Flaming for weed control in sunflower (Helianthus annuus L.): results of a four-year research.

Field experiments over 4 years (1981>-1 <)91) were carried out in Central ltaly in order to study the effectiveness of flaming for weed control in sunflower. The effects of two interrow flamings (24 and 34 days after sunflower emergence), hoeing and pre-emergence herbicide (Melobromuron + Prometryn) application were compared to control (untreated). Thermal treatments were carried out by a machine provided with six burners stocked with LPG and equipped with nozz!es of 0.5 mm diameter. The results showed that hoeing and pre-emergence treatment were more effective in controlling weeds. As a matter of fact, weed fresh biomass and density were reduced by 84% and 87% respectively compared to conlro. Early flaming treatment reduced fresh biomass and weed densily by 63% and 60% respectively. All treatments were able lo reduce viable weed seed number in the upper 20 cm of soil. Soob after sunflower harvesting, mean potential flora was 5.200 seeds per m 2, 60% lower compared to control. Pre-emergence herbicide application was the best in reducing the viable seed of redroot pigweed (Amaranltus retroflexus L.). Regarding common lambsquarters (Cltenopodium album L.) and black nightshade (Solanum nigrum L.), results were not significantly di'fferent from those obtained with hoeing. Yields and achene oil content obtained by flaming treatments were not significanlly differenl from those obtained by hoeing and herbicide application. With a gas consumption or 60 kg ha, early flaming cost did not result higher than pre-emergence treatment (139.000 Lit ha). In order to reduce flaming cost by 40%, ou-row flaming and inter-row hoeing could be combined in one single operation. In conclusion, flaming could be a good technique to be included in integrated or completely chemical-free methods for the control of weeds in sunflower. However, further researches are necessary for the setting-up of machines, the effectiveness of treatments and the cost of flaming application in different areas of cultivation.