Dr. D. I. JIRALIRAVI S. MUKKUND2018-04-202018-04-202015-06http://krishikosh.egranth.ac.in/handle/1/5810044244A field experiment was conducted at Main Agricultural Research Station, University of Agricultural Sciences, Dharwad during kharif 2014 to investigate the physiological studies on weed control efficiency in Maize. The results revealed that pre-emergence application of Metribuzin was phytotoxic while, Atrazine, 2, 4-D and Pendimethalin @1.0 kg a.i ha-1 were not phytotoxic. The data on monocot, dicot and total number of weeds were found maximum in unweeded control and the herbicide treatment Atrazine @ 1.0 kg a.i ha-1 fb two hoeings fb Atrazine @ 1.0 kg a.i ha-1 decreased these parameters. The weed control efficiency was maximum with Atrazine @ 1.0 kg a.i ha-1 fb two hoeings fb Atrazine @ 1.0 kg a.i ha-1 followed by Atrazine @ 1.0 kg a.i ha-1 fb two hoeings fb 2, 4-D@ 1.0 kg a.i ha-1. The morpho-physiological, biochemical and growth parameters viz., plant height, leaf area index, photosynthetic rate, transpiration rate, stomatal conductance, chlorophyll content in leaf and total dry mater accumulation were lowest in unweeded control and the application of Atrazine @ 1.0 kg a.i ha-1 fb two hoeings fb Atrazine @ 1.0 kg a.i ha-1 followed by Atrazine @ 1.0 kg a.i ha-1 fb two hoeings fb 2, 4-D@ 1.0 kg a.i ha-1 increased the above said parameters. Weeds decreased grain yield significantly. Grain yield was highest in Atrazine @ 1.0 kg a.i ha-1 fb two hoeings fb Atrazine @ 1.0 kg a.i ha-1 followed by Atrazine @ 1.0 kg a.i ha-1 fb two hoeings fb 2,4-D@ 1.0 kg a.i ha-1 and they recorded significantly lowest weed index. The benefit cost ratio was highest in Atrazine @ 1.0 kg a.i ha-1 fb two hoeings fb Atrazine @ 1.0 kg a.i ha-1 followed by Atrazine @ 1.0 kg a.i ha-1 fb two hoeings fb 2,4-D@ 1.0 kg a.i ha-1.ennullThesis