Corn and Soybean Hormone and Antioxidant Metabolism Responses to Biosolids under Two Cropping Systems

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.