Every participating grower in one of the polders mentioned is going to measure the nitrate content and EC of the surface water at a certain point. Marc Noordam: "We are going to take the point where the basin water of the Heenvaart and the Geestvaart flows in and out of the polder. At that point we conduct a manual measurement of the EC and the nitrate content every fourteen days." He is leading the lily company together with his father Peter.
The newly developed EC meters and color strips for the nitrate content are made available by the district water board. There is a smartphone app to determine the coloring of the strip. After a measurement has been conducted, the data can be uploaded to a special platform and can be viewed by participating growers. Now the water quality is improving it makes sense to extend the measurements. The impact of greenhouse farming on the water quality is being reduced because of measures taken by companies. The impact of other factors is relatively growing. For greenhouse farming it is important to, besides their own impact, to chart those external factors, and that is a motivation to participate.
Good quality surface water
The grower of lilies: "As a company we have an impact on our own surroundings. We benefit from good quality surface water, because we use it besides rain water for irrigation. The ditch water here is sufficient for lilies because of the pH value of 8 and an EC value of 0.8. Moreover, it contains lots of bacterial life, which stimulates life in the ground. Lilies are luckily not as sensitive to high NaCl values. By monitoring the surface water at multiple points we can see what happens on cold and warm days, or when it rains.
80% of the irrigation water the lily grower uses, is rainwater, which is caught in six silos with a total capacity of 4,000 m3. Noordam: "This is sufficient for eleven months of the year, with a little use of surface water. About four weeks a year we don't have rainwater. Then we fill a silo with decontaminated ditch water.
Drainage is at 90 cm depth and the ditch water level is higher, which means the draining away of (good quality) surface water. The quantity drainage water coming from the drain well is 160% of the quantity of irrigation water. The draining water goes to the dirty water silo equipped with liter counter, and the water the lily grower cannot reuse, is drained through telemetrics unfiltered to the sewer system.
New purification techniques
Noordam has registered with AWZI in Hook of Holland for water purification. "We think that new purification techniques will become available. We do want to invest in a more affordable and easier to maintain installation to purify the drainage water ourselves."
Noordam does not use fungicides, but lots of bacteria preparation and soil stimulators. The lily grower deploys ichneumon wasps and gall flies against lice and thrips. About 50 chickens eat the weeds.
Noordam: "We have been occupied with biology as much as possible for two years, but there is still a long road ahead of us. We are doing this to keep the level of chemical pesticides as low as possible in the draining water. What is not in there, does not have to be purified."
source: Glastuinbouw Waterproof