Culture durable

Grodan Prestige: Comparative test under Breton conditions

After just over a month of harvesting, the initial results of a comparative trial between stone wool and coco substrates are encouraging. The Grodan Prestige stone wool slab adapts well to soilless tomato production conditions. At 8.25 kg/m² after 6 weeks of harvesting, Grodan Prestige improves yield by 7 to 10%.

In partnership with Grodan, the Caté experimental station in Saint Pol de Léon, at the heart of Brittany's vegetable and horticultural production zone, has set up a trial of soilless tomato cultivation, with the aim of comparing the behaviour of the plants and the environmental efficiency of the crop as a function of the nature of the substrate. "The Grodan Prestige stone wool slab was chosen for its versatility and competitive edge over coco substrates", explains Hans Baekelmans, Grodan's technical advisor for the Brittany and Northern Europe regions. Three types of substrate were compared in the trial: Grodan Prestige 10cm-high slab, buffered coco and unbuffered coco in the reference volumes commonly used in Brittany. The trial was set up in mid-December 2020 (pre-planting in week 50) with the truss tomato variety Luminance and an initial density of 2.33 plants/m². This density was then increased to 2.9 plants/m² from week 5, rising to 3.5 plants/m² from week 10. Harvesting began on 18 March, initially with trusses of 5 fruit. It continued from the beginning of May with trusses that had been pruned to 6 fruit.

20210520 RW-GR PHO 5460
^{Grodan Prestige}

^{Dabbed coco}

^{Unbuffered coco}

The first differences between the substrates became apparent as soon as cultivation started, particularly when the slabs were saturated with the solution. Unbuffered coco, naturally high in sodium, had to be washed out by a calcium-rich solution. Approximately 50 l/m² of solution were needed to remove the sodium from the unbuffered coco to acceptable levels, a leaching period of around two months, which delayed the possibility of starting to recycle the drain water with this substrate. In addition, the high tannin content of coco substrates leads to discolouration of the drainage water at the start of cultivation. This colouration can pose a problem during the UV disinfection process. "Under these conditions, only the method grown on stone wool is able to recycle the drainage water from the start of cultivation, giving the Grodan Prestige substrate an advantage", stresses Hans Baekelmans.

With a lower drainage percentage, the results of Grodan Prestige show that stone wool improves irrigation efficiency. More water is absorbed by the plants, which synthesise more dry matter, resulting in higher yields.

20210527 GR ILL 5134

This trial experienced a period of low light levels in January and February, followed by very sunny months in March and April. The relatively high levels of salinity at the start of cultivation did not cause any particular problems; on the contrary, they enabled better control of the generative development of the plants. From this point of view, the three types of substrates behaved fairly similarly. On the other hand, during the very bright period, the stone wool substrate was watered later at the end of the day, while maintaining a total loss of humidity comparable to that of the two coco substrates. This extension of the irrigation period enabled the plants to remain active and to prolong their transpiration phase, thus favouring fruit size.

After the first month of harvest (April), the production data is favourable for Grodan Prestige. Although the number of trusses harvested was more or less the same, the average weight of the fruit was slightly higher in the case of Grodan Prestige, giving this variety a certain lead in terms of cumulative yield. After the first 6 weeks of harvest, production on Grodan Prestige reached 8.25 kg/m², i.e. 7 to 10% higher than the other two methods. These results are all the more interesting given that the period corresponds to favourable market conditions, before the increase in production drives prices down.
For Alain Guillou, who was in charge of this trial as part of his mission to monitor the greenhouse and soilless farming vegetable trials at Le Caté, it is important to have good control over the management of the crop throughout the season. The end of May corresponds to the first harvests of 6-fruit trusses and the start of production of all the stems corresponding to a density of 3.5 heads/m². "It is important to be familiar with the behaviour of each type of substarte in order to adapt the cultivation management accordingly. The ramp-up in production and changing weather conditions in late spring and summer are important factors to take into account. After that, it will be interesting to study the behaviour of each of the substrates during the period of waning days and right up to the end of the season", adds Alain Guillou, who looks forward to seeing you in a few months' time to assess the results of this experiment.

Our Blogs

Water Management

“In ten years we will be eating lit cultivated cucumbers all winter long”

Growing cucumbers year-round in the Netherlands is feasible, meeting the rising demand for local, reliable fruit and vegetable production.

By Gursel Karacor

e-Gro

Video Vlog: Combining plant science with data science

Blending plant and data science is essential for efficient and sustainable fruit and vegetable cultivation. How can this integration be effectively applied?

How Grodan and Walker Environmental Solved a Waste Management Challenge

Whitepaper: The future of medicinal crop cultivation

Whitepaper: How Grodan and Fluence are mastering the art of growing medicinal crops

Whitepaper: Optimal irrigation strategy for large-scale production of medicinal crops

Sustainability

Grodan Prestige: Comparative test under Breton conditions

Our Blogs

“In ten years we will be eating lit cultivated cucumbers all winter long”

Video Vlog: Combining plant science with data science