Originally Posted by Mr. Greengenes
Cool thread, thanks everyone for contributing. I do what troutman says, I use regular playground sand in my soilmix. Quite a bit, actually. Sometimes it's probably 25% of the total. I flower plants quite root bound, so they visibly reduce the mass of the soil in that last container. Since I recycle 100% of my mix (have been for decades), I get an opportunity to see how much of each amendment gets used over time. On average, I go through 1-1/2 90lb. bags of playground sand a year. Some of that is just waste that I couldn't shake off the roots and ends up in the garden, but the rest is being 'eaten' by plants. It took me a couple decades to wrap my head around that. Apparently, plants 'eat' sand!
Other growers often remark that my plants have very strong stems. Of course, I often credit genetics, but I have no doubt that silica plays a role there too. But, there are many variables to consider. Like troutman, I also add greensand.
thanks for that, both very interesting and confusing at the same time haha!
Originally Posted by Mr. Greengenes
I also use crushed up hardwood charcoal, which makes quite an obvious difference not only in stem strength but also in leaf color(s).
I learned today biochar made from wheat, barley and rice (or other high silicon accumulating plants) works well to as a silicon source, i bet the hardwood has a good amount. Speaking of natural sllicon sources horsetail is high in it.
Excerpt From Source Article In Post #27:
Because of the added value of plant-based silicon sources to overall soil quality, the silicon-rich materials from plant biomass as potential sources of bioavailable silicon were evaluated. The application of biochar improved the soil chemical properties (e.g., the pH and cation exchange capacity, among others) and the soil physical properties, such as water-holding capacity and aggregation (Glaser et al. 2002;Chan et al. 2007).
According to Ma and Takahashi (2002), rice straw has been widely used as source of silicon primarily because of the long-term effect (40 years) of rice straw on the plant-available silicon concentrations in soil. The silicon in the rice straw is not fully available in the short-term, but the amount of silicon that becomes plant-available in the long-term could exceed 70 % of the amount applied. The silicon-rich materials from industrial wastes and plant biomass are applied
in large amounts. Because most of these materials are also good liming agents, the pH values of the soils that receive these materials commonly increase substantially (Tubaña et al. 2012a; Haynes et al. 2013)
Originally Posted by Bud Green
I have a question...
Silica sand is mined not too far from me...
I can get a trailer load of it for the taking..
It is fairly fine, (like sand for iron casting molds) and is very white and pure...
Other than for creating drainage in my soil, would silica sand do any good in my garden,
or is the silicon locked up in the grains and unavailable for plant uptake??
From what I understand currently the silicon in sand is in a very unavailable form for plants and microorganisms, and the small portion that does become available silicon is lost to oligomerization/polymerization...I planned on making the bioavailabilty/Oligomerization/polymerization portion a thread of its own lol, Ill try and network with a few people (like only ornamental, jidoka and maybe slownickel) for more insight as they probably have more experience in this area.
Originally Posted by jrelax
Originally Posted by Malato
You guys think if youre using a mix with actual soil(dirt mixed in with my compost) that this doesnt apply? Since there would certainly already be loads of silica. Or does the form of silica make a difference?
interesting you would mention bio silica (its silicon dioxide...its water soluble, but minimal plant silicon bioavailability from what i understand). Malato
there are both available and non available forms of Silicon. Silicon chemistry is complicated...Things are about to get complicated...For starters, Silicon is best taken up by the roots for use in growth, foliar application is more as a preventative for pest/disease (stabilized monosilicic acid is the exception as it has been shown to give overall improvements to many crops from foliar sprays explained below).
Silicon is the second most abundant element in the earth’s crust after oxygen, Content of soils ranges from 1% to 45% dry weight (Sommer et al 2006), with an average of 28% Si by dry weight. In rocks, the concentrations of silicon range from 23 % (e.g., basalt) to 46.5 % (e.g., orthoquartzite) (Monger and Kelly 2002). Trace amounts of silicon are also in carbonaceous rocks such as the limestones and the carbonites (Monger and Kelly 2002). Certain soils contain low levels of this element, These soils include the Oxisols and the Ultisols, which are typically characterized as highly weathered, leached, acidic and low in base saturation (Foy 1992), and the Histosols, which contain high levels of organic matter and very low mineral contents (Snyder et al. 1986). Additionally, the soils that are composed of a large fraction of quartz sand and those that have been under long-term crop production typically have low plant available silicon (Datnoff et al. 1997).
The vast majority of Si compounds in the soil consists of silicate minerals, aluminum silicates and several forms of silicon dioxide (sand/quartz) none of which are available for plant uptake. Several silicon fertilizers are made with silicates (potassium silicate) and silicon dioxides (bio silica/biogenic silica, rice hull ash etc and diatomaceous earth). The only plant bioavailable silicon compound is H4SiO4 monosilicic acid (synonym: orthosilicic acid). The large quantities of silicon present in soil do not reflect the amount of soluble and plant-available monosilicic acid, the conversion of these solid silicon compounds into monosilicic acid is very low. In addition, the MSA concentration in the soil is also low due to the polymerization of MSA into oligomeric and polymeric silicic acids, resulting in a relative deficiency of monosilicic acid in the soil.
