Here is the link to the original article from the LA Times.
view link The link I posted in my message was just the instructions on how to build a garden like this guy does. He is not concerned with it being pretty. I believe that given how thick this is, little if any water percolates through all the layers and the only moisture that will be on the inside of this pile is what was put there during the building of the bed. The same thickness that keeps more water from penetrating the bed in any great quantity would keep it from evaporating, as well, so ideal conditions would exist for decomposition to take place and the blood meal and bone meal provide the nitrogen needed for the soil microbes to rapidly decompose all this organic matter.
While I will have to check this out to be sure, I do not believe that farmers use herbicides on fields that are used for haying. Would be kind of counter productive. I suspect that little, if any, pesticides would be found on most hays or alfalfa. Hay fields are usually pretty low maintenance on a farm, mostly they involve the initial planting and then cutting several times a year. Eventually, the hayfield needs to be renovated, and at that point it is possible that an herbicide might be used, although I doubt that it would be.
Straw would be another issue altogether. There could be pesticide residue on some types of straw, depending on what kind of straw it is. In my part of the country it is not difficult to find organic farmers, so I would not have a problem finding what I need that is grown organically.