In previous blog posts, we've explored the benefits and functions of silica and silicic acid in plants. Today, we'll delve into the importance of stabilized monosilicic acid (MSA) and some of the methods for stabilizing it in horticultural products. We'll also highlight the unique advantages of polyol-stabilized MSA solutions, such as Front Row Si.

The Importance of Stabilizing Monosilicic Acid

Silica products not only increase plant growth rates and yield, but also protect plants from various stresses, making them a valuable addition to any horticulture operation. These products are highly effective against biotic stresses (bacteria, fungi, viruses, insects) and abiotic stresses (heat, drought, acidity, salinity).

One way or another, to confer these benefits all silica products must ultimately increase the MSA concentration around the roots or foliage.

It's important to note that traditional forms of silica (potassium silicate, for example) generally aren’t absorbed via foliar action. While there is evidence of prevention of powdery mildew, applying foliar potassium silicate with this method won’t produce the growth or yield benefits that foliar MSA confers. Potassium silicate must remain at a very high pH to maintain solubility.

This points to another major benefit of stabilized MSA solutions: they don’t contain additional minerals that need to be compensated for in your main fertilizer formulation. For example, using potassium silicate at 0.3 g/gal will add 22ppm of K along with the 20ppm of elemental Si, and this will require compensation.

As mentioned, plants benefit greatly from MSA, however it is highly reactive and needs to be stabilized to ensure that its reaching the plant surfaces as monosilicic or disilicic acid. At higher pH levels, MSA disassociates into silicate ions, and at high concentrations, unstabilized MSA polymerizes creating larger molecules. Since only the smaller molecules of mono- and di- silicic acid can be absorbed by plants, this polymerization into oligomeric and polymeric silicic acid needs to be prevented.

The commercial availability of MSA products has been made possible with the development of processes that prevent the polymerization of silicic acid, enhancing stability at a variety of concentrations, pH levels, and over longer durations.

Stabilization Methods

One common method of stabilizing MSA solutions include acid stabilizations in combination with molybdenum, zinc, choline, or polyethylene glycol (PEG). These methods allow concentrations of up to 2.5% silicic acids, however these stabilized silica solutions must remain at a very low pH to prevent polymerization in concentrated form.

Another method involves using organosilicon precursors, such as tetraethyl ortho-silicate. These products don't contain water and are very concentrated, allowing up to 40% equivalent concentration of MSA after conversion. As precursors, they don't actually contain MSA but their components break down into MSA once diluted in water. Unfortunately, they also produce other organic compounds such as ethanol (alcohol) in the solution, which can exert strong negative effects on root growth and plant development.

Polyol-Stabilized MSA Solutions: Front Row Si

Among the various methods of stabilizing silica, polyol-stabilized MSA solutions stand out for their remarkable properties and effectiveness. One such example is Front Row Si, which contains 10% MSA. This product uses sugar alcohols, which form soluble 2/1 (sugar alcohol/silicic acid) silicate complexes with basic silicic acid. Silicate is very selective about the sugar alcohols it reacts with, but certain combinations result in readily soluble complexes at high concentrations.

While potassium silicate solutions require very high pH levels to stay in solution and acid-stabilized MSA products require very low pH to prevent polymerization, the polyol stabilization process used in Front Row Si overcomes this challenge. Front Row Si has significantly improved mixing properties compared to other silica products on the market; the mono- and di-silicic acid components are stabilized to be soluble at all pH levels, making them easier to use in a variety of applications and methods. Additionally, Front Row Si does not contribute any potassium or other minerals that would require adjustment of the overall nutrient recipe.

The low-molecular weight MSA in mono- and di-silicic forms created by the polyol stabilization process in Front Row Si are easily available for plant absorption in contrast to the higher molecular weight Si polymers that are less effective for plant uptake. This superiority in terms of cost, stability, solubility, and availability for plant absorption makes polyol-stabilized MSA solutions like Front Row Si a valuable addition to any horticultural operation.

