جستجوی مقالات مرتبط با کلیدواژه "درصد ماده خشک" در نشریات گروه "زراعت"

In terms of harvested land area, potato ranks fourth in the world after wheat, corn and rice. In addition to providing energy and good quality protein, it is also considered as a source of vitamin C and minerals. Despite the fact that iron is the fourth most abundant element in the earth's crust, only a small amount of iron can be used by plants in well-ventilated soils. Therefore, iron deficiency is one of the factors limiting the growth and development of plants.
 

This experiment was carried out in a factorial trial in the base of a completely randomized design in three replications in a greenhouse conditions of Agricultural Research Institute of Hamedan (Jorqan) during the crop years of 2017-2018 and 2018-2029. The experimental factors include the weight levels of microtuber at three levels of 3-1, 3-5 and 5-10 grams and different iron fertilizers at seven levels, control, iron chelate in the form of soil consumption at the rate of 20 micromolar, nano iron oxide in the form of soil consumption to The amount of 20 micromolar was 1 and 2% foliar spraying of iron chelate and 1 and 2% nano iron oxide foliar spraying. The internal temperature of the greenhouse was provided by adjusting the air conditioning system and central heating in the range of 18 to 20 °C  at night and 26 to 28 degrees during the day. The humidity of the greenhouse was also 60-65%. At the end of the experiment, after processing the crop, the plants were harvested and the yield and yield components were determined. Leaf greenness index in this experiment using SPAD device (Minolta 502 model) using three fully developed terminal leaves from ten plants in the budding stage in the middle part of the leaf on one side of the main vein, at 9:30 to 10:00 in the morning. It was measured in order to minimize daily changes. To measure the percentage of dry matter, 200 grams of tubers were randomly selected from each treatment, then the tubers were chopped and placed in an oven at a temperature of 75 degrees Celsius, and after their weight was fixed, they were weighed again. Then, based on the ratio of fresh and dry weight of the tubers, the percentage of dry matter of the tubers was determined (Hagman and Martenssen, 2009). 

The results showed that the height of the plant, the number of stems per plant, the number of tubers per plant, the weight of tubers, the weight of tubers per plant, the percentage of dry matter and the greenness index increased with the increase in the weight of microtubers, and the most improvement in the morphological and qualitative characteristics of potato in microtubers. 5-10 grams were observed. With the application of iron chelate and nano iron oxide fertilizers, potato yield and yield components increased. The maximum tuber weight in the plant was shown in the treatments of 20 micromolar nano iron oxide and 2% nano iron oxide. The highest tuber weight in the plant in the 1-3 gram microtuber is 405.23 grams related to the consumption of 20 micromolar nano iron oxide, in the 3-5 gram microtuber is 444.61 grams related to the application of 2% iron chelate solution and in the microtuber 5-10 grams in the amount of 556.92, 544.52, 482.6 and 465.82 grams corresponding to the treatments of 20 micromolar nano iron oxide, foliar spraying of 2% nano iron oxide, foliar spraying of 1% nano iron oxide and solution The application was 2% iron chelate 

Microtuber 5-10 grams was able to acquire the best size of microtuber due to having suitable nutrients and accelerating the greening of plants and increasing photosynthesis and providing nutrients. The application of nano iron oxide fertilizer was more effective in improving the quantitative and qualitative yield of potatoes compared to iron chelate.

Determination of the most suitable time for crop planting is one of the basic requirements to gain the highest yield and income. Planting date is one of the most important factors in growth, development and yield production in potato planting effects of temperature fluctuations on growth and tuber abnormality and inappropriate quality comes from the special features of the that region being uncontrolled by farmers.

This study was conducted in 2015-2016 in research station of Faculty of Agriculture, Ferdowsi University of Mashhad as split-plot based on Complete Randomized Block Design with three replications. Treatments were combination of four planting dates (March 5th, March 19th, April 3th and May 4th) as main plot and three potato cultivars (Agria, Fontane and Sante) as sub-plots. Harvesting was done 90 days after 50% of emergence.

