PARENT SESSION
Poster Session 24: Agro-Ecology
Wednesday, August 10, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal
Earthworm community dynamics in field enclosures under soybean production.
Eriksen-Hamel, Nikita 1, Whalen, Joann1, 1 Macdonald Campus, Montreal, Quebec, Canada
ABSTRACT- Earthworms are well known for their role in enhancing soil fertility. However, the contribution of earthworms to plant nutrition under field conditions has not been adequately described. The number of earthworms present and composition of species in the earthworm community are expected to influence plant nutrient uptake and growth. The objective of this study was to manipulate earthworm populations in controlled field enclosures and record the effect of different population abundances and species on soil and plant properties. Sheet metal enclosures were buried in the soil to prevent earthworm migration and earthworm populations were reduced using a carbaryl pesticide at the beginning of the experiment. Then, earthworms were added to the enclosures based on their ecological functional group (endogeic, anecic) and population level (normal or double background populations). The earthworm species Aporrectodea caliginosa and Lumbricus terrestris were used as the representative species for the endogeic and anecic species respectively. Earthworm populations were sampled after soybean harvest and identified to the species level. The weight and body length of individuals in three age classes was determined. We found that individuals of A. caliginosa dominated in all enclosures (66-80% of individuals) followed by L. terrestris (16-24%) and Aporrectodea longa (6-11%). Recently born earthworms (<0.2 g fw) represented about 39-50% of the population in all enclosures, indicating that a large number of earthworms were born in the autumn. We estimate that only 20-36% of individuals added in the spring survived until autumn and that 20-33% of the population were juveniles born from cocoons that survived the pesticide application. Earthworm numbers (222-378 ind/m2) and biomass (77-92g fw/m2) were significantly higher in treatments with double the background population compared to the control,which had the fewest earthworms (78 ind/m2) and lowest biomass (34g fw/m2). Soybean yield, nutrient content and nodulation was significantly higher in treatments with more earthworms than the control. Our results suggest that earthworm communities, when sufficiently numerous, can increase soybean production in agroecosystems.
Key words: earthworms, population dynamics, nutrient dynamics, community structure