In February , scientists from Wageningen University & Research in the Netherlands and other institutes published an article [link (behind paywall)] about multi-year research performed at a field test location in Vredepeel in the Netherlands. They concluded that after 13 years of organic cultivation, organic agriculture was almost as productive as conventional agriculture, and with less nitrate leaching into the groundwater.
However, other scientists from Wageningen University & Research identified inconsistencies in the publication [link (behind paywall)] regarding the approach of the research and the interpretation of the results, and decided to reanalyse the setup and results. This showed that the crops cultivated were inconsistent over the 13 years: the early years involved more sugar beets while the later years saw more maize. This made it seem like the yield of the organic crops increased on average, although this was not the case for each crop.
In a comparison between the systems in later years (2011-2016), which saw the same crops being cultivated every year, the difference between organic and conventional agriculture in Vredepeel was a constant 20%. This percentage is in line with all recent meta-analyses, which examined the difference between organic and conventional agriculture based on a large number of studies.
Read full, original post: New analysis of research results: organic agriculture less productive than conventional agriculture