Effect of weed management on weeds, growth and yield of toria

ABSTRACT A field experiment was carried out at Ludhiana, Punjab during 2009 and 2010 to study the effect of different weed control treatments on growth and yield of rapeseed. Eight herbicide treatments, viz. trifluralin at 0.48 kg and 0.60 kg/ha (pre-plant and pre-emergence), pendimethalin at 0.56 kg and 0.75 kg/ha (preemergence), pendimethalin at 0.75 kg/ha (pre-plant) and oxyfluorfen at 0.25 kg/ha (pre-emergence), two hand weeding (25 and 45 days after sowing) and unweeded control were kept. Two hand weedings, preplant application of trifluralin at 0.60 kg/ha, and pre-plant and pre-emergence application of pendimethalin at 0.70 kg/ha significantly decreased dry weight of associated weeds as compared to unweeded control. Weed control efficiency recorded similar trend as of dry matter of weeds. Accordingly, the increased with application of these weed control treatments. Key words: Pendimethalin, Oxyflourfen, Trifluralin, Toria, Yield Among the various oilseeds grown in India, rapeseed and mustard group is the second most important crop after groundnut, contributing nearly 18% of the total oilseed production in the country. These crops are grown on an area of 5.59 million ha with a production of about 6.61 million tonnes, out of which Punjab occupies 30,000 ha and produces 39,000 tonnes, respectively (Anonymous, 2011). The agro-climatic conditions in Punjab are congenial for the production of oilseed crops. Rapeseed (toria) is an important oilseed crop. Adoption of high-yielding varieties with the judicious use of inputs and irrigation plays an important role in boosting its production. As it is exclusively grown under irrigated conditions, problem of weeds poses a serious threat to its potential production. The crop is infested with both grasses and broad-leaved weeds, which pose a serious competition during early period of crop growth, and reduce seed yield by 15-20% (Brar et al. 1991). Weeds cause enormous damage to the mustard and the magnitude of losses ranges from 30-50%, depending upon the growth and persistence of weed population MATERIALS AND METHODS The field investigation was carried out for two years at Punjab Agricultural University, Ludhiana during 2009 and 2010. The soil of the experimental field was loamy sand in texture, low in organic C, low in available N (230 kg/ha), medium in available P (18.6 kg/ha), available K (150 kg/ ha), and neutral in reaction. The trial was laid out in randomized block design with four replications. Among the herbicidal treatments, trifluralin at 0.48 kg and 0.60 kg/ha, pendimethalin at 0.56 kg and 0.75 kg/ha as pre-emergance, pendimethalin 0.75 kg/ha as pre-plant and oxyfluorfen at 0.25 kg/ha were applied pre-emergence. In addition, two hand weedings (25 and 45 days after sowing) and unweeded control were also kept for comparison. The sowing of rapeseed (toria) variety 'TL 15' was done during mid-September, using a seed rate of 3.75 kg/ ha at a distance of 30 cm in rows. Plant to plant distance of 10 cm was maintained by thinning after 20 days of sowing. All the nutrients, i.e. 62 kg N and 20 kg P 2 O 5 /ha were applied at the time of sowing. Herbicides were sprayed after dissolving in water as per the treatment with knapsack sprayer fitted with flat fan nozzle using a spray volume of 375 litres/ha. The data on dry matter production by weeds was recorded at 45 days after sowing with the help of quadrat (30 × 30 cm) placed randomly at two spots in each plot. Observations on plant height, branches/ plant and siliqua/plant were recorded at harvest from randomly selected five plants from each treated plot. Crop was raised using recommended agronomic practices and protected against insects and diseases. The data on weeds were subjected to square root transformation to normalize their distribution. Weed control efficiency was calculated by using standard formul