Numerous studies have confirmed that forests have the potential for a significant contribution to carbon sequestration, but afforestation of former agricultural land can be attempted to adopt technologies that further encourage carbon sequestration. The aim of this study was to evaluate the impact of different soil cultivation methods, including deep ploughing and soil cultivation by making microsites and furrows prior to afforestation of former agricultural land, on chemical soil properties and tree growth in 20 years old Scots pine plantations. A naturally regenerated Scots pine stand, representing the non-ploughed soil, was included as a control site. Deep ploughing, among other soil cultivation methods, significantly altered the chemical soil properties. Furthermore, significant effects were indicated in the sites afforested after cultivation by making furrows. A recent study found that, due to deep soil cultivation, higher stocks of soil organic carbon (SOC) and total nitrogen (N) were incorporated into deeper soil layers and were protected from direct environmental impact. Twenty years post afforestation in deeply ploughed sites, we still found a decreased C:N ratio and disbalanced relationship between the concentrations of SOC and total N. The SOC and total N stocks were higher in the subsoil than in the topsoil in the sites afforested after deep ploughing. Moreover, deep ploughing and soil cultivation by furrows prior to afforestation resulted in higher total SOC and total N stocks in the forest floor and mineral 0–80 cm soil layer. A higher total phosphorus (P) concentration in the subsoil and total potassium (K) in the upper mineral soil layer were obtained in the deep ploughing sites and the sites, cultivated by furrows, compared to the non-ploughed sites. Significantly higher total P stock per entire profile was found for the deep ploughing sites and the sites cultivated by furrows than in the naturally regenerated stand. Different soil cultivation methods caused no differences in tree diameter at breast height (DBH) in 20 years old Scots pine stands both in the afforested sites and in the naturally regenerated forest. However, significantly larger tree height in all afforested sites than in the naturally regenerated Scots pine stands was obtained. A lower differentiation in tree DBH was obtained in the deep ploughing sites.

Deep ploughing—which inverts, covers, or mixes soil organic layer (forest floor) and surface mineral A horizon into the mineral subsoil, burying the upper soil horizon in deeper layers, and disrupting pedogenic processes—is a debatable topic in forest plantation management. Overall, this review article aimed to identify the impacts of deep ploughing on the properties of forest plantations, adapting experiences from the agricultural sector. This paper examines the main impacts of deep ploughing technology on soil physical, chemical, and biological properties, ground vegetation, and tree aboveground and belowground biomass in afforested former agricultural land. Analysis of the published literature shows that deep ploughing can be used under different climatic and soil conditions, but it induces site-specific changes in soil properties and vegetation. Mechanical site preparation during afforestation and reforestation should follow the requirements of sustainable soil management, in order to avoid negative effects on the environment and biodiversity. Based on this analysis, we suggest key indicators that may be specific to deep ploughing responses in afforested sites and can contribute to risk assessment, aimed at achieving sustainable forest management. To date, most studies on mechanical site preparation for forest plantation have been performed using a few conifer tree species; therefore, it is important to expand empirical studies.