We began the project in 1990 and planted cover crop to assist us with ongoing mildew and mite problems that had been occurring for many years. The vineyard is planted in deep yellow sandy clay loam. We planted perennial rye and sub-clovers to reduce vigor and allow for early entry into the vineyard. This cover crop was too aggressive causing vineyard nitrogen levels to drop 80% in 2 years time. Because vigor was reduced so greatly, we needed to change cover crops due to crop loss and vine deterioration.
In 1995 we re-planted to annual rye, Idaho fescue, crimson clover and rose clover. The way we treat this area is by mowing only three times a year. The first time is in March for frost control. The second time is after the Idaho fescue and rye have seeded out, and the third time usually takes place in July once the clover has dried.
The results are that we have adequate vineyard growth that only requires trimming twice a year. Crop levels are consistently between 4 to 6 tons per acre. No irrigation or discing has occurred since 1995. Mildew has been greatly reduced because we are able to enter the vineyard earlier to apply the sulfur at the proper time. Mites have been reduced due to predatory mite population being maintained with proper cover crop regimen. Nutrient levels in the vineyard have fluctuated very little with nitrogen levels returning to normal range without fertilizer inputs.
In closing, the results from permanent cover crop have been that we have reduced mildew, eliminated mites as a problem and we have had the added bonus of improved wine quality.