Number of stem per plant as one of the effective potato yield components was not affected by planting date. Results indicated that as planting date was delayed from March 5th to May 4th, leaf area index was increased by 64 and 85% in two cultivars of Agria and Fontane while a decreasing trend of this parameter was observed in Sante. Number of tubers per plant was decreased by delaying planting date from March 5th to May 4th except in Fontane in which number of tubers per plant was increased in April 3th and was reduced thereafter. The highest and lowest tuber yield with a difference of 12391kg.ha-1was found in April 3th and March 19th, respectively and was observed in Fontane cultivar. Tuber dry matter percentage of Agria was increased as planting date delayed while it was increased till April 3th and reduced in Fontane. The highest (22.13) and lowest (18.50) tuber dry matter percentage of Sante was found in March 5th and 19th, respectively. An increasing trend of potato tuber specific weight was observed with delaying planting date in a way that the highest and lowest mean of this parameter was found in March 19th and May 4th, respectively. No significant difference was observed between Agria and Fontane in different planting dates according to reduced sugars content of tubers. Total antioxidant and starch of potato tubers was increased in all three cultivars as planting date was delayed and reduction sugar decreased by delayed in planting date.

The number of tubers per plant as well as the number of tuber <30mm per plant decreased with the delay in planting dates, which was affected by the photoperiods of the growing season. Although the tuber yield decreased with delay in planting dates, but the percentage of marketable tubers was higher in late planting dates than in early planting. Late planting dates were better than early plantings. Sante showed a better performance in early planting dates compared to the two other cultivars, producing more marketable tubers with higher quality and dry matter percentage. Generally, it could be concluded that in Mashhad weather conditions, Sante is more appropriate for early planting compared to Agria and Fontane but its superiority is lost when planting date is delayed.

Maize (Zea mays L.) has high yield potential and suitable ensiling properties and is a valuable source of energy and nutrients for cattle (Johnson et al., 1999). Timely planting is critical for maximizing yield for both grain and biomass in maize and therefore, growers are concerned about the yield response of maize to planting date. However, optimum planting date may vary from area to area due to differences in climate and the length of the growing season where the crop is produced (Maresma et al., 2019). The cultivation of maize hybrids in Hamedan is done regardless of their growth period. So, the present study was conducted to determine the appropriate date for planting the hybrids of silage maize in the different maturity groups in Hamedan region.

A two-year experiment (2017 and 2018) was conducted at Ekbatan station of Agriculture and Natural Resources Research and Education Center in Hamedan province, Iran. The statistical design of experiment was a split plot, where planting dates (22 May, 10 June, 1 July and 21 July) were used as the main plot, and the hybrids with different maturity time (KSC201, KSC260, KSC400, KSC647, BC678, KSC703 and KSC70) as the subplots. Ten plants were randomly selected from each plot and plant height, stem diameter and fresh weight ratios of ear, stem and leaf to plant aerial parts were measured. To determine the fresh forage yield, a sample of 4 square meters was taken from each plot and weighed. Then, the samples were placed in an oven at 70 °C for 48 hours and after drying, they were weighed again to estimate the dry forage yield. The percentage of crude protein in dry forage was measured by Kajeldal method. Considering the occurrence of severe autumn cold in early of November that prevented the timely harvesting of hybrids with long growth period of KSC703 and KSC704 cultivated on the forth planting date, only the data obtained from the first to third planting dates was subjected to statistical analysis. Analysis of variance and comparisons of the mean effect of planting date and hybrid and their interactions were performed based on the least significant difference test (LSD) at a 5% probability level.

