Intensive cultivation of agricultural soils causes soil degradation which emphasizes the need for sustainable soil management. Biochar, a pyrolysed carbon rich material has gained great interests among the researchers because of its eco-friendly benefits in addition to soil quality enhancement. Reviews on biochar, mainly confined to its environmental benefits like carbon sequestration and climate change. In this review, we summarize i) the effect of biochar application on soil properties (physical, chemical, biological), ii) remediation potential of biochar in heavy metal contaminated soils and iii) its impact on crop productivity. The properties of biochar like pH, greater surface area, cation exchange capacity, and nutrient content positively influences the soil properties and ultimately improves the soil fertility. Their effectiveness depends on biochar type, its dosage, soil type, etc. General trends from this review indicated that biochar as an effective amendment in acid soils than the alkaline or calcareous soils. Furthermore, the biochar effects are studied mostly under controlled conditions in laboratory, which needs to be validated under field conditions having varied soil types and agro-climatic zones.

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Fly Ash, a waste material from thermal power station is used as a nutrient source in agricultural sector to enhance soil fertility and also as a soil ameliorant. The present investigation was carried out during 2015 -2016 at Rice Research Station, Ambasamudram, Tamil Nadu to reclaim acidic soil of pH 4.75. The treatments include control, 100% RDF alone, Lime + RDF, Dolomite + RDF, FA @ 10,20,30 and 40 t ha -1 along with RDF, 50% Lime + 50% FA + RDF and 50% Dolomite + 50% FA + RDF. The application of 50% Dolomite + 50% Lime + RDF significantly increased the soil reaction (7.08) whereas in case of EC only a small magnitude of increase was observed over control. The highest CEC was observed with 50% Dolomite + 50% FA + RDF (43.1 cmol(p+) kg -1 ). The addition of FA @ 40 t ha -1 recorded higher BS % value of 34.1% which was on par with the treatments receiving 50% Dolomite + 50% FA + RDF, 50% Lime + 50% FA + RDF and Dolomite + RDF with the values of 33.5, 32.6 and 31.4%. The lowest sesquioxide value of 5% was recorded with the application of 50% Dolomite + 50% FA + RDF. The highest grain yield (5.93 t ha -1 ) and straw yield (6.32 t ha -1 ) were registered with 50% Dolomite + 50% FA + RDF which was then followed by 50% Lime + 50% FA + RDF (grain yield-5.72 t ha -1 and straw yield -6.10 t ha -1 ). The application of Fly Ash supplemented with other liming materials like Lime and Dolomite can alleviate soil acidity and enhance soil fertility.

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