Helmy, Amal A. ; A.A. Abo El- Soud; A. H. Desoky and N. Rajab ( 2014). The negative impacts of mineral nitrogen fertilizer on inoculated berseem clover with rhizobia .Egypt. J. of Appi Scl, 29 (5) 2014 317-335
Abstract: Two field experiments were earned out at the Agricultural Research Station Farm, Agric. Res. Center (ARC), Giza, Egypt located at Latitude of 29" 59' 55.046" N and Longitude of 3l" 12' 49.272" E, to evaluate the negative impacts of mineral nitrogen fertilizer dose and form on forage yield of berseem clover inoculated with efficient strain of rhizobia. An experiment was conducted during 2010/2011 and 2011/2012 seasons. Six different treatments of nitrogen fertilization were done in RCBD. Four cuts were taken after 7, 13, 17 and 21 weeks from .sowing. Results revealed that, berseem clover nodules number and dry weight as well as nitrogenase activity affected positively significantly due to rhizobia inoculation supported with starter dose of nitrogen fertilizer either in the form of NH4NO3 or urea. On the contrary, nodules number and dry weight reduced markedly due to raising nitrogen fertilizer level up to 40 kg NH4NO3 in the same cut. Maximum ARA was achieved at the second cut which could be related to highly nodules number and dry weight formed on berseem root. In general, rhizobia inoculation combined with basal dose of N fertilizer either NH4NO3 or urea fonn affected significantly berseem clover yields. The increases over control ranged from 20.55 to 26.57 % for fresh yield. The same treatment led to a significant increase of the leaf/stem ratio by 30.36 and 33.93%, respectively. The inoculation combined with N fertilization 15, 45 and 60 kg N fed"1 increased progressively crude protein yield in individual cuts as well as total seasonal yield. Inoculated berseem, in general, harbored higher bacterial number in its root rhizospher, while considered lower number recorded for non-inoculated ones. Azospirllum, Pseudomonas spp. and Klebsiella Spp. were found in almost similar number of count of bacteria. Gram positive
Keywords: (mineral nitrogen fertilizer,forage,berseem clover,rhizobia,nitrogen fertilization,nodules,)
