Silica for plants5/19/2023 In general, crystalline silicates with lower impurities release more silicic acid than amorphous silicates with higher concentrations of contaminants. The terms amorphous and crystalline silica are used to describe the lattice structure of the compound ( Dixon and Schulze 2002). Silicone (R 2SiO, where R is an organic group) is used in the manufacture of plastic substances and other synthetic rubber-like compounds. Silicic acid, Si(OH) 4 (aka monosilicic acid or ortho-silicic acid) refers to the soluble form of Si that is readily available for absorption by plant roots. Silicates are found in association with the cations Ca +2, K +, Mg +, and Na + to form the most commonly known crystalline or amorphous compounds – CaSiO 3, K 2SiO 3, Na 2SiO 3, and MgSiO 3. Silica refers to silicon dioxide (SiO 2) and is the principal constituent of sand. It has an atomic number 14 and is a tetravalent metalloid. Silicon refers to the chemical element Si in the periodic table of the elements under column IVA, directly beneath carbon (C). We also provide an overview of the terms used in the discussion of Si in soil and plants, its status as an essential versus beneficial nutrient, and its role in ameliorating both abiotic and biotic types of stresses. The purpose of this review is to provide some general insights into what Si does and why it has not been adopted in plant management programs. Even with these outcomes, the use of Si as a plant protectant or as a fertilizer in agricultural production by growers in many countries have been slow to materialize. In 2015, an International Society of Silicon in Agriculture was established ( ). Seven international conferences on Si in Agriculture (United States 1999, Japan 2002, Brazil 2005, South Africa 2008, China 2011, Sweden 2014, and India 2017) were held with the overarching theme of providing a forum where the benefits of Si were discussed among plant scientists, agricultural managers, and companies producing Si materials. An awareness of Si deficiencies in soils has become recognized as being a limiting factor in overall plant development, production, and health. However, in field and greenhouse environments, plants are regularly exposed to different stresses, especially in soils that are deemed to be low or limited in soluble Si. As a result, plant physiologists have largely disregarded this element from any meaningful plant experiments. Unfortunately, the benefits from Si were mainly overlooked until the beginning of the 20th century, partly due to the element’s abundance in nature and also due to the lack of visible symptoms of either deficiency or toxicity. Silicon (Si), the second most abundant element in the earth’s crust after oxygen, helps plants to overcome various abiotic and biotic stresses ( Debona et al. Many of these issues mentioned above will need to be resolved if silicon is to become a standard practice to improve agronomic and horticultural crop production and plant health. What is holding producers and growers back from using silicon? There are several possible reasons, which include: (i) lack of consistent information on which soil orders are low or limited in silicon, (ii) no universally accepted soil test for gauging the amounts of soluble silicon have been calibrated for many agronomic or horticultural crops, (iii) most analytical laboratories do not routinely assay plant tissue for silicon and current standard tissue digestion procedures used would render silicon insoluble, (iv) many scientists still state that plants are either silicon accumulators or non-accumulators when in reality all plants accumulate some silicon in their plant tissues, (v) silicon is not recognized as being necessary for plant development, (vi) lack of economic studies to show the benefits of applying silicon, and (vii) lack of extension outreach to present the positive benefits of silicon to producers and growers. However, even with this robust body of information, silicon is still not routinely used for alleviating plant stress and promoting plant growth and development. The science for silicon is well-documented and comprehensive. Numerous reviews and hundreds of refereed articles have been published on silicon’s effects on abiotic and biotic stress as well as overall plant growth and development.
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