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Can we fight climate change without irrigation?

Can we fight climate change without irrigation?

Low rainfall and higher temperatures in the vineyard due to climate change can lead to a reduction in production levels, changes in the qualitative parameters of the harvest and an acceleration of phenology.

To deal with this situation, the most immediate response is irrigation, a technique which, however, only partially compensates for its effects. On the other hand, the growing concern for the preservation of water resources makes it necessary to evaluate the application of alternative techniques.

At the vineyard level, there are alternative techniques such as vine shading, mulching or density management, which, in order to be effective, must be integrated into a global strategy of adaptation to climate change and not carried out individually.

The IFV (Institut Francais de la Vigne et du Vin) has published a report on the results obtained recently evaluating some of these alternatives:

Actions at the plant level: leaf/fruit ratio management.

Trials were conducted in the vineyard to study the effect of yield on water stress. The results show that, if water stress differences occur, they are observed late (after veraison) and/or at high water stress levels, which do not allow an acceptable level of production. The main conclusions of these tests are the following:

  • In a situation of moderate to high water stress, modulating grape load does not provide a sufficient response to compensate for the effects of drought. Reducing the grape load does not allow to better withstand the period of high stress, also causing effects on ripening that tend to accelerate the concentration of sugars in the grapes in situations where early maturity is often a problem.
  • Acting on vegetation height has very little influence on sensitivity to water stress and does not compensate for a period of drought.
  • If the measurements show a greater sensitivity of high-density plots to water stress, the interpretation of these results should be complemented by taking into account the effects induced on the one hand on the quality of the harvest and on the other hand on the conservation of yields.


Climate-related actions

Possible actions in the vineyard to limit climate pressure mainly involve reducing light intensity. Different solutions for shading the vineyard are currently being implemented, mainly using shading nets or photovoltaic panels. Trials are underway to study the effect of the period and intensity of shading.

First results: the effect of shading on water stress is significant and long-lasting, even in a situation of high sensitivity to drought. On grapes, shading induces a delay in sugar maturity and a delay in the harvest date of about 7 to 10 days, but it is accompanied by a decrease in the color intensity of the grapes, therefore, it will have to be evaluated according to the variety or type of wine.

Actions at soil level

Improving the water status of the plots at soil level involves two main types of action: limiting water losses by direct evaporation through the use of surface mulches, or improving the water retention capacity by modifying the physicochemical characteristics.

Regarding the reduction of water losses by direct evaporation, several tests were carried out by applying a RCW mulch about ten centimeters thick. The results under different pedoclimatic conditions did not show a significant effect of this type of practice on sensitivity to water stress.

Regarding the improvement of soil water holding capacity, measures related to soil organic matter content were studied. Soil performance was greatly improved, but the results did not show a positive effect on the reduction of sensitivity to water stress, although the use of soil improvers and water retainers are certainly very promising tools. The problems to be solved are: for the former, the timing of application, which must be early enough to induce product durability, sometimes incompatible with the biodegradability that characterizes them, and for the latter, placement in the root zone, which is physically difficult to achieve in adult vines, unless products capable of migrating in depth are used.

The use of biochard (products obtained from roasting organic matter) is currently being studied. This involves the use of by-products from the wine industry as part of a virtuous circle by creating biochard from purified grape skins. This biochard is nutritionally inert organic matter, but stable over time and with water adsorption properties. This type of product contributes to improving the organic matter content of the soil and to storing carbon. Compared to simple compost inputs, biochards are shown to be effective in reducing water stress, growth dynamics and improving berry weight. New trials are underway with these products, which remain, along with shading, one of the only effective solutions for limiting the effects of drought in the vineyard.

Conclusions

There are not many technical options that can be applied in the vineyard to limit the effects of climate change. These actions, taken individually, are not very effective, with the exception of shading or water retention in the soil, which offer interesting prospects. The effects induced by delayed ripening are more numerous and must be evaluated considering the typicity of the wines produced and the possible risks of delayed harvests on the yield or the health of the grapes.

Therefore, the impact of a single cultivation practice seems to be rather limited in scope; it is necessary to evaluate the impact of the sum of these individual actions as an adaptation strategy in the face of climate change. Moreover, in a context where water resources are limited, the optimization of irrigation quantities used combined with these technical options should be evaluated. Among these options, soil management, leaf/fruit ratio or planting densities represent interesting possible avenues. On the other hand, the choice of plots according to their agronomic potential and the evaluation of planting material are more relevant than ever.

Read the original article in French

Source: IFV

Published on 05/09/2023
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