Without control though your data on yeild will mean nothing.
I equate this to the theory of "stem Splitting" or "Nail Splitting"
I took the following exerts from the following webpages:
totse.com | The Marijuana Grower's Guide
"
Tacks and Nails
Some growers hammer nails or tacks into the stems of plants several weeks before harvest. Many growers use long thick nails; others prefer to use several half-inch-long tacks. The nails are usually placed at the base of the stem. This is supposed to "increase potency." {Figure 72. Wilted plant. Unless watered it will die
.}
Stem Splitting
This is a popular way to stress used by cultivators in the United States. The stem is split (not cut) at the base to from a space through the stem. Growers place a rock, small piece of wood, an old Cannabis stem, or piece of opium (in Africa) in the split. Sometimes the wound is bound with cloth or plastic. We don't recommend this procedure, and advise you to be careful not to kill the plants and ruin the harvest."
http://users.lycaeum.org/%7Esky/data/grow/c15.html