Vasarinių rapsų sėjos laiko ir žemės dirbimo įtaka pikžolių plitimui besikeičiančio klimato sąlygomis

Abstract

Field experiments were carried out in the Experimental Station of Aleksandras Stulginskis University in 2016. The soil type Calc (ar) i-Endohypogleyic Luvisol. The 1st field experiment - soil tillage: l)Traditional soil tillage (by ploughing); 2)Reduced soil tillage (without ploughing, hoeing).The 2ndfield experiment - sowing time: 1) 10 04 2016; 2. 15 04 2016;3. 20 04 2016; 4. 25 04 2016; 5. 30 04 2016; 6. 05 05 2016; 7. 10 05 2016; 8. 20 052016; 9. 25 05 2016.The purpose of the investigation was to evaluate the influence of sowing time and soil tillage on the spreading of weeds in spring oilseed rape crop. The first analysis of weed sprouts was carried out with the rapeseed being at 3-4 leaves. The evaluation of the weed density of the crops was carried out for the second time at the end of spring rapeseed vegetation (during the seed ripeness) before harvesting. In the course of the research, the time of sowing had the major influence on the sprouting of weeds: the number of weed sprouts in the rape crops of early sowing (10 04, 15 04) was less by 41.2 % in comparison to those sowed later. This could have been influenced by the small quantity of precipitation and cool weather during the first decade of April. The sprouting of weeds intensified when the quantity of precipitation and average daily air temperature increased. When the rapeseed crop was sown into unploughed soil, the quantity of weed sprouts in the crop was higher by 43.3 % in comparison with sowing into the soil ploughed in autumn. Early (10 04, 15 04) and late (10 05, 20 05) spring rape sowing significantly reduced the weed density before harvesting. The highest number of weeds was investigated in rape crops sown on April 20 and April 30. Autumn ploughing did not have significant influence on the number of weeds in spring rapeseed crop before harvesting: their number was not significantly (by 15.3 %) lower in comparison with the rapes that were sown without ploughing.