PHENOLICS ADSORPTION TO SOIL REDUCES THEIR ALLELOCHEMICAL ACTIVITY

Abstract

Allelopathy could be used to reduce weed infestations, but adsorption of afielochemicals to soil can reduceits effects in agro-ecosystems. The objectives of this work were to study the effect of caffeic, ferulic, and salicilic acids, andcatechol on Selaria faberi (SETFA) germination in Petri-dish and soil bioassays, and to determine the adsorption of thesephenolic compounds to a silt clay loam soil. Petri-dish experimenta, using SETFA as the indicator species, showed that theallelopathic potential of the phenolics tested was: iferulic acid > catechol > salicilic acid > caffeic acid. Caffeic acid, up to 27mM, did not affect SETFA germination. SETFA germinated better in soils than in Petri-dish experimenta, suggesting thatadsorption plays an important role on the performance of the phenolic acida. Adsorption of the phenolics to soil ranged from10 to 40 % of the applied concentration. Caffeic acid and catechol had more affinity with the soil than salicilic and ferulicacids. The rate of these phenolics in 12 t/ha of wheat straw is not enough to reduce SETFA germination in the field. Theseresulta indicate that allelochemical activity may be limited by their adsorption to the soil.'

Keywords

• no-tillage, wheat, selaria faberi, giant foxtail