Fertigation of cucumbers – the basics

Cucumbers are sensitive to water stress (to little water) and to water logging (over watering).  Any of these two conditions will reduce plant vigour and cause physiological fruit disorders such as crooked fruit.  The frequency of water application cannot be standardized because of so many factors that vary within each farming system.  Fertigation scheduling should be regulated according to crop stage, climate and the characteristics of the growth medium.  The coarser the texture of the medium the more frequent and less water at a time should be applied.  Crops grown in high density medium should receive water less frequently but more at a time.

Cucumbers consume more water per day than any other crop grown in hydroponics.  It is estimated that a mature cucumber plant will absorb up to 3 L of water per day.  The high water requirement is a result of the large soft leaves.  It is important to keep the electrical conductivity of the nutrient solution low enough for easy water uptake but not too low to cause a reduction in energy which will result in crooked fruit.  The ideal EC should vary between 1.6 mS.cm-1 and 2.0 mS.cm-1.  During periods of high temperature the EC should be lowered and during periods of lower temperatures, the EC should be increased.  However, never increase the EC above 2.5 mS.cm-1.

It has been found that cucumbers grow better in bag culture systems than in NFT or GFT systems.  The reason can be attributed to the high water requirements of cucumbers.  In GFT systems small volumes of the root systems is in contact with the water solution, whereas with bag culture systems the whole root is in contact.   This allows the cucumber plant to absorb greater volumes of water at any time of the day.

A general nutrient formulation that can be used for cucumbers is provided below.  However, the fertilizer combinations presented should be adapted to the grower conditions and variety.  Informed decisions should be based on water and plant analysis with the help of an expert.  Many books provide fertilizer recipes, but they are not the alpha and omega of plant fertilization.  There is very little doubt that one fertilizer program will be significant better than the other if the basic principles are followed regarding plant nutrition.  The main problem found with recipes are their implementation in the irrigation system.  Factors such as how the fertilizers are mixed, at what pH are they mixed and the quality of the various components making up the fertilizers.   Another very important factor is the quality of the water which can have a significant effect on the growth of the plant.