The testing was done using the Morrow plots which have been cultivated since 1876 and carefully studied with respect to soil chemistry ever since so this is no slap-dash study. This is really not new to us organic types and as far back as 1947 Sir Albert Howard the great British agronomist who advocated organic practices stated unequivocally in his landmark book The Soil and Health that:
The use of artificial manure, particularly [synthetic nitrogen] ... does untold harm. The presence of additional combined nitrogen in an easily assimilable form stimulates the growth of fungi and other organisms which, in the search for organic matter needed for energy and for building up microbial tissue, use up first the reserve of soil hummus and then the more resistant organic matter which cements soil particles.or , in other words, synthetic nitrogen degrades the soil. While I and my fellow organic gardeners and farmers have known it from direct experience it is nice to see the scientific community come up with hard science to back us up.