The results of compound analysis indicated that different planting dates differed in terms of all traits, except protein yield, and the highest amounts of fresh and dry forage yields (60008 and 18595 kg.ha-1, respectively) were for the first planting date and the lowest amounts of the mentioned traits (50643 and 14672 kg.ha-1, respectively) were for the third planting date. It seems that the high forage yields on the first planting date were due to the suitable temperature conditions that allowed the plant completed its growth period and increased the accumulation of photosynthetic materials. The effect of hybrid on all the traits was significant and KSC703 and KSC704 hybrids gave the highest values of fresh (71322 and 68443 kg.ha-1, respectively) and dry matter (21527 and 20197 kg.ha-1, respectively). The superiority of late (and medium) maturing hybrids over early maturing hybrids in terms of fresh and dry yields, may be due to the longer growth period. Despite KSC201, KSC260 and KSC400 hybrids gave the lowest amounts of growth period (78.06, 89.61 and 97.22 days), fresh yield (37469, 40499 and 45732 kg.ha-1, respectively) and dry yield (11620, 12395 and 14720 kg.ha-1, respectively), these hybrids showed the highest values of crude protein (14.63, 14.09 and 14.04%, respectively) and ear to plant weight ratio (38.44, 35.97 and 34.95%, respectively). Therefore, cultivation of the early maturing hybrids is recommended if high quality forage is targeted. Also, it is not recommended to delay the planting FAO maturity groups 700 and 600 maize to early summer season, due to excessive delay in land preparation for the cultivation of autumn crops.

Due to the possibility of timely harvest, acceptable yield and suitable forage quality of early maturing hybrids on the last planting date, in case of delay in planting date to late July in Hamedan region and areas with similar climate, planting early maturing hybrids (especially KSC400) is recommended.

Increasing fruit yield and improving fruit size along with high dry matter percentage, is the main goal of kiwifruit growers in the worldwide. There are deferent techniques to access exportable fruit size with high dry matter content in kiwifruit including summer pruning, root pruning and flower and fruit thinning. Furthermore, trunk girdling and plant growth regulators such as Forchlorfenuron (CPPU) are widely used in modern kiwifruits orchards to increase fruit yield and quality.

In this study, the effect of vine trunk girdling at different times (spring, summer, autumn), CPPU (10 mg L-1 of active ingredients in water), combined effect of CPPU and summer girdling as compared to control (without girdling and CPPU treatments) on fruits quality of Hayward kiwifruit at harvest and the end of cold storage was evaluated in complete randomized block design in 1398. Fruits were harvested based on soluble solids index and fruit quality was measured immediately after harvest and after three months storage at 1o°C.

The results showed that the summer girdling with CPPU, CPPU alone and spring girdling increased 37.99, 32.19 and 22.11% of kiwifruit weight compared to control respectively. Application CPPU increased fruits weight, length and diameter, but decreased fruits dry matter percentage and the ratio of soluble solids content to titratable acidity (SSC/TA) the compared to control. No significant differences were found between CPPU treated fruits and control for fruit tissue firmness, soluble solids content at harvest time and after three months storage in cold storage. The summer trunk girdling together with CPPU spray increased fruit weight (38% as compared to control). In addition, this treatment showed the highest fruit dry matter percentage, soluble solids and SSC/TA at harvest time and the lowest fruit weight loss (0.66%) with the highest fruits tissue firmness (3.96 kg force) at the end of three months storage time. Summer girdling showed the highest fruit weight loss (2.54%) at the end of storage, while no significant difference was found between autumn and spring girdling treatments compared to the control.

Overall, the results showed that summer vine trunk girdling with CPPU spray not only improved kiwifruit size and yield but also improved fruit quality by increasing fruits dry matter percentage and soluble solids content. Such fruits showed the longer postharvest life as compared to control and other treatments. Therefore, it is recommended for improving fruit size and quality in Hayward kiwifruit, CPPU spray was applied with summer vine trunk girdling.

In order to study the effect of foliar application of salicylic acid (SA) and biostimulants on growth, physiological characters, nitrogen, phosphorus and potassium concentration and pod yield of common bean cv. Sanry under different irrigation regimes, the experiment was conducted split plot in a randomized complete block design with three replicates in research filed of university of Zanjan during 2015. Three different irrigation (I) regimes (100, 75 and 50% ETc) and foliar application of salicylic acid (0.5, 1 and 1.5 mM), Megafol (0.1, 0.2 and 0.3% MF) and to distilled water as control were conducted. The results showed that water deficit stress significantly reduced growth and pod yield. Foliar application of SA and MF enhanced growth and fruit yield. The irrigation × foliar treatments interactions results suggested that maximum leaf number (43.1), leaf area (2729.3 cm-2) and pod yield (6193.9 kg.ha-1) was obtained using MF 0.2% under I100 %ETc. Plants sprayed with SA 1.5mM and MF 0.2% exhibited higher stomatal conductance (205.27 mM.m-2s-1) under I100 %ETc. The highest N (2.47%), P (181.6 ppm) and K (0.88%) concentration was found in plants sprayed with MF 0.2%, SA 1mM and MF 0.3%, respectively under I100 %ETc. According to the results, MF 0.2% and SA 0.5 mM had the highest effects on growth and pod yield under water deficit stress.

