عنوان مقاله [English]
Background and Aim: Meta-analysis is a method for comparing the results of independent studies on a subject, in fact, the meta-analysis is a type of research on other research, and it can be used to re-investigate several studies on a specific topic. Studied and compared statistically, and this approach is considered an independent research. In the meta-analysis of the statistical community, the previous research set and the research unit are each of the early and independent prior studies. Therefore, the analysis is a kind of analytical analysis. In order to assessment and continuity to results of effects of different levels of nitrogen fertilizer on some important industrial plants, this research performed using of two calculation method as effect size and logarithmic of response ratio. The first, depend on range and availability to papers, data of effects of different levels of nitrogen fertilizer (urea based) on seed yield, node, percentage of sugar, oil and protein in some important industrial plants (sesame, sugar beet, safflower, sunflower, potato, cotton and soybean) collected which fertilizer treatments were compared with control. The effect size and logarithmic of responses ratio were estimated by Hedge method. Finally the significant of effect size and logarithmic of responses ratio tested by the range of standard error with zero.
Materials and Methods: In this research, various agricultural studies published in valid academic journals, citation databases of the Islamic world in which, depending on the scope and extent of access to papers on the effect of nitrogen fertilizer from urea source on the seed yield, , tubers, sugar percentage, oil and protein are some of the most important industrial crops (sesame (16 articles), sugar beet (12 articles), safflower (20 articles), sunflower (13 articles), potato (17 articles) cotton (20 articles), soybean (10 articles), in which fertilizer treatments were compared to the control.
Finding: Results of meta-analysis released the effects of nitrogen fertilizer exception of some traits as: oil percentage of sesame, sugar percent in sugar beet (exception of 180-200 kg/ha), yield of vash and seed in cotton (50-70 kg/ha) had significant effects on yield of industrial plants. Also, the optimum level for using of nitrogen fertilizer was for soybean (200 kg/ha with 71.90% increase in yield), potato (80-100 kg/ha with 67.85% increasing in yield), safflower (90-100 kg/ha with 48.85% increasing in yield), sunflower (150 kg/ha with 43.17% increase in yield), seed yield of cotton (300 kg/ha with 28.84% and 34.76 increasing in seed yield), sugar beet (180-200 kg/ha with 35.43% increasing in root yield), seed yield of sesame (50 kg/ha with 49.63% increasing in yield), protein percentage of sesame (90-100 kg/ha with 24.47% increasing in yield). The output of this results showed that the optimum level of fertilizer for achieving of maximum yield was finalized in this situation. So, using of the recommended level of nitrogen fertilizer had some benefits as: decreasing of inputting to farm, diminishing of farmer costs, obtaining of maximum yield and coming down of environmental pollution.