Effect of the Time of Herbicide Application and the Properties of the Spray Solution on the Efficacy of Weed Control in Maize (Zea mays L.) Cultivation

A field experiment was carried out in 2019–2021. The effect of an increased amount of iron in water and the addition of citric acid on the efficacy of herbicides applied in maize cultivation at various times was tested. In the pre-emergence treatment, thiencarbazone-methyl + isoxaflutole were applied, while in the post-emergence treatment, nicosulfuron + tritosulfuron + dicamba were applied once in a full dose or in low dose system at two times in half of the recommended dose with the addition of an adjuvant. In selected combinations, FeSO4 × 7H2O and citric acid were added to the composition of the spray solution. The species composition of weeds and the efficacy of the herbicides used were determined. Plant stress caused by competition from weeds was investigated by measuring the plant chlorophyll fluorescence. The height of the cultivated plants and their yield level were also determined. The lowest efficacy of weed control was observed when the post-emergence herbicides were applied once. Increasing the iron content in water reduced the efficacy of the herbicides, but the addition of citric acid made it possible to decrease this problem.