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Two growers' experiences with Grodan Water Management
Even better control over the root environment
(Source: Onder Glas Nummer 4 June 2004)
Grodan water management can be used to monitor and manage watering in order to achieve the optimum growth and development of the plant. Rose grower Boonekamp uses the system mainly as a means of checking the situation. Tomato grower Rutten now has greater peace of mind as he can monitor the water consumption and the EC continuously.
Marcel Boonekamp: "We use water management to check and adjust the starting and finishing times, for example."
On Boonekamp's 23,000 m3 large property (run by father Leo, mother Petra and their sons Erik and Marcel) in municipality of Berkel en Rodenrijs, red Grand Prix roses are grown on a stone wool substrate medium under artificial lighting (10,000 lux). The grower switched from tomatoes to roses in September of last year.
Boonekamp has been using the Grodan WCM-continuous water content meter for two years now. This meter can be linked up to the graphics program of any brand and type of climate computer. The WCM-control, a hand-held meter, can also be used when making a weekly walk around the farm, taking measurements at 40 points.
Rose grower Boonekamp wants to counter imbalance
By interpreting the graphs provides by the WCM-continuous meter (showing water content, EC and temperature), the grower can check – in the substrate – whether his watering settings are correct and whether they are appropriate for the conditions in the root zone, the state of the crop and the climate. According to Marcel Boonekamp, "depending on the irradiation, the resting time and the drainage percentage, the slab needs to have reached saturation point within the first three watering sessions, and have started to drain off.
The first trickle irrigation session is larger in scale, in order to push through the old water. After that, we use the same quantities of water for each trickle irrigation session, which are partly dependent on the time of year. During the day, the water content of the slab therefore fluctuates at around the same level. We aim for 50 to 55% drainage in order to counter the imbalance. This percentage may be lower for tomatoes as the plants grow more evenly. However, for roses, the crop is more uneven in its growth, and there are more differences in pH and EC in each rose bed."
Monitoring
Boonekamp does not use the measurement data to steer by means of the water content. They have occasionally noticed incorrect figures that would cause problems in watering. A single continuous meter is then the decisive factor and that can be punished severely. "We use the water management for monitoring and adjusting the starting and stopping times, for example. Due to the cutting effect in roses, the number of roses each week may be greater or lesser. We adapt our watering accordingly."
According to Boonekamp, growers tend to be more afraid of using too little water than they are of using too much. Growing in conditions that are too dry brings a risk of extremely low figures, resulting in a sacrifice of production in certain dry spots. The water content meters mean growers can be more aware of the situation. "The fewer mistakes that are made in terms of watering, the better the yield."
Tomato grower Rutten works with large-scale watering sessions
The Bleiswijk-based Rutten brothers, Jacques and Hans, grow three hectares of truss tomatoes (RZ 72,454) using non-grafted plants in rock wool grooves. They have been using the WCM-continuous meter since February of last year, and have been using the new Gronow water management software since the start of the current growing season.
Jacques Rutten examines the measurement graphs closely, particularly the EC values, which he wants to be as constant as possible.
"We like to work with large-scale watering sessions of 470 cc/m2 per session in order to refresh the water, and not to cause drainage every day. On an annual basis, drainage is between 20 and 25%, which is favourable for root development. The EC value of the water is also fairly constant and – dependent on the weather – lies between 2.6 and 3.0 mS/cm. If the drainage rate is higher, we water less," says Rutten, who also takes account of the state of the crop when watering. " A good water content level in the slab combined with good roots results in a strong crop."
Constant watering
Large-scale watering sessions are used from mid February onwards. In the morning of the third trickle irrigation session, Rutten checks whether the slab is draining, and adjusts the irrigation accordingly. If irradiation increases, the frequency of watering is also increased. "For large-scale watering sessions, you do need a certain type of rock wool (Grotop Mastermat), otherwise the substrate gets too wet. Drainage only takes place on one cross cut side of the 1.20m long slab. This results in a good levelling out of the water before being absorbed by the plants, two out of three of which have an extra stem."
Yield Rutten considers water management to be a good monitoring tool, as the water consumption and the EC can be seen. The advantage of this is more control and monitoring, even on the drainage EC, and the fact that the data is more up-to-date. "Otherwise, we would only become aware of the situation when we saw the actual crop. Now we are ahead of the game!" according to the tomato grower.
"The direct yield is difficult to ascertain, but we have greater peace of mind regarding watering. We only make adjustments for irradiation, and our production is currently at an optimum level. Our production last year was over 60kg per m2." He also picks up new things from communicating with other growers via Grodan.
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Daily dynamics, WCM (2 days)
Crop: RZ 72,454
The two-day trend in water content and EC in the
slab are plotted against the quantity of water and
the rate of drainage. Together with the combination
of daily data of irradiation levels, cc per joule and
drainage percentage, both the grower and the
remote adviser are able to analyse the situation in
the slab at a glance.
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