18:54 Mar 21, 2011 

There's nothing wrong with "reduced vigour".

You might want to rephrase slightly:

Traditional Friulian training system adapted by our/estate agronomists to ensure lower yields and enhanced quality by restricting vine vigour and reducing bud load.

Note that "aziendale" refers to the estate or winery ("azienda agricola") so "company" might be inappropriate or misleading. The training system referred to is presumably the fairly high-yielding Cappuccina, or Friulian arched cane.