Weeds are a major problem in organic cereal production. The most common weeds are wild poppy, forking larkspur, cleavers, chamo-mile, common speedwell, podium Anthemis, combine, stork‘s bill, burdock, Bermuda grass and Sorghum halepense. Weed develop-ment before tillering can reduce yields, hinder the harvest, and in-crease weed pressure in the subsequent crop.
Solution
In organic farming, the use of herbicides is prohibited. Therefore, organic farmers depend on preventive weed control measures such as crop rotation and mechanical control measures for weed control. In many countries, the comb har-row is a standard tool for weed control in early stages of cereal growth. The aim is to achieve the lowest possible weed density until the end of tillering. Growth of problem weeds such as cleavers, chamomile, hollow tooth, field foxtail, mustard, etc. should be prevented until the end of stem extension.
In Bulgaria, many farmers are not familiar with the comb harrow, and some have doubts about its efficiency. Hence, the effect of harrowing was tested in Bulgaria on 3 farms for 3 cereals (wheat, spelt and einkorn). Within each field, 2 experimental plots were created: one with comb harrow use, and a control plot without harrow use.
Description
In the beginning, weeds with shallow roots were successfully eradicated by the harrow. Others (e.g., burdock and stork’s bill) were controlled to a certain extent. The results of FAO "Bioselena" show that the application of the comb harrow had a significant impact on the yield, with an increase of 12.7 % for wheat, 16.7 % for spelt and 23.4 % for ein-korn. The weeds decreased by 51.15 %, 58.14 % and 36.37 %, respectively.
Practical recommendations
• Drill winter cereals in rows with an increased sowing rate of 7-10 % compared to conventional cereal crops during the most appropriate period (September 25 to October 5 for Northern Bulgaria, 5 to 15 October for Southern Bulgaria).
• When the crop is in the „3-leaf“ stage, control the emerging weeds with a comb harrow.
• Repeat the procedure, when the wheat plants start tillering.
• Use the harrow again at the earliest possible time in spring to destroy the soil crust and aerate the soil.
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