Abstract

Most of Sweden's municipalities have forbidden chemical weed control on hard surfaces in towns. This has led to a growing need for new environment-friendly alternatives to chemical weed control. Several municipalities are interested in acetic acid for weed control. Trials have been carried out using acetic acid and Foraform to control weeds. Perstorp Specialkemi Formox have financed these trials. Acetic acid is a natural substance. It is formed when plants decompose under anaerobic conditions and is broken down under aerobic conditions. Previous trials have shown that acetic acid can curb the growth of barley plants' roots and also prevent seeds from germinating. Foraform is a liquid used in farming for ensilating grass. Foraform is made from formic acid (HCOOH), linked to ammonia (NH3) in a chemical compound called ammoniumtetraformiate (HCOONH4 ∙ 3HCOOH). We carried out trials during the summer of 1993 to investigate what concentration of acetic acid and Foraform is required for 90% of the weeds to die (LD90). We used concentrations of 24% and 6%. The test weeds were Sinapis alba and Poa annua. We investigated how the acidity of peat soil was affected by spraying with acetic acid or Foraform. To kill 90% of the Sinapis plants (LD90) treated in the four to six leaf stage required 0.27 l/m2 24% acetic acid (= approximately 0.064 l/m2 100% acetic acid) and 0.29 1/m2 for 24% Foraform (= 0.069 l/m2 100% Foraform). The equivalent values for the 6% concentration was 0.80 l/m2 (= 0.048 1/m2 100% acetic acid) and 0.72 l/m2 (= 0.045 l/m2 100% Foraform) respectively. The plant density in the trial was 354 plants per m2 and the weight of the weeds was 616 grammes per m2. The trial showed that acetic acid and Foraform had a similar effect on the tested weed Sinapis alba. To kill 90% of the Poa annua (34 500 shoots/m2 and 8 cm tall) required 0.28 l/m2 24% Foraform (= approximately 0.068 l/m2 100% Foraform). The LD9O values were 0.96 l/m2 for 6% acetic acid (= 0.058 l/m2 100% acetic acid) and 0.75 l/m2 for 6% Foraform (= 0.045 1/m2 100% Foraform). No conclusion can be drawn from the trials concerning any similarity in effect between acetic acid and Foraform on Poa annua. A smaller quantity of the active substance (dose) was required with 6% solutions than with 24% solutions at (LD9O). The dose could be reduced by a quarter for the acetic acid and by a third for Foraform, when Sinapis alba and Poa annua were treated with 6% solutions. The pH-value of peat soil sank from 7.3 to 5.6 after treatment with 0.24 l/m2 of 24% acetic acid or Foraform. The original pH-value of the soil was restored after two days. Even though the trials with acetic acid and Foraform in concentrations of 6% and 24% show that they can be used for weed control, they cannot be recommended for use on a large scale on hard surfaces until we have investigated their impact on the environment and the implications for the user. Moreover, we lack knowledge and experience of how surrounding vegetation and surface material (concrete, paving etc) are affected by the treatment.

Keywords

ogräsbekämpning; alternativ ogräsbekämpning; ogräs; ättika; Foraform; organiska syror; karboxylsyror; hårdgjorda ytor

Published in

Rapport - Sveriges lantbruksuniversitet, Institutionen för lantbruksteknik
1994,
Publisher: Institutionen för lantbruksteknik, Sveriges lantbruksuniversitet

Permanent link to this page (URI)

https://res.slu.se/id/publ/125586