Evaluation of Trellis System and Subsurface Drip Irrigation for Wine Grape
This study is being conducted in a 15 acre Sauvignon Blanc vineyard located on the California State University, Fresno Agricultural Laboratory. The vines are grafted to Freedom rootstock and were planted on a spacing of 8′ x 12′ (vine x row) in 1992. Row direction is north to south with approximately 70 vines per row. The experimental design used is a randomized complete block and data are analyzed as a two-factor factorial. Treatment factors include four trellis systems and four irrigation methods. Trellis system treatments are as follows: 1) Bilateral Cordon (BC) on standard two-wire vertical trellis; 2) Open Lyre (OL); 3) Geneva Double Curtain (GDC); and 4) Minimal Pruning (MP). Irrigation scheduling treatments are as follows: 1) Above ground drip (AGD) with water application of 0.8 of crop evapotranspiration (Et); 2)Subsurface drip irrigation (SDI) with water application of 0.8 Et.; 3) SDI with water apphcation of 0.6 Et.; And 4) SDI with water application of 0.4 Et. The 1997 season represents the third year of data collection for this project. As in previous seasons, differences were observed in the management of the irrigation systems. Use of SDI allowed for reduced apphcation of herbicides. One or two applications of glyphosate could be avoided because berms were dry. Conversely, use of SDI required increased efforts for control of gophers. Flow reductions were noted in certain SDI plots during the 1997 season. Examination of the affected areas showed that flow rate was reduced due to root intrusion. The concentration of trifluralin in affected emitters was measured. Trifluralin levels were found to be lower than that required to prevent root intrusion. This problem was traced to improper installation of the SDI tubing. New tubing was installed in all SDI plots during the dormant season. Significant irrigation method effects on yield and fruit composition were observed in 1997. In general, as irrigation deficit increased, yield level decreased. However, the number of clusters per vine was not statistically different. Cluster and berry weights were lowest for the 0.4 Et^e SDI treatment. Fruit maturation was delayed for the 0.8 Etvine AGD treatment. Consequently, the 0.8 Etvine AGD treatment had the lowest soluble solids and pH while having the highest titratable acidity. Trellis system also had a significant impact on yield and fruit composition in 1997. Yields were highest for the OL and MP treatments. Increased yield generally resulted from higher numbers of clusters per vine. Cluster weights were highest for the BC training system. Bilateral cordon and OL trellis systems produced higher berry weights than the other trellis treatments. Fruit maturation was delayed significantly for those training systems which had the highest yields. Vines which were minimally- pruned had significantly lower pH than the other treatments. Fruit from GDC vines had the lowest titratable acidity. Trellis system had a greater impact on vegetative growth than irrigation method during the 1997 season. Shoots per vine were significantly higher for minimally pruned vines. Total vegetative growth as indicated by mature nodes per vine was greatest for the GDC, OL, and the MP vines and lowest for the BC vines. Irrigation method had no significant effect on vegetative growth.