Effect of a tillage system on the chemical properties of sandy loam soils

A tillage system can affect significantly the concentration of some heavy metals and their availability to plants which grow on the tilled soil. The purpose of this study has been to determine the impact of different tillage systems on the chemical properties of arable sandy loam soils under the same crop rotation, organic residue management and mineral fertilization. A single-treatment field experiment in a randomised block design was performed on sandy loam soils. Four-year tillage study data were compiled and compared with respect to full-inversion tillage (FIT), strip-till (ST) and reduced tillage (RT) systems. Soil samples were mineralised in a mixture of HF and HClO4 acids to determine the total content of metals. Total organic carbon (TOC) and total nitrogen (Nt) were also assayed. The content of available metal forms was determined using diethylene triamine pentaacetic acid (DTPA). The soil maintained in the FIT system contained significantly more Zn and Fe available to plants than the soil cultivated according to the RT and ST systems. The FIT and ST systems decreased the total Zn, Cu, Mn and Fe content in soil significantly compared with the RT system. Relative accumulation of the heavy metals at the depth of 30-50 cm can be related to the distribution of the clay fraction in soil profiles. In the topsoil (0-30 cm), the average content of TOC was significantly higher under the RT than under FIT and ST systems. The results confirm that a tillage system is one of the factors affecting the content of heavy metals, TOC accumulation and heavy metal distribution in sandy loam soils, although the pedogenic processes determining the quality of arable soils quality must be considered as well.