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A field experiment was conducted in sandy loam soils of eastern farm, Agricultural Engineering College and Research Institute, Kumulur, Tamil Nadu, India to study the effect of silicon on yield and uptake of rice (var. BPT 5204) during Kharif season of 2010-11 by taking the treatment combinations based on graded levels of Fly Ash (FA), Silicate Solubilizing Bacteria (SSB) and Farm Yard Manure (FYM) at fixed fertilizer schedule. The experimental soil (0-15 cm) had pH 7.22; organic C 1.4 %; available Si 66.0 mg kg-1; available N 266.0 kgha-1; available P 14.42 kgha-1 and available K 107.50 kgha-1. The results of graded levels of FA show that all the growth and yield attributes were significantly influenced by silicon uptake. The mean silicon uptake at panicle initiation, straw and grain at harvest varied from 53.8 - 98.7, 105.5 - 197.2 and 21.4- 62.3 kgha-1 respectively, in rice. Number of filled grains per panicle and grain yield displayed conspicuous relationships with content of Si in grains. The highest mean grain yield of 3622 kg ha-1 was recorded by the addition of SSB+FYM followed by FYM (3530 kg ha-1), SSB (3310 kg ha-1) and control (3240 kg ha-1). The combined application of 25 t ha-1 FA with SSB+FYM was recorded the highest grain yield of 3710 kg ha-1 which was 16.3 per cent moreover yield of control. The results further show that 25 t ha-1 FA and SSB+FYM have been proved to be superior treatments for best management of silicon in coastal loamy sand soils under irrigated rice ecosystem.

A global positioning system (GPS) based soil survey was conducted during September 2011 in the sugarcane dominant tracts of Theni district, Tamil Nadu to map the soil fertility status using GIS software and link with different cane yield potentials. The soil samples were taken from 400 spatially distributed locations from a depth of 0 to 30 cm and analyzed for texture, pH, EC, organic carbon, available nitrogen, phosphorus, potassium and micronutrients viz., Fe, Mn, Zn and Cu. The 'Asis' survey data regarding fertilizer management practices, adoption of new technologies, irrigation practices and other crop production techniques were also collected from the farmers. The interpolated maps for the status of macro and micronutrients show a clear deficiency of available Nitrogen in 96% of the soil samples of the cane growing areas and DTPA -extractable Zn deficiency in almost 60% of the regions surveyed. However, the available phosphorus and potassium contents were reported to be moderate to high in 90% of the samples indicating the possibility to reduce the P & K fertilizer application to sugarcane in this tract of Tamil Nadu. Majority of the soils were sandy loam to sandy clay loam in texture and reported to have low organic carbon context (<0.5%). The outcome of this study has provided an insight into the unbalanced fertilization practices adopted in some of the cane dominant tracts of this district and the need to evolve a GIS based balanced fertilization model through the conduct of field experiments with graded levels of fertilizer doses and Institute (TNAU) -Industry (RSCL) recommended packages.

To evaluate the effect of four silicon fertilizers, field experiment was conducted in farmer's holding at Poovanthi village of Sivagangai district, Tamil Nadu during 2017-2018 against sugarcane leaf hopper, Pyrilla perpusilla Walker and its parasitoid, Epiricania melanoleuca (Fletcher). Silicon fertilizers were applied @ 500 and 1000 kg ha-1 before planting and the leaf hopper population was recorded at 150, 180, 210, 240 and 270 days after application. The results of field experiment revealed that Pyrilla population was minimum in the plots treated with calcium silicate @ 1000 kg ha-1 (8.20 numbers/leaf) followed by calcium silicate @ 500 kg ha-1 (8.80 numbers/leaf) as compared over untreated check (98.20 numbers/leaf) and the percent reduction over untreated check was 82.45 and 73.71 per cent, respectively. Similarly, the per cent parasitism was maximum in the treatment with calcium silicate @ 1000 kg ha-1 (82.33%) during November, which was on par with untreated check. Hence, Pyrilla population declined to an extent of 82.45 per cent by enhancement of E. melanoleuca parasitism (82.33 %) due to the application of silicon fertilizers.

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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.

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