Evaluation of some Herbicides for Potato (Solanum tuberosum L.) Weed Control in Jiroft and Karaj

Potato (Solanum tuberosum) is an annual crop that belongs to the Solanaceae family. It contains abundant starch and ranks as the world’s fourth most important food crop, after maize, wheat and rice. It is one of most important crops in Iran. The total area under potato cultivation was 186 thousand hectares during 2011 and 2012. Weeds are one of the greatest limiting factors to efficient crop production. Application of herbicides is the key method of weed control in potato fields, both in the world and Iran. Herbicides that commonly are used for weed control in potato fields of Iran are metribuzin, paraquat, rimsulfuron, pendimethalin and sulfosulfuron.
In order to study the effect of herbicides to control weeds of potato fields, field experiments were conducted at the Agricultural Research Center of Jiroft and Karaj. Plots were located on a sandy loam soil with a pH of 7.4 in Jiroft, and loamy soil with a pH of 7.7 in Karaj. The experiments were conducted during 2009-2010. Potato variety used in Jiroft was Santeh and Satina in Karaj. The experimental design was the randomized complete blocks design (RCBD), with four replications. Weed control treatments included paraquat (20% SL) at 3 lit/ha as early post- emergence, metribuzin (70% WP) at 750 gr/ha as preemergence, pendimethalin (33% EC) at 3 lit/ ha as preemergence, rimsulfuron (25% DF) at 60 gr/ha applied with adjuvant cytogate at 2.5% volume of water early post emergence, sulfosulfuron (75% DF) at 35 gr/ha (postemergence), metribuzin at 750 gr/h rimsulfuron at 60 gr/ha with adjuvant cytogate at 2.5% volume of water, , metribuzin at 750 gr/ha pendimethalin at 3 lit/ ha, metribuzin at 750 gr/ha sulfosulfuron at 35 gr/ha, paraquat at 3 lit/ha rimsulfuron at 60 gr/ha with adjuvant cytogate at 2.5% volume of water, paraquat at 3 lit/ha pendimethalin at 3 lit/ha, paraquat at 3 lit/ha sulfosulfuron at 35 gr/ha and hand weeding. Each plot was 4 m wide and 8 m long with 4 rows and 75 cm distance among rows. Density and dry weight of weeds and potato yield were recorded.
Results indicated that 6 broadleaf weeds were dominant in the fields included prostrate pigweed (Amaranthus blitoides), bindweed (Convolvulus arvensis), malva (Malva neglecta) in Jiroft, and red rooted pigweed (Amaranthus retroflexus), datura (Datura stramonium), bladder hibiscus (Hibiscus trionum) in Karaj. Visual observation confirmed that the most weeds were effectively controlled using herbicide treatments. The statistical analysis of the data revealed that the herbicides applied for weed control in potato have significantly decreased weed density and dry weight. The lowest weed density and dry weightof prostrate pigweed were observed in plots treated with paraquat rimsulfuron. This treatment reduced density and dry weight of prostrate pigweed by 70% and 69% in Jiroft. However, Red rooted pigweed was controlled better than prostrate pigweed in Karaj. All treatments of mixed herbicides reduced density and dry weight of red rooted pigweed by 100% in Karaj. Maximum control of bindweed was obtained with metribuzin rimsulfuron. This treatment reduced density and dry weight of bindweed by 35 % in Jiroft. The highest control of malva was achieved with metribuzin plus rimsulfuron in Jiroft. This treatment reduced density and biomass of malva by 61 and 56%, respectively. The best control of datura was obtained with paraquat plus rimsulfuron in Karaj. This treatment reduced datura biomass by 98%. Maximum control of bladder hibiscus was obtained with paraquat plus rimsulfuronin which dry weight was reduced by 98%. The highest potato yield (48 ton/ha) was obtained by application of metribuzin plus rimsulfuron in Jiroft. Potato yield was also increased with this treatment by 40%. The least potato yield (32 ton/ha) was obtained with pendimethalin in Jiroft. The maximum potato yield (32 ton/ha) was obtained by application of paraquat plus rimsulfuron and paraquat plus pendimethalin in Karaj, and minimum potato yields were obtained by application of sulfosulfuron and pendimethalin.
Results of both years and locations showed that application of herbicide mixture improved weed control and potato yields. Pendimethalin and rimsulfuron are suitable alternatives for herbicide rotations in potato fields and can replace metribuzin and paraquat.