Reproduced from Journal of Environmental Quality. Published by ASA, CSSA, and SSSA. All copyrights reserved. Soil Properties Affecting Wheat Yields following Drilling-Fluid Application T. A. Bauder, K. A. Barbarick,* J. A. Ippolito, J. F. Shanahan, and P. D. Ayers ABSTRACT crease in waste drilling-fluid production. For example, Colorado drilling permits for oil and gas wells increased Oil and gas drilling operations use drilling fluids (mud) to lubricate by over 100% from 2000 to 2003 (Anonymous, 2004). the drill bit and stem, transport formation cuttings to the surface, and seal off porous geologic formations. Following completion of the well, Few studies have addressed the impact of drilling- waste drilling fluid is often applied to cropland. We studied potential fluid land application on plant growth and soil proper- changes in soil compaction as indicated by cone penetration resistance, ties. Previous research indicates that the drilling-fluid pH, electrical conductivity (EC e ), sodium adsorption ratio (SAR), impact on plant growth is largely negative due to high extractable soil and total straw and grain trace metal and nutrient plant available trace metals and soluble salts (Nelson concentrations, and winter wheat (Triticum aestivum L. ‘TAM 107’) et al., 1984; Miller et al., 1980; McFarland et al., 1992a, grain yield following water-based, bentonitic drilling-fluid application 1992b, 1994; Younken and Johnson, 1980). However, (0–94 Mg ha -1 ) to field test plots. Three methods of application (nor- some researchers (Nelson and Mikesell, 1982) also found mal, splash-plate, and spreader-bar) were used to study compaction positive or no impact from drilling fluids applied at effects. We measured increasing SAR, EC e , and pH with drilling- lower rates or drilling fluids produced with more benign fluid rates, but not to levels detrimental to crop production. Field measurements revealed significantly higher compaction within areas materials. Differences between studies have primarily affected by truck travel, but also not enough to affect crop yield. In resulted from the wide range of drilling-fluid compo- three of four site years, neither drilling-fluid rate nor application nents and rates used by various investigators. The fate method affected grain yield. Extractions representing plant availabil- of trace metals in soil following drilling-fluid application ity and plant analyses results indicated that drilling fluid did not has also been investigated. Some workers (Deeley and significantly increase most trace elements or nutrient concentrations. Canter, 1986) conducted fractionation studies that sug- These results support land application of water-based bentonitic dril- gested trace metals would not be significantly released ling fluids as an acceptable practice on well-drained soils using con- while others (Bates, 1988) found increases in plant avail- trolled rates. able forms of trace metals and movement in a column study. Impacts of application on farm land in Colorado are T he oil and gas drilling industry uses drilling fluid primarily anecdotal, with some farmers claiming im- (often referred to as drilling mud or muds) to lubri- proved moisture retention on sandy soils (L. Avis, Colo- cate and cool the drilling apparatus, transport formation rado Oil and Gas Conservation Commission, personal cuttings to the surface, and seal off porous geologic communication, 1995). The Colorado Oil and Gas Con- formations. Following completion of a well, spent dril- servation Commission (Anonymous, 2001) lists land ap- ling fluids and formation cuttings are allowed to settle plication of water-based bentonitic fluids disposal as an in a reserve pit before disposal. Waste drilling fluids are acceptable method of disposal with limits on the depth often land-applied following completion of an oil or gas of the drilling fluid. The waste shall be applied to pre- well in Colorado and other areas of the Western United vent ponding or erosion and must be incorporated as States. This material usually contains production water, soon as practicable. The regulations also specify limits bentonitic clays, formation cuttings, barite, Na com- following application for concentrations of metals and pounds, and synthetic organic polymers. During the early total petroleum hydrocarbons in soil, and limit soil EC e 1990s, explosive growth in natural gas drilling created to less than 4.0 dS m -1 or two times background, SAR over 800 000 m 3 of mixed water, mud, and formation cut- to less than 12, and pH to 6 to 9. tings in one Colorado county (Weld) in two years (L. Avis, The drilling-fluid hauling contractors in our study Colorado Oil and Gas Conservation Commission, per- area (Weld County, CO) usually land apply waste dril- sonal communication, 1995) with much of this material ling fluid with water trucks. These vehicles can approach applied to agricultural land. More recently, high natural a gross vehicle weight of 25 Mg when fully loaded. gas prices coupled with political mandates to explore Trucks apply the drilling fluid by opening rear-facing domestic energy sources have increased drilling activity valves and driving across fields until empty. While applying in the Western United States with an accompanied in- drilling fluid, the maximum swath width is about 1.5 to 2.5 m. Drilling-fluid application rates vary greatly due T.A. Bauder, K.A. Barbarick, and J.A. Ippolito, Department of Soil to uneven truck speed, irregular drilling-fluid solids con- and Crop Science, Colorado State University, Fort Collins, CO 80523. tent, changing hydrostatic pressure in trucks, and appli- J.F. Shanahan, USDA-ARS, Lincoln, NE 68583. P.D. Ayers, Depart- cation overlap. Generally, contractors attempt to utilize ment of Biosystems Engineering and Environmental Science, Univer- sity of Tennessee, Knoxville, TN 37996. Received 12 October 2004. most of a field’s area and apply drilling fluid in closely *Corresponding author (Ken.Barbarick@.colostate.edu). Abbreviations: AB-DTPA, ammonium bicarbonate-diethylenetriamine- Published in J. Environ. Qual. 34:1687–1696 (2005). Technical Reports: Waste Management pentaacetic acid; CSUCTS, Colorado State University Crops Testing Service; EC e , electrical conductivity saturated-soil paste extract; ICP– doi:10.2134/jeq2004.0384  ASA, CSSA, SSSA AES, inductively coupled plasma–atomic emission spectrophotoscopy; SAR, sodium adsorption ratio. 677 S. Segoe Rd., Madison, WI 53711 USA 1687 Published online August 9, 2005