Phytoliths: Persistence & Release of Silicon in Soil and Plants – A Review

Phytoliths are formed from silica carried up from groundwater and some plants. The weathering of silicate minerals at the Earth’s surface provides large amounts of soluble silica, some of which is absorbed by growing plants. In solution, silica exists as mono silicic acid Si (OH4) with pH values of 2–9. It is carried upward in the vascular system and becomes concentrated during transpiration around the leaf stomata. The supersaturated solution begins to polymerize or gel then solidifies and forms solid opaline silica (SiO2:nH2O) bodies (phytoliths) within and between some of the plant cells. Phytoliths were extracted from the 7.4 meter loess core and analyzed morphologically and isotopically from the occluded carbon. Rates of isotopic fractionation between plant and phytolith were determined by measurements from many modern tree, fern, and grass species. The use of phytolith biochar as a Si fertilizer offers the undeniable potential to mitigate desilication and to enhance Si ecological services due to soil weathering and biomass removal. Silicon is accumulated at levels equal to or greater than essential nutrients in plant species belonging to the families Poaceae, Equisetaceae, and Cyperaceae. However, the abundance of silicon in soils is not an indication that sufficient supplies of soluble silicon are available for plant uptake.

Sustainable and Clean Utilization of Coal Gangue: Activation and Preparation of Citrate-Soluble Silicon Fertilizer

Silicon (Si) fertilizer is of great significance to modern agricultural production; the citrate-soluble silicon fertilizer based on coal gangue is one way to protect the environment and meet the agricultural needs of China. In this study, we produced high-efficiency coal-gangue based silicon fertilizer by calcining a mixture of coal gangue, calcium carbonate (CaCO3) and corn stalk powder at high-temperature (i.e., high-temperature activation technology); the effect of temperature and mixing ratio on the available-Si content of activated coal gangue was studied, followed by an analysis of the mechanism of available- Si formation. The results showed that the layered structure of coal gangue was severely damaged above 600 ℃, and the kaolin began to transform into metakaolin and other substances, where the available-Si content was not high (less than 10%). When CaCO3 alone was added, the peak intensity of quartz and muscovite in coal gangue decreased significantly with the increase of CaCO3. However, CaCO3 mainly played a catalytic role in the entire calcination and activation process, forming only a small amount of calcium silicate on the contact surface with coal gangue; however, the available-Si content was still below 12.60%. When corn stalk powder alone was added, the oxides of the corn stalk ash participated in the chemical reaction involving coal gangue, forming nepheline (K(Na, K)3Al4Si4O16) and other silicates, and the available-Si content was significantly higher than that with CaCO3. When coal gangue, CaCO3, and corn stalk powder were mixed and calcined, the available-Si content was as high as 22.97% under the synergistic effect of CaCO3 and corn stalk powder; the concentration of harmful heavy metals was below 0.025 mg/L. The above is in line with the requirements of silicon fertilizer for use in agriculture, thus confirming the preparation of coal gangue-based silicon fertilizer in an efficient manner.

A Review on the Role of Silicon Treatment in Biotic Stress Mitigation and Citrus Production

This paper reviews the threat of citrus pathogens during citrus production, with a focus on two pre-harvest diseases, citrus leaf spot, caused by Alternaria alternata (Fr.) Keissl. (1912) and brown rot, caused by Phytophthora citrophthora (R.E. Sm. and E.H. Sm.) Leonian, (1906) as well as green and blue mold post-harvest disease, caused by Penicillium digitatum (Pers.) Sacc. and P. italicum Wehmer, (1894), respectively. Furthermore, it reviews the role of soluble silicon, Si nutrition in biotic stress mitigation and potential mitigation mechanisms. Previous studies on the use of Si fertilizers have focused on high accumulator Si crops. These have demonstrated the potential of Si to reduce the occurrence of biotic stresses, which takes place through both physical and biochemical mechanisms. However, few studies have demonstrated the potential of Si to mitigate biotic stress in citrus, or the mechanisms involved. There is a clear need for studies on the impact of Si on various stress biochemical pathways in plants generally, and specifically for citrus due to the huge loss caused by pre- and post-harvest pathogens. This will assist in deepening our understanding of the pathophysiology which is essential to develop resistant cultivars.

Development of means to improve productive health in dairy cattle breeding

In this article the treatment method of osteodystrophy in cows by oral administration of mineral-sorption vitamin additive "Carbosil AD" (consisting of zeolite, bentonite, hydrated soluble silicon and calcium carbonate with forage forms of vitamins A and D) is studied. And its effect on haematological, hepatological, productive indicators, calcium deficiency.