Title: Eucalyptus globulus leaves incorporated as green manure for weed control in maize
Abstract: The use of Eucalyptus globulus (eucalyptus) leaves for weed control in maize-based cropping systems is proposed. Aqueous extracts of E. globulus are known to exert phytotoxicity on many weeds and crops, but there is also experimental evidence of the relative tolerance of maize. Based on in vitro dose-response bioassays of leaf aqueous extracts, we conducted greenhouse pot experiments testing incorporated eucalyptus leaves as green manure. The phytotoxic effects were tested on the germination, establishment and growth of maize and some representative accompanying weeds, in comparison to the pre-emergence herbicide metolachlor. Eucalyptus fresh leaves incorporated into the soil as green manure at 1 and 2 % w/w controlled the emergence of the dicotyledonous weed species redroot pigweed and black nightshade. After one month of incorporation, both doses reduced more than 94 % the aerial biomass of two monocotyledonous weed species (barnyardgrass + large crabgrass) with respect to the eucalyptus-free pots, and around 80 % for the small seeded dicotyledonous. Although the aerial biomass of maize suffered a 33 % reduction, the final relative yield of maize biomass with respect to the untreated control increased by 37 %. On the assessment of the temporal phytotoxic effects, the reduction of aerial biomass in maize could be overcome by adopting a relay-planting of maize after 12 to 15 days from eucalyptus incorporation. Our results constitute evidence that the incorporation of E. globulus residues to soil could be a feasible practice to reduce the reliance on synthetic herbicides in maize-based cropping systems. [Carolina G. Puig, Lorena Álvarez-Iglesias, Manuel J. Reigosa Roger & Nuria Pedrol (2012). Eucalyptus globulus leaves incorporated as green manure for weed control in maize. Weed Science, online 18 July 2012. doi: dx.doi.org/10.1614/WS-D-12-00056.1] ${imageDescription} Comment
Keywords: Bioherbicides, Zea mays, phytotoxicity, dose-response, pot experiment, relay-planting