Effect of different types of main soil tillage on the vertical distribution of maize seeds in the soil layer and on the development of the plants

P. Yankov, M. Drumeva
Abstract. The investigation was carried out during 2008–2010 in the trial field of Dobrudzha Agricultural Institute on slightly leached chernozem. To determine the effect of different types of soil tillage on the vertical distribution of the maize seeds in the soil layer and the subsequent development of plants, the following variants of a stationary field experiment were analyzed: plowing at 24–26 cm, disking in autumn and double cultivation in spring (check variant); cutting at 24–26 cm, pre-sowing treatment with total herbicide (adapted direct sowing); double disking at 10–12 cm accompanied by autumn disking and double spring cultivation. Hybrid Anasta was sown at plant density 55 000 plants/ha. The most even vertical distribution of the maize seeds in the soil layer was ensured at adapted direct sowing performed with high quality. Under constant cutting and annual disking, the percent of maize seeds below and above the optimal depth increased in comparison to adapted direct sowing. The variation in the depth of planted seeds was the highest when sowing the seeds in the plowed soil. At planting under conditions of lower temperatures, cutting, adapted direct sowing and disking retarded the rates of germination in comparison to plowing and elongated the developmental stage of maize with 3–5 days. The number of germinating plants under these main types of soil tillage decreased by 6 to 15 %. Under favorable thermal regime after planting, the rate of germination of maize seeds in the variants with reduction and exclusion of the main soil tillage was more intensive only at the beginning. The duration of the germinating stage and the percent of germinating plants were the same under all types of tillage. At the early stages of maize development, plant growth in height was the most intensive after shallow main tillage performed as disking. With the advance of vegetative development, the stems of maize were higher and with greater diameter after adapted direct sowing, plowing and cutting in comparison to annual disking.