2019 ASHS Annual Conference

Humic acid refers to a group of compounds produced during the breakdown of organic matter that may improve plant productivity and soil structure. As interest in soil health and organic agriculture have increased, so has interest in humic acid. We measured the response of lettuce and soil to humic acid applications in a field experiment. Humic acid increased the concentrations of some micro- and macro- nutrients in lettuce tissue but had variable effects on yields. The effect on the soil microbiome was most striking, with an increased humic acid application rate being directly related to microbial population number and diversity. Humic acid applications increased the relative abundance of several species of bacteria involved with nutrient cycling and availability.