Evaluation of the Efficiency of Clipfort (Clopyralid, SG 72%) Herbicide in Rapeseed Fields of Fars Province

 Brassica napus L. is one of the most important crops in the world and Iran which accounts for about 20% of the world total oil production. The area under cultivation of this crop is 13,000 hectares in Fars province. Weed interference is also one of the most important limiting factors which decrease crop yields. Weed can decrease crop yield by competing for resources such as water, light and nutrients and production of allelopathic compounds. Weed competition reduced average onion yield by 50% compared with the weed-free control. The most important broad leaf weeds of rapeseed in Fars province are including Carthamus oxyacanthus M.B., Capsella bursa-pastoris, Centaurea solstitialis L., Polygonum aviculare L., Mavla neglecta wallr, Descurainia Sophia (L.) Webb&Berth, Veronica persica L., Sinapis arvensis L. Application of herbicides is the most prevalent method of weed control in Rapeseed fields. Herbicides are recommended for control of broad leaf weeds in rapeseed included of trifluralin, clopyralid and butizanstar. Clipfort is a new herbicide of broadleaf weeds product from Barzegar Barjesteh containing 720 g kg-1 Clopyralid, formulated as a soluble granule (SG). This experiment was conducted to evaluate the efficacy of Clipfort herbicide with some preplant, preemergence and postemergence registered herbicides on weed control and rapeseed yield.

 In order to study the effect of herbicides to control broad leaf weeds of rapeseed fields, an experiment was conducted during 2020- 2021 at Fars Agricultural and Natural Resources Research and Education Center, Darab, Iran. Plots were located on a clay loam soil with pH 7.9. This experiment was carried out in randomized complete block design with 9 treatments and 3 replications. The treatments included post emergence application of Clipfort (Clopyralid, SG 72%) at dose rates of 150, 167,184, 201 g/ha or 108, 120, 132 and 144 a.i. ha-1, post emergence application of Lontrel (Clopyralid, SL 30%) at dose rate of 800 mm/ha or 240 a.i. ha-1, post emergence application of Watch (Clopyralid, SL 30%) at dose rate of 800 mL ha-1 or 240 a.i. ha-1, preemergence application of butisanstar (quinmerac+ metazachlor, SC 41.6%) at dose rate of 205 mL ha-1 or 1040 a.i. ha-1, preplant soil application Treflan (trifluralin , EC 48%) at dose rate of 2000 mm/ha, or 960 a.i. ha-1 and ) and weed free. The narrow leaf weeds were control by Gallant-super (haloxyfop-r-methyl ester 10.8% EC) at dose rate of 1000 mL ha-1 in the 3–4 leaf weeds. The herbicides were applied using a Matabi sprayer equipped with an 8002 flat fan nozzle tip delivering 300 L ha-1 at 200 kP bar spray pressure. Weed numbers and dry weights were determined in random 0.50-m2 quadrates per plot. The grain yield and biological yield were recorded for a 2 m2 and 0.30 m2 from each plot, respectively. Traits were recorded including density, biomass of weed and control percentage of weed, and grain yield and biological yield. Statistical analyses of data were done with SAS var 9 software and comparison of mean was tested using the LSD test at 5% level.

 Broad-leaf weeds infestations included Hirschfeldia incana L., Decurania sophia L., Carthamus oxyacanthus L., Centaurea pallescens L., Veronica persica L., Malva neglecta L. The highest and lowest relative density was V. persica and H. incana 52 and 7 percent respectively. The highest and lowest relative weight was C. oxyacanthus and V. persica 31 and 11 percent respectively. The statistical analysis of the data on the weed density and biomass revealed that herbicides were applied significantly decreased the weed density and biomass. Visual observation confirmed that these weeds were effectively controlled using the Clipfort herbicide. Results showed that applications of Clipfort herbicide at dose rates of 201 g ha-1 provided excellent control of the mention weeds. Thise treatment decreased weed density of H. incana (90 %), D. sophia (98 %), C. oxyacanthus (98 %), C. pallescens (100%), V. persica (66 %), M. neglecta (80 %) and total weed (88%) compared to weed infested control. Also, this treatment decreased weed biomass of H. incana (95%), D. sophia (98%), C. oxyacanthus (99%), C. pallescens (100%), V. persica (68%), M. neglecta (82%) and total weed (91%) compared to weed infested control. However, butizan-star herbicide had the highest control of V. persica. This herbicide decreased density and weed biomass of V. persica by 94 and 97 percent comported to infested control. The grain yield and biological yield were 2.2 and 7.6-ton ha-1 respectively when applied Clipfort herbicide at dose rates of 201 g ha-1. This treatment also increased grain yield and biological yield by 36 and 30 percent, respectively.

 Results showed that the best results achieved from applications of Clipfort herbicide at dose rates of 201 g ha-1. This treatment decreased density and biomass weeds, and increased rapeseed yield. Therefore, the application of Clipfort herbicide (201 g ha-1) is recommended for canola fields.