Climate change, more frequent heat waves and restrictions on water use are leading many growers to rethink the way they water. In particularly hot or dry areas – such as southern Europe, California or Australia – optimising water use is not just a smart choice: it actually becomes a necessity.
In both home and professional cultivation, the same question arises:
How to keep moisture in the substrate without choking the roots or relying on constant watering?
The answer lies in water-saving substrates: mixes designed to retain moisture better, reduce evaporation and release water just when the plant needs it.
What makes a substrate "water-saving"?
It’s not enough for a substrate to absorb water well: to be considered water-efficient, it has to meet a number of key conditions:
1. High water holding capacity without waterlogging.
The ideal substrate stores water in its interior and releases it little by little, as the plant demands it. This prevents drainage losses and reduces the frequency of watering.
2. Good aeration
Retaining water should not mean drowning the roots. A good substrate should still allow oxygen to circulate to maintain root activity and avoid problems such as rotting or oxygen stress.
3. Stable structure
Frequent watering and the passage of time can compact some substrates, making drainage difficult and oxygenation worse. A substrate with a stable structure maintains its texture and porosity, even after many watering cycles.
4. Evaporation reduction
Water loss from the substrate surface can be significant, especially outdoors or in hot climates. A good substrate minimises this loss through its texture, colour and composition, and can be combined with mulching to be even more effective.
What materials help to retain water in the substrate?
Not all substrates retain water in the same way. Some materials stand out for their ability to store moisture without waterlogging or suffocating the roots. Here we explain which ones are most commonly used, how they work and how to integrate them intelligently into your crop.
1. High retention organic materials
• Coco fibre: A favourite in hot climates and demanding crops.
o It acts like a sponge: it absorbs water quickly and releases it little by little.
o Improves the structure and oxygenation of the substrate.
o It is reusable, sustainable and pH stable.
✅ How to use it? You can use it on its own (as in Cocos Substrate by Atami) or mix it with your usual substrate to improve its water retention capacity.
• Composted organic matter: Compost or worm castings also improve moisture retention.
o They increase water and nutrient exchange capacity.
o They support microbial activity, which is key to soil health.
🔎 Please note: some materials such as peat can become compacted if they dry out completely. It is advisable to combine them with elements that provide aeration.
2. Water-retaining inorganic compounds
• Vermiculite: Very light and with high absorption capacity.
o It absorbs water and nutrients like a sponge.
o Ideal for seedbed mixtures or areas with infrequent irrigation.
• Perlite: Although associated with aeration, it also retains some water in its pores.
o Prevents caking of the substrate.
o Improves the air/water balance, especially in small pots or clay soils.
3. Additives and complementary techniques
In addition to choosing the right substrate, you can apply certain techniques or materials to further reduce water consumption and improve irrigation efficiency. Here are some of the most effective ones:
• Padding (surface coating)
Covering the top of the substrate with organic materials such as straw, hemp or bark helps to conserve moisture in the root zone.
o Reduces direct evaporation by up to 70 %.
o Stabilises the temperature of the substrate, which is key in very hot climates.
o Improves the efficiency of substrates such as Bi-Grow-Mix or mixtures with Cocos Substrate.
It is a simple, economical technique that is fully compatible with organic or live soil cultivation.
• Water retaining polymers (professional use)
These polymers act like sponges that absorb irrigation water and gradually release it as the plant needs it.
o Its use is more widespread in technical gardening, landscaping or nurseries.
o They can maintain moisture for several days, which reduces the frequency of watering.
o Not recommended for organic farming, as they are not biodegradable.
• Other tricks that make a difference
o Large plastic pots: they take longer to dry out and retain moisture better than clay or fabric pots.
o Avoid waterlogging: a good substrate does not need to be soggy; light, regular watering is best.
o Water in cool hours (morning or evening) to avoid evaporation losses.
o Control drainage: too much can cause water to be lost before it can be used.
Atami tips on how to save water from the substratum
At Atami we offer effective solutions that optimise water use in all types of crops. If you want to reduce water consumption without sacrificing the yield of your plants, these tips can make a difference:
1. Use substrates with high water retention and good aeration.
Cocos Substrate is formulated with washed and stabilised coco fibre that acts like a natural sponge: it absorbs water quickly and releases it little by little as the plant needs it.
It is an ideal choice if you grow in warm climates, under LED lighting or with controlled irrigation systems.
• Supports constant oxygenation of the roots.
• Avoids waterlogging without water stress to the plant.
• Perfect for drip or automatic irrigation.
You can also mix it with your usual substrate (30-50 %) to improve water holding capacity and structure without having to completely change your growing mix.
2. Improve soil structure in outdoor crops
Whether you grow directly in soil or in large pots outdoors, Bi-Grow-Mix is a versatile option that combines selected peat, perlite and organic matter.
• Retains moisture in depth without compacting.
• Supports beneficial microbial activity.
• Helps regulate hydration even on hot days.
Ideal for urban gardens, organic farming and living soil.
3. Accompany with adequate liquid nutrition
Good water retention is of little use if the plant cannot access nutrients when it needs them.
To ensure a perfect balance, combine your substrates with liquid fertilisers such as B’cuzz Soil A&B, Terra Leaves or VGN base nutrients. If you prefer slow release granular nutrition, ATA NRG Upgrade is ideal.
All guarantee a constant supply of nutrients, even when watering cycles are more spaced out.
4. Protects the substrate surface
Covering the top of the substrate with organic materials such as bark, hemp or straw helps reduce evaporation by up to 70%.
This simple gesture boosts the water efficiency of substrates, especially outdoors or in crops with high sun exposure.
Conclusion: optimise irrigation from the substratum
The use of substrates with good water retention capacity is not just a trend: it is a smart strategy, especially in hot areas, demanding crops or limited irrigation systems.
Choosing the right substrate and combining it with the right techniques can make the difference between a crop that barely survives… and one that thrives.
What to remember:
• Not all substrates retain water in the same way: those that combine water retention and aeration (such as coco or peat with perlite) are ideal.
• The substrate is only one part of the system: factors such as the type of pot, the timing of watering and the use of mulch also play a major role.
• Prevention is better than correction: investing in a good substrate and applying complementary techniques from the start helps you to save water and avoid stress on your plants.
• Atami products such as Cocos Substrate or Bi-Grow-Mix are designed to offer real solutions, both indoors and outdoors, in organic or technical systems.
In short, taking care of water starts with taking care of the soil. And with the right tools, it is possible to grow more… with less.
