Adel Ghoneim Abdulla Al-Modaihsh Saied Naeem Tamer Metwally Elsaied Gewailly Azza Ebid Soil Science Department, College of Food and Agricultural Sciences, King Saud University, P.O. Box 2460, Riyadh, 11451, Saudi Arabia Agricultural Research Center, Rice Research and Training Center (RRTC), Sakha, 33717, Kafr El-Sheikh, Egypt Department of Biology, College of Science, Princess Nora Bint Abdul Rahman University, P. O. Box 376114 Riyadh 11335, Saudi Arabia Proceedings of the International Academy of Ecology and Environmental Sciences ISSN 2220-8860 http://www.iaees.org/publications/journals/piaees/online-version.asp 2014 4 1 30 38 International Academy of Ecology and Environmental Sciences Hong Kong 2 September 2013 18 October 2013 1 March 2014 sorghum rhizosphere soil nitrification inhibition Biological nitrification inhibition refers to release some chemical substances from plant root that suppresses/slowdown soil nitrification. This study was conducted to clarify whether sorghum (Sorghum bicolor) inhibit nitrification in soil around the root. Sorghum cultivated in pots filled with a brown lowland soil and examined nitrification rate in the soil around its root comparing with bare soil. Two experiments were conducted. In the first experiment, sorghum was cultivated in a growth chamber and soil sample were collected four times during the growth period. Nitrogen in the form of (NH4)2SO4 (120 mg N /kg soil) was mixed with the soil samples and incubated at 30oC, for 21 days. Nitrification rates were estimated based on NO(2-)+NO(3-)-N accumulation per unit time. Results showed that in sometime nitrification rate in the soil around sorghum root was lower than that in the bare soil however, in other times there were no difference between them. Second experiment was conducted by using soil samples collected from the pots in which sorghum was cultivated in a greenhouse. The results showed nitrification in the soil around sorghum root was lower than that in the bare soil. Nitrification was inhibited in soil around the sorghum roots, however, this inhibition varied with incubation period. The differences of N application showed a little effect of nitrification inhibition rates. DOI 10.0000/issn-2220-8860-piaees-2014-v4-0004 http://www.iaees.org/publications/journals/piaees/articles/2014-4(1)/nitrification-inhibition-by-sorghum-in-soil.pdf