The evaluation of efficacy of pendimethalin (prowl) as compared to common herbicides on weeds control in Hamedan potato (Solanum tuberosum L.) fields

Potato (Solanum tuberosum L.) is one of the important crops in Iran with high nutritional value. Potato is grown on approximately 159.061 ha-1 in Iran during 2015-2016 (Sajedi et al., 2012). Even though potato plants have robust growing and quick spreading nature but it turns as a weak competitor with weeds. Potato yields and quality can be seriously affected by the presence of weeds. It was observed that the most critical period of crop-weed competition is first 4-6 weeks after planting when the crop must be kept free from weeds. The yield reduction due to weeds in potato is estimated to be as high as 10 to 80 percent (Auskarniene et al., 2010). The most important weeds in potato field are redroot pigweed (Amaranthus retroflexus L.) and common lambsquarters (Chenopodium album L.). Chemical techniques have been still preferred by growers due to less cost and easier implementation. Weed control with herbicides is limited to a few older compounds with the primary criterion for herbicide selection being previous weed problems, or standard routines not only in Iran but also in the North America (Ivany, 2010). Among herbicides registered (e.g. metribuzin, sulfosulfuron, paraquat and rimsulfuron) in Iran, pendimethalin (Prowl) is a new selective herbicide belong to dinitroaniline family used to control most annual grasses and certain broadleaf weeds in field potatoes.

In order to evaluation of the best herbicidal treatment to weeds control on potato field, an experiment carried out as randomized complete block design with eight treatments and three replication at Hamedan Agricultural and Natural Resources Research Station, during 2017. Experiment treatments included, the application of metribuzin at 0.75 Kg.ha-1, sulfosulfuron 30 gr.ha-1, paraquat 3 lit.ha-1, rimsulfuron 100 gr.ha-1 and pendimethalin in three levels of 2.5, 3 and 3.5 lit.ha-1 with Hand weeding and untreatment. 15, 30 and 45 days after spraying, sampling of weeds and potato carried out in middle of the plots with 0.5 × 0.5 quadrate, respectively. Then, samples were dried at oven-dried at 75 °C for 48 h and weighed. At the final harvest to determine yield, all treatments sampling performed from four lines of each plot by 1 × 1 quadrate. Based on final yield, tubers classified to three groups involved, small tuber (< 35 ml), middle (between 35-75 ml) and large tubers (> 75 ml), then weighted. Results

The results of analysis of variance showed the application different herbicidal treatments had significant effect on weeds density and dry matter and also potato yield. According results, In spite of significant reduce in all of herbicidal treatments on weeds, the lowest weeds density and dry matter were showed in metribuzin. Also, the different applied treatments had significant effect on potato tuber number and yield. The best treatments on increase potato plant dry weight at 15, 30 and 45 days after emergence were hand weeding with 70, 75.02 and 78.64 percent and then metribuzin with 65.09, 70.28 and 72.35 percent, respectively. The highest percentage of increase on potato tuber yield was shown in hand weeding with 22.2 percent and then in metribuzin with 19.8 and rimsulfuron with 16.9 percent.

In conclusion, metribuzin was the best of herbicidal treatment for weeds control and yield enhance in potato. In spite of being particular of paraquat in potato, this herbicide did not enough control of weed at 30 and 45 days after emergence, hence resulted a lower total yield compared to other treatments. Despite the favorable of weeds control by sulfosulfuron, yield reduce caused due to the negative effect of sulfosulfuron, necrosis and clouding of potato leaves and finally the degradation of photosynthesis in potato. Rimsulfuron was as the best treatment after metribuzin on weeds control and yield boost. But application of rimsulfuron not suggestion in potato with barley, rapeseed and alfalfa alternation because of the rate of low decomposition and long-term residues in the soil. The application of pendimethalin at the highest dose e.g. 3.5 l.ha-1 caused to 32.4 percent to promote in potato tuber yield compared to control treatment, whilst the same rate was achieved 49 percent for the metribuzin at 0.75 kg.ha-1. Hence, metribuzin at 0.75 kg.ha-1 is suggested as the best herbicidal treatment in Hamedan potato fields.