APPLICATION OF DEFECATION LIME IN PADDY FIELD: EFFECTS ON RICE (ORYZA SATIVA L.) PLANTS AND SOIL CHARACTERISTICS

This work aimed to evaluate the effects of the defecation lime (DL) at the paddy rice field scale. According to the prescriptions of the Italian D.Lgs (Legislative Decree) no. 75/2010 defecation lime is defined as a “product obtained by the chemical hydrolysis (or enzymatic attack) of biological materials by lime and/or sulphuric acid and subsequent calcium sulphate precipitation.” This product is classified as "lime and magnesia soil conditioner". They must contain at least 20% of calcium oxide (CaO) and 15% of sulphuric anhydride (SO3) both related on a dry basis. According by law origin of the hydrolysed biological material must be reported on the label. Raw biological material for the DL used in this experiment was sewage slugde deriving from municipal and industrial wastewater treatment plant. DL effects were evaluated both during and at the end of growing season, on rice (Oryza sativa L.) plants and soil chemical characteristics. The analysis of the effects was conducted over two year – two growing season – in the same paddy field in order to know also the effects of repeated application of the product. After spreading, incorporation of DL and soil tillage, rice, Volano variety, was immediately seeded by a row seeder. In order to evaluate the effects of depth of incorporation, for the first year DL was placed into soil by plowing instead for the second year by harrowing using a disc harrow. For the rice plants the analysis were conducted over different variables i.e. number of emerged plants, development stage, aboveground biomass at the harvesting, yield, milling yield and trace metals concentration in grains while for the soil pH, TOC, CEC and trace metals concentration were evaluated.