An assessment study was conducted infive sugarcane yielding blocks of theni district viz., Jeyamangalam, P.C.Patti, Chinnamanur, Andipatti and Usilampatti.The cane yielding zones of the district was classified into three categories viz., low yielding (less than 75 t ha ) which resulted in maximum cane productivity. It was concluded that application of organic matter, amendments rich in calcium and magnesium in acidic soil and application of gypsum and other amendments rich in sulphur in alkali soils of low cane yielding zone can maximize productivity of sugarcane.

Biochar is considered as a possible and potential tool for soil fertility improvement, climate change mitigation and long term sink for atmospheric carbon dioxide. Soil application of biochar enhances the soil properties indirectly. A field experiment was conducted to evaluate the influence of organic manures viz., Farm Yard Manure (FYM), Vermicompost, Biochar, Biochar composite on soil properties, growth and yield of bhendi, Abelmoschus esculentus in Somayyanur soil series of Madurai district, Tamil Nadu. The experiment was laid out in randomized block design (RBD) with eleven treatments and three replications during the summer season (March – June) 2021 with the inclusion of inorganic fertilizers based on soil test crop response (STCR) based recommendation. Application of biochar composite (5 t ha-1) along with STCR based NPK (75% STCR) increased the total carbon content in soil by 0.538 %. This, in turn, increased the available nitrogen status to 295 and 244 Kg ha-1 at 40 and 70 DAS, respectively. Similarly, the available phosphorous (22.4, 19.3 Kg ha-1) and potassium (344.70, 323.70 Kg ha-1) status also showed a considerable increase with the same treatment. The yield attributes of bhendi viz., fruit length, girth, weight, dry matter production and yield recorded maximum values of 15.23 cm, 6.93 cm, 21.56 g, 11.9 t ha-1 and 25.20 t ha-1 with the combined application of biochar composite and NPK. The findings revealed that 25 % STCR based NPK could be reduced with the application of 5 t ha-1 of biochar composite, which is economically an option besides promoting soil health.

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.

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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.