In soils, silicon is generally grouped into three different fractions: the liquid phase, the adsorbed phase and the solid phase (Matichencov and Bocharnikova 2001; Sauer et al. 2006). The components of silicon in the liquid and adsorbed phases are similar, with exception that those in liquid phase are dissolved in the soil solution, whereas those that are adsorbed are held onto soil particles and the Fe and Al oxides/hydroxides.
The uncharged form of H4SiO4 (monosilicic acid) is the only form that is absorbed by plants and microorganisms.
The absorbed silicon is later deposited as polymerized silica within the plant tissues or the cell structure of the microorganisms. These polymerized silica bodies return to the topsoil in the litter fall, and the remains of microorganisms eventually enter the highly soluble biogenic silica pool that contributes to the silicon in the soil solution (Drees et al. 1989; Van Cappellen 2003; Farmer et al. 2005; Saccone et al. 2007; Fraysse et al. 2010). Silicon is also added to soils with applications of manure and compost, and the decomposition of silicon-rich manure can increase the level of available soil silicon (Song et al. 2013).
Comprehensive Cycle Of Silicon In Soil:
Green arrows represent transformation or processes which raise silicon concentration in soil solution.
Yellow arrows represent the transformation or processes which reduce silicon concentration in soil solution.
Red arrows represent processes that result in silicon loss from the soil system or production of stable plant unavailable form of silicon.
Blue arrows represent transformation processes of silicon into a silica pool that contributes this element into the soil solution.
Takahasi et al. 1990 categorized plant species based on the mechanisms of silicon uptake. The plants that rely primarily on active, passive or rejective mechanisms are classified as high, intermediate or non accumulators, respectively. The plants in the high-accumulator category have a silicon content in the shoot that ranges from 1.0 % to 10 % dry weight, an amount equivalent to, or even exceeding, several macronutrients (Epstein, 1994).
The dicots examined (cucumber/tomato), which accumulate <0.2 % shoot dry weight silicon, form the low-accumulator group. Mitani and Ma (2005) attributed the low silicon accumulation in this group of plants to a lack of specific transporters to facilitate the radial transport and the xylem loading of silicon and suggested that the transport of silicon across cells was accomplished via a passive diffusion mechanism. Later, Liang et al. (2006) showed that both the active and the passive uptake of silicon, which occur in high-accumulator plants like Sunflowers (another hyper accumlator like Cannabis) are also found in the intermediate-accumulator plants.
The absorbed H4SiO4 is transported through the xylem and is deposited in the leaf epidermal surfaces in which it is condensed into a hard, polymerized silica gel (SiO2·nH2O), also known as a phytolith (Yoshida et al. 1962; Jones and Handreck 1965, 1967; Raven 1983). According to Lanning (1963), the phytoliths are best classified as biogenic opal (Si-O-Si bonding). The absorbed H4SiO4 is preferentially deposited in the abaxial epidermis, but as the leaf grows, the deposition occurs in the epidermis (Hodson and Sangster 1988). The deposited silica is immobile and is not transferred to actively growing or meristematic tissues (Elawad and Green 1979; Ma et al. 1989; Epstein 1999). Transpiration remains a viable option as one of the primary drivers in silicon transport and deposition in plants, and therefore, the duration of plant growth significantly affects the concentration of silicon, for example older leaves contain more silicon than younger leaves (De Saussure 1804; Henriet et al. 2006).
In the amelioration of biotic-related stresses, the role of silicon was first recognized in the modification of plant cell wall properties (Horst et al. 1999; Fawe et al. 2001; Lux et al. 2002; Iwasaki et al. 2002a, b). The deposition of biogenic silica in shoots increases the structural component of the plant and creates a hard outer layer (Rafi et al. 1997; Bélanger et al. 2003). Most of the reported benefits in crop quality and yield following silicon fertilization resulted from the improved overall mechanical strength and an outer layer of enhanced protection for the plant (Epstein 1999, 2001; Ma and Takahashi 2002; Epstein and Bloom 2005)
Figure Shows Effect Of Ph On Silicon Plant Availability:
Matichencov and Bocharnikova (2001) provided an overview of the formation of the different silicic acid species in soil solution as affected by the rates of silicon fertilization. Three phases were established based on the changes in the concentrations of monosilicic and polysilicic acids. At the lowest end of the range of silicon fertilization rates the concentration of H4SiO4 in the soil solution is the highest. As the rate of added silicon increases, the concentration of the monosilicic acid reaches a certain point and then begins to polymerize (the formation of polysilicic acid) becoming unavailable to plants.
The polymerization of silicic aicd is strongly pH dependent. Shown below is the concentraition of monosilicic acid of different Ph solutions after 24hr (Top line) and 75hr (bottom line). In a very acid solution (Ph 0-4.8) after both 24 and 75hr no polymerization (loss) takes place. The monosilicic acid concentration decreases rapidly in the Ph 5-7 (where most plants prefer).
Temperature Effect On Silicic Acid Polymerization at Ph 8.5: