The low water-holding capacity and low nutrient levels of roadcuts in northern California cause many of these disturbed areas to remain chronically barren. Yard waste compost was incorporated into four nonvegetated substrates found along roadcuts (decomposed granite [DG], lahar, serpentine, and sandstone) in order to regenerate topsoil infiltration, water-holding capacity, and nutrient availability. Soil physical and chemical properties, as well as the vegetative response of a native perennial grass, were compared between treatments (non-tilled, tilled, and tilled with compost amendment). Tillage and compost addition decreased soil bulk density compared to the nontilled treatment, and the compost treatment increased the soil carbon and nitrogen contents compared to the nontilled and tilled treatments. Tillage alone resulted in an increase in saturated hydraulic conductivity in soils that did not contain a large amount of coarse fragments. Tillage also reduced sediment loss in all soils except the DG. Foliar C 13 content did not predict water stress consistently between treatments. The incorporation of yard waste compost increased plant available water in coarse but not in fine-textured soils, and aboveground plant biomass was significantly greater in the compost treatment than in either of the other treatments. Although the incorporation of yard waste compost generated the greatest revegetation success, tillage alone may be a sufficient treatment if residual soils have adequate nutrient levels.

The results indicate that clomazone does not sorb appreciably to sandy or clay soils. Its sorption affinity and capacity is greater in humic acid, and consequently clomazone has difficulty desorbing from soil organic matter. Sorption appears to follow processes explained by the dual-mode model, the presence of fire residues (black carbon) and a recently proposed sorption mechanism.

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Inorganic amendments (IA) added to the rootzone of turfgrass are used to increase plant available water (PAW), however conflicting amounts of PAW contents have been reported for some of these amendments. The concept of PAW and the common technique used to estimate PAW in IAs have been reviewed. We hypothesized that hydraulic nonequilibrium in pressure‐plate measurements results in an underestimation of PAW. An alternative standardized method of measuring PAW in coarse‐textured inorganic amendments is proposed using a combination of pressure plates, saturated salt solutions and a dew‐point potentiometer. Water release curves were measured for four IAs (calcined clay, calcined diatomaceous earth, calcined volcanic ash mixed with diatomaceous earth, and zeolite) and their PAW contents determined. Results show that the proposed method provides a more accurate −1500 J kg−1 water content measurement than the pressure‐plate method. Pressure‐plate hydraulic nonequilibrium at −1500 J kg−1 resulted in a 0.002 to 0.012 m3 m−3 underestimation of PAW. The IAs examined in this study did not release appreciable amounts of internally held water until they were exposed to matric potentials more negative than usual in turfgrass management (<−300 J kg−1). The use of a standardized methodology for estimating PAW in IAs, such as the one described in this paper, will help to provide needed consistency and accuracy in information to practitioners.