In the case of grape and other perrenial crops, there is a need for water management because water is highly involved in yield (as for any plant) and more importantly in quality. It is well known that some water constraint is necessary for high quality winegrape production.
Classical drainage is in use since the beginning of agriculture but is not sufficient for intermittently water-logged areas and perched water tables
Water-logging is detrimental to the growth of plants and no solution has yet been proposed to solution this problem. Water-logging is usually intermittent but most of the time affects strongly the plant at blooming time, reducing fruit production. Hence the need to find a way to recover proper plant growth and production ... see the solution below.
Perched water tables is a different story. Their effect can be un-noticed because nothing betrays their presence except a higher vigor of the plant. The problem here is that this kind of high vigor often translates as low quality fruit ... grape has to endure some sort of water constraint to produce secondary metabolites, markers of high quality wine during and after oenological processing. Thus if a perched water table is present, as ascertained by a higher vigor zone (among other physiological markers), the fruit produced will never reach the expected quality level.
Water is the most important input for winegrape quality and yield and requires specific attention. We propose the setup of efficient vertical drainage solutions in zones where water-logging occurs and zones where perched water tables are present. This action is the first step towards obtaining correct yields and quality and needs to be correctly performed. We have designed an original protocol (patent pending) for the precise location of the vertical drainage solution.
In the case of annual crops, the strategy is to optimise yield to the highest attainable level (Another aspect is the last Nitrogen input in the case of wheat to improve protein quality ... but this is another story) with the best possible inputs doses in order to reduce environmental impact. The zones where inputs have to be dose-adapted are delimited by UAV imagery or other means and the amount of inputs are defined by soil analyses results. Soil analyses locations are found by comparing imagery acquired for selected vegetation indices.
This approach is more time-consuming than considering only Nitrogen levels (generally proposed precision agriculture solution) but has the advantage of being rational and having a lot more chances of success. While it is not possible to give detailed data on ROI because of its high reliance on site/crop combination specificities, this ROI relies on multiple factors : highest yield, reduced input levels, reduced phytopathology treatments. All these factors are inter-related and achieved by improved water management (drainage, irrigation) and improved inputs levels. Drainage is a very important aspect often under-appreciated but its impact is primarily to avoid water-logging and secondarily to reduce pathogen efficiency. A zone where drainage has not been optimised is the place where pathogen outbreak usually occurs when conditions are favorable. This is the reason why we always perform a drainage study at the start of precision agriculture projects.
The following animated gif (eventually click on it to see the animation) gives you an example of what can be done to recover correct plant growth (1) in case of water-logged areas or (2) in case of perched water tables.
