The experiments were carried out during the period 2005-2007 in the experimental fields of the Agricultural University – Plovdiv. The maize hybrid Florence (group 480 by FAO) of Pioneer Company was sown at a density 6500 plants per decare. The traditional for the crop agrotechnical practices were applied for growing the maize. Three soil-acting herbicides of early vegetation application were the object of the experiment. For control of the weeds that were not killed by the herbicides during the vegetation period, three different types of inter-row vegetation tillage were applied in the separate variants – without inter-row hoeing, one inter—row hoeing and two inter-row tillages – hoeing and earthening up, respectively. The experiment was carried out under irrigation.
The effect of the studied factors – soil-acting herbicides and herbicides of early vegetation application, as well as vegetation tillages – on the specific diversity of the weeds and the weed infestation rate in the maize plantation were followed out in dynamics. Significant differences in herbicide efficiency and in yields were reported in the separate years, which were mainly due to the differences in the amount and distribution of rainfalls in the experimental years.