Saving water while increasing yield and quality? This is possible.

vineyard technology

Thanks to a grant received from the Water Metropolitan District of Southern California, we set up an experiment last year with the help of 6 independent wineries, under contrasted California climates. The goal of the experiment was to evaluate how much irrigation water could be saved and how was affecting yield and maturation compared to traditional irrigation practices.

The experiment consisted of comparing plant-based irrigation using sap flow sensors with traditional irrigationIn the sap flow-based treatment, irrigation was triggered each time vine water use dropped below a certain threshold. In the traditional treatment, irrigation was applied based on visual cues, site empirical knowledge and water potential measurements. Aerial pictures obtained in May were used to select uniform vineyard areas. Each area was divided to apply the 2 treatments side to side while vine water use was monitored continuously on both treatments. Fruit was sampled every 7-10 days to keep track of sugar loading and berry growth. 

Less than 5 irrigations across all location during a drought year

Because vine water use was continuously available online, sap flow-based irrigation resulted in less than 5 irrigations across all locations, versus 6 to 30 times in the traditional treatment. As a result, water savings using sap flow sensors were dramatic with on average 65% less water applied. Contrary to common thinking, water savings did not affect yield negatively and no difference was observed between treatments (NB: yield ranged from 2 to 4  tons/acres at each location). In fact, dehydration was sometimes observed when more water was applied early season. Thus, yield was even lower under the traditional treatment in 3 situations. There was also no difference in sugar accumulation rates between treatments. Brix at harvest was between 23 and 27 degrees; fruit quality was preferred in the sap flow treatment, which is a direct benefit from imposing moderate water deficit before veraison.
Conclusions
A lot of water can be saved in California by simply delaying irrigating particularly before veraison. Triggering irrigation according to a sap flow-based signal does not jeopardize vineyard production. On the contrary, it improves fruit quality by enhancing color and flavor. It also trains the root system to grow deeper and contributes to establishing a more sustainable vineyard. In some situations, applying less water makes berries less susceptible to pre-harvest shriveling in response to late season heat wave.
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