Physical and Cultural Weed Control Working Group of - European ...

9 th EWRS Workshop on Physical and Cultural Weed Control 65
Samsun, Turkey, 28 – 30 March 2011
Effect of flame weeding at different time intervals before crop emergence
D. Hansson and S-E. Svensson
Swedish University of Agricultural Sciences, P.O. Box 104, SE–230 53 Alnarp, Sweden. Email:
David.Hansson@slu.se
A research project studying ‘Effective weed management in row-grown organic carrots’ was
carried out at SLU Alnarp. The project used a slightly modified form of the ‘participatory research’
concept, which meant that it was associated with a reference group consisting of the growers
participating in the project, advisors and researchers. The aim of the project was to examine various
weed control methods combined into entire weed management strategies. After discussions with the
growers in the group, the studies focused on weed control measures to be carried out before crop
emergence, since these measures were considered to be the most important in the weed management
strategy.
One experiment carried out in Karlskrona, in the county of Blekinge in southern Sweden
studied the importance of weed flaming shortly before the emergence of an organic carrot crop. The
experiment included four replicates and examined four different times of flaming treatment in
relation to the seeding date. The field in which the experiment was carried out was tilled with a
rotary power harrow on 16 May and the carrot crop was sown on 27 May. Weed flaming was
performed 5, 6, 7 and 9 days after sowing. The first carrot plants began to emerge from the soil 7 days
after sowing. The plots were weeded by hand 29 days after sowing.
The results showed that the number of weeds in the carrot crop decreased by 10% and the
manual weeding requirement was reduced by 10-15 hours per hectare for every day flaming was
delayed in relation to carrot emergence. Weed flaming one day too early increased the cost of manual
weeding by SEK 2600 per hectare (approx. € 280 per hectare). The optimal conditions for successful
weed flaming were found to be careful seedbed preparation, resulting in an even soil surface, and
sowing in a moist seedbed, resulting in simultaneous and uniform emergence of weeds and
cultivated plants.
It was concluded that it is important to flame as late as possible before crop emergence. The optimal
time is just before crop emergence, or when a few percent of the carrot plants have emerged. Losses
in crop plant numbers due to planned late flaming relative to emergence can be compensated for by
slightly increasing the seed rate.