Guano Organic Fertilizer News

Why Silica and Calcium?

Discover the importance of combining silica and calcium.

© Copyright in this work is owned by Guano Australia Pty Ltd. All rights reserved.

When farmers think of guano products, they focus tends to be on guano as a phosphorus [P] source. Then the second question of how available is it and, what form is this phosphorus? With seabird guanos the phosphorus has a higher citric soluble phosphorus rate than non-seabird guanos that are higher in non-citric soluble phosphorus. However, when looking at Seabird guanos we need to look beyond the P % and focus a little on the calcium [Ca] and the silica [Si] and how these elements work together and interact.

By weight, calcium and silica in a good quality Guano Gold® make up over 50% of the product. Adding the calcium percentage to the silica percentage is a good test of how well the Guano Gold® you are going to buy is going to perform.

Generally, if the silica level is low then the phosphorus available, in terms of citric verses non-citric soluble, will be low. So, what are the benefits of calcium and silica? Rather than look at each element, let’s look at how they interact.

JIAN FENG MA and EIICHI TAKAHASHI from the Kyoto University in Japan used soft X-ray irradiation for detection of Silica bodies, they tested shoot and leaf from plants treated with high calcium and low silica, low calcium high silica and then equal amounts of calcium and silica.

The theory behind the testing was to show that the plant would use silica as a preference in physical structural development instead of calcium.  The results showed that even if calcium levels where applied in field trails at 6.5 times the level of silica, silica was still significantly present in the flag leaves of cereals. 

It concluded that increased silica resulted in reduced calcium in the shoots and developing leaves. It could be drawn from this that the addition of the silica with the calcium leaves more calcium available for metabolic functions in the plant as the silica forms silica bodies in the leaf blades.

The movement of calcium in the plant is relative to transpiration rate, increase transpiration (movement of water) slows down calcium movement. Calcium is required by the plant in fruit and grain set.

If transpiration is affected by excessive evapotranspiration (elevated temperature and water stress) then less calcium is available to increase both yield and fruit or seed quality. It logically follows that increased available silica reduces the distance calcium needs to move in the plant (long flow) and also silica due to its placement and structure reduces evapotranspiration (drought tolerance).

JIAN FENG MA and EIICHI TAKAHASHI commented that “This might mainly result from a decreased transpiration rate caused by increased Si.”  Secondly it was shown that “Silica uptake was not affected when the Ca levels were increased” this indicates that by having adequate levels of both silica and calcium will result in increased silica structure in the plant and more available calcium in the plant.

So to conclude in simple terms, silica and calcium used together, such as is available in seabird Guano Gold®, increase the plants silica structure and increases tolerance to biotic and abiotic stresses but doesn’t effect available calcium, however enhances the flow and movement of calcium at critical times such as seed or fruit set.


Article 4 of 12 Written by;

Robert Drewitt | BcSc(Ag) | Agronomist
Agronomy Services Australasia Pty Ltd

< Return

Have a question? Ready to place an order?



Being so far away from our markets, durability is critical and the Silica is really good in terms of hardening up the skin and making the melons better to transport.Ord River WA irrigator David Menzel-Barradale
The problem with many organic fertilisers is that they have very low rates of nutrients, meaning you need to put out high rates. A product like Guano Gold has 12pc P, whereas Guano Sulphur Gold has 10.5pc P, obviously with additional sulphur. These figures compare very favourably with something like a single superphosphate product. Agronomically, it’s a good product in any setting, not just for organic producers.Garry Allison, Landmark Agronomist. Mount Gambier, SA
For the broadacre croppers, Guano Gold works really well in paddocks where they have had issues with nutrient tie-up. He said the majority of synthetic P products have large rates of water soluble P. The problem with that is that you can have instances where it ends up tying up zinc in the soil so you run into problems with zinc deficiencies. Not only does the slow release nature of the Guano Gold product work well over the entire season, it also contains zinc for the crop as well as the other nutrients.Moree agronomist Rob Drewitt
We strongly recommend the Guano Gold products to fellow farmers if they are looking at improving their Calcium and Silica levels using various methods of application such as foliar and granular.James and Aimee Thomas Falkirk Macadamia Farm
I have recommended Guano Gold products for 20 years and in all cases had excellent long-term results increasing in pasture productivity.Paul Baguely - PB Ag Consulting
They are high analysis products so you get your nutrients without having to put too much fertiliser out.Anthony Beutel, Googa Farm Organics
We have known since the 1930s that phosphorus is one of the main elements required to grow a successful crop of not just the (flax) plant but the seed. It was one of those products that was first out in a granular type form and it was so much easier to get an even coverage over the ground, rather than a powder form. Later on the product became a little more refined, so we could put it through our air-seeder. We also broadcast some of it, prior to seeding, when we are cultivating ground. The products have great characteristics in relation to phosphate and silica, which is exactly what we need for flax.Waltanna Farms flax-seed farmer & Ambassador for Guano Australia, Michael Nagorcka

Read more testimonials