Math Interlude: Calculating solution Si ppm

Much of the research literature reports the effective ppm ranges for elemental Si rather than a silica salt or of MSA. It may be useful to see how to calculate the elemental ppm of Si from MSA in a solution.

1a - What % of MSA is Si?

Let’s walk through the steps for deriving the percentage by weight of Si in MSA. MSA’s molecular composition is H₄SiO₄, or Si(OH)₄, meaning it contains silicon, hydrogen, and oxygen.

1. To find the percentage of Si by weight, you need the molar masses of each of these elements:
   • Silicon (Si): 28.085 g/mol
   • Hydrogen (H): 1.008 g/mol
   • Oxygen (O): 16.00 g/mol
2. Calculate the total molar mass of MSA:

Take the sum of the molar masses of all elements in the compound multiplied by their respective number of atoms:

• 1 Si atom: 1 × 28.085 g/mol
• 4 H atoms: 4 × 1.008 g/mol
• 4 O atoms: 4 × 16.00 g/mol

Molar mass of MSA = (1 × 28.085) + (4 × 1.008) + (4 × 16.00) = 28.085 + 4.032 + 64.00 = 96.117 g/mol

1. Calculate the percentage of Si by weight:

Divide the molar mass of Si by the total molar mass of MSA and multiply by 100% to get the percentage:

Percentage of Si by weight = (Molar mass of Si / Molar mass of orthosilicic acid) × 100% = (28.085 g/mol / 96.117 g/mol) × 100% ≈ 29.20%

So, the percentage of Si by weight in MSA is approximately 29.20%.

1b - What % of SiO2 is Si?

Many product labels or labs report Si concentrations as SiO2 equivalents. To determine the percentage of silicon (Si) by weight in silicon dioxide (SiO₂), we first need to know the molar masses of silicon and oxygen:

• Molar mass of silicon (Si): 28.0855 g/mol
• Molar mass of oxygen (O): 16.00 g/mol

Silicon dioxide has one silicon atom and two oxygen atoms, so its molar mass can be calculated as:

Molar mass of SiO₂ = (1 x 28.0855 g/mol) + (2 x 16.00 g/mol) = 28.0855 g/mol + 32.00 g/mol = 60.0855 g/mol

Now we can calculate the percentage of silicon by weight in silicon dioxide:

Percentage of Si = (28.0855 g/mol / 60.0855 g/mol) x 100% ≈ 46.74%

Thus, the percentage of Si by weight in SiO2 is approximately 46.74%

What does the research show about foliar MSA applications?

Since 2003 a number of trials in various crops have been carried out to determine the effects of foliar application of Si. Most research uses solutions of 7-45 ppm Si, sprayed 3-4 times starting early in the crop life cycle. The excellent 2018 review paper by Laane and colleagues reports on these effects, summarized below:

