What Are The Effects Of Drought On The Fertilization?

In the glass horticulture there is a need for fresh water or good quality. The quantity of rain that falls in the Netherlands meets this demand. In coastal areas, like the Westland, where a lot of glass horticulture takes place, fresh water is also required to reduce salinization in the groundwater. Climate change has created new questions and solutions. What to do in case of an empty water basin? Switching to another water source is required. But which one? There are many possibilities. Our specialist will be explaining them in this article.

Climate change

Nowadays we are facing more and more extremes. There is an increased risk of dry springs and dry summers, while also wetter winters and more severe precipitation occurs. 
Due to these extremes, the climate and consequently the water storage are harder to predict. 
Therefore, always ensure different fallback scenarios, in case of a sudden switch to another water source, to guarantee water issuing of the crops.

What different water sources are available?

During an extremely dry period one can switch to another water source. Below there is an overview of possible water sources. 

Rain water
Rain water is the most commonly used source of supply water. By reusing water deriving from precipitation (recirculation), the grower won't be affected by long periods of drought as much. However, this does not exclude the risk of shortage, because these will emerge after 5 weeks of drought.

Rainwater is a soft-water source, which means that few elements can be found in the water. This may lead to increased issuing of fertilizers. 

Tap water
Tap water can be used for the water issuing of the crops. One of the risks involved in the use of tap water is the fact that it contains bicarbonate. This bicarbonate ensures increased pH in the tap water, so it must always be acidified, before it can be used for supply. 

Surface water
Surface water predominantly implies water from ditches, rivers, lakes and channels. The use of surface water can be used as an alternative in times of drought. The inconsistent compound of the water must be considered though, as well as a risk of harmful particles like fungi, bacteria or viruses, that are present in the water. Also, in times of drought, there is a chance of increase of the salt content (EC) in the water, as a result of vaporization. 

Drainwater
Drainwater is water that is captured and subsequently circulated.
Drainwater can be recycled, but attention must be paid to the sodium concentrate in the water. Under hot conditions this water will partly evaporate, which leads to more concentrated water with a higher salt content and increased EC. This concentration can be possibly reduced by use of the Poseidon, that removes the sodium from the system, but leaves the remainder of the fertilizers and pesticides. Therefore the Poseidon is suitable for use in a circular system.

Osmosis water
During the process of reverse osmosis the salts are removed from the water.
With a view to a possible shortage of water, as from 2021 the use of osmosis water will be restricted. The reason is that it causes lowering of the ground water level.

The risk to be considered when using osmosis water, is that this water is so clean that it contains no elements. This will increase the issuing of fertilizers.  

Which water source should I choose?

If heat and drought force us to use a different kind of water, also the fertilizing schemes must be adjusted. 

It would be logical to choose a source that contains the most water. But also abovementioned disadvantages and risks, that come with the different sources, should be considered. 

As every water source has a different original pH value and different properties, all the different sources require separate contingency schedules. 
It is imperative that the grower has a timely contingency schedule for each scenario to make fast switching possible. 

Anticipating dry periods

Drought can not be prevented, but it can be predicted. That is why the Department of Waterways and Public Works ‘developed’ the Drought Monitor. This way the expected precipitation can be monitored and if necessary, a different water source can be chosen, as well as a suitable contingency schedule.