Long-term effects of tillage systems on soil health of silt loam soil in Lower Austria

Tillage is an important management practice that can be necessary to loosen the soil and allow for seeding and aims at enhancing productivity. However, the long-term effects of a particular tillage action on soil health depend on the local soil characteristics and differ amongst soils. The main aim of our study was to evaluate the possible effects of various physical, chemical, and biological soil quality indicators in dependence of three different tillage practices: Conventional Tillage (CT), Mulch Tillage (MT), and No-Till (NT). A long-term tillage experiment that started in 1994 in Mistelbach, Lower Austria, was comprehensively sampled in 2002 and 2021. The research attempts to fill the knowledge gap in the long-term soil health changes due to shifting conventional tillage. To evaluate the soil health changes over time, we assessed the impact of the three tillage practices on selected soil quality indicators in the 0-20 cm layer and below 20 cm, which we determined as being below the plowing depth. The "Soil Management Assessment Framework" (SMAF) procedure was applied to assess and compare the overall soil quality. Twenty-one indicators were selected to compare and evaluate the long-term effects of the three tillage systems (a.); fifteen indicators were used to investigate the temporal changes since the last monitoring (b.); thirteen indicators were selected to assess overall soil quality (c.). The study shows that the tillage practices and temporal conditions significantly affected soil organic carbon (SOC) content. The SOC amount in the 0-20 cm layer was twice as high under no-till (31.2 t/ha) compared to conventional tillage (15.3 t/ha). The SMAF reveals that NT increased SOC content and enhanced soil's physical indicators, such as available soil water, porosity, and coarse pores in the 0-20 cm layer. We found soil quality improvements with MT and NT in the 0-20 cm layer; however, the SMAF also indicates that the soil quality was better below 20 cm in 2021 compared to 2002, independent of the tillage practice. According to our results, conservation tillage practices (such as MT and NT) enhanced overall soil quality, particularly the physical (available soil water, coarse pores) and soil biological indicators, mainly SOC.