Background: Effect of seasonal changes in human reproduction has been intensively researched. Some studies acknowledge influences of seasonal variation on natural conception, while others can not confirm them. The aim of this study was to investigate the effect of seasonal changes on different stages of assisted reproductive technology (ART) in Tehran. Materials and Methods: This study was carried out on 268 cycles which were the first intracytoplasmic sperm injection (ICSI) cycle of the couples between July 2005 and March 2007. Multiple logistic regression was used to model the influence of different clinical factors on pregnancy rate and a bivariate Poisson regression model was used for modeling the number of mature oocytes and obtained embryos. Results: Based on the logistic regression model, the duration of infertility, female age, number of mature oocytes, and transferred embryos were only the significant predictors. In this series, seasonal changes had no predictive value on the pregnancy rate. Bivariate Poisson regression model showed that only the female age and duration of infertility were the factors simultaneously affecting the number of embryos and mature oocytes.Conclusion: The suspected seasonal variability on the outcome of ICSI cycles has not been confirmed. Furthermore, among different seasons, there are no significant differences in the number of mature oocytes, obtained embryos, and transferred embryos.

A national project was carried out in 10 provinces in order to compare the fertilization method of farmers with the integrated method of soil fertility recommendation for canola plants. The experiment included 54 farms in the provinces of Golestan, Mazandaran, Khuzestan (Dezful), Khuzestan (Ahvaz), Ardabil (Maghan), East Azerbaijan, Isfahan, Bushehr, Khorasan Razavi, Kermanshah, Fars and Varamin regions. These areas consisted of a wide range of canola cultivation regions, climatic conditions and a different range of soil characteristics. In a part of selected fields, fertilization was recommended based on the soil test (optimal use of fertilizers) and in the other half of the fields, application was according to the traditional method of the farmer in the region. At the end of the growth stage, the seed yield of treatments was compared in each province and in each region. According to the results, phosphorus had the highest percentage of deficiency in the soil of the fields, and among the micro nutrients, the highest deficiency was related to the zinc element. On average, the increase in grain yield of first year was 600 kg ha-1 or 24%, compared to the conventional treatment. In the second year, the increase in grain yield was 784 kg ha-1 or 27.4%. For the average of two years, the amount of 692 kg ha-1 or 25.7% increase in grain yield was obtained. The benefit to cost ratio of different regions depended on the characteristics of the soil and the amount of used fertilizers. The highest value of this ratio was obtained from the region of Neishabur (26.52) and Darab (22.31. The lowest was obtained from Bushehr (0.28). The results showed that the consumption of fertilizers with considering the time, quantity, source and method of application will improve the yield of canola in all regions.