I own a small vineyard in Oregon, where the hills are steep and it is wet and muddy way too much. I have about 3600 Pinot plants, planted at 8foot spacing about 20 years ago. I have never used a tractor with more than 35 hp, and neither do most people with small plots around here,big mega farms are a different story. you don't need a muscle bound tractor to run a 50-100 gallon sprayer,it's overkill. The same goes for a flail mower or brush hog, remember you can only get 5 foot wide or so equipment down your rows. I don' allow my vines to protrude 2 feet out into the row, that would create too much shade on the berries, and prevent your fungicides from covering everything adequately. my footprint going down the rows is 66 inches, the rear tire are loaded with beet juice for traction. remember, soil compaction is bad for your plants,muddy vineyard floor( aggressive tire tread) creates a planting bed for weeds,using weed killer to kill weeds is bad for your grape plants,so step lightly on your vineyard floor. Also, your vineyard will soon create it's own terrace as you work it, it always does, and that will help in keeping traction on the hill. I never use the four wheel drive on my vy as it is not needed, and tears up the cover crop between the rows, which leads to......more weeds.
by the way, if no one ever told you, raising good wine grapes is a fascinating challenge,no two years are ever the same, and that's why vintage is such a big deal in wine.