• Five studies exploring the effects of on potato growth, yield, and infection rate showed increased disease resistance, yield improvements of up to 40%, and other growth enhancements.
• Four sprays of 30 ppm Si applied to two different onion cultivars grown in clay soil in the Netherlands resulted in yield increases of 9.9% and 10.8% respectively.
• In a Colombian study, four sprays at 30 ppm Si using two different spraying regimes led to increased papaya plant height (6.3% and 7.8%), stem diameter (7.3% and 8.2%), fruit weight (11.9% and 13.2%), superior fruit flavor.
• Three studies on rice demonstrated that MSA sprays led to various growth and yield improvements, including increased grain size and quantity, shorter crop cycles, and enhanced nutrient uptake, with yield increases up to 32%. Additionally, the studies found that MSA application reduced infection rates, such as a 70% reduction in one study, and allowed for decreased pesticide usage while maintaining high yields.
• A study on strawberries found that three sprays with 7 and 14 ppm Si significantly improved growth parameters, including root length, root mass weight, diameter of root neck, and leaf blade area, across all tested soil types.
• Two studies on grapes found that MSA sprays at various concentrations led to significant improvements in growth parameters, yield, and quality, with one study reporting a maximum yield increase of 39%. The treatments positively influenced factors such as nutrient uptake, total soluble solids, acidity, total sugar, and reduced the percentage of rotten berries, while another study observed increased berry length, diameter, bunch weight, and overall quality.
• A study on ten different finger millet varieties found that two sprays of 15 and 30 ppm Si significantly increased grain and straw yield, with the greatest increase at the 4 mL/L rate, and improved Si uptake by 54.6% over the control. Additionally, the MSA sprays reduced blast disease by 50.4-69.8% across the different genotypes.
• MSA sprays led to various improvements in sugarcane growth, yield, and quality in three studies. One study found a 26% yield increase with foliar MSA sprays, and the combination of soil and leaf application provided a 33% yield increase. Another study demonstrated that MSA sprays significantly decreased mite populations and leaf dryness.
• A study on seasonal ornamental plants found that three sprays with 15 and 22 ppm Si from MSA led to increased growth and quality. The number of lateral shoots, buds, and flowers or inflorescences increased in all ornamental plant varieties, with flower diameter also dependent on the concentration of the spray.
• MSA sprays improved growth, yield, and quality in white oat and wheat. In wheat, the sprays increased nutrient concentrations, shoot dry matter, and resulted in a 26.9% grain yield increase. MSA sprays also showed efficacy in alleviating drought stress, increasing relative water content, and improving growth and quality parameters.
• MSA sprays improved growth, yield, and quality in soybean, common bean, and peanut. Four sprays of 15 ppm Si from MSA increased seed yields by 14% for soybean, 15% for common bean, and 9.6% for peanuts. In soybean, three sprays were the most effective foliar application, increasing plant height, leaves, pod and seed yield, as well as protein and oil yield.
• MSA sprays improved growth, yield, quality, and infection rates in tomato plants. Three sprays of 30 ppm Si led to taller transplants with larger stem diameters and increased nutrient concentrations. MSA sprays of 15 and 30 ppm Si reduced powdery mildew disease by 26% and 56%, respectively, with the latter sprays being more effective than the standard fungicide.
• A study on maize found that MSA sprays at concentrations of 7, 15, and 22 ppm Si applied at 20-day intervals, along with the application of silicon granules, improved growth and yield parameters in both sandy loam and clay loam soils. The highest yield resulted from the combination of the foliar MSA application at 22 ppm Si with the soil application of silicon granules.
• A study on mango trees compared the efficacy of four 4 30 ppm Si from MSA sprays applied at three-week intervals with other silicon treatments and a control. All soil and foliar silicon applications enhanced growth and yield, but the MSA foliar sprays were more effective in terms of yield increase, total soluble solids (TSS), and shelf life. The shelf life of the fruits from MSA treated trees increased by five days compared to other silicon-containing product applications.
• A study on mandarin plants evaluated the efficacy of one, two, and three MSA sprays at concentrations of 7, 15, and 30 ppm Si applied at 30-day intervals during the pea stage and ripening stages. Sprays with 15 ppm at the pea stage enhanced nutrient status, increased fruit size by 25%, and improved juice volume during the ripening stage, particularly with 30 ppm sprays. The treatments increased biogenic silicon layers in the rind, sugar content in the juice, nutrient ionic status, and fruit shelf life.

Conclusion

Stabilized silica products are a game changer in horticulture, offering numerous benefits to plant growth and protection. By understanding the importance of stabilizing monosilicic acid and the methods used to achieve this, growers can make informed decisions when selecting silica products for their horticultural operations. With the right stabilized silica product, such as the polyol-stabilized Front Row Si, growers can enjoy higher growth rates, yields, and improved plant health.

Getting the benefits of MSA with Front Row Si is easy: In practice, 3 - 5 foliar applications with 1-2 ml/gal over the first 5 weeks of a plants life ensures the crop is receiving the benefits on growth rate, yield, disease resistance, and quality.