Growing substrates play a key role in increasing nursery efficiency. It is therefore very important to choose the right substrates to optimize water use, reduce agrochemicals and improve soil fertility for more sustainable production.
In addition, growing media also influences the improvement of root structure as well as rooting rates in the nursery, which helps increase plant survival.
Here we present growing media, what they are, their physical characteristics, and the benefits they offer for the optimal development of plants.
What is growing media and what is it used for?
Also called "substrates", growing media are materials other than the soil in which the plants grow and which are mainly used in hydroponic systems.
They are used for growing a wide variety of plants, such as vegetables, fruits, shrubs, floriculture and even ornamental tree plants.
The main function of growing media is to provide the necessary moisture and oxygen to the roots of plants, as well as to support their weight and keep them in an upright position.
They also perform another very important function: to allow the roots to be exposed as much as possible to nutrients.
What are the types of growing media?
There is a wide variety of growing media, each with its own advantages and disadvantages, but the best known are:
- coconut fibre:
- peat moss;
- balls of expanded clay;
- rock mineral wool;
- rice husks;
- start caps;
- pumice stone;
- oasis cubes.
What are the physical characteristics of growing media?
Physical characteristics refer to the attributes of growing media when interacting with a hydroponic system. Some of these include:
Porous space refers to the volume available for air or water in a substrate, expressed as follows:
- Percentage of pore space volume in a substrate (pore space volume/total media volume x100)
Roots need oxygen to breathe, so the porous space between solid particles makes up most of the volume of a substrate.
Adequate porosity in the roots allows plants to get the oxygen needed for breathing, while making the roots less likely to rot.
Permeability measures the ease with which water passes through a substrate. The structure of the substrate is therefore of vital importance to allow water to move through the pores to the roots.
In this sense, the permeability of a substrate depends on the size of the pores and how they are connected to each other.
Based on their permeability, substrates are classified into two categories:
- High permeability: this is when they have high porosity and allow water to pass more easily.
- Low permeability: refers to a compact substrate with low porosity or low connectivity, which reduces the space available for water movement.
Water retention capacity
One of the main functions of substrates is to retain water so that it can be absorbed by the plant.
Total water retention capacity refers to the ability of substrate components to retain water (or fertigation solution) against the force of gravity.
Considering that water is retained in soil pores, the water retention capacity depends on the capillary action, pore size and the total space between soil particles.
The culture system and production strategy also influence water retention capacity, so that growing media are not alone in influencing this capacity.
For example, a lower tank height means an increase in water-filled interstitial space and a decrease in air-filled interstitial space.
On the other hand, when the container height is higher, the water retention capacity is reduced due to the effect of gravity pulling the water down.
In hydroponic systems, some are more compatible with a lower water retention capacity, while in other cases, it is the opposite.
In these two examples, we will show you how a higher or lower water retention capacity can be beneficial depending on the hydroponic system used:
- Deep Water Cropping Systems: This is a type of cropping system that benefits from low water-holding growing media, as plants are constantly exposed to the nutrient solution.
- Nutrient Film Technology Systems: These systems, unlike previous ones, have a greater water retention capacity, as they keep the nutrient solution easily accessible without constant exposure to water.
What is the importance of cultural media?
The importance of growing media lies in the fact that they perform certain fundamental functions in the optimal development of plants, such as, for example:
- Provide physical support to roots and plants.
- Create a space for gas exchange between the roots and the atmosphere.
- Provide water in an accessible form to the plant.
- Serve as a reservoir or access point for plant food and important microorganisms in the nutrient cycle.
As you can understand, growing media are essential to ensure that plants' water and nutrient requirements are met, thus providing them with the best growing conditions.
In summary, an ideal growing medium must have the following characteristics:
- Maintain the right proportion of water and air depending on the culture system used.
- Be made organically, biodegradable and environmentally friendly.
- Help protect plants from pH changes.
- Be light and easy to carry.
Now, with all the information we have shared, you will have more clarity to choose the best growing medium that will allow you to continue the development of your crops and ensure that the quality is the best.
To learn more, we invite you to consult the following sections solutions we offer you to improve the yield of your vegetables, herbs and greenhouse greens!