Earthworm influence on N availability and the growth of Cecropia schreberiana in tropical pasture and forest soils
This greenhouse study examines the effects of Pontoscolex corethrurus on the growth of Cecropia scheberiana in forest and pasture soils. Four treatments (0, 2, 20 worms and 0 worms + urea fertilizer) were applied to the soils to test if earthworms affect nitrogen availability, and consequently the growth of C. scheberiana. We recorded the number of seedlings, leaves, and height of plants, and measured NH4+ and NO3- concentrations in water leachates during a six month period. The growth of C. scheberiana and nitrogen concentration in leachates differed between pasture and forest soils. Addition of 20 worms per pot doubled nitrate and ammonium concentrations in leachates as compared with the controls. However, earthworms did not affect the germination of C. scheberiana in both pasture and forest soils. Although earthworms did enhance nitrogen availability and mineralization, we conclude that nitrogen is not a limiting factor for Cecropia growth in either pasture and forest soils.