Differential response of two medium duration rice varities to time of planning and graded doses of nitrogen

Abstract

An experiment to study the differential response of two medium duration rice varieties to time of planting and graded doses of nitrogen was conducted during the mundakan season of 1980 – 81, at the Research Station and Instructional Farm Mannuthy. The experiment was laid out in split plot design, with combinations of four time of planting (September 25th, October 10th, October 25th and November 9th) and 2 varieties (Jaya and Sabari) in the main plot and 3 levels of nitrogen (60, 90, 120 kg/ha) in subplots. Observations on the plant growth characters were recorded at 30th day, 60th day after planting and at harvest. Chemical analysis of plants at these stages were also done. Time of planting significantly influenced the growth characters as well as the yield and yield attributes. Plant height, panicle length, number of spikelets, number of filled grains, percentage of filled grains, dry matter production, grain yield, straw yield, harvest index, grain straw ratio, total nitrogen uptake at harvest, nitrogen uptake by grain, content of phosphorous in straw and grain and the total uptake of phosphorous at harvest and potassium uptake by grain were significantly higher in the early planted crop, than in later planted crops. However, number of days taken to 50 per cent flowering, and to maturity, production of tillers and productive tillers, phosphorous content of straw and potassium content of grain were positively influenced by delayed planting. Sabari recorded significantly higher number of days to flowering and maturity than Jaya. Higher levels of nitrogen were found to increase the dry matter production and nitrogen, phosphorous and potassium content of straw.