عنوان مقاله [English]
Introduction: Potato (Solanum tuberosum L.) is one of the most important root crops in the world. Weed is biotic stress that reduces yield and quality of crops through competition. Chemical weed control seems indispensable and has proved efficient in controlling weeds. Metribuzin and Paraquat are registered herbicides for potato production in Iran which are using early in the growing season. Metribuzin and Paraquat are dual purpose herbicides and destruct photosystem sites of action (Metribuzin is photosystem Ⅱ inhibitor and Paraquat is photosystem Ⅰ inhibitor) which are not control summer weeds. Oxadiargyl belongs to the oxidiazole chemical group and acts as a protoporphyrinogen oxidase inhibitor and primarily has been developed for general weed control in rice and sugar cane. It is commonly used in rice, potato, sunflower, onion, cabbage, chickpea, spanish and lettuce and lavender. Weed control obtained with oxadiargyl at rates above 0.30 kg a.i/ ha was comparable to the standard metribuzin at 1.0 kg a.i/ ha; Oxadiargyl was superior comparing to the standard on Solanum nigrum, a weed of common occurrence in potato plantations, and Panicum subalbidum. The objective of our research was to evaluate the efficacy of Oxadiargyl for weed control and determination of appropriate application time in potato fields.
Materials and Methods: Trials were conducted in Ardabil Agriculture and Natural Resources Research Station during 2013. The factorial experiment with control (with and without weeding) was performed based on randomized complete block design with three replications. Potato cultivar was Agria (common cultivar in Ardabil). The first factor was Oxadiargyl dosages with six levels (0.05, 0.1, 0.2, 0.4, 0.6 and 0.8 Lit a.i/ ha), and the second factor was time of application (at different potato growth stages; potato emergence, stoloning and tuber bulking), as well as two treatments (with and without weeding) were considered as control. Tubers were hand sown on 22th May in rows 75 cm apart and 20 cm on the rows at 10 cm depth. Oxadiargyl was applied by backpack sprayer fitted with 8001 flat fan nozzles. Three weeks after treatment, Weed sampling was carried out by a (0.75× 0.50 m2 quadrate). Tubers were harvested from center row to determine total tuber yield per hectare.
Two three parameter model were fitted to the data including:
Three parameter logistic function ( )
Three parameter sigmoid function ( )
a: maximum weed biomass and total yield, b: The slope and x0 (ED50): the dose causing 50% reduction in weed biomass.
Data were statistically analyzed using SAS 9.1 software and MSTAT-C. Analysis of variance was used to test the significance of variance sources, while Duncan’s Multiple range test (P = 0.05) was used to compare the differences among means.
Results and Discussion: Results showed that maximum reduction percent for redroot pigweed (Amaranthus retroflexus L.), prostrate pigweed (Amaranthus blitoides S. Watson) and total weed biomass achieved by 0.8 lit a.i/ha application. Interaction between oxadiargyl dose and application time showed maximum reduction percent for common lambsqurter (Chenopodium album L.) at 0.8 lit a.i/ha in potato emergence. Alebrahim et al.(2) reported that application of oxadiargyl as pre and post emergence 160 gr/ha reduced biomass of common lambsquarter by 78 and 87 percent, respectively, and oxadiargyl application pre and post emergence 200 gr/ha educed biomass of common lambsquarter by 84 and 93 percent, respectively. Also oxadiargyl application pre and post emergence 240 gr/ha reduced biomass of common lambsqurter by 87 and 94 percent, respectively. Alebrahim et al. (1) reported application of oxadiargyl post emergence 0.4, 0.5 and 0.6 Lit ai/ ha reduced biomass of common lambsqurter 87.75, 93.25 and 94.75 percent respectively. Alebrahim et al., (3) reported greenhouse application of oxadiargyl post emergence 0.1 and 0.6 Lit ai/ ha reduced biomass of common lambsqurter 70.17 and 100 percent respectively. Alebrahim et al., (2) reported that application of oxadiargyl pre and post emergence at 160 gr/ ha reduced biomass of redroot pigweed 76 and 82 percent respectively and applying 200 gr/ ha pre and post emergence reduced redroot pigweed biomass 79 and 90 percent respectively. and 240 gr/ha reduced redroot pigweed biomass 85 and 95 percent respectively. Alebrahim et al., (1) reported application of oxadiargyl post emergence 0.4, 0.5 and 0.6 Lit a.i/ ha reduced redroot pigweed biomass 82.75, 90.75 and 95 percent respectively. Furthermore greeonhouse application of Oxadiargyl post emergence 0.1 and 0.6 Lit a.i/ha reduced biomass of common lambsqurter 65.92 and 100 percent respectively (3). Barb et al., (7) reported application of oxadiargyl 0.25, 0.30, 0.35, 0.40, 0.45 and 0.50 kg a.i/ ha reduced total weed biomass 73, 77, 77, 82, 82 and 86 percent 5 week after treatment and 74, 73, 80, 80, 83 and 84 percent 8 week after treatment respectively. Among oxadiargyl application time at different potato growth stages, potato emergence reduced redroot pigweed and total weed biomass 60.01 and 44.51 percent respectively as compared to control (weedy); also tuber bulking reduced Prostrate pigweed biomass 67.49 percent as compared to control (weedy). Application of 0.8 Lit a.i/ ha and potato emergence stage produced maximum total tuber yield per hectare. Alebrahim et al., (1) reported potato tuber yield 27.60, 32.30 and 35.3 ton/ha while oxadiargyl applied 0.4, 0.5 and 0.6 Lit a.i/ ha pre emergence and 33.17, 35.93 and 36.85 ton/ha while applied 0.4, 0.5 and 0.6 Lit a.i/ha post emergence.
Conclusion: Results showed that maximum reduction percent for redroot pigweed, prostrate pigweed and total weed biomass was achieved by 0.8 lit a.i/ha application. Interaction between herbicide dose and application time showed 0.8 lit a.i/ha at potato emergence reduced common lambsquarter biomass 87.94 percent. Application of oxadiargyl at potato emergence stage reduced redroot pigweed and total weed biomass and increased total tuber yield. However suggested to carry out the experiment over several years, to evaluate potato tolerance of varieties to Oxadiargyl and the effectiveness of other herbicides mixing with Oxadiargyl for future researches.