Biosolids Impact On Corn and Soybean Drought Tolerance Associated with Hormone and Antioxidant Metabolism.

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 field study was designed to investigate effects of Blue Plains (lime-stabilized) and Alexandria (anaerobically digested) 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 Blue Plains and Alexandria increased leaf photochemical efficiency (PE), hormones (auxin and cytokinin), 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, indole-3-acetic acid (IAA), trans-zeatin riboside (ZR), protein content and SOD activity when compared to the one without biosolids treatments. The Blue Plains and Alexandria increased grain yield by 87% and 77%, respectively, in corn and 15% and 18%, respectively, in soybean when compared to the control. No difference in PE, hormone, proline levels, and SOD activity was found between CT and NT practices.  The results of this study indicated that biosolids application could improve PE, auxin, cytokinin, proline, and antioxidant metabolism, and thus promoted grain yields, especially under drought stress environments.