Surfactant effects on the water‐stable aggregation of wettable soils from the continental USA

Abstract

Surfactants may affect soil structure differently depending upon the soil or the quality of rainfall or irrigation water. This study examined whether the water‐stable aggregation of 11 wettable soils was affected by surfactants and the water in which the soils were sieved. The study also examined whether the wettable soils' water drop penetration time (WDPT) was affected by surfactants, water drop quality, and elapsed time since the surfactants were applied. Two nonionic surfactants and a surfactant‐free water control were sprayed (by misting) upon air‐dry soil, then WDPT was measured 1 and 72 h thereafter. Subsequently, this treated soil was slowly wetted with an aerosol to its water content at a matric potential of −3 kPa, then immediately sieved for 600 s in water that contained either appreciable or few electrolytes. Water‐stable aggregation, quantified as mean weight diameter (MWD), varied widely among soils, ranging from 0.10 to 1.36 mm. The MWDs were affected (at p = 0.06) by surfactant treatments, depending upon the soil but not sieving water quality. Surfactants affected the MWD of an Adkins loamy sand and Feltham sand, two of the three coarsest‐textured soils. Although WDPTs never exceeded 5 s, depending upon the soil WDPTs were affected by surfactant treatments but not by water drop quality. After surfactant application, WDPTs generally decreased with time for three soils but increased with time for one soil. Findings suggested that surfactants interacted (1) with clay mineralogy to affect MWD and (2) with soluble calcium to affect WDPT for certain soils. Surfactant treatments but not water quality affected both MWD and WDPT for some but not all of 11 wettable, US soils. Published 2012. This article is a US Government work and is in the public domain in the USA.

Biochar, Manure, and Sawdust Alter Long‐Term Water Retention Dynamics in Degraded Soil

“…The water repellency of the original, air-dried organic materials was assessed through the use of water drop penetration time (WDPT) to explore potential repellency effects on water retention dynamics. We measured WDPT for organic materials via the technique described by Lehrsch (2013). Previous research has indicated that WDPT values of <1 s, 1 to 60 s, 60 to 600 s, and >3600 s correspond to the nonrepellent, slightly repellent, strongly repellent, and extremely repellent classes (Leelamanie et al, 2008;Devereux et al, 2012).…”

Nutrient loads and sediment losses in sprinkler irrigation runoff affected by compost and manure

“…The decreasing Ca loads with increasing application rates of compost and manure (figures 2a and 2b, respectively) suggest that Ca was not present in excess in our runoff. The Ca concentrations in the amendments we applied ( ; as reported by Lehrsch [2013], for the nearly identical Rad soil) likely limited, though only to a slight degree, the P concentrations in our sprinkler irrigation runoff (Turner et al 2004) and, thereby, the DRP loads measured in our study (table 6). Moreover, our runoff 's Ca-an effective flocculating agent-may have decreased the runoff 's suspended sediment concentrations.…”

“…King and Bjorneberg (2011) also found-like we did- (table 5), much variability in runoff among irrigations. They found that runoff from the Portneuf silt loam often increased with successive irrigations, likely due to decreasing infiltration as a consequence of a continually developing surface seal on this poorly structured soil (Lehrsch andKincaid 2001, 2006). That runoff did not vary with manure rates was also reported by Volf et al (2007).…”