P. Yankov*, M. Drumeva, D. Plamenov

Department of Plant Production, Faculty of Marine Sciences and Ecology,Technical University Varna,1 Studentska, 9010 Varna, Bulgaria

Abstract. The investigation was carried out during 2008 – 2010 in the trial field of Dobrudzha Agricultural Institute on slightly leached chernozem. To clarify the effect of some ways of pre-sowing soil tillage for wheat on the development of its roots, the following variants of a stationary field trail were analyzed: double disking at depth 10 – 12 cm (check variant); plowing at 20–22 cm + disking; direct sowing – pre-sowing treatment of the area with total herbicides. The development of the roots was followed layer by layer every 10 cm down the 0 – 50 cm soil profile by washing the soil units sized 30х30х10 cm. The soil samples were taken at stages autumn tillering and heading. The root mass was determined under air humidity. At stage autumn tillage of wheat, the root mass per plant was the highest after direct sowing, followed by pre-sowing tillage of soil by disking. At this stage of the crop development the amount of roots per wheat plant was the lowest after plowing. The effect of the applied type of pre-sowing soil tillage for wheat on the distribution of its roots by layers at heading stage was statistically significant at depth up to 30 cm. The relative percent of the roots in the 0 – 10 cm layer according to their net weight was the highest after direct sowing and disking. This value was the lowest after plowing. At depth 10 – 30 cm, the quantitative share of roots under minimal and no-tillage decreased, and under intensive tillage with turning of the soil layer it increased. In the 30 – 50 cm layer, the investigated factor was with the same level of effect on the investigated trait.