EFEKTIVITAS HAMBATAN SERESAH Paraserianthes falcataria, Acacia auriculiformis, DAN Zingiber officinalis TERHADAP POTENSIAL NITRIFIKASI DAN POPULASI BAKTERI NITRIFIKASI DI TANAH ALFISOL, JUMANTONO

Ratih Septiyani. H 0204016. THE Effectivity Of Inhibition Paraserianthes Falcataria, Acacia Auriculiformis, And Zingiber Officinalis Litter Toward Nitrification Potential And Activity Of Nitrifying Bacteria In Alfisols, Jumantono. Nitrification in soil must be controlled, because it make inefficient nitrogen fertilizing, stimulate base cation has been leach. So it causes decrease base saturation and increase acidity in soil. Efforts to control nitrification indirectly can be achieved by control litter quality input. Litter quality will influences nitrifcation because NH4 + of the soil will be soon immobilized by heterotrof microbial during litter decomposition. The purposes of this experiment were a). to learn the effect of litter from Paraserianthes falcataria, Acacia auriculiformis, and Zingiber officinalis to nitrifyer population and potential nitrification; b). to learn period of incubation that can inhibit nitrification; c). to learn litter quality has the strength correlation with nitrification potential. The experiment was carried out in Green House, Soil Biology Laboratory and Soil chemistry Fertility of Agriculture Faculty of Sebelas Maret University Surakarta from Juni 2007 to September 2007. This study was a functional relationship study by using Nondestructive Soil Sampling and Completed Random Design which was divided in to two factor, that is type of litter of plants and period of incubation.Type of litter of plants represent low (Acacia auriculiformis), medium (Paraserianthes falcataria), and high quality (Zingiber officinalis). Variables observation are nitrification potential, activity of the nitrifyer microbe and heterotrophic microbe, soil pH, soil temperature, soil moisture,and soil carbon and nitrogen ratio. The data was analyzed with ANOVA F 5%, Duncan Multiple Range Test (DMRT) 5%, and correlation test. The result of the research were a). the application of litter quality of plants and period incubation have the significant effects in declining nitrification rate (Pvalue = 0.000- ). The present of low litter quality (Acacia auriculiformis) decreased nitrification potential is 76.9 %, medium litter quality (Paraserianthes falcataria) is 73.5 % and hight litter quality (Zingiber officinalis) can decreased nitrification potential is 73 %; b). The most period of incubation to inhibit nitrification potential and population of nitrifyer bacteria in period of incubation 20th; c). The quality of litter which has straight correlation with nitrification potensial is nisbah (P+L)/N 56,3%, following lignin 54,7%. Polifenol 43,4% and the last is nisbah C/N 26,4%. Giving the litter of all plants observed in the study can decline the nitrification rate significantly so that using the litter of these plants can be recommended as an alternative way in controlling nitrification process naturally, environmental safe and supporting continuous agriculture system. Key words: Nitrification potential, Nitrifyer bacteria, Litter qualit