To evaluate some fruit characteristics and yield of seven promising olive genotypes a field experiment was carried out- using randomized complete block design with three replications in 2016 in Dallaho research station, Sarepol Zahab, Iran. Fruit yield and some fruit characteristics including; fruit weight, stone weight, drymatter (%), oil content were measured. Results showed that genotypes were significantly different for fruit yield and fruit characteristics. Genotype × year interaction effect was significant on fruit weight, fruit flesh weight, stone weight, flesh percentage, fruit yield and oil yield. Dd1 genotype with mean of 7.87 g had the heighest and Ps1 genotype with 3.31 g had the least fruit weight. Genotype, year and genotype × year interaction effects were significant on fruit yield and oil yield. The highest fruit and oil yield belonged to Bn6 with 17653 kgha-1 and 2362.1, respectively. Cultivar Sevillano had the lowest fruit yield (3000 kgha-1) and oil yield (218.9 kgha-1). Considering fruit and oil yield, Bn6 and Dd1 were identified as superior genotypes.

The storage life of mushrooms is less than the other vegetables due mainly to high water contents and a porous and thin epidermal structure. This research was aimed at obtaining a suitable compost combination and an optimal condition of maintenance for increase the storage life of button mushroom. The experimental factors consisted of two maintenance temperatures (4°C and 25°C), two types of packages (transparent and covered with foil) and four types of composts (wheat straw and chicken manure, wheat straw and horse manure, rice straw and chicken manure, rice straw and olive bagasse). Attributes such as percent of weight loss, browning area, percent of dry matter, total phenol and antioxidant capacity of stored samples were assessed 7 days after harvest in room temperature and 25 days after harvest in refrigerator temperature. Mushrooms grown in rice straw and olive bagasse compost had the highest dry matter (11.62%), when stored in room temperature. Mushrooms grown in rice straw and olive bagasse compost had the highest antioxidant capacity in both refrigerator and room temperatures when stored in the package covered with foil. According to our results, rice straw and olive bagasse compost is potent to increase the storage life of the button mushroom and merits further studies.

In order to study the effect of cultivar and different cuts on forage yield and protein content of alfalfa cultivars (Mesasirsa, Santetic, Yazdi, Bami, Nik Shahri and Baghdadi), an experiment was conducted in the form of split plot arrangement in randomized complete block design with four replications at Agricultural and natural resources research center of Yazd in 2013-14 growing season. The results showed that effect of cultivar and different cuts was significant on all traits. Misasirsa, Yazdi, Bami and Santetic had the highest fresh forage yield (17.29, 17.02, 17.37 and 18.27 ton/ha) and dry forage yield (4.47, 4.7, 4.56 and 4.59 ton/ha) respectively. Among the cultivars and different cuts, NikShahri and Yazdi had the highest (1.16 and 1.18 respectively) and first harvest had the highest (2) leaf stem ratio. Among the cultivars, the percent of dry matter of NikShahri cultivar was higher than (27.8) other cultivars. First and third harvest had the highest dry matter percent (30.5 and 29.99 respectively). Among the different cuts, First harvest had the highest dry forage yield (6.55 ton/ha). Protein percent of mesasirsa cultivar (21.98) was higher than other cultivars. First and third harvest had the highest protein percent (22.81 and 21.98 respectively). Generally, Yazdi cultivar in first harvest had the highest leaf stem ratio (2.68), dry matter percent (34.68) and dry forage yield (8.03 ton/ha), So, this cultivar was most suitable for Yazd region.

