Weed control in sunflower (Helianthus annuus L.) on the interface of agro-climatic conditions of maize and sugar beet growing region

Abstract

In the experiment, we focused on the occurrence of weed density and weed diversity, in maize and sugar beet growing region and the effectiveness of herbicide treatments on field experiment performed on site Santovka and Plave Vozokany in canopy of sunflower (Helianthus annuus L.) in 1998-2000. Plave Vozokany site is located in the south-eastern part of the district Levice in maize growing production region. The average daily air temperature in the region is a 9.6°C, and the annual amount of rainfall represents 604 mm and 330 mm during the growing season respectively. Santovka, the second experimental site, is located in the north-eastern part of the district of Levice in sugar beet growing region. The average daily air temperature in the region is 9.2°C and the annual amount of rainfall represents 637 mm and the annual amount of rainfall during the growing season is a 354 mm. Actual weed infestation was carried out by the numerous method with a five replication on the control treatments (without herbicide application), as well as on the areas treated with herbicides. The occurrence of weeds in sunflower was assessed for 3 times per growing season. The evaluated sites were infested on the level of high weed infestation. The total abundance of weeds without herbicidal treatments ranged from 39.62 pcs to 63.50 per m-2. Herbicides application effectively decreased the weed infestation in range from 3.13 pcs to 14.81 pcs per m-2. The most dominant weed species were one year late spring weeds as follows: Chenopodium album L., Echinochloa crus-galli (L.) P. BEAUV, Persicaria lapathifolia RAF. S. F. GRAY, Persicaria maculata RAF. S. F. GRAY, Amaranthus retroflexus L. and Atriplex spp. in the canopy of sunflower. Another most abundant weeds species designated as very dangerous species were Tripleurospermum perforatum (L.) SCHULTZ-BIP., Avena fatua L., Elytrigia repens (L.) DESV, Cirsium arvense (L.) SCOP. and Convolvulus arvensis L. In pursuing the weed species diversity, we found medium relationship with air temperature during the year (r=0.363427), and indirect relationship with rainfall pattern (r=-0.08196). The average weed density was in negative relationship with the air temperature (r=-0.98317), but strongly related to rainfall (r=0.889926). Higher weed infestation was noted in the growing years when early spring to early summer was warm and humid. Lower weed infestation was observed when this period was dry. Differences in overall weed infestation, as well as the effectiveness of the used herbicides between experimental sites were at the same level of importance.