Abstract
 Climate variability of the world have negative impact on physiological processes of many of the world's grains, especially soybeans. Thus, the purpose of the research was to study the effects of different levels of temperature on nitrogen accumulation in different tissues; roots, stems and leaves of two Thai soybean cultivars (glycine max (l.) Merrill). In a study conducted using area on Converted Agricultural Research at the Naresuan University, Phitsanulok province. The soybean planting under different temperature conditions 3 levels. Lower air temperature (LT), Higher air temperature (HT) and Control air temperature (CT), Uses electronic controls system, from 8:00 to 17:00 pm. By controlling the time of occurrence of weather conditions that different from the abnormal state for about 70% of the planting season. From V3 stage up to harvest under open top chamber system. During the trial operation showed that the temperature inside the cabinet can control the temperature averaged 25.52±1.26 C, 36.86±3.39 C and 35.01±1.93 C in treatment LT, HT and CT, respectively. The study found that Soybean planting under conditions increased temperatures or lower affect the accumulation of nitrogen in the tissues; roots, stems and leaves of two Thai soybean varieties different on stages of development. The study in V3 did not find a statistically significant effect (P≤0.05) in SJ.5 cultivar However, significant differences were statistically significant (P≤0.05) in Chiang Mai 60 effects occur only in leaf tissue. It was found that the nitrogen in the leaves decrease in experimental LT compared to equal treatment CT 25.08%. When the results of the stage R5 study find statistically significant (P≤0.05) prominently in Chiang Mai 60 because of find negative effect on the tissue, the stem and leaves. In a decrease of in the experimental LT 25.25% and 47.27% respectively. While the amount of nitrogen in the treatment of HT decrease 37.79%. The results of the nitrogen in the soybean SJ. 5 The decrease was statistically significant (P≤0.05) in the roots of 28.57% in the HT trial compared treatment with CT. The study concluded that the temperature is higher or lower than the natural growing season. Impact negatively on the accumulation of nitrogen in the tissues; roots, stems and leaves of soybean significantly statistically the two species, but the results clearly than in soybeans Chiang Mai 60 because find effects since the V3 until the stage R5.