Untitled - MendelNet 2013 - Mendelova zemědělská a lesnická ...

MENDELNET 2013INTRODUCTIONAcid sulfate soil is the common name given to soils and sediments containing iron sulfides, themost common being pyrite. When exposed to air due to drainage or disturbance, pyrite is oxidised,resulting in production of sulfuric acid, often releasing toxic quantities of iron, aluminium andheavy metals. In the soil profile we will meet yellow mottle from jarosite. Disturbing acid sulfatesoils can have a destructive effect on plants.Acid sulfate soils reduce farm productivity. The sulfuric acid lowers pH, which makes several soilnutrients less available to plants. The acid dissolves iron and aluminium from the soil so that theybecome available to plants in toxic quantities in soil water. These conditions reduce plant growth.Thailand has around 1.5 million ha of acid sulphate soils or 5.75% of cultivated lands. Around 60%of them are in the Center plain and the South of Thailand reaching 0.89 million ha. Acid sulfatesoils are often planted under rice, so if they are not suitable for plants and crop management, theymight increase the yields of rice.There are many traditional and modern practices which can improve soil chemical properties ofacid sulfate soils. One practice is the application of liming material. Lime is often more suitable fortreating acid soil due to its higher solubility in the amount of about 6.25-12.5 ton/ha. The use oflime material together with chemical fertilizer, particularly nitrogen and phosphorus, can increaserice productivity. Moreover, silicon (Si) application can reduced aluminium toxicity to plantsincluding rice (Hara et al.,1999). Silicon enhances the photosynthesis of rice and increases riceresistance to several rice diseases and insects (Ma and Takahashi, 2002)“MK” as soil conditioner is a by-product from concrete manufacturing. The components of MK arecalcium compounds and hydrosilicate compounds. About 60-70% forms other components such assilicon, aluminium and anhydrous silica. Its electrical conductivity is 2.1 dS/m, the cation exchangecapacity is 25.0 cmol/kg and pH is very high (pH 10.2). Based on their properties, MK can be usedas soil conditioners. Major goal of this project was to study the effect of MK on growth and yield ofrice grown under acid sulfate soil.MATERIAL AND METHODSThe experiments were carried out in 2010 at The Experimental Study Project for Acid SoilSolution, The Chaipattana Foundation, Nakhon Nayok province, Thailand. Before establishingfield trials, soil samples were taken for analysis. Soil samples were air dried at room temperaturefor four days and sieved through a 2 mm mesh sieve. The samples were characterized for soil pHwhich was determined using a 1:1 ratio of soil to deionised water. Electrical conductivity (EC) wasdetermined using a1:5 ratio of soil to deionised water. Textural classification was measured usingthe pipette method (Gee et al. 1986). Organic matter content was determined by wet oxidation andtitration using the Walkley and Black method (Nelson et al. 1982). The cation exchange capacity(CEC) was determined with 1 M NH 4 OAc solution buffered at pH 7 (Soil Survey Laboratory Staff,1992). Total N in soil samples was determined by the Kjeldhal method. The available phosphoruswas extracted with BrayII and was determined by flame emission. The exchangeable K in theNH 4 OAc solution was determined by atomic absorption spectrophotometry (AAS). Extractable Siwas extracted by CH 3 COOH and the Si in the solution was determined by AAS.Soil samples had the following characteristics: The Rs series (Rangsit soil series) had a claytexture; 1.96% organic matter; pH of 3.10; EC of 0.55 dS/m; CEC of 23.8 cmol/kg; total N of 1.2%; available P of 5.83 mg/kg ; exchangeable P of 66.7 mg/kg and extractable Si of 5.83 mg/kg. Theresult showed that the soil had very low pH, P and extractable Si. Therefore it is necessary to usesoil conditioners for improving soil pH and some elements such as P and Si.148 | P age