Not surprising Dan. I think the farmers I deal with in Northern Alberta when I work over there said expect around 30% of your normal harvest if you use chemical fertilizers. A few that checked into it with the idea that they might give it a try said that the extra money for organics don't compensate for the reduced yields.
The laughable part is that nitrogen is an element. The plant couldn't care less what type source it comes from and it doesn't matter the source, it still has the same number of protons, neutrons, and electrons otherwise it's not nitrogen anymore. The biological part of the organic fertilizer may affect the plants uptake of the nitrogen but it's still nitrogen. Same goes for the phosphate and potash components and sulphur as well.
As for the chemicals that fight crop pests and diseases, well we can't do without them anymore. Worldwide there already isn't enough food to go around and without intensive farming practices that include the use of genetically modified seed and crop protection chemicals there would be a lot less and what there is would be more expensive. One of my clients in Grande Prairie, a 3rd generation farmer who farms about 7000 acres, says that if we went back to non GMO seed that it would condemn 100,000 people to die everyday until there was a substantial population reduction.
A little "food" for thought.
Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.