Alleviation of Soil Compaction, Using a Fodder Radish Cover Crop As a Biological Tillage Tool.

Soil compaction within agriculture is considered an increasing problem, because it can cause increased soil strength, which will cause a reduced aeration and water flow. This may then lead to root growth being influenced both temporally and spatially, which can lead to a reduced crop yield. New methods should be investigated, as deep subsoiling the most common method for alleviating soil compaction has not presented satisfactory long term results. For this, we have chosen the biological tillage method, in which a crop is used to penetrate the compacted soil layer, thereby creating biopores. Biopores can subsequently be used by the main crop to penetrate the compacted layer. Here Fodder Radish was chosen as the biological tillage crop, as it is known for having large deep growing roots, and spring barley as cash crop. Root images from horizontal minirhizotron tubes in and below the compacted layer was investigated. The investigation was conducted during 2013-2016, in three different compaction levels (0, 3 and 8 Mg wheel load). The hypothesis is that biological tillage mitigates soil compaction and improves root growth below the compacted soil layer. The results show a tendency towards root occupation for the 0 Mg than the 8 Mg compaction treatment at 30 cm depth both years and 50 cm in 2014. The opposite was found for 70 cm depth both years and for 50 cm 2016. Results also show the relative difference in root frequency between 0 and 8Mg decreased from 2014 to 2016 for spring barley. These results indicate that fodder radish worked as a tool for alleviating the compacted soil layer and improved root growth conditions for the spring barley crop. This is supported by the fact that a treatment effect in root occupation at 30 cm depth in 2014 (0Mg>8Mg) was not found in 2016.