The status of manganese in the soil and rice plants under different water systems and fertilizer applications

An experiment was conducted in the greenhouse at Assiut University (Assiut, Egypt) to study the status of manganese in both the soil and rice plants under different water and fertilizer treatments. Rice seeds were sown in pots containing a clay loam soil submerged with water for a period of 45 days after which treatments were initiated. Water treatments consisted of five systems: continuous submergence, field capacity, saturation percentage, and alternative submergence for either 4 or 6 days followed by one day of drainage. Fertilizer treatments included the application of ammonium sulphate and/or manganese sulphate at three rates. Both the soil and rice plants were sampled at three intervals: 4,8, and 12 weeks after treatment initiation. Samples were properly prepared and analyzed for manganese. Statistical analysis of the obtained data was carried out for both the separate as well as the combined effects of all treatments. Results showed that the concentration of Mn in both the soil and the rice shoots was significantly increased as the period of water submergence was extended. Continuous submergence proved to be superior to all other water systems tested. Due to the slightly acidic nature of ammonium sulphate, its application resulted in increasing the concentration of Mn in the soil and subsequently in the shoots. Addition of manganese sulphate did not materially affect the level of Mn in the soil except after enough time was allowed (about 3 months). However, plant uptake of Mn was increased appreciably under such addition.