Abstract

                                Field experiment was conducted during pishanam, 2017 (October to January)with 32 numbers of short duration rice varieties / cultures grown in TamilNadu province as main plot and N levels (0, 50, 100 and 150% recommendedN) as subplot in split plot design replicated twice at Rice Research Station,Tamil Nadu Agricultural University, Ambasamudram to delineate and classifyrice varieties into N utilization and responsive classes. The experimental soilwas sandy loam in texture with acidic pH (4.16) had 0.35% organic matter,available nitrogen - 270 kg ha-1, available phosphorus - 10 kg ha-1 andavailable potassium - 63 kg ha-1. The 32 short duration rice varieties usedunder this study were delineated and classified into highly responsive (10),moderately responsive (5), low responsive (7) and non-responsive cultures(10) based on the responsiveness and utilization of applied nitrogen by thevariety. The technique of selection of highly efficient and responsive ricevariety / cultures under low nitrogen input can be used as a tool for cropimprovement programme to evolve better crop variety.

Key words : Rice; Nitrogen use efficiency; Classification; Organic farming