In all areas where irrigation is necessary for crop production, salinization of soil is also unavoidable. Therefore, to guarantee the continuation of crop production in such areas, growing crop species with threshold of yield reduction well above the salinity of the irrigation water is needed. Agriculture and animal husbandry in arid and semi-arid regions always have been together. Therefore, provide forage for livestock in these areas is one of the main concerns of farmers. Kochia (Kochia scoparia L.) is an annual salt- drought tolerant plant. It is capable to rapid established in salinity soils, and is a ground cover plant that can introduced as an alternative fodder, in arid and semi-arid areas. Therefore, the aim of this study was to evaluate the drought tolerance of kochia in irrigation with saline water at different growth stages with emphasis on the forage characteristics.
Experiment was conducted as split-plot based on Complete Randomized Block Design with three replications to evaluate some photosynthetic characteristics of halophyte plant, Kochia scoparia, in different salinity levels at the Salinity Research Station of Ferdowsi University of Mashhad, Iran in 2008. Three levels of drought stress (control, no irrigation in vegetative stage (recovery treatment) and no irrigation at reproductive stage for one month (stress treatment)), and two kochia local cultivars (Birjand and Borujerd) were allocated as main and sub plots, respectively. Plants were irrigated with underground water having electrical conductivity (EC) of 5.2dS.m-1. Forage harvesting was carried out after the third-stress treatment, in full flowering stage.
The results showed that plant height in vegetative growth stage was more sensitive to water stress than the reproductive stage in kochia. In all irrigation treatments at different growth stages, Boroujerd local cultivar produced taller plants than Birjand local cultivar and the greatest reduction plant height in both local cultivars occurred in drought stress at vegetative growth stage. Branch number and forage yield in kochia were not affected by Irrigation treatments. Total dry matter percent of drought stress treatment at both vegetative and reproductive stages were significantly higher than control full irrigation. Stems and leaves yield of Boroujerd and Birjand local cultivars were not significantly affected by irrigation treatments. The highest and lowest leaf to stem ratio were obtained in drought stress at vegetative and reproductive growth stage, respectively.
Four weeks irrigation cuts at vegetative and reproductive stages did not affect forage yield of kochia, and this plant showed the high capability to recover the adverse effects of drought stress in the vegetative growth stage. Generally, kochia has morphological features for introduction as a forage crop and arid and saline areas. In addition, the physiological mechanisms of drought and salt tolerance of kochia may introduce it as a candidate forage species for cultivation and to help feed the livestock in areas where salinity and drought stress is dominant.

