Billy wrote: ...
unfortunately there isn't one overall study of the whole 30yrs, but instead a series of smaller studies and they did change their methods every so often for the organic plots as they learned a better rotation schedule.
i've skimmed through a few of them and found a few items of interest. when i get more rainy weather and have a bit more time i'll write up reviews of each.
organic methods can still have nitrogen leaching problems (if the nitrogen generating cover crop (they had a bumper hairy vetch crop) is turned under and the following crop doesn't grow well (weed problems caused a failure with the corn crop) then the leftover nitrogen still goes into the ground water). i'm not sure how that compared to the nitrogen leaching from a conventional fertilized field for that same season. i still have to go through that one again more slowly.
though i think the overall comparisons were done well enough, including accounting for any extra labor that was required for the organic spaces.
i'm not really sure if they gave the organic method a credit for generating the nitrogen that was used by the following crops and of course they did put the seed costs down as minus, but for an organic farm that is saving seeds this expense could be much less too (after the equipment for seed cleaning has paid for itself the rest is all gravy).
songbird