Effectiveness of Liming and Subsoiling to Ameliorate a Compacted Arable Clay Subsoil

The effectiveness of mechanical subsoiling for alleviating subsoil compaction is controversially discussed, particularly due to the sensitivity of mechanically loosened soils towards re-compaction. In order to improve the alleviation potential by subsoiling it was hypothesized that the loss of soil stability by mechanical subsoiling of compacted soils can be reduced by top and subsoil liming. The primary objective was to evaluate whether (a) mechanical subsoiling (to a depth of 35 cm with a subsoiler or a plough with a pan-breaker) could alleviate compaction in a clayey Stagnosol and (b) whether liming could stabilize soil structure to minimize re-compaction. Undisturbed soil samples were collected to assess physical properties in both "compacted", "subsoiled", and "limed", as well as in untreated plots. The Compaction Verification Tool (CVT) identified potentially harmful soil compaction in the subsoil. The results showed that wheeling increased the extent of harmful subsoil compaction (from 8% to 33%) in the first year, which was accompanied with a reduction in crop yields. Subsoiling with a pan-breaker combined with high liming intensity improved soil physical properties and yields and may have mitigated re-compaction in the loosened subsoil. Nevertheless, it is expected to be not economically viable on the studied clay soil.