A single grapevine in the San Joaquin Valley may require up- wards of 12 gallons of water per day at peak demand. Most drip irrigation systems incorporate a wire hung approximately 16 to 24 inches above the ground to support the irrigation tubing along the entire length of the grape row. During system operation, water is applied between the vines from the drip emitters. While this system has proven effective, several caveats also must be considered. First, above ground drip irrigation promotes weed growth and moisture directly under the vines.
Weeds are more difficult to control here as opposed to the row centers.
Preemergent herbicides are washed out during the growing season due to the large amount of water applied under the drip emitters. Most vines are grown on berms, and in tighter soils water runs off to form tire ruts in the rows. Finally, moisture is always problematic under the vine canopy, especially where the drip emitters are placed. Mechanized harvest equipment can also cause dam-age to drip emitters hung from the wire. These harvesters employ beaters and shakers which are apt to strike the emitters and tubing during harvest.