Introducing potato cultivars with high yield, early maturing and desirable quality have a key role in food security, decreasing the fluctuation of the price and the store costs and also providing fresh crops throughout the year. Potato (Solanum tuberosum L.) plant is one of leading agricultural products in the world with 365 million ton glands in year stands in fourth place after wheat, rice and corn.
The main objective of the breeding program is yield. Increase in plant yield in the past due to the gradual elimination of defects visible by experts and today the new criteria for selection are based on principles of morphological and functional characteristics associated with the plant. Variety is one of the effective factors on plant growth and development on potato that yields components of potato is heavily dependent on it. Yield increasing in each variety affect the genetic and natural structure of variety.
Nine clones of Solanum tuberosum L. cv. Kennebec from sources in Victoria, South Australia and Tasmania, and the commercially grown clone, clone 1, which was imported from Vancouver, were multiplied from pathogen-tested seed and compared in 3 Victorian potato districts during 2 seasons. The results showed that differences exist in total and size grade yield and tuber number and appearance between clones of a cultivar. They further highlight the importance of selection work to maintain desirable characteristics of established cultivars and to remove mutants with undesirable characteristics.
The results of the study, Hassanpanah and Hassanabadi (2012) showed that the clones 397003-7, 396151-27, 397045-100 and Savalan (check) produced higher total and marketable tuber yield, tuber number and weight per plant, plant height, main stem number per plant, tuber size average and stable tuber yield. These clones produced high and mid-uniform tuber, tuber inner crack and tuber inner ring, mid-late maturity and mid and high dry in comparison to those of check. Based on results of this experiment, the clones 397003-7, 396151-27 and 397045-100 could be selected for Ardebil region.
The objective of this research was to evaluate the quantitative and qualitative traits of cultivars and advanced potato clones in spring cultivation (Jolge-e-Rokh region).
In this research, 18 potato clones for the quantitative and qualitative traits were compared with three check cultivars including: Agria (suitable for French-fries), Marfona (suitable for boiled eating) and Lady Rosetta (suitable for chips) in Jolge-Rokh Agriculture Research Station, the location 35'¸ 50° north latitude and 59° east longitude and 1721 m above sea level, in crop year 2011. Experimental design was Randomized Complete Block Design (RCBD) with three replications. Treatment consisted of 18 advanced potato clones: 396151-8, 397045-4, 397045-10, TP12-13, TP21-29, TP12-8, 397007-16, 397007-17, 396140-6, 397009-8, 397015-14, 397003-7, 396151-27, 397045-100, 397097-9, 396151-20, 397045-7 and 69 indigenous with three control cultivars (Agria, Marfona and Lady Rosetta). Tubers were planted on two rows with 6 meters length. Distance between row and plants on the row were 75 and 25 cm, respectively. Area of each plot was 9 square meter. The evaluated characters were total yield, marketable yield, eye number, dry matter percentage, tuber number per plant, tuber weight per plant and mean of tuber weight. In order to measure total yield, after maturity, and remove the aerial organs, all of the tubers were harvested and the fresh weight was obtained. After removal of the tumor in bad shape, with soft rot and smaller than 30 mm that cannot be sold as part of the marketable yield, rest of them were used to measure marketable yield. Tuber dry matter percentage (TDM%) was determined from the relationship between fresh and dry weights of sub-sample of 8-10 thinly sliced tubers dried for 48 h at 80° C. Data were analyzed using SAS 9.1 software. The analysis of variance on test data and comparison to the middle of the LSD test was performed at the 5% level.
The results showed that differences were significant among cultivars and clones in total yield, marketable yield, dry matter percentage, tuber number and weight per plant and mean of tuber weight. Based on the results of the analysis of variance of total tuber yield were observed among the clones, there was significant difference at 1% level. The maximum total yield of tubers related to the 397007-16 clone among the clones and the lowest total yield of tubers, related to the 397097-9 clone. The 397007-16 clone and Marfona cultivar had the highest tuber weight and the 397097-9 clone had the lowest tuber weight. The indigenous 69 and the 397045-10 clones had the highest and lowest number of tuber per plant, respectively. The 69 indigenous clone had the highest amount of dry matter percentage compared to other clones meaning that this clone is suitable for chips production.
Behjati et al (2013) in their research in order to the evaluation of yield and effective characteristics on yield of promising potato clones, showed a treatment effect on number of tubers per plant, average weight of single tuber per plant, total yield of tubers and marketable tubers yield was significant at 1% level.
In general, present results showed that 397007-16 clone was better in tuber weight per plant and total yield compared to other clones.

To evaluate the yield and nitrate concentration in five Iranian spinach landraces, a study was conducted in 2011 using a randomized complete block design with four replications at Isfahan Agricultural and Natural Resources Research Station. In this field experiment, the evaluated landraces included spiny seed Varamin, Varamin leafy, Shahreza, Najaf Abad and Kashan. Varamin spiny seed landrace with 47830 kg ha-1 produced the maximum yield among the landraces. Greater numbers of leaves (more than 20 leaves) and lateral branches (more than 3.5) in the spiny seeds Varamin, Varamin leafy, and Kashan was the reason behind their higher yield. In all five landraces tested, nitrate concentration in the middle leaves of the plant was higher than the upper or lower leaves, though there was no significant difference between the upper and lower leaves in terms of nitrate content. Leaf nitrate concentration in spiny seed Varamin landrace was the highest (1380 ppm based on fresh weight) but there was no significant difference between the amounts of nitrate in this landrace and other landraces (except Kashan landrace). The results showed that the spiny seed Varamin landrace, with acceptable yield and nitrate content can be used as a substitute for genotypes that are common in Isfahan province.

