BayCEER Workshop 2023

Effects of herbal treatments on ARD-soils considering soil texture

P 3.9 in Zooming in: Small scale findings

Apple replant disease (ARD) is caused by a shift of the soil microbiome and affects replanted apple trees in growth and yield. Since treatments like fumigation with chemicals (Basamid) are to be prohibited due to their negative impact on the environment, new treatments including a biodiversity approach (Catch Crop Mix (CCM)) and so-called biopesticides (Tagetes) are in the centre of research. It is poorly understood how these treatments influence the microbial life in ARD-soils and whether this depends on soil texture. Therefore, we hypothesized that 1) as silt content in soil increases, microbial biomass and basal respiration increases, as silt provides a better habitat for microorganisms due to its ability to hold water , 2) that Tagetes and CCM treatments narrow the C/N ratio, resulting in higher nutrient availability in soil, and that 3) CCM treatments have a more positive effect on microbial activity than Tagetes, as biodiversity was shown to positively affect microbial biomass .To test these hypotheses, measurements of soil microbial biomass, basal respiration, nutrient availability, C/N ratio, pH, d¹⁵N and water holding capacity were performed. It was shown that the effect of soil texture like silt content had a significantly positive influence on the microbial biomass and basal respiration. We found only positive trends for the CCM and Tagetes treatments on microbial biomass, basal respiration and nutrient availability which might become relevant for longer periods of respective treatment.

Keywords: apple replant disease soil texture herbal treatments