Abstract

Field experiment was conducted during summer season of 1988 to evaluate the availability of N, P, K, Ca and Mg in lowland rice soil (Typic Haplustalf) with the application of graded doses of magnesium and potassium at Tamil Nadu Agricultural University, Coimbatore. Rice crop (Var. IR 64) was grown with four levels of magnesium (0, 20, 40 and 60 kg/ha) combined with four levels of Potassium (0, 25, 50 and 75 kg K20/ha). Application of Magnesium influenced the availability of nitrogen and phosphorous during later stages of the crop growth. The availability of potassium at all stages and calcium in the panicle initiation stage decreased with increasing dose of magnesium indicating antagonistic effect. The availability of magnesium in soil increased due to increased magnesium fertilization while application of potassium decreased the availability of nitrogen and magnesium.

Keywords: Magnesium and Potassium availability, rice yield