The water content is the quantity of water contained in the substrate. Adjusting the water content is a valuable tool for controlling the plant balance and maintaining root health.

To assist with optimising the water content, we have developed Season Dynamics, a seasonal crop planning strategy (see [link]). In it, we recommend target water content levels for each of the critical periods in a crop cycle. These recommendations are made for specific reasons during each period:

• During extended periods with low light levels, it’s beneficial to maintain a lower water content as the plant is less active. This makes the substrate more responsive and allows more oxygen to penetrate the substrate, which promotes a generative effect.
• When light levels are high and transpiration levels increase, it’s advisable to maintain a higher water content to provide more buffer for the plant’s usage. This also offers greater security in the event of a system failure.

Measure your substrate systematically using a continuous monitoring system such as Growficient sensors and set EC targets for the different periods .

“Managing this water buffer enables you to fully utilise the substrate’s potential for optimising plant balance.”

The distribution of water and nutrients in the substrate is key to achieving uniform root distribution. Ensuring that roots have good access to nutrients is essential for optimizing both quality and yield. Adjusting the EC is also a valuable tool in managing the plant balance.

To assist with optimising the EC, we have developed Season Dynamics, a seasonal crop planning strategy (see [link]). In it, we recommend setting target EC levels for each of the critical periods in a crop cycle before the start of the season. These target levels are set for specific reasons:

• During extended periods with low light levels, it’s beneficial to maintain a higher EC to promote generative growth and ensure a plentiful supply of nutrients.
• When light levels are high and transpiration levels increase, it’s advisable to reduce the EC to encourage nutrient uptake for transpiration.
   

With crops like cucumber, for example, a high nutrient uptake in a small volume of substrate can lead to low levels of certain nutrients. Therefore, more irrigation is needed to ensure the correct nutrient composition. The volume of substrate used is a key factor in this.

Measure your substrate systematically using a continuous monitoring system such as Growficient sensors and set EC targets for the different periods.

“Managing EC enables you to fully utilise the substrate’s potential for optimising plant balance.”

The plant’s ability to take up the nutrients it requires depends on the pH of the nutrient solution. So it’s crucial to maintain the correct pH around the root system. 

For most plants, the ideal pH is between 5.5 and 6.5. This should therefore be your target range. The pH in substrate can change due to selective nutrient uptake by the roots. For example, when potassium is absorbed by the roots, an H+ ion is released which causes the pH to drop. When the roots absorb nitrate, bicarbonate (HCO3) is released, causing the pH to rise.

Additionally, some elements can be consumed by microorganisms, further affecting the pH of the substrate. Changes in the concentration of NH4 and NO3 fertilisers can also impact the pH of the substrate.

To manage this, it’s important to adjust the pH of the source water in the irrigation rig. Keep an eye on the following:

• If source water bicarbonate levels are very low (no buffer), it may be necessary to add bicarbonate to provide some buffering capacity.
• When bicarbonate levels are low, you may need to dilute the acid used to correct the pH to prevent it from suddenly dropping below 5.0.
• Ammonium usage can also cause a rapid drop in pH, particularly with low bicarbonate levels.

Regularly check the pH of the source water in the storage tank, in the irrigation rig and at the dripper. pH levels of below 5.0 can harm both the roots and the substrate. Remember that the plants receive water from the dripper, so ensuring the correct pH at that point is critical!

All parts of the plant – leaves, stems and roots – need oxygen. In the substrate, roots need oxygen for cell respiration. When there is sufficient oxygen at the roots, the root system can function optimally.

Oxygen is also consumed by microorganisms. In conditions with low oxygen levels, these microorganisms may compete with the roots for the available oxygen.

A supply of oxygen in the substrate is crucial for healthy plant and root growth. In practical terms, this means that even the wettest part of the substrate needs to be replenished with air. With a water content of 80% or less, the air channels ensure that oxygen can reach the water and plant roots through diffusion. 

Roots require a lot of oxygen, more than what is dissolved in water. Therefore, dissolved oxygen is not enough on its own to keep roots healthy and growing. Oxygen from the air needs to be able to diffuse into the water. Maintain the water content at below 75-80% so that sufficient oxygen can enter the substrate, providing the roots with adequate access to oxygen.

“Managing the O2 enables you to fully utilise the potential of the substrate.”

The temperature of the root zone is not always measured, although this is very important. The ideal temperature around the roots is between 18°C and 25°C.

As the temperature in the root zone increases, the availability of dissolved oxygen from the irrigation water decreases. Additionally, higher root zone temperatures lead to increased root activity, which promotes water and nutrient uptake. 

When root temperatures exceed 25°C, especially with poor root distribution, this, along with competition between roots for water, nutrients and oxygen, can lead to root death. This in turn increases the risk of secondary infections by root pathogens such as Pythium.

To measure is to know: so keep on measuring the substrate temperature to understand the conditions in the root zone.

Microbiological life in the substrate is crucial because it forms a symbiotic relationship with the plant, enhancing its resilience and health and making nutrients available too it. Increased resilience leads to more balanced plant growth.

The presence of microbiological life in substrate offers several benefits, such as:

• Improved root health and activity
• Better plant balance
• Higher yields and superior quality
• Reduced disease and pest problems