Enchytraeid-stimulation of nitrogen mineralization from green plant residues in an organic soil

Abstract

Faunal-mediated nutrient cycling, especially N mineralization, has the potential to make a significant contribution to nutrient supply to crop plants in production systems involving e.g. green manure cover crops. We investigated the effects of enchytraeids on N mineralization from mung bean residues in microcosm experiments using an organically-farmed soil with an inherently large population of enchytraeids. Enchytraeids promoted N mineralization by 23% after a distinct lag of between four and 12 weeks, concomitant with a substantial increase in population size followed by an almost complete collapse. Nitrogen release from the necromass would have contributed a small but significant fraction of the N mineralized, and the result suggested the presence of other mechanisms. Enchytraeids suppressed nematode populations, while did not affect the mean weight diameter (MWD) of soil aggregates, although mung bean residues increased MWD. We conclude that enchytraeids have potential to play significant roles in mediating N supply to crops but matching supply-and-demand periods may be challenging.