Hello MMM,
Yes, I know that there is <font color="green">some root pruning</font> when you cultivate inside the drip zone, but this has been shown to stimulate growth (unless you go nuts and cultivate too deeply.) in citrus trees. The main thing to keep in mind is not too often. Tolerate ankle to knee high weed growth as that is a good indication of soil moisture and nutrients.
There have been studies that demostrate to both conclusions that chemical residue ends up in fruit (personally, I beleive that who ever funds the study, can make it say what they want). While I don't go organic completely (I do fertilize twice a year with ammonium sulfate [21-0-0]) I don't use anything else on the fruit. If you like the way the crap from the grocery store tastes, well you are getting the full load of the commercially grown flavor that the pesticides leave. Once in the store, the stores themselves continue to dose the fruit with chemicals to lengthen the shelf life and for cosmetics. If you enjoy the herbicide grown type of fruit, enjoy.
For me, I'll pass and I'll continue to cultivate my fruit thank you.
phil