No abstract

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.

The experiments were carried out during 2012–2017. There were 5 crops in rotation: Red clover, winter wheat, pea, potato and barley undersown (us) with red clover. There were 5 cropping systems in the experimental setup: 2 conventional systems with chemical plant protection and mineral fertilizers; 3 organic systems which included winter cover crops and farm manure. The aim of the present research was to study the effect of cultivating barley undersown with red clover and the preceding winter cover crop on the soil microbial hydrolytic activity, the change in the content of soil organic carbon (SOC) and total nitrogen (Ntot) compared to the same parameters from the field that was previously under potato cultivation (forecrop of barley in the rotation). The cultivation of barley with red clover (barley (us)) had a positive impact on the soil micro-organisms activity. In organic systems the soil microbial hydrolytic activity increased on average by 19.0%, compared to the conventional systems. By cultivating barley (us) the soil microbial hydrolytic activity had a significant effect on the SOC content only in organic systems where winter cover crops were used. Organic cultivation systems had positive impact on the soil nitrogen content; Ntot in samples taken before sowing the barley (us) was higher by 17.4% and after the cultivation of barley (us) by 14.4% compared to conventional systems, as an average of experimental years. After cultivation of barley (us) with red clover the soil microbial hydrolytic activity had no effect on the soil Ntot content in either cultivation systems.

Nowadays, in sustainable agriculture growing winter cover crops and using organic manure have been widely implemented to improve soil quality which leads to increase of microbial activity. Six-year study was performed to evaluate the effect of cropping system on soil microbial hydrolytic activity, content of soil organic carbon (SOC) and total nitrogen (N tot) under potato cultivation by considering various management systems, while comparing the soil parameters after previous crop. The experiment consisted of five-field crop rotation with two different organic (Org 0 as control and Org II with winter cover crops plus added composted manure) and conventional (Conv 0 as control and Conv II with mineral N, 150 kg ha-1) farming systems. The results showed that hydrolytic activity of soil microbes decreased in every farming system under potato cultivation. Interestingly, after potato cultivation, the lowest and highest decrease in the soil microbial hydrolytic activity were seen in Org II and Conv II systems, respectively. The highest soil microbial hydrolytic activity was measured in system Org II where incorporation of biomass from winter cover crops and cattle manure was used. Finally, SOC and N tot were higher in organic farming systems and there no significant changes after potato cultivation.

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.