Hydroxamate siderophore content of organic fertilizers

Abstract
To estimate siderophore input into soil through fertilization, the hydroxamate siderophore content was determined in five organic fertilizers: granulated bacterial biomass (BAC); granulated fungal biomass (BIO); grape marc compost (BIV); chicken, dung (ITA); and bacterial single cell protein biomass (PRU). Siderophore content, expressed as Desferrioxamine B equivalents as determined by a modified version of the Arthrobacter flavescens JG‐9 bioassay, ranged from 0 to 20,647 ng g‐1 dry wt. of fertilizer (PRU < BIV < ITA < BAC < BIO). Recommended application rates of BIO would result in a calculated siderophore input of about 10 μg kg‐1 of soil in the plow layer. Such additions could affect iron nutrition of plants and alleviate of iron chlorosis.