GROWSIL AS A GROWTH MEDIUM IN HYDROPONICS - A CASE STUDY

INTRODUCTION

Silica Earth Resources (SER) are a Western Australian miner, producer and supplier of natural amorphous silica. Our amorphous silica is non-toxic, insoluble and supplied in granulated form (GrowSil) for easy handling and application. Our GrowSil material has optimal physical, chemical and hydraulic properties to improve plant productivity, decrease irrigation requirements, increase plant resistance to pests and reduce environmental impacts.

HYDROPONICS

Hydroponics, both at a household and commercial scale, has seen a rapid growth in Australia in recent years as a result of food and water security issues associated with climate change. The hydroponics industry is now the fastest growing food producing sector in Australia currently valued at AUD$1.8 billion annually, with a CAGR of 8 %.

The benefits of hydroponics over traditional soil-based plant production techniques are that more food can be produced with fewer inputs (water and fertilisers) and it is not dependant on climate (rainfall) or suitable arable land. A typical commercial-scale hydroponics operation is shown in Plate 1.

Whilst hydroponics may seem as an environmentally better option, the use of unsustainable, single-use growth mediums detract from its environmental credentials.

 
Silica Earth GrowSil 2

Plate 1: Typical commercial-scale hydroponics operation

SILICA EARTH RESOURCE's GROWSIL

Over the last 12 month SER have undertaken extensive hydroponic trials using a wide range of plants (Plate 2). To date the following plants have been successfully growth using GrowSil as the growth medium:

  • Kale
  • Carrots
  • Warrigal greens
  • Beans
  • Beetroot
  • Native limes
  • Peas
  • Chinese vegetables
  • Strawberries
  • Spinach
  • Chilli
  • Watercress
  • Tomatoes
  • Capsicum
  • Jalapeno

 
Silica Earth GrowSil

Plate 2: Hydroponic trials using GrowSil as the growth medium

THE BENEFITS OF OUR GROWSIL PRODUCT IN HYDROPONICS INCLUDE:

Optimal pore size distribution

Unlike nearly all of the commercially available growth mediums (e.g. rockwool, coir, perlite and vermiculite), which are dominated by macropores, our GrowSil product has an optimal pore size distribution that promotes not only aeration, but also maximises water holding and more importantly the plant available moisture levels.

A comparison of the water retention properties of our GrowSil product against rockwool is shown in Figure 1. This figure shows that the plant available water content of GrowSil is around 27 % (v/v), whilst for Rockwool it is only 4 %.

This optimal microporosity means there is less water (irrigation) requirements as the GrowSil stores the water in available pores for the plants to access.

 
Silica Earth GrowSil Figure 1

Figure 1: Soil water characteristic curve (SWCC) for GrowSil (Amorphous Silica) and Rockwool

Chemically inert

Our GrowSil product consist of 85-90% non-crystalline SiO2 and therefore it remains permanently negatively charged over the full pH range. The importance of this is that because the surface of the material is negatively charged there is no adsorption of nutrients (e.g. N, P, S) because they are negatively charged also. This is in contrast to most other growth mediums on the market, including rockwool, perlite, vermiculite and zeolite, which are manufactured from aluminosilicate minerals, which are variably charged, and therefore they lock-up nutrients so that it is unavailable to plants.

Optimal particle size distribution

Our GrowSil product typically has a particle size range between 0.8 – 5 mm, with around 20 % silt + clay fraction. This particle size distribution is ideal for both seed germination as well as plant growth, and therefore one pot can be used for the full growth cycle, removing the need to transplant seedlings.

If seedlings are transplanted into the GrowSil product, its optimal pore size distribution means that there is no ‘transplant-shock’ and the transplanted seedling remain healthy and rigorous.

GROWTH PERFORMANCE

The growth performance of our GrowSil product against a range of other commercially available growth mediums is shown in Figure 2 and Figure 3, and Plate 3.

In all trials our GrowSil product performed as well as, if not better, than all existing growth mediums.

 
Silica Earth GrowSil Figure 2

Figure 2: Strawberry growth results (GrowSil is the Washed and Unwashed Silica)

 
Silica Earth GrowSil Figure 3

Figure 3: Kale growth results (GrowSil is the Washed and Unwashed Silica)

 
Silica Earth GrowSil 3

Plate 3: Comparison of growth performance of Kale and Strawberries using GrowSil (plants on the right) and Expanded Clay (plants on the left).

ENVIRONMENTAL SUSTAINBILITY

SER have calculated the total supply chain carbon footprint of our GrowSil product and compared it with other typically used growth medium materials, including rockwool, perlite, vermiculite, coir and zeolite.

Our GrowSil product has a total supply chain carbon footprint of only 88 kg CO2-e/t, compared to 600 kg CO2-e/t for coir and 1,000 kg CO2-e/t for rockwool, perlite, vermiculite and zeolite.

In addition, our GrowSil product is completely reusable with plant roots and microbial activity easily removed by solar drying and it is environmentally friendly so that it can be applied to gardens when finished with to improve their productivity.

ORGANICALLY CERTIFIED

Recently our GrowSil product was organically certified by Australian Certified Organic (ACO) as an Allowed Input. Our GrowSil product is the only hydroponics growth medium on the market that is organically certified and this pays the way for hydroponics systems to also become organically certified in the future.

Find out more about Growsil here