GRAPE IRRIGATION IN SWITZERLAND
The criterion for irrigation was based on the mean value of three tensiometers located at a depth of 60 cm with 0.4–0.5 bar of suction.
After nine years of testing it was possible to confirm that irrigation in Leytron increased yield up to 21% on Casselas and Gamay and only 8% on Pinot. In these cases the water and the increased crop slightly raised the total acidity content of juice and the importance of botrytis and slightly decreased the concentration of sugar content.
After seven years of testing in Changins, irrigation only once had (1984) an effect on yield (+27%) with an important negative effect on sugar content of juice (-9%). In the other years, the effect was null on yield, although it sometimes increased total acidity and decreased sugar content. During this period, we observed no interaction between irrigation and cultural practices on yield and quality of juice.