Abstract: Field experiment was conducted at the wetlands, Tamil Nadu Agricultural University, Coimbatore in Noyyal series deep clay soil (Vertic ustochrept), to standardise the Leaf Colour Chart critical value (LCC cv.) and the rate of nitrogen application in CO 47 rice variety. The study was conducted in factorial randomized block design with three replications. The treatments included three levels of LCC cv. (LCC cv. 3, 4 and 5) with different rates of N application (20, 25, 30 and 35 kg ha-1 at a time) along with three checks (control, blanket N (150 kg N ha-1 in four equal splits) and manage N practices (150 kg N ha-1 in four unequal splits)). LCC readings were measured every week from 21 Days After Sowing (DAS) to 84 DAS and nitrogen fertilizer was applied as per treatment schedule. The performance of blanket N and manage N were almost comparable among themselves in all aspects. Grain yield and straw yield increased with increasing LCC levels. The physical and economic optimum doses were found to be 141 and 139 kg N ha-1 to get the grain yield of 5356 and 5350 kg ha-1 respectively. LCC cv.5 which received 30 kg N ha-1 each time with a total dose of 150 kg N ha-1 recorded a grain yield of 5045 kg ha-1 was in corroboration to the predicted optimum dose and yield and also it gave a higher net income than blanket N. LCC cv.4, which received 20 kg N ha-1 each time with a total dose of 60 kg ha-1 recorded comparable yield with blanket N with a saving of 50% fertilizer nitrogen. Hence, under direct wet (drum) seeded condition, L5N30 (LCC cv.5 at the rate of 30 kg N ha-1 each time) can be recommended for a high resource farmer to get higher net income and L4N20 (LCC cv.4 at the rate of 20 kg N ha-1 each time) can be recommended for a low resource farmer to get 50% fertilizer N saving and comparable rice yields with the blanket N.