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 earthworm manipulations and agroecosystem fertility treatments on corn (maize, Zea mays) and weed biomass, and on nitrogen content. The experimental design consisted of inorganic (ammonium nitrate) and organic (cover crop and manure) fertility treatments. Within each fertility treatment, earthworm manipulations consisted of ambient, augmented and reduced populations. Both ambient and augmented earthworm population treatments resulted in greater weed biomass compared to earthworm reductions. Early season crop biomass was significantly influenced by earthworm reductions. Early season crop biomass was significantly influenced by earthworm × N source interactions, with greater maize biomass in the earthworm reduction treatment. In fertilizer and manure treatments, grain yields were higher in the reduced earthworm treatment compared to either 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.