EFFECT OF SOIL COMPACTION AND DIFFERENT SOIL TILLAGE SYSTEMS ON CHEMICAL PROPERTIES OF SOIL AND PRESENCE OF EARTHWORMS IN WINTER OILSEED RAPE FIELDS

The research objective has been to assess the impact of soil compaction and reduced tillage on changes in the chemical properties of soil, and on the number and biomass of earthworms in soil cropped with two varieties of winter oilseed rape. The experimental factors were: soil compaction before sowing the crops (with and without soil compaction) and 4 tillage systems (U-1 ploughing tillage - the control: U-2 subsoiler, disc harrow, cultivator, harrow and pre-sowing ploughing to a depth of 20 cm; U-3 shallow ploughing; U-4 single ploughing). The highest soil pH in fields cropped with the winter oilseed rape cultivars Californium and Mendel was recorded after a single ploughing treatment without soil compaction. The U-2 tillage system decreased the soil content of organic carbon on plots with compaction. The tested tillage systems significantly increased the content of K in both varieties of winter oilseed rape grown on plots with soil compaction. Once oilseed rape plants (cv. Californium) emerged, a single ploughing treatment (plots without compaction) raised by 73% the number of earthworms in soil and more than doubled their mass relative to the analogous treatments on plots with soil compaction. Before oilseed rape harvest, after a single ploughing treatment (plots with compaction) the number of earthworms more than doubled and its biomass increased by nearly 2.5-fold relative to the analogous treatments on plots without soil compaction. After emergence of winter oilseed rape (cv. Mendel), the U-3 tillage method before the harvest (plots with compaction) - compared to the analogous treatment on plots without compaction - raised the number of earthworms by over two-fold, and the U-2 tillage before the harvest (plots with compaction) significantly reduced the biomass of earthworms relative to the complete ploughing system (control).