This spring, there was little rainwater, so reserves are already being drawn on. In a previous Horticultural Newsmail, Groen Agro Control already drew attention to rules on human pathogens in water according to GlobalGAP. That is about human health. But of course, your crop also requires ‘healthy’ water. “The whole water system is quite complex on many farms. In every pipeline, storage silo or in the unit, or with water treatment via technique or with agents, the water can change and with it the properties on the crop,” says Ines van Marrewijk, product manager at Groen Agro Control.
The focus in microbiology is on monitoring water at a number of places in the system. At the very least, one should regularly check the starting water before and after disinfection and certainly the drip water for germ counts. This can be a limited check on bacteria and fungi alone, but more and more companies are finding it important to have what is known as an ‘Extended Germ Count’ determined, which also shows the lowest possible contamination of Fusarium, Pythium and Phythophthora. And that can be critical for a good assessment of the system, because even though the grower checks and disinfects the water, microbiology can unfortunately multiply again in storage or in the system because a few spores have been left behind.
Sufficient oxygen in water and substrate will be a challenge in summer, with higher temperatures. Measuring is knowing when it comes to oxygen and that can be done very easily with sensors. It is good to realise that as a lab, we normally determine bacteria as aerobic germ count at 300 degrees Celsius. Under anaerobic, i.e. somewhat more oxygen-poor conditions, anaerobic bacteria develop more. If required, we can also count them via anaerobic bacterial count in water. Do this determination additionally and not as a replacement of the aerobic bacterial count. Biological and chemical oxygen consumption as an analysis can also give an impression of the activity in water.
It is often not immediately clear what kind of bacteria it is. “An example: For many years, Groen Agro Control named certain root growth ‘beaded roots’ and yet another image ‘thick roots’. Both appear to have a bacterial cause. It is not yet known that many bacteria can be harmful to plant and/or root growth. We now know more, but by no means everything. The bacterium Ralstonia was also such an ‘unknown factor’ when it suddenly appeared in roses and anthuriums; it had not previously been described as a disease in those crops worldwide.”
Don’t just check nutrients in drain water or output water, but also regularly take a sample of the toxic water, is the advice. That way, you can see that the settings and adjustments actually reach the plant. And take a sample of the poison as it reaches the plant or from a day’s supply. Preferably, do not take a sample from the mixing container, not while it is running and certainly not while it is standing still. The mixing of A and B tank with drain water and fresh water is done by pulses and is often not very homogeneous in the mixing tank itself.
Through drift, crop protection agents and even herbicides in the open rainwater basin occur more often than you might think. Therefore, ditch water is sometimes not a safe source. When in doubt, do not only have screening residue done but a more extensive analysis for inhibitors and herbicides.
“We have suitable packages for every type of water. So ask in advance what your goal is so that our lab can use the right analyses. Also take note of the information on sample materials and amount of sample required through our Materials for Sampling page.”
For more information, please contact Ines van Marrewijk, product manager at Groen Agro Control, Distributieweg 1 – 2645 EG Delfgauw, phone 015 2572511
Publication date: Tuesday