Abstract:
Environmental degradation and consumer awareness are raising concerns about the sustainability of conventional farming
while increasing interest in organic farming as an alternative
food and fiber production. Well-replicated studies during the
transition are necessary for testing the causes of observed
changes. To test soil property changes following conversion,
we collected data from 18 dairy farms (nine converting and
nine that remained under conventional methods) in the
Waikato, Taranaki, and Manawatu regions of New Zealand. Soil
properties on the converting group were compared with
matched farms that continued with conventional methods.
Converting to organic did not result in increased total carbon
or nitrogen, but phosphorus decreased by 42%. Bulk density
decreased by 3.5% in converted farms but increased by 9.8% in
conventional farms. Earthworm densities were higher in organic
farms but there was no significant change in soil microbial
parameters. Total nitrogen was lower where microbial respiration was higher but there was no evidence of a link between
earthworms and soil nutrient levels. This observation challenges
whether the observed changes in studies of farms that have
already converted are indeed caused by organic farming methods themselves. Long-term studies are needed before the
broader implications of conversion can be fully assessed.
