The presence of biologically active substances (BAS) in biosolids may enhance plant stress tolerance and growth, but the underlying mechanisms are not well understood. This greenhouse study investigated the effects of two biosolids: Alexandria (anaerobically digested; Class A product from the Alexandria Sanitation Authority Wastewater Treatment Facility in Alexandria, VA) and Blue Plains (lime-stabilized; Class B product from Washington, DC, Water and Sewer Authority) on tall fescue [Lolium arundinaceum (Schreb.) S.J. Darbyshire] antioxidant enzyme activity associated with drought resistance. Treatments included a fertilizer control, Alexandria (11.9 g·kg−1 soil) and Blue Plains (17.6 g·kg−1 soil) biosolids to match the nitrogen in the control. Tall fescue physiological responses were measured under well-watered or drought-stressed conditions. Drought stress reduced turfgrass quality, photochemical efficiency (PE), and catalase (CAT) activity while increasing superoxide dismutase (SOD), ascorbate peroxidase (APX), and peroxidase (POD) activities. The two biosolids improved turfgrass quality and root mass under both soil moisture regimes and delayed leaf wilting during moisture stress. The biosolids also improved PE, SOD, and APX activities relative to the control under both soil moisture regimes. The data suggest that biosolids application may improve antioxidant enzyme activity and subsequent drought resistance.

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Biosolids applied at agronomic rates have been shown to improve hormone metabolism and drought tolerance in greenhouse trials, but no research has demonstrated such effects in the field. This study was designed to investigate effects of lime‐stabilized (LS) and anaerobically digested (AD) biosolids on hormone and antioxidant metabolism and grain yields in a corn (Zea mays L.)–soybean (Glycine max L.) rotation under both conventional tillage (CT) and no tillage (NT) practices during 2009 to 2011. Application of both biosolids increased leaf photochemical efficiency (PE), hormones (indole‐3‐acetic acid (IAA) and trans‐zeatin riboside (ZR)), proline, and superoxide dismutase (SOD) activity in corn at all sampling dates. The soybean grown in the plots previously amended with the biosolids exhibited greater PE, IAA, ZR, and SOD activity when compared with the control. The LS and AD biosolids increased grain yield by 87% and 77%, respectively, in corn and 15% and 18%, respectively, in soybean compared with the control. No difference in PE, hormone, proline levels, and SOD activity was found between CT and NT practices. The research demonstrated that biosolids application improves leaf antisenescence hormones, osmoprotectant, and antioxidant metabolism to increase grain yields, especially under drought stress.

Sand and gravel mine reclamation in eastern Virginia is hampered by low mine soil water holding capacity and fertility levels. Application of biosolids at higher than agronomic rates has been recommended for these areas, but agency concerns over the potential for NO 3-N leaching to shallow ground water persist. In the fall of 1998 and the spring of 1999, a mixture of two different biosolids was applied to a 20-ha reclaimed site in the Virginia Coastal Plain at various rates ranging from 1.5 to 5x the agronomic N rate for corn (Zea mays). By the end of the 2000 growing season, the majority of the biosolids treated areas supported at least 90% vegetative cover, and most of the area supported 100% ground cover, with average standing biomass > 5 Mg/ha. Nitrate-N levels remained low in all wells within the treated areas over the winter/spring/summer of 1998/1999, indicating that a mixed application of two biosolids materials to the majority of the site had little effect on ground water with regard to NO 3-N. Of 13 monitoring wells under and downgradient of the application areas, only three showed any significant treatment effects, and all levels dropped to < 2 mg/L by the spring of 2001. Nitrate-N levels in several wells directly adjacent to an area receiving a 3x agronomic rate application of lime-stabilized biosolids slowly began to increase in the fall of 1999, peaked at 50 mg/L in late winter/early spring of 2000, and then dropped below drinking water standard levels (10 mg/L) by May, 2000. Neither the surface water within the site nor two external downgradient wells adjacent to the Mattaponi River showed any elevation in NO 3-N levels through the late winter of 2001. Significant background levels of NO 3-N appeared to be entering the site via ground water flow from an adjacent agricultural field. Overall, these data support earlier findings that while application of biosolids at higher than agronomic rates will lead to an ephemeral (first winter) leaching loss of NO 3-N, that the impact to ground water is highly localized, small in magnitude, and relatively short lived.