This article describes what topsoil is and is not.
The term “topsoil” is used widely, often reverentially, by people referring to the value of Australia’s soils. The following are the top five misconceptions about topsoil and its role as a resource:
BeneTerra was selected as a New Technology finalist in the Rocky Mountain Region for this year’s Oil & Gas Awards. Finalists are chosen by a panel of distinguished peers in the energy industry.
Last year, BeneTerra was named the Water Management Company of the Year in the Rocky Mountain Region by the Oil & Gas Awards, in recognition of its innovative solutions in water and land management, as well as environmental due diligence. Since 2003, BeneTerra has treated and dispersed more than seven billion gallons of CSG water through irrigation in the Rocky Mountain Region.
Development of coalbed methane (CBM) as an energy resource typically requires extraction of large volumes of water from underground coal seams. In the semiarid Powder River Basin of Wyoming and Montana, some of the CBM water is put to beneficial use through use for irrigation. Careful management is necessary due to elevated conductivites (2-3 mS/cm), high sodium adsorption ratios (SAR = 20-50) and sodium-bicarbonate composition of the water. One management strategy is deep subsurface drip irrigation (SDI), where drip tapes are placed ~92 cm below the surface in conjunction with a deep-rooted crop like alfalfa. CBM water is acidified to reduce alkalinity prior to application and is applied to fields year-round.
On March 12th, 2013 BeneTerra was named the 2012 “Water Management Company of the Year” for the Rocky Mountain region by the Oil and Gas Awards Committee which is comprised of organisations and journals supporting the industry. The award recognizes organisations that provide water management services to the upstream sector of the oil and gas industry. It also acknowledges water management companies that demonstrate the ability to provide innovative solutions in the areas of storage, transportation, treatment, and disposal. Considerations are also made for environmental due diligence. Since 2003 BeneTerra has treated and dispersed more than 27,000 ML CSG water through irrigation in the Rocky Mountain region.
Carleton Bern of the US Geological Survey was the lead author on a two-part paper covering 1) water and solute movement and 2) geochemistry beneath BeneTerra’s longest operating deep subsurface drip irrigation system. The articles appear in the February 2013 issue of Agricultural Water Management. These can be accessed at Science Direct or by email request to BeneTerra.
- a Crustal Geophysics and Geochemistry Science Center, U.S. Geological Survey, Denver Federal Center, Denver, CO, USA
- b National Research Program, U.S. Geological Survey, Denver Federal Center, Denver, CO, USA
- c BeneTerra LLC, Sheridan, WY, USA
Waters with low salinity and high sodium adsorption ratios (SARs) present a challenge to irrigation because they degrade soil structure and infiltration capacity. In the Powder River Basin of Wyoming, such low salinity (electrical conductivity, EC 2.1 mS cm−1) and high-SAR (54) waters are co-produced with coal-bed methane and some are used for subsurface drip irrigation (SDI). The SDI system studied mixes sulfuric acid with irrigation water and applies water year-round via drip tubing buried 92 cm deep. After six years of irrigation, SAR values between 0 and 30 cm depth (0.5–1.2) are only slightly increased over non-irrigated soils (0.1–0.5). Only 8–15% of added Na has accumulated above the drip tubing. Sodicity has increased in soil surrounding the drip tubing, and geochemical simulations show that two pathways can generate sodic conditions. In soil between 45-cm depth and the drip tubing, Na from the irrigation water accumulates as evapotranspiration concentrates solutes. SAR values >12, measured by 1:1 water–soil extracts, are caused by concentration of solutes by factors up to 13. Low-EC (<0.7 mS cm−1) is caused by rain and snowmelt flushing the soil and displacing ions in soil solution. Soil below the drip tubing experiences lower solute concentration factors (1–1.65) due to excess irrigation water and also contains relatively abundant native gypsum (2.4 ± 1.7 wt.%). Geochemical simulations show gypsum dissolution decreases soil-water SAR to <7 and increases the EC to around 4.1 mS cm−1, thus limiting negative impacts from sodicity. With sustained irrigation, however, downward flow of excess irrigation water depletes gypsum, increasing soil-water SAR to >14 and decreasing EC in soil water to 3.2 mS cm−1. Increased sodicity in the subsurface, rather than the surface, indicates that deep SDI can be a viable means of irrigating with sodic waters.
Keywords:Gypsum;PHREEQC; Powder River Basin, Wyoming; Sodium adsorption ratio; Sulfuric acid
Published by Elsevier B.V.
- Carleton R. Berna
- George N. Breita
- Richard W. Healyb
- John W. Zupancicc
- Richard Hammackd
- Crustal Geophysics and Geochemistry Science Center, U.S. Geological Survey, Denver Federal Center, Denver, CO, USA
- National Research Program, U.S. Geological Survey, Denver, CO, USA
- BeneTerra, LLC., Sheridan, WY 82801, USA
- National Energy Technology Laboratory, Pittsburgh, PA, USA
Land Resources Leader, Glenn Bailey and his South Australia colleague, Brian Hughes, presented a paper to the Soil Science Australia conference regarding their work with soil delving. The process of “delving” clay to the surface began in the south east of the state in order to address the limitation of water repellency. Clay delving was seen to mimic the water repellency ameliorating effects of clay spreading, only without the expense of importing the clay. Subsequently it has become clear that the delving process also addresses a number of other limitations associated with sandy soils. This paper discusses some of the improvements observed in the A2 horizons of 12 sand over clay soils. For the full paper in PDF click here.
As of the 2nd of April 2012, Glenn Bailey has joined the BeneTerra team in the capacity of Land Resources Leader. He brings a strong background in soil science, forestry and land resources research to the team. He will be focused on those aspects of our business that require land resource assessment, decision making and management. He will support other team members and will interact with external land resource decision makers – regulators, resource companies, earth scientists, and such.