STUDIES ON WEED FLORA, BARNYARDGRASS COMPETITION AND WEED CONTROL IN THE PUNJAB RICE TRACT

This study was undertaken to give an uptodate account of the weed flora of the Punjab Rice Tract, to study the levels of occurrence/infestation of the most important weeds, to study the weed communities etc.\ud \ud In all 89 species belonging to 73 genera and thirty eight families were recorded. 29 species (32.5%) show all season competition, 16 species (18%) start competition at the time of in-undation by flood water, 3 species (3.5%) compete from midseason and 41 species (46%0 compete late in the season.\ud \ud In region I (zone I & II) 18 species show 30% or more frequency. Out of them, Echinochloa crus-galli spp. hispidula, E. colona, Oryza sativa (red rice), Paspalum paspalodes, Scirpus maritimus, Fimbristylis miliacea, Schoenopectus juncoides, Ammania baccifera, Striga angustifolia, Sagittaria gauyanensis and Ipomoea aquatica show 4th level of occurrence/infestation. All others show lower levels of infestation and are not so important. One showed 5th level of infestation.\ud \ud In region II (one zone, zone III) 14 species show 30% or more frequency. Out of which Echinochloa crus-galli spp. hispidula, E. colona, Oryza saliva (red rice), Scirpus maritimus, Paspalum paspalodes and Cyndon dactylon show 4th level of infestation. All other species show lower levels of infestation.\ud \ud Six weed communities have been recognised in the rice tract. Echinochloa crus-galli spp. hispidula-Scirpus maritimus-Paspalum paspalodes community type. Echinochloa crus-galli spp. hispidula-Sphenoclea zeylanica-Cyperus difformis-Shoenoplectus juncoides community type. Scirpus maritimus-Shoenoplectus juncoides community type. Fimbristylis miliacea-Ammania baccifera-Striga angustifolia community type. Monochoria vaginalis community type. Algae and other aquatics community type.\ud \ud Effect of various barnyardgrass densities on rice was studied. Various barnyardgrass densities decreased rice tiller number, rice plant height, rice straw weight and rice grain weight as compared to the control. The decrease was the least in plant height followed by tiller number, rice grain weight/rice straw weight.\ud \ud An all season competition/interference of barnyardgrass decreased rice straw dry weight according to linear regression equations (Y=1389 - 23.0X, R2=0.93) 23.0 g m-2 density-l% and (Y=1416 - 29.2X, R2=0.93) 29.2 g m-2 in no-lodging and lodging treatments respectively. An all season competition/interference decreased rice grain dry weight according to regression equations (Y=359 - 5.5X, R2=0.90) 5.5 g m-2 density-l% and (Y=318 - 6.9X, R2=0.71) 6.9 g m-2 density-l% in no-lodging and lodging treatments respectively.\ud \ud An all season competition/interference decreased rice straw dry weight according to linear regression equations (Y=1686 - 23.0X, R2=0.93) 23.0 gm-2 density-l% and (Y=1670 - 23.0X, R2=0.93) 23.0 gm-2 density-l% in no-clipping and clipping treatments respectively. According to linear regression equations an all season competition/interference in no-clipping and clipping treatments decreased grain dry weight (Y=419 - 5.4X, R2=0.92) 5.4 gm-2 density-l% and (Y=425 - 5.1X, R2=0.90) 5.1gm-2 density-l% respectively.\ud \ud Effect of various competition/interference periods, 21, 42, 63, 84 and 105 days (season-long) of barnyardgrass was studied at 20 percent density on rice parameters.\ud \ud Rice straw dry weight decreased 0.8, 7.5, 18.1, 22.9 and 24.3 percent as compared to control. Based on linear regression equations season-long competition/interference of barnyard grass reduced rice straw dry weight (Y=1395 - 7.3X, R2=0.89) 7.3 g m-2 day-1.\ud \ud Rice grain dry weight decreased 1.1, 5.9, 12.6, 20.2 and 31.8 percent as compared to control. Based on linear regression equations season-long competition/interference of barnyard grass reduced rice grain dry weight (Y=579 -3.3X, R2=0.83) 3.3 gm-2 day-1.\ud \ud Increase in barnyardgrass shoot biomass dry weight, based on linear regression equations was (Y=-144 + 7.5X, R20.79) 7.5 gm-2 day-1.\ud \ud The effect of various groups of weed control measures on weed biomass and rice yields was studied.\ud \ud On the basis of rice grain yields the following results were shown:-\ud \ud In the row spacing group the best results were shown by 10x10 cm followed by 15x15 cm, 20x10 cm and 20x20 cm. treatments.\ud \ud In the weedicide group the best results were given by Butachlor followed by Saturn, Propanil, Ronstar and 2,4-D treatments.\ud \ud In the water management group the best results were given by flooding followed by normal water and field capacity treatments.\ud \ud In the miscellaneous group the green manure gave the best results followed by hand weeding and fanner’s method treatments