Impact of weather conditions on the critical period for weed control and corn yield in Serbia

Corn is one of the leading crops grown in Serbia (on over 1 000 000 ha), mostly in the territory of Vojvodina (about 60%), with the rest being grown in Central Serbia. Corn production is affected by a number of different factors during the vegetation season, both abiotic and biotic. Weather conditions during the season are a factor which can affect both the crop yield directly and the development of weeds that can be found in the corn field, and consequently determine the critical period for weed control (CPWC). Therefore, the aim of this paper is to study the impact of weather conditions during two vegetation seasons on the start of the critical period for weed control in conventional corn production. Field experiments were conducted during 2015 and 2016 in the area of Padina (South Banat region). The experiment was set up as a randomized block system, divided into two sections. Soil-applied herbicides (PRE-EM) based on S-metolachlor (1.5 L ha-1) + terbuthylazine (1.5 L ha-1) were applied in the first section, while the second section was left untreated. Seven treatments (seven weed control periods) were tested in each section, in three replicates. The size of the experimental plot was 10 m x 4.2 m. The obtained results have shown that the highest corn yield (12803 kg ha-1) was achieved in the treatment with PRE-EM herbicide application in 2016, when the precipitation was 526.4 mm, while in the same year the untreated plots yielded 9.5% less (11588 kg ha-1). In 2015, with the precipitation of 281.1 mm, corn yield in the PRE-EM treatments was 9045 kg ha-1, which was approximately 30% less, when compared to 2016. In 2015, which was a dry season, the corn yield in PRE-EM treated plots was 2.6% higher, when compared with the untreated plots. In 2015, the CPWC started in the four leaves growth stage (BBCH 14) in the PRE-EM treatments and in the two leaves growth stage (BBCH 12) in the untreated plots. In 2016, the CPWC in PRE-EM treatments started in the five leaves growth stage (BBCH 15), while in the untreated plots it began with the first leaf growth stage (BBCH 11). Therefore, soil-applied herbicides and better suited weather conditions enable a more flexible weed control, in terms of the start and length of the CPWC in corn fields in the region of South Banat.