EFEKTIVITAS PENGHAMBATAN SERESAH Anacardium occidentale, Manihot esculenta DAN Curcuma domestica TERHADAP POTENSIAL NITRIFIKASI DAN BAKTERI NITRIFIKASI DI ALFISOLS JUMANTONO

Nitrification can decreased of N soil and N fertilizer and caused environmental problems such as eutrofikasi and methemoglobinema on babies and cattle if the drinking water contaminated by NO3 - from nitrification. Efforts to control nitrification indirectly can be achieved with litter quality input. Litter quality will influences nitrification because NH4 + of the soil will be soon immobilized by heterotrof microbial during litter substance decomposition until there is no substance for nitrification process. The objectives of research were to study the effect of litter quality input as first Anacardium occidentale, Curcuma domestica and Manihot esculenta toward nitrification potential and population of nitrifying bacteria, to know long time of incubation and kind of litter quality which the most effective inhibiting nitrification potential and population of nitrifying bacteria in AJfisols Jumantono. This research is an axperimental was carried out in June to August 2007 at green house and conducted by using soil pots (Non Destructif Soil Sampling) with elementary basic pattern of Completed Random Design (CRD) then was analysed at Soil Biology Laboratory Agriculture Department Sebelas Maret. The litter observation substitused hight litter quality (Manihot esculenta), middle litter quality (Curcuma domestica) and low litter quality (Anacardium occidentale). All of threatment were giving 0.072 g (NH4)2SO4 fertilizer expect control, soil did’t give litter but was added fertilizer. The observation variables are nitrification potential, population nitrifying bacteria and heterotof microbial, C/N ratio, pH of soil, soil temperature and humidity soil. The result of research showed that: a). The result of research showed that: a).Anacardium occidentale, Curcuma domestica and Manihot esculenta litter very real influence decreased nitrification potential, population of nitrifying bacteria and heterotrof microbial with P-value =0.000. b) Manihot esculenta litter (hight litter quality with 4.75% of polifenol, 15.92% of lignin, 18.17 of C/N ratio, and 17.42 of (P+L)/N ratio) decreased nitrification potential 8.82%, Curcuma domestica litter (medium litter quality with 2.53% of polifenol, 11.18% of lignin, 22 of C/N ratio, and 19.87 of (P+L)/N ratio) decreased nitrification 34.26% but Anacardium occidentale (low litter quality with 16.44% of polifenol, 27.28% of lignin, 25.56 of C/N ratio, and 24.50 of (P+L)/N ratio) can decreased nitrification potential Alfisols Jumantono up to 70.54 % (from 4.99 became 1.47 mg NO2 - kg-1 jam-.1.c).The efective time to decrease potential nitrification on last incubation (on 20 day that is 1.47 mg NO2 - kg-1 jam-1.d). Kind of litter quality which the most correlated toward decrease potential nitrification is (P+L)/N ratio (27.4 %) then lignin (27.2 %), C/N ratio (19.6 %) and polifenol (16.7 %) with separated.e).Nitrificaton potential NH4 + nitrifying oxidizer bacteria and fungi was positive correlated however, was negative correlated with Actinomycetes, heterotrof bacteria and NO2 - nitrifying oxidizer bacteria. Key words: nitrification potential, nitrifying bacteria, litter qualit