ORDIAmur

2026-03-05

What causes replant problems in tree nurseries and fruit farms that repeatedly grow apples in the same soil? The interdisciplinary team at ORDIAmur has studied this complex topic and developed and tested sustainable countermeasures based on the latest findings. Goal and approach In fruit tree nurseries and apple orchards worldwide, there is a risk of high crop losses if apples are planted in soils where apples have previously been grown. The causes of these replant problems are not fully understood and sustainable management measures are missing. The BonaRes project ORDIAmur aimed to develop alternatives to chemical soil disinfection that are based on a better understanding of apple replant disease and are economically and ecologically viable. Therefore, researchers from 14 German universities and research institutions worked on the topic. At three locations, reference plots with apple disease were created through repeated apple cultivation and control plots were created on which no apples were cultivated. Humus, nutrients and structural properties were analysed in the soil from these plots and the organisms, primarily nematodes, fungi and bacteria, were characterized using classical isolation approaches and modern sequencing techniques. Plants grown in regrowth and control soils were analyzed for differences in gene expression and the content of secondary constituents in roots. Important partners were also farms that were interviewed for risk analyses and where counteractive measures were tested.