Water is the lifeblood of tomato cultivation

Sébastien Manelli uses GroSens to precisely manage the irrigation of his tomato crops. Fully convinced of the benefits of increasing the number of measurements to improve the precision of the tool even further, he told us all about how he combines the data collected from fixed sensors with that from a mobile one that passes through all his production areas each day.

For three generations, the Manelli family has been based in the commune of Saint Martin de Crau at the foot of the Alpilles Regional Natural Park and just to the north of a stony and windy plain that stretches between the Rhône delta, the Camargue and the Étang de Berre. This family of market gardeners were originally from Marseilles and lived in the Mazargues neighbourhood, the former green belt of the beautiful port city, but their property was requisitioned 1980. When they arrived in Saint Martin de Crau, they discovered untouched land and plenty of water. Once settled, they gradually specialised in the production of tomatoes in greenhouses. Today, Sébastien Manelli manages Scea Saint Paty. It’s a family company with his father still heavily involved and his sister just joined the team.

Today the company cultivates their tomatoes on an area of over 4 hectares in some of the latest greenhouses, their farm has been completely rebuilt over the last 10 years. The irrigation system is set up to independently manage 8 units each covering 5000 m2. Their production is entirely dedicated to cultivating tomatoes on a rockwool substrate, more specifically on 10 cm-thick Grotop Master slabs. Over time, their single-variety vine tomato crop has been replaced by a more diversified range of crops. In line with the trade policy of the Rougeline group which the company, due to their membership of the Primeur de la Crau growers’ cooperative, belongs to.

A loyal GroSens user

For four years now, Scea St Paty has been producing at least 5 different varieties of tomato (cocktail, beefsteak, black, yellow...) with each variety benefiting from one or two production units that have autonomous irrigation management systems.

Sébastien Manelli has always used GroSens to help manage the irrigation on the farm. GroSens is the measurement system from Grodan that allows users to monitor the electrical conductivity, water content and temperature inside the rockwool slabs. Each of the 5000 m2 production units are equipped with two fixed sensors. They are positioned strategically in order to provide an accurate representation of the production zone. They’re usually not moved for the entire season. However, the GroSens sensors are very easy to move when this is necessary. “If a plant is ill or a bag has been pierced for example, we might move some sensors to make sure that the measurements that they take remain representative of the production zone,” clarified Manelli.

Easy to install, easy to use

The 16 sensors that the company owns (4 sensors per hectare) are all connected to the central computer by WiFi. A WiFi extender placed in the centre of the greenhouse ensures that all production zones get excellent network coverage. The sensors transmit electrical conductivity, water content and temperature measurements every 3 minutes. This data is supplemented with measurements taken by some older wired sensors (WCM) and, above all, by measurements taken manually with a GroSens mobile sensor. This task is carried out by Barbara Manelli who covers all production zones and takes between 30 and 50 measures per hectare every day to get the most precise picture possible of what is going in the centre of the stonewool slabs. At the same time, Barbara must also observe the plants. “Today, Barbara’s new position is absolutely essential because the more measurements we take, the better the GroSens system performs and the more reliable the information that it provides is,” explained Manelli, who finds this tool particularly easy to install and use. “GroSens is a tool that allows me to be more precise without losing too much time. You just need to take a minute every day to interpret the lines and pick out the information that’s useful for the crops, particularly with regards to irrigation.”

More measurements for more precision

“With our greenhouses oriented north south and the mistral as the prevailing wind, we often notice a difference in the water consumption between the north and the south zone. Thanks to GroSens, we can clearly see this disparity in the graphs and simply have to take a few hours to rectify the situation by adjusting the amount of water that we give the plants,” explained Manelli. “Our irrigation strategy evolves more or less in real time depending on the water consumption of each production zone.”

Since we started recuperating all drainage water and installed a closed circuit on the farm, the irrigation strategy has evolved in favour of increasing the rate of drainage. “Today we allow up to 50% of drainage whereas before we never went over 25% to minimise losses. This change has meant that we can now better cover the water needs of the plants throughout the greenhouse, thus reducing any disparities. To do this, we measure the amount of drainage in each production zone, the total drainage of the greenhouse and the electrical conductivity of the drainage water. The more data we have, the more precise we can be!” added Manelli. “The aim isn’t to give the plants more water, but to irrigate at the best moment to ensure maximum efficiency. From the month of April onwards, water is the lifeblood of tomato cultivation, particularly in our region.”

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