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  I recall in the early/mid 80's  my father telling me that he felt the Fusilade we applied to remove grasses from the legume pasture had caused some detrimental effects.

At the time  in my youthful short sightedness, I attributed the comment largely to senile foolishness.  

It is well documented here  now,  that the grass selectives DO upset the soil biota, and will disrupt the N fixing of legumes.

Dad has been gone 21 years, but in some ways he still comes back to haunt me, about a good few subjects.

Everything is trade off against conflicting needs.