EARTHWORM EFFECTS ON CROP AND WEED BIOMASS, AND N CONTENT IN ORGANIC AND INORGANIC FERTILIZED AGROECOSYSTEMS

Results are reported from an experiment comparing the effects of earth worm manipulations and agroecosystem fertility treatments on corn (mai ze, Zea mays) and weed biomass, and on nitrogen content. The experimen tal design consisted of inorganic (ammonium nitrate) and organic (cove r crop and manure) fertility treatments. Within each fertility treatme nt, earthworm manipulations consisted of ambient, augmented and reduce d populations. Both ambient and augmented earthworm population treatme nts resulted in greater weed biomass compared to earthworm reductions. Early season crop biomass was significantly influenced by earthworm r eductions. Early season crop biomass was significantly influenced by e arthworm x N source interactions, with greater maize biomass in the ea rthworm reduction treatment. In fertilizer and manure treatments, grai n yields were higher in the reduced earthworm treatment compared to ei ther augmented or ambient earthworm treatments. This effect on yields was probably related to interactions with the weeds and damage to the maize by an insect pest. (C) 1997 Elsevier Science Ltd.