Table 11 presents comparison results of the meta-analyses for EE
and GHGE. The structural variables of data source, sample size and
product type significantly affected the EE of organic farming in
comparison to conventional farming, whereas product type, cropping
pattern, and measurement unit significantly affected the
GHGE of organic farming in comparison to conventional farming.
The better EE effects for organic farming were primarily associated
with the field study's data source and sample size of more than 100,
whereas better GHGE effects for organic farming were primarily
associated with monoculture in cropping patterns and area based
measurement unit. The results support previous studies that
investigated EE with superior performances for organic farming
when the data were obtained from field surveys and experiments
rather than from secondary data. However, there were no differences
based on data sources for studies that investigated GHGE.