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Changes in soil penetration resistance and yields of winter rapeseed, winter wheat and spring barley cultivated in the 3-year rotation system under the influence of soil compaction and four tillage methods were evaluated in a field experiment conducted in 2009-2012. During the stage of full emergence of winter rapeseed, at the depth of 0-10 and 10-20 cm (lots without compaction) after U-2 cultivation (subsoiler 40 cm, disk cultivator, harrowing, cultivating, sowing ploughing 20 cm), the resistance of the soil decreased significantly as compared to the plough cultivation (control lot). At the level of 20-30 cm, after conventional cultivation, significantly lower compaction of the soil was found compared to the other cultivation variants. On the compacted lots, the opposite situation was found. During the full blossom stage, in the lots without compaction, tillage increased the soil compaction significantly within the studied soil levels, compared to the reduced tillage variants. On the other hand, at the depth of 20-30 cm (lots with compaction), regardless of the reduced tillage variant, significantly higher compaction of the soil, as compared to the plough cultivation, was recorded. After rapeseed harvest, at the depth of 10 cm (lots without compaction), after U-2 cultivation, almost 2-fold increase in the value of the analysed characteristic was recorded as compared to the plough cultivation. During the wheat stem elongation stage, on the lots without and with compaction, the highest soil compaction was found at the depth of 20-30 cm after U-3 cultivation. In the lots without compacting, during the heading, the application of the ripper (U-2 cultivation) significantly decreased the compaction of soil down to 10 cm. In the 20-30 cm layer (lots with compaction), soil resistance increased, assuming the highest values after subsoiler and single ploughing. After the harvest of crops from the lots without compaction, an increase of soil compaction, as compared to the plough cultivation, was recorded after U-2 cultivation at the depth of up to 10 cm and in the 10-20 cm layer after the application of subsoiler and single ploughing. The degree of compaction and the method of soil cultivation diversified significantly the yields of the analysed cereal. Following spring barley harvest, in the lots without compaction, significantly higher soil resistance was found after applying full plough cultivation compared to the lots with compaction (depth 10-20 cm). Similar outcomes were obtained at the levels of 0-10 and 10-20 cm after U-2 cultivation (skimming, cultivator, harrow + pre-winter tillage to 25 cm) and at the depth of 20-30 cm after the application of the cultivator and performance of pre-winter tillage to the depth of 25 cm (U-3 cultivation). On the compacted lots, as compared to the lots that were not compacted, a significantly higher yield of winter rapeseed was obtained following U-3 cultivation. Postharvest cultivation using the subsoiler and pre-sowing cultivation by single ploughing decreased the winter wheat yield the most as compared to the traditional cultivation. The yield of grain from lots with soil compaction, compared to lots without compaction, was significantly higher. In the case of lots with compaction, the application of skimming, cultivator treatment and harrowing of the field after harvest of the forecrop and performance of pre-winter tillage to the depth of 25 cm (U-2 cultivation) increased spring barley yield significantly compared to the conventional cultivation.
The extreme soil compaction and standard indices for Estonian soils sted to sustainable crop production are worked out which could be a basis for chracterizing the agro-ecological conditions for some particular soils. Comparison of measurements showed, that increase of subsoil hardness by compaction is mostly visible in soils with relatively weak agro-technical capability (90 and 120 kPa). The penetration resistance of arable soils is quite different depending on Estonian area. We are briefly introducing our results concerning the influence of soil compaction on penetration resistance of different soils in Estonia, on uptake of nutrients and new viewpoints concerning the changes in cellualar fluid pH of barley as depended on the soil compaction. Concerning degree of intracellular fluid pH we could conclude that this method is rather sensitive and allows us to find out plausible relations between the CpH compaction of soil and the level of the nitrogen fertilizer. Our contribution to this work justified itself and allowed us to analyse from a new point of view the positive as well as negative aspects of the effect of soil compaction and level of nitrogen fertilizer. Without nitrogen fertilizer the influence of soil compaction is rather negative. The effect of soil bulk density on cellular fluid pH of barley leaves generally depends on the number of passes. The experiment showed also that stronger decrease of nutrient content started at the same soil bulk densityvalue, at which the cellular fluid pH quickly increased. If the soil bulk density- increased up to level of 1.52-1.54 Mg·m⁻³, the cellular fluid pH increased very quickly.
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