Is your dosing pump feeding your plants correctly?
Mark Huey Horticulture Adviser CAFRE
Fertigation supplies essential nutrients as soluble nutrients through the irrigation system to produce a healthy crop. The concentration of nutrients in the irrigation water is controlled by a dosing pump or dilutor.
To ensure the dosing pump or dilutor is working correctly growers should test or calibrate the dilutor at least once a year. To do this they should make up a diluted sample from the stock solution at the same dilution set on the dilutor, for instance if it is set at 1:100, take 100ml of stock and add to 9.9 litres of water.
Run 10 litres of water from the dilutor (minimises any EC ‘spikes’ in the sample) and compare the two readings. If the EC from dilutor is lower than the EC from the prepared sample, then decrease the ratio on the dilutor (i.e. alter ratio from 1:100 to 1:80) and vice-versa. Growers can also create calibration curves for every fertiliser they use on site which will remove need to make up a diluted sample every time a check is carried out. AHDB have released a factsheet on how to do this ‘Calibrating a water-powered proportional dilutor’ which can be accessed here.
If you would like further information on fertigation calculations, please contact Mark Huey, Horticulture Development Adviser, CAFRE by email; firstname.lastname@example.org or mobile telephone 07785344244.