Chemical investigations of Si-rich organic and inorganic amendments and correlation analysis between different chemical composition and Si contents in amendments

Application of silicon (Si) in agriculture, especially in degraded soils, is a promising, sustainable, and agro-environment compatible strategy. However, dilemma is the poor availability of monosilicic acid (SA) in soil solution due to intensive polymerization. Commercial silicates have severe limitations due to low solubility, inaccessibility, and high prices. Thus, identification of cheaper, soluble, and sustainable Si sources is an exigent requisite for utter and cost-effective remediation. Presence of high quantities of soluble Si in Si hyperaccumulating plants and industrial by-products provides an enticing choice. Therefore, chemical characteristics of 28 amendments were explored. Investigated amendments were plant residues, ashes, biochars (BCs), and industrial by-products. Our findings declared that total Si contents (TSi) were higher in BCs (5.7–71.6%) > ashes (49.5–53.6%) > plant residues (13–5%) > biosolids (3.6–41%) > by-products (15.9–36.8%). The phyto-available Si (PASi) was also highest in BCs (0.82–34.7%) > ashes (23.5–28.7%) > plant residues (6.2–26.9%) > by-products (4.8–13.3%) > biosolids (1.8–12%). Overall, the water-soluble Si (WSi) ranged from 0.04 to 1.09%. The carbon (C) contents ranged from 14.2 to 67.4% among amendments. BCs also showed higher pH (7.0 to 12.7). Pearson correlation and path analysis indicated that strong relationship existed among chemical properties. Rice residue-based amendments showed promising characteristics with high contents of TSi, PASi, WSi, and other essential nutrients.