Soil health on organic farms : linking organic farmer practices to soil health and yield

Sammanfattning: Soil health is a part of the sustainable agriculture which the EU is trying to develop. Organic farming can be one way of working towards more healthy soils. The term soil health can be divided into biological, chemical, and physical aspects of the soil that are necessary to sustain the plants grown. This master thesis was conducted within the CONSTRAINTS-project which aims to provide knowledge to help improve the expansion of organic agriculture systems in regions of high productivity with proportionally few organic farms. The purpose of this master thesis was to assess the soil health on a group of organic fields with varying management in Västra Götaland, Sweden. The fields were included in the CONSTRAINTS-project and had varying management. The soil health was studied by analysing the bulk density (BD), potential mineralisation of nitrogen (pot-min), visible and near infrared reflectance (vis-NIR), clay content, pH, and plant nutrients. The BD, pot-min and vis-NIR were measured using soil samples collected during the summer of 2022. Clay content was retrieved from a digital soil map whereas soil pH and plant nutrients were analysed in an earlier soil sampling during autumn 2021 within the CONSTRAINTS-project. The different soil health indicators were related to the farmers’ management, which was collected through interviews, and the yield. The results showed variations in the measured indicators between the different fields and statistical analyses were made to link the measured indicators to the yield. The soil health indicators that were closest related to the winter wheat yield were pH, and vis-NIR measurements (which are strongly related to clay and SOM content). The management practices that were most correlated with yield were connected to the fertilisation, age of the ley and proportion of legumes in the ley. Keywords: organic farming, bulk density, farm management.