A field experiment was carried out to determine the interactions of cultivar planting date on total and marketable yields of potato. cvs. Cosima، Sante، Savalan، Santana and Almera، were planted in four planting dates، 22 December)mean daily air temperature was 16 and 14. 1 ºC in the first and second year of experiment، respectively)، 01 January)mean daily air temperature was 16. 5 ºC in both year of experiment)، 11 January)mean daily air temperatures were 10 and 17. 3 ºC in the first and second year of experiment، respectively) and 21 January)mean daily air temperature was 11. 5 and 4. 4 ºC in the first and second year of experiment، respectively) in two years (2009-2010 and 2010-2011) in Behbahan Agriculture Research Station، Khuzestan، Iran. A split-plot arrangement with four planting dates as main plots and five cultivars as sub plots in randomized block design with three replications was used. One week before harvesting haulms were defoliated. Tubers were harvestd in mid May. The longest duration period between planting date and 50% emergence (51. 83 days) belonged to planting date of 22 December. By delaying planting date، days to 50% emergence decreased at 1% probability level. Effect of planting date on total and marketable yield، yield components and tuber dry matter (%) was not significant. Cosima produced the highest stem number plant-1 (3. 34) and tuber number plant-1 (7. 15). The highest tuber weight (64. 04 g) and tuber dry matter (22. 26%) belonged to Santana and Savalan، respectively. Planting date × cultivar interaction effect on total and marketable yield was significant. The marketable yield of Savalan was higher than the other cultivars in most of planting dates. Results of this experiment showed that planting of Savalan on 22 January is recommended for winter season potato planting in Khouzestan Province.

To study the effect of different irrigation intervals on the yield and plant characteristics of potato (Solanum tuberosum L.), a field exoeriment was carried out in split plot arrangements using randomized complete block design with three replications at research field station, faculty of agricultural, the university of Urmia, in 2008 growing season. Experimental treatments were included irrigation intervals at four levels: 6 (I0), 10 (I1), 14 (I2)and 18 (I3) day assigned to main plots, and growth stages at two levels: 50% emergence to 50% flowering (GS1) and 50% flowering to physiological maturity (GS2) randomized in sub-plots. Results showed that tuber fresh yield, tuber dry yield, mean of tuber fresh weight.plant-1, stem diameter, plant height, tuber size and dry matter at1%, and the number of stem and relative water content in 5% probability level were affected by different irrigation intervals. However, irrigation intervals had no significant effect on mean of tuber dry weight.plant-1,specific weight and cell membrane stability. Significant difference was also observed between the growth stagesfor stem diameter, plant height and cell membrane stability. Interaction effect between irrigation intervals ×growth stages was not significant on any traits except for stem diameter and plant height. It was concluded that irrigation intervals had a significant effect on plant characteristics of potato, but growth stages had no effect on these traits.

In order to study effects of drought stress at different growth stages in potato, three cultivars: Marfona, Agria and Draga were planted in 20 lit. pots-using a completely randomized design (CRD) with five replications. Three levels of drought stress (40%, 60%, 80% of soil available water=SAW) and a control (100% SAW) were applied in three growth stages (Planting to emergence, emergence to stolon initiation and stolon initiation to tuber initiation) and were arranged in factorial combination together with potato cultivars. Results showed that drought stress decreased relative water content (RWC), water use efficiency (WUE), Tuber no./plant, dry matter percent (DM%) and tuber yield, but increased leakage from cell wall. Agria demonstrated the highest tuber yield and WUE but the lowest leakage from cell wall. However, Draga had the lowest tuber yield, RWC and Tuber no./plant, but the highest DM%. Drought stress at stolon initiation stage decreased tuber yield. Drought stress levels of 60% SAW severely affected the tuber yield, however the difference between 40% and 80% SAW was not significant. Differences of drought stress levels were significant only for Agria. The result indicated that high RWC together with medium Tuber no./plant led to optimum assimilate partitioning among tubers, hence higher tuber yield.