فهرست مطالب پریسا شاهین رخسار احمدی

In order to comparing the regeneration and diversity in natural and created gaps, all of the gaps in two compartments in Asalem forests were identified and divided into three categories: small gaps (2), medium gaps (200-500 m2), and large gaps (>500 m2). Seven plots with an area of 4m2 (2m×2m) were taken in each gap. The number of individuals of tree seedlings and saplings were recorded and coverage percent of herbaceous species were estimated in each plot based on extended Braun - Blanquet cover - abundance scale. In addition to counting the number of species, diversity indices including Simpson (1-D) and Shannon-Wiener (H') and Smith- Wilson’s evenness indices were calculated. The Kolomogrov-Smirnov test was used to study the normality of data and then one-way ANOVA test was performed using SAS software. Totally 38 natural and 30 created gaps were identified. The results revealed that mean of each gap size was 371 m2. There were no significant difference between the size of natural and created gaps but the number and total regeneration were significant differences among natural and created gaps. The least abundance of seedlings were obtained in the small gaps. Also diversity indices had maximum in the created gaps.

Fertigation is the application of fertilizers, soil amendments, or other water soluble products through an irrigation system. Fertigation can be applied for different kind of crops and horticultural plants as well as different types of irrigation systems, including surface and pressurized irrigation systems. Irrigated land in Golestan province is about 200000 hectares that most of them do not use fertigation system. So a research project has been done on the effectiveness of these systems on corn crop in two successive years 2007 and 2008. The experiment was laid out in a randomized complete design where each treatment was replicated three times. Two treatments were 200kg ha -1(N200) and 300 kg ha-1(N300) of pure nitrogen. Amount of considered urea fertilizers were applied through split application twice in two sprinkler and furrow irrigation systems separetly. Crop was SC704 sweet corn that is planted 75 to 20 cm intervals in July after wheat harvesting in the Gorgan agricultural station. During two years of testing, 8 and 7 times irrigation were applied respectively in which two of them accompanied by fertigation. Amount of irrigation water in the first year were 527 and 313 mm for furrow and sprinkler systems respectively and in the second year were 474 and 299 mm. Average grain yield that can be canned in the first year and N200 treatment were 3375 and 4072.3 kg ha-1 and in the second year, were 2637.3 and 4165.3 kg ha-1 for furrow and sprinkler systems respectively. Average grain yield that can be canned at treatment N300 in the first year were equal to 3124.3 and 2930.3 kg ha-1 and in the second year were 2647 and 3278.3 kg ha-1, for furrow and sprinkler systems respectively. The results showed that irrigation method had significant effect at 1% level on yield and yield components. The maximum values of grain yield 4165.3 kg ha-1 from N200 treatment in 2008, cob yield of 8795.6 kg ha-1 from N200 treatment in 200, biomass of 33184.6 kg ha-1 from N200 in 2007 and total dry matter of 7598.3 kg ha-1 from N200 in 2007 has been obtained from sprinkler irrigation that shows the effectiveness of sprinkler fertigation through ventory injector. Different nitrogen fertilizer rates had a significant effect on grain yield and total dry matter at 5% level and maximum grain yield and total dry matter production were obtained in N200 treatment. Different nitrogen fertilizer rates had no significant effect on cob and biomass. In general two years results indicate the effectiveness of fertilizer use efficiency in sprinkler fertigation.

Olive harvesting is the most important step in olive cultivation because of its direct impact on the quality of olive oil. Harvesting method and harvesting time are two effective factors in harvesting olive. This research was carried out in the olive orchard of Mazrae Novin Iranian Agro-Industry Farm, located in the cities; Manjil & Roudbar in Guilan province, Iran. In this research, olive trees were pruned in the central leader method. An Italian Verdegiglio VMA 95 trunk shaker was used to harvest the olive fruit for both table olives and oil olives stages. Vibration times by the shaker were at four levels (5, 10, 15 and 20 seconds). The percentage of the harvest and the harvesting rate, in each stage of the harvest (table and oil olives) were calculated. Based on the results of the project, the percentage of the fruit harvest and the harvesting rate in vibration times were significantly different in each stage of the harvest (table and oil olives). The maximum percentage of the fruit harvest for table and oil olives were 64 and 86, respectively. The highest harvesting rate for table and oil olives were 102.79 and 127.32 kg/h, respectively The best duration to shake the olive trees was found to be 10 seconds.

Though plant growth and development is a function of genetic characteristic but the effects of weather factors are important as well. Since weather factors have complicated relationship with plant growth and development stages. Each stage of plant growth should receive optimum temperature and growth degree days (GDD) to enter to the next stages. Therefore sowing date, intercultural operations and growth period should be adjusted in order to match with plant development optimum conditions. Thus, phonologic stages of wheat (Tajan variety) were studied in Hashemabad agrometeorological Research Station in Gorgan city in 2003-2004. Results showed that during emergence period plants did not received enough rainfall to fulfill uniform germination. In tailoring period the plant were faced with shortage of light and rainfall and also temperature in emergence and stemming periods was less than optimum. Reducing of temperature in these periods was caused of spike and spikelet initiation. Also necessary temperature for leaf appearance was not supplied. On the other hand increasing of temperature was caused thermal tension in periods of pollination and grain filling resulted reduction of grain weight and yield.