Yogi Zulfikar, 2015. The Effect of Organic Materials Plant Biduri For Against Nature Chemical Biology and Soil Ultisol. Thesis, Department of Agrotechnology Faculty of Agriculture UNSYIAH, under the guidance for Ir. Fikrinda M.Si and r Yusnizar S. P. M. Si. This study aims to determine the effect Biduri applications as organic materials against chemical and biological properties Ultisol. The research method using a randomized block design (RAK) non factorial, There are eight treatments with three replicates in order to obtain a 24 unit trial. This research was conducted in two series of experiments that during the 30 days after incubation (DAI) and the 45 DAI. The research process is conducted in several stages, including: (1) preparation of the planting medium, (2) preparation plant Biduri as organic material that is as green manure and compost, (3) application of organic materials (4) parameters were observed. These results indicate the application Biduri as organic matter significantly affect P available soil at 30 DAI, very significant effect on total microorganisms at 30 and 45 DAI, C / N at 45 DAI and significantly affect total N at 45 DAI but the effect is not real against the soil respiration at 45 DAI, organic C at 30 and 45 DAI, N total at 30 and 45 DAI, P available in 45 DAI, C / N at 30 DAI, total microorganisms at 30 DAI, soil respiration at 30 DAI and 40 DAI , organic C at 30 and 45 DAI, N total at 30 DAI and C / N at 30 DAI. Keywords: Organic Materials, Biduri, compost, Soil Incubation period, Ultisol.