Soil Water Repellency Development in Amended Sand Rootzones

Abstract

Particulate organic matter (OM) and surface area–limited sands are associated with soil water repellency (SWR) in turfgrass systems. The increasing ubiquity of amended sand rootzones warrants investigation of factors contributing to SWR. Our objective was to identify how amendment type and/or inclusion rate affect rootzone SWR over a range of irrigation regimes. A U.S. Golf Association–specified sand was amended with dried turfgrass roots and either sphagnum peat moss (SPM), reed sedge peat (RSP), biosolid compost (BSC), or calcined clay (CC) at 0, 0.1, or 0.2 m3 m−3 Mixes were saturated, gravitationally drained, incubated under isothermal ventilation having mean vapor pressures of 1.78, 2.19, or 2.45 kPa, and reirrigated when matric tension exceeded 300 kPa. After 138 d, rootzone subsamples were eluted of particulate OM before measuring mineral‐adsorbed hydrocarbon content (MAHC) by infrared spectroscopy. The repellency index was used to quantify SWR of intact (Rintact) and eluted (Reluted) samples. Amendment rate (0.2 > 0.1 > 0 m3 m−3) and type (BSC > RSP = SPM > CC) significantly affected Rintact Only CC‐amended rootzones were more wettable than the control. Severely elevated Reluted and MAHC were observed in all sands amended by BSC. Inclusion of SPM or RSP at 0.1 m3 m−3 resulted in Reluted and MAHC values statistically equivalent to the control rootzone. At 0.2 m3 m−3 inclusion, all organic amendments significantly increased Reluted and MAHC relative to the control (BSC > RSP = SPM).

Soil Water Repellency Index Prediction Using the Molarity of Ethanol Droplet Test

“…clear polyvinyl chloride tube, capped at the soil contact interface with 48‐μm nylon mesh. The top end was sealed with a barbed cap and connected to a closed liquid reservoir (200 mL) under a −0.5‐cm pressure head (Moody et al, 2009). Although earlier studies measured sorptivities at higher tensions (Hallett and Young, 1999; Hallett et al, 2001; Tillman et al, 1989), this apparatus was set to the lowest tension possible before liquid would spontaneously flow from the infiltrometer to maximize infiltration into the greatest number of pores.…”

Characterization, Development, and Management of Organic Matter in Turfgrass Systems

“…Murphy et al (1993) reported that the thatch-mat ρ b of 3-yr-old 'Penneagle' creeping bentgrass maintained under greens conditions increased following reincorporation of hollow-tine cores and ranged from 0.24 to 0.70 g cm −3 . The bulk density of reed sedge peat and sphagnum peat moss used for organic root-zone amendments has been reported as 0.253 and 0.141 g cm −3 , respectively (Moody et al, 2009). The particle density (ρ s ) of materials in three organic horizons in undrained and naturally vegetated Carolina Bays averaged 1.6 g cm −3 , which is similar to the density of glucose, cellulose, and lignin (Kellogg and Wangaard, 1969;Dinar et al, 2006).…”

“…That humic substances cause localized dry spot may be a result of the conformation and spatial orientation of the polar (i.e., aliphatic) and nonpolar (i.e., carboxyl) surface groups in relation to the surfaces of the sand particles, and the ratio of OM phase to the mineral phase (Karnok et al, 1993;Ellerbrock et al, 2005). Particulate organic ma er and organic coatings on mineral-fraction constituents are the recognized causes of hydrophobicity in soils (Moody et al, 2009). Fungi may contribute to soil water repellency by producing hydrophobic mycelia and exuding compounds such as waxes and fa y acids that form hydrophobic fi lms (Fidanza et al, 2007;Moody et al, 2009).…”

“…Particulate organic ma er and organic coatings on mineral-fraction constituents are the recognized causes of hydrophobicity in soils (Moody et al, 2009). Fungi may contribute to soil water repellency by producing hydrophobic mycelia and exuding compounds such as waxes and fa y acids that form hydrophobic fi lms (Fidanza et al, 2007;Moody et al, 2009). The hydrophobicity associated with OM is a management consideration, because it may lead to environmental problems such as leaching of surface-applied pesticides (Larsbo et al, 2008).…”

“…The electrical conductivity for both cultivars averaged 1.43 dS m −1 . Moody et al (2009) reported that organic root-zone amendments had carbon/nitrogen ratios ranging from 18.6 to 68.1 and electrical conductivities from 0.51 to 13.52 dS m −1 . Wu et al (2003) presented data in which the carbon/nitrogen ratio of agricultural runoff material varied from 4.9 to 10.6 and was highly correlated with the size fraction (light or heavy).…”