Utilization of Waste Materials from Monosodium Glutamate Factory as Source of Nitrogen for Paddy in Acid Sulfate Soil

Abstract

The efficiency of glutamic mother liquour (GML) and humus, the waste materials from a monosodium glutamate factory, as a source of nitrogen for paddy in an acid sulfate soil (Rangsit soil) was studied in the laboratory and pot experiment. The application rate of GML, ‘humus’, (NH₄)₂SO₄ and urea in both the laboratory and pot experiment was 266.7 ppm N. In the laboratory experiment, the effects of GML, ‘humus’, (NH₄)₂SO₄ and urea on NH⁺₄ content and the reduction state in submerged acid sulfate soil were investigated during a 6 – week incubation period. GML and ‘humus’ significantly increased the NH⁺₄ content in submerged acid sulfate soil after 6 weeks of incubation to 74 and 70 percent of that in acid sulfate soil amended with (NH₄)₂SO₄ respectively. Application of GML and ‘humus’ enhanced the reduction stage in submerged acid sulfate soil but urea and (NH₄)₂SO₄ had no effect. In pot experiment, the effects of GML, ‘humus’, (NH₄)₂SO₄ and urea on growth and yield of rice plant grown in submerged acid sulfate soil were elucidated. GML significantly increased growth, and yield of rice plant, having grain yield of 83 and 82 percent comparing to those of the rice plant grown in the soil amended with (NH₄)₂SO₄ and urea respectively. ‘Humus’ increased growth and yield of rice plant but the effectiveness of ‘humus’ was very low as compared to that of GML. Grain yield of rice plants grown in the soil amended with ‘humus’ was 34 and 33 percent compared to those of the rice plant grown in the soil amended with (NH₄)₂SO₄ and urea respectively. The low efficiency of ‘humus’ in increasing growth and yield of rice plant might be due to the effects of some toxic substances released from ‘humus’ which appeared to have its main effect on reducing the number of grains set per panicle.