Many of these factors can be corrected most effectively before planting, without existing plants or trellises obstructing access to the entire block. In a new vineyard, you have the most options and the greatest chance f success with complete vine and trellis removal before replanting. This is your only choice hen the existing vineyard has serious, correctable limitations. Renovation allows deep ripping to loosen hard pans and pull up old vine roots. You can leave blocks fallow or plant cover crops to improve soil health and reduce phylloxera and nematode populations.
Fumigation is only an option in the absence of growing plants.
Soil nutritional modification requiring deep incorporation of phosphorous, potassium, or lime is most convenient in the absence of plants or trellis structures. Permanent modifications of new blocks such as changes in trellis systems or vine spacing or installation of drainage tile also require a fresh start. Replanting with the existing trellis You should only replant within an existing row if the plan and organization of the vineyard is acceptable and the trellis system has a minimum of 10 years of life remaining. Many of the major vineyard modifications discussed above are not possible if the trellis structure is retained. How to remove the old vines may be a difficult decision.