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In order to investigate the effect of levels of drought tension and nitrogen on yield and qualitative  and physiological traits of potato, this experiment as split plots was carried out  based on randomized complete blocks design, with three levels of drought tension S₁ (control, providing 100 percentage water requirement), S₂ (providing 75 percentage) and S₃ (providing 50 percentage of water requirement of potato after emergence to the end of the growing period) as the main factors and four nitrogen fertilizer treatments  N₁ (providing 100 percentage fertilizer requirement), N₂ (66 percentage), N₃ (33 percentage) and N₄ (without applying nitrogen fertilizer) as the sub factors in Agriculture and Natural Resources Research Center of Chahar Mahal va Bakhtiari province. In this experiment maximum tuber yield gained from without tension treatment (S₁) by the amount of 55/9 tons per hectare that had no significant difference at five percent level with S₂ treatment but S₃ with significant difference than two mentioned treatments, produced the average yield 31/7 ton per hectare. N₁ and N₂ treatments produced the highest tuber yield without statistically difference at five percentage level, but lack of nitrogen consumption (N₄) led to the lowest tuber yield (38/7 ton per hectare). Generally, in S₂ and S₃ tension levels, N₂ treatment caused access to the maximum tuber yield. Due to the reduction of tuber yield in S₂ and S₃ treatments within the highest nitrogen consumption level (N₁), the interaction between drought tension and nitrogen on tuber yield was significant at one percentage level.

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In order to investigate the effect of effect of date and depth of tuber cultivation on some agronomic traits of potato cultivars in autumn and spring cultivations, a split factorial experiment was carried out based on randomized complete blocks design with three replications in Ardabil Agricultural and Natural Resources Research Station during the two cropping year 2017-2018. Planting date as the main-factor at three levels (10 Novomber, 10 December and 10 May) and a combination of four potato cultivars (Esprite, Marfona, Savalan and Agria) and four planting depths (10,15,20 and 25 centimeters) as a sub-factor was considered. The results of the investigated traits showed that the height of all four cultivars was significant on average 68 centimeters on the planting date of December and they were at the highest plant height. The highest average number of main stems (4 stems) during two years was observed in November planting date. Savalan cultivar with 9 tubers per plant had the highest number   in November cultivation at a depth of 10 and 15 centimeters. On 10 May planting date, Marfona cultivar had the highest tuber weight (on average with 675 grams) per plant in four planting depths. Single stem in plants is not a desirable trait. In Marfona cultivar, it was three in November and in single-stemmed plants in December, it was less than in November and May. The highest water use efficiency was observed in the cultivar of Sprite in 10, 15 and 25 depths in November and December planting dates. The highest tuber yield was in planting date May compared to two planting dates November and December. The Marfona cultivar at four sowing depths in May planting date 35.86, 32.39, 27.45 and 25.02 ton per hectare, respectively. Finally, it can be concluded that autumn cultivation of potato is suitable, especially in areas with water shortages. The highest water use efficiency in autumn cultivation at depths of 10, 15 and 25 centimeters was related to Esprit cultivar.

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Potato cultivation has a decisive role in the economy of Ardabil province and the basis of economic changes and even people's livelihood is affected by the production and supply of this strategic product and is somehow involved in the economic life of the people. The aim of the present research was to increase water use efficiency and potato tuber yield by choosing an appropriate planting pattern in Ardabil region during 2017-2018. In the present experiment two factors including(planting pattern and potato cultivars) each at four levels (two rows with a planting width of 150 centimeters with two type strips on two stacks, three rows with a planting width of 150 centimeters with two type strips on one stack, four rows with a planting width of 150 centimeters on two stacks and two rows on each stack and the conventional method is a type tape and two rows with a planting width of 150 centimeters with flood irrigation) and the potato cultivars named (Agria, Milwa, Jeli and Banba) with certified seed class based on split block experiment based on randomized complete blocks design in three replications were performed. Based on the obtained results, planting pattern on plant height, number of main stems per plant, number of tubers per plant, tuber yield, water use efficiency, percentage of total nitrogen, vitamin C and regenerative sugars of tubers were significant. Maximum tuber yield and water use efficiency related to Milva and Jeli cultivars with four-row planting pattern with 150 centimeters planting distance spaced on two stacks and in each stack two rows and one type strip, respectively, 75.80 and 72.32 tons per hectare and 10.13 and 9.66 kilogram per cubic meter was obtained. So that the tuber yield of these two cultivars increased by 49 and 41.85 tons per hectare and water use efficiency of 8.25 and 7.52 kilogram per cubic meter, respectively, compared to the conventional cultivation method. Based on the results of factor analysis, the traits plant height, number of main stems per plant, tuber yield and water use efficiency in four-row planting pattern with a planting width of 150 centimeters in Milwa cultivar had the highest values.
 
 

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Due to the trend of population growth, the need to produce more potatoes by improving agricultural management is inevitable. One of the important challenges in agriculture is the management of weeds that, if not controlled, can lead to the destruction of agricultural products and decrease the productivity of agricultural lands. The use of chemical pesticides in agriculture in addition to being able to harm human and animal health, but also lead to environmental pollution and weed resistance to pesticides. For this reason, searching for non-chemical methods of weed management is of particular importance. Today, many believe that the key to successful weed control, especially in sustainable agricultural systems, is the use of cultivars with high competitive ability. This experiment was carried out in 1400-1401 and 1401-1402 on potato plant as a split plot in 3 replications. The first factor was the cultivation of three different potato varieties (Agria, Jely and Lady Rosetta) and the second factor included 5 types of management (complete weeding, rye cover crop, clover cover crop, paraquat herbicide and control). In total, rye, paraquat and clover treatments reduced the dry weight of weeds by 53.63%, 2.40% and 48.36%, respectively. Potato tuber yield increased by 63.75%, 53.21%, 47% and 1.72% in weeding, rye, clover and paraquat treatments compared to the control. According to the results, it was said that cover plants appeared effectively in reducing the density of weeds. The speed of height increase and the percentage of cover were also different in all three cultivars. In the trait of height Agria > Jeli > Lady Rosetta and in the percentage of cover Lady Rosetta > Agria > Jeli appeared.