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The objective of this work was to evaluate the effect of tractor wheeling with a light tractor on the root growth and soil properties of smooth brome in South Estonia. Field experiment was conducted on sandy loam Haplic Luvisol in 2007. Data were collected during September 2008 in both an uncompacted and compacted area. Because of the compaction, the precompression stress increased in the upper soil layer (0−10 cm) by 12.6% and 15.2% at a depth of 10−20 cm. Compaction had only a minor effect on the bulk density, values increased 4.7% in the upper soil layer and 1.8% in the deeper layer. Differences in the saturated hydraulic conductivity (k s ) were not significant; however, the decrease in the k s was 26.6% in the upper level and 12.5% in the deeper (10−20 cm) layer. At a depth of 0 to 30 cm compaction decreased the root length by 44.7% and the root mass by 60.5% compared with the uncompacted soil. Altogether, this study confirms the unfavourable effect of wheeling on grasslands even when the wheeling is performed with a light tractor on dry soil.

In soil compaction research, more attention has been given to arable land than to grasslands. Our objective was to investigate the effect of agricultural machinery on the physical and mechanical properties of soil under intensively cut lucerne (Medicago sativa L.). A field experiment was conducted in South Estonia, near the city of Tartu, on a second-year mainly lucerne field on a sandy loam Calcaric Cambisol (CMca). After the third silage cut, soil properties were measured in the wheel traffic lanes (compacted) and between the traffic lanes (uncompacted). Our results showed that wheeling significantly affected the soil structure. Soil compaction increased soil bulk density (BD) by 0.19 g cm-3 at 5 cm depth and by 0.14 g cm-3 at 10 cm depth. Soil compaction also affected the pore distribution: soil air capacity (AC) in compacted soil at 5 and 10 cm depth was significantly (more than 10 vol. %) lower than in uncompacted soil, and plant-available water (PAW) increased at 10 and 20 cm depth but decreased at 5 cm depth. Air conductivity (k a) and saturated hydraulic conductivity (k s) decreased significantly at 5 and 10 cm depth. Soil precompression stress (P c) was lower in the uncompacted area: soil compaction increased P c by 60 kPa at 5 cm depth and by 30 kPa at 10 cm depth. Cohesion was greater in the compacted area than in the uncompacted area (mean difference 10 kPa). This study clearly indicates that soil compaction is a problem for grasslands.

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