Microbial activity of a clay soil amended with glucose and starch under live oaks

Abstract

Research was conducted to investigate the effect of glucose and starch on soil respiration under live oaks. Soil from a field-grown tree nursery was amended with glucose (C6H12O6), starch (C 6H12O6)n, or a 50:50 mixture of both carbohydrates at increasing concentrations (0, 40, 80 and 120 g/L). Solutions were applied once as 10-L drenches within 0.5 m from the trunks of live oaks (Quercus virginiana P. Miller). In a companion study, soil samples treated with the same carbohydrates and concentrations were studied under laboratory conditions. Carbon dioxide evolution was significantly impacted by glucose and starch applications. Glucose applications caused a significant increase in soil respiration compared with the control within a week after application, and it lasted two to three weeks. Elevated soil respiration was most noticeable in the field experiment for starch treatments; however, the increase in soil respiration for higher concentrations (120 g/L) did not become apparent until the fourth week after application and lasted eight to nine weeks. This knowledge about the differing durations and magnitude of glucose and starch on soil respiration may be useful for developing carbohydrate application regimes for soils where increase respiration is desirable for managing urban trees. © 2010 International Society of Arboriculture.