Plantation management induces long-term alterations to bacterial phytohormone production and activity in bulk soil

Phytohormone production and modification by soil bacteria has the potential to influence plant growth and performance. We studied the long term effects of nitrogenous fertilisation and weed control on the concentration of IAA equivalents and 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity in bulk soil in a Pinus radiata plantation. IAA equivalent concentrations were increased by weed control and ACC deaminase activity was increased by weed control and fertilisation. Measurements of P. radiata growth were positively correlated with IAA equivalent concentrations. ACC deaminase activity was positively correlated with P. radiata growth only in the absence of fertilisation. These results suggest that plantation management can induce long term effects on soil bacterial phytohormone production and modification, which may influence plant growth.