG) production in the Powder River Basin of Wyoming, USA and is being beneficially used in places as irrigation water. This study evaluated effects of 2years of natural precipitation on soil properties of a hay field after the cessation of managed irrigation with CBNG water. The hay field had been irrigated with only CBNG water [CBNG(NT)], CBNG water amended with gypsum [CBNG(G)] or gypsum plus sulfur via a sulfur burner [CBNG(GSB)] in combination with soil amendmentsgypsum (+G), elemental sulfur (+S), and both (+GS). Results indicated that infiltration rates were the lowest on fields irrigated with CBNG(NT), followed by CBNG(G) and CBNG(NT)+G treatments (122, 132, and 135cmh(-1), respectively). The CBNG(GSB)+GS treatment had the highest infiltration rates (335cmh(-1)). By the second year, salinity and sodicity of treated soils had decreased in the A-horizon of most CBNG-water irrigated plots, whereas in Bt(1)- and Bt(2)-horizons salinity generally decreased but sodicity increased; S and GS soil amended plots had higher profile salinities compared with NT and G soil treatments. Although Na+ leaching was observed in all fields that received soil and/or water amendments, CBNG(GSB)+GS plots had the lowest sodicity in the A- and Bt(1)-horizons. Effective managed irrigation requires knowledge of site-specific soil properties, plant suitability, water chemistry, and amendments that would be needed to treat the CBNG waters and soils. This study indicates the greatest success was realized when using both soil and water amendments.