The influence of soil compaction and N fertilization on physico-chemical properties of Mollic Fluvisol soil under red clover/grass mixture

Tractor traffic leads to soil structure degradation which in turn results in unfavorable changes in the physical properties of soil. The lower porosity of soil and its air permeability impacts on the biological and chemical properties, including the availability of macro and micronutrients. Additional N input in soil supplies substrates in biological processes in soil. Thus, it could be expected that the combined effects of compaction and N fertilization are reflected in the chemical quality of the soil. The objective of the study was to determine the effect of multiple tractor passes and mineral N fertilization on the physical and chemical properties of soil under red clover/grass mixture. This study was conducted in a split-plot design, with fertilization as a main plot and compaction as a subplot. The N treatments used were: untreated control (NO), 80 kg N ha(-1) (N80) and 160 kg N ha(-1) (N160). Four compaction treatments were applied using the following number of tractor passes: untreated control (PO), two passes (P2), four passes (P4) and six passes (P6). The soil samples were collected on April 2010 and after the third harvest in October 2010, 2011 and 2012 and the physical parameters and chemical analysis were determined. The results obtained in this study demonstrate that tractor traffic leads to unfavorable changes in soil physical parameters. The more intensive the wheeling applied, the higher the value of BD and PR recorded and the lower the value of TP. The maximum values of these parameters (BD of 1.67 g cm(-3), PR of 2.16 MPa and TP of 0.37 cm(3) cm(-3) for the P6 treatment), obtained for strongly compacted treatments (P6), exceeded the critical values for root growth. In the presented study, soil compaction decreased the pH value which also caused an increase in the Zn content in the soil. The nitrogen fertilization applied significantly increased the mineral N content in the soil and lead to a depletion in P and K contents. A significant correlation was observed between N fertilization and pH. Higher N rates resulted in lower pH in the soil, with the lowest value of 6.02 recorded for the N160 treatment. The changes in soil reaction led to enhancement of the content of some microelements, namely Mn and Zn in proportion to the N fertilization rate. (c) 2014 Elsevier B.V. All rights reserved.