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Item Direct and residual effect of different forms and levels of magnesium on yield and magnesium uptake in rice(Kerala Agricultural University, 1993) Susan Varughese; Jose, A IA potculture experiment was conducted using rice as the test crop grown continuously for two seasons to study the direct and residual effect of added Mg under rice culture in waterlogged condition. The performance of the rice plant with respect to yield and Mg uptake was better in karappadam soil during the first crop season; while in the second crop season, it was higher in laterite soil. Different sources and levels of Mg applied did not have any significant influence on yield and Mg uptake of the rice plant. There was no marked difference in total Mg uptake between the two seasons, indicating a substantial release of Mgfrom added sources during the second crop season also.Item Forms of magnesium in soil as influenced by added magnesium sources under submerged condition(Kerala Agricultural University, 1993) Susan Varughese; Jose, A IA laboratory incubation study was carried out using two acid rice soils of Kerala under submerged condition for 180 days. The soil samples drawn at regular intervals were analysed for chemical forms of Mg. The insoluble Mg fractions dominated over the soluble ones. Acid soluble Mg and mineral Mg together constituted about 74.03 per cent of the total Mg content. Ammonium acetate extractable Mg of the soils was 19.09 per cent. The content of organic complexed Mg was very low and that of water soluble Mg was practically nil. Total Mg content as well as the content of various Mg fractions was higher in karappadam soil than in the laterite soil. The soluble Mg fractions were higher in samples supplied with magnesium sulphate while the insoluble fractions were higher in samples supplied with carbonate forms of Mg. The difference between the Mg levels tried in this experiment became conspicuous only under conditions of prolonged submergence.Item Influence of added magnesium sources on soil characteristics under submerged condition(Kerala Agricultural University, 1994) Susan Varughese; Jose, A IAn incubation study and a potculture experiment were conducted with two acid rice soils of Kerala, using three Mg sources, viz., magnesite, dolomite and magnesium sulphate tried at two levels of Mg (25 and 50 kg MgO ha ) to study the influence of added Mg on soil characteristics. Available Mg of the karappadam soil was significantly higher than that of the laterite soil. There was no significant difference between the three Mg sources with regard to their contribution to available Mg in the soil. But the Mg availability increased with raised levels of Mg application. A negative relationship was noticed between available K and Mg fractions in the soil. Different sources and levels of applied Mg did not have any significant influence on NILjOAc extractable Ca. Magnesium application raised the pH of the soils. Efficiency of the different Mg sources in correcting the acidic soil reaction was in the order of magnesite dolomite magnesium sulphate.