P. Yankov

Abstract. The investigation was carried out during 2004-2006 in the trial field of Dobrudzha Agricultural Institute on slightly leached chernozem soil. In a stationary field trial, 24 systems for soil tillage based on different soil tillage tools and operations were tested. A 6-field crop rotation involved the following field crops: wheat, grain maize, bean and sunflower. For the purpose of this investigation the following variants of pre-sowing preparation were chosen: double disking at 10-12 cm (check variant); plowing at 14-16 cm + disking; direct sowing – pre-sowing treatment of the area with total herbicides. The depth of sowing of the seeds was determined in the variants with wheat sown after maize. Following germination, the length of the etiolated part of the stems of the uprooted plants was measured at interval of grouping 1 mm. The most even vertical distribution of wheat seeds was provided after well performed direct sowing. In annual disking, as contrasted with nil tillage, the percent of wheat seeds under the optimal depth was higher. The variation in the depth of sowing of the seeds was the highest after sowing of wheat in plowed soil.