Use of Autochthonous Organic Inputs for Amelioration of Fluoride Toxicity and Sustainable Agriculture

In recent years, one of the main pollutants causing much concern is fluoride. Fluoride (F) is a potential air, water, and soil pollutant and also a common phytotoxic element (Reddy and Kaur, 2008). Fluoride is a natural component of the earth crust and also found in many minerals like fluorite (CaF ), fluoroapetite (Ca (PO ) F ) etc. (Tripathi and Singh, 1984; Garg et al., 2 10 4 6 2 1998) due to high electronegative. Problems tend to occur in places where these minerals are most abundant in the host rocks. During weathering and circulation of water in rocks and soils, fluoride leached out and dissolved in ground water and thermal gases (Brunt et al., 2004). The fluoride content of ground water varies greatly depending on the geological settings and type of rocks (Brunt et al., 2004). Climate and contact time between fluoride in ground water and aquifer minerals (Frencken et al., 1992) are also associated with high fluoride concentration in ground water. The main sources of fluoride in soil are weathering of volcanic ashes (Cronin et al., 2003), application of phosphate fertilizer in agriculture (Loganathan et al., 2011) and several industrial processes, especially the aluminum and phosphate fertilizer industries ( Arnesen and Krogstad, 1998). Some soils contain a very high level of natural F (Weinstein, 1977). Plants, poorly take up the soluble Fions from soil solution (Brewer, 1966). Fluoride can be transported by the symplastic or apoplastic pathway in the roots. Different pathways are responsible for the variations in fluoride concentrations in the plant (Muggler, 2009). Apart from these it can also enter into the plant body through the stomata from the air (Stevens et al., 1997; Mezghani et al., 2005). It adversely affected various physiological features of plants including causing decreased plant growth, chlorosis, leaf tip burn, and necrosis of leaf tip and leaf margin (Elloumi, 2005; Klumpp et al., 2006; Miller, 1993). Fluoride has deleterious impact not only on plant species but also on human beings (Maitra et al., 2013). The accumulation of fluoride in soil has raised concern that the dietry intake by grazing animals may steadily increase to reach unhealthy levels. Not only grazing animals but dietry intake of fluoride by human beings through consumption of edible plants/ vegetables may also steadily increase to unhealthy levels. Through these a part of food chain in which it is transmitted from vegetation to herbivores and hence to the carnivores (Murray, 1981). Excessive fluoride ingestion can cause disease known as fluorosis (Kugli and Yadawe , 2010 ; Beg et al., 2011). There are numerous number of research papers which acts as an evidence of deleterious impact of fluoride upon plants (Bhargava and Bhardwaj, 2010; Datta et al., 2012; Dey et al., 2012; Ram et al., 2014). According to Bhargava and Bhardwaj, 2010 sodium fluoride had significant impact on seed germination and seedling growth of wheat. Ram et al., 2014 also reported that sodium fluoride reduced the percentage of germination(%), root and shoot length, vigor index, pigment content, chlorophyll stability index(CSI) and membrane stability index (MSI). In the present investigation Brassica campestris L. cv. B was selected as a test species. Since rapeseed (Brassica campestris L. cv. B ) is one of the most 9 9 important oil yielding plant in our country and grown prevalently during winter months which can be used successfully to clean up heavy metal polluted soils if their biomass and metal There are very limited number of works so far undertaken for the amelioration of fluoride toxicity under field condition with the help of indigenous organic inputs such as use of vermicompost, compost etc (Szymanska, 2003; Alharbi, 2008). Such type of indigenous organic resources are chosen for the bioremediation measure in conventional agricultural practices. Chemical fertilizers are industrially manipulated, substances composed of known quantities of nitrogen, phosphorus and potassium and their exploitation causes air, ground and water pollution by eutrophication of water bodies (Youssef and Eissa, 2014). Vermicomposts are rich in microbial populations and diversity, particularly fungi, bacteria and actinomycetes (Moradi et al., 2013). Vermicompost enriched soil with microorganisms (adding enzymes such as phosphatase and cellulase) and improve the water holding capacity in soil. It can also increase the nutrient status in the soil specially nitrogen (Sreenivas, 2000; Kale et al., 1992; Nenthra et al., 1999). Vermicompost has a large particulate surface area that provides many microsites for microbial activity and strong retention of nutrients. Compost also have many beneficial roles such as buffering action neutralize both acid and alkaline soils, bringing pH levels to the optimum range for nutrient availability to plants. 

For such above mentioned beneficial characters, in this work, vermicompost and compost both have been used to study their impact towards bioremediation of fluoride under field condition. Also there indigenous inputs has some potentiality towards the combating of stress condition as well as to reduce the uptake and transportation of toxic metals through the plant system (Lallawmsanga et al., 2012; Rangasamy et al,. 2013).Bacterial consortia in general consist of diverse naturally occurring microbes whose inoculation to the soil ecosystem advances soil physico-chemical properties, soil microbes biodiversity, soil health, plant growth and development and crop productivity (Sahoo et al., 2013). The ultimate goal of sustainable agriculture is to develop farming systems that are productive and profitable, conserve the natural resources, protect the environment and enhance health and safety (Mukhopadhyay et al., 2013).

 Hence, in the present investigation, an attempt have been taken to evaluate the impact of fluoride on growth, metabolism and yield of mustard and the potentiality of different treatment combination towards sustainable agriculture along with in-situ management of fluoride.