Mount Sinabung eruption caused the soil covered by volcanic ash with various thickness. Changes in soil conditions will affect population and diversities in the soil. The research aims to identify soil macro-fauna on andisol in Karo County with various thickness of volcanic ash of Mount Sinabung with different vegetation after 5 years of eruption. The Plots were placed onto eight locations, I = processed land (0 cm) grass vegetation, II = uncovered by ash land (0 cm) coffee vegetation, III = covered by thin layer of ash land (≤2 cm) grass vegetation, IV = covered by thin layer of ash land (≤2 cm) coffee vegetation, V = covered by medium layer of ash land (2-5 cm) grass vegetation, VI = covered by medium layer of ash land (2-5 cm) coffee vegetation, VII = exposed by thick ash land (≥5 cm) grass vegetation, VIII = exposed by thick ash land (≥5 cm) coffee vegetation. Sampling was done by method Pitfall Trap, Square Monolith, and Hand Sorting. The result shows that the change of soil will affect soil macro-fauna - based on macro-fauna identification results, found 3 phylum(s), 7 class(es), 12 ordo(s), 18 family(ies), and 20 species.

Fungi is a microorganism that has been widely used to accelerate the rate of decomposition of organic matter. This research was conducted in the soil biology laboratory of the Faculty of Agriculture, University of Sumatera Utara. This study was aimed to examine the potential of fungi isolates derived from palm oil trunks. This research begins by isolating the fungi contained in the cutting of oil palm trunk from the plant rejuvenation. The isolate is purified to obtain a pure culture. Selected isolates were identified by DNA sequencing using PCS 28s ITS and the results were identified as Rhizopus arrhizus Strain ATCC 111450 (A), Rhizopus microspores var rhozopodiformis Strain IFM 46417 (B) Syncephalastrum racemosum isolate VPCI 1857/11) (C), Trichoderma asperellum Strain ATCC 52438 (D), and Trichoderma asperellum Strain G (E). All isolates were applied to sterilized palm oil trunks. The results of this study were Rhizopus microspores var rhozopodiformis Strain IFM 46417 capable of growing well in pH 4, 6, and 8, Trichoderma asperellum Strain G (E) had the fastest growth rate of 64.58 mm / day. Test of cellulase enzyme production by using a method of Fehling A and B aiming at the fungus Trichoderma asperellum Strain G (E) produces the highest cellulase enzyme.

Acid sulphate soil has potential to be good agricultural land if the condition meets. Therefore This research was conduct to learn the effect of several amendment, fertilizer and sulphate reduction bacteria (SRB) on the growth of oil palm seedlings and increasing nutrient content of oil plam seedlings.This research did on april 2017 until desember 2017, and used acid sulphate soil from Unit Payarambe PT. Mopoli Raya Aceh Tamiang Indonesia, and used oil palm seedling (3 month old). This research used Randomized Block Design with 3 treatments : Several amandment (without amandement, empty fruit bunches oil palm 30 tonnes/ha, Dolomie 15,8 tonnes/ha), fertilizers (without fertilizer, given fertilizer 2,5grams/seedling), and sulphate reduction bacteria (without SRB and given SRB 15 ml with total population 10 8 /cc) with 6 replication. The results showed that the application empty fruit bunches oil palm compost 30 tonnes/ha increased plant height and stem statiscally significant after 28 weeks application. The best treatment was empty fruit bunches oil palm compost 30 tonnes/ha combined with inoculum of sulphate reduction bacteria. ABSTRAKLahan sulfat masam berpotensi sebagai lahan pertanian bila dikelola dengan baik dan benar dengan penamabahan amandemen. Tujuan penelitian ini untuk mengetahui pengaruh pemberian berbagai bahan amandemen, pupuk, dan bakteri pereduksi sulfat untuk meningkatkan kadar hara dan pertumbuhan bibit kelapa sawit. Penelitian ini dilaksanakan di rumah kaca pada bulan april 2017 sampai dengan desember 2017 menggunakan tanah sulfat masam dan bibit kelapa sawit umur 3 bulan. Rancangan penelitian yang digunakan adalah Rancangan Acak Kelompok dengan 3 faktor perlakuan yaitu berbagai bahan amandemen (Kontrol, Kapur Dolomit 1xAldd , Kompos TKKS 30 ton/ha), pupuk kimia (tanpa diberi pupuk NPK, diberi pupuk NPK 2,5 g/bibit), serta bakteri pereduksi sulfat (tanpa BPS dan diberi BPS 15 ml dengan total populasi 10 8 /cc) dengan 6 ulangan. Hasil penelitian menunjukkan bahwa pemberian kompos TKKS (30ton/ha) dapat meningkatkan pertumbuhan tanaman kelapa sawit secara signifikan, yaitu pertambahan tinggi tanaman, diameter batang setelah 28 minggu aplikasi. Perlakuan terbaik terdapat pada pemberian kompos TKKS (30ton/ha) dan diberi bakteri pereduksi sulfat.

This study aims to determine the effect of the combination of Sulfate Reducing Bacteria, Rhizobia, and amendment matters on the soil pH acid sulfate soil planted with soybeans, carried out at the Greenhouse, Soil Biology Laboratory, Research Laboratory, Faculty of Agriculture, Universitas Sumatera Utara, from March to September 2021. This study used a factorial randomized block design with 2 factors and 3 replications. Each factor consists of 4 levels. The first factor were H0 (Control); H1 (Sulfate Reducing Bacteria); H2 (Rhizobia bacteria); H3 (Sulfate Reducing Bacteria + Rhizobia Bacteria), and the second factor was B0 (Control); B1 (EFB organic matters doses 15 tons/ha); B2 (EFB organic matters doses 30 tons/ha); B3 (Lime of CaCO3 doses 7.5 tons/ha). The research showed that Sulfate Reducing Bacteria, and Rhizobia were able to increase soil pH significantly. Application of EFB organic matters doses 30 tons/ha, and Lime of CaCO3 doses 7.5 tons/ha can increased soil pH.

Acid sulphate soil has several problems such as low pH, low P-availability, and high solubility of Al. Efforts to optimize the productivity of acid sulphate soils are through the utilization of tolerant acid sulfur plants, soil microorganisms and organic fertilizers. This study aims were to determine the effect of applying azolla and the solubilizing phosphate bacteria on the growth and production of paddy (Oryza sativa L.) on acid sulphate soil. This research was conducted in greenhouse of Faculty of Agriculture, University of Sumatera Utara, from September to December 2017. The design used was factorial randomized block design with 4 replications. The first factor was fresh azolla with 4 levels viz A0=0, A1=30, A2=60 and A3=90 g/pot and the second factor was solubilizing phosphate bacteria with 2 levels,viz P0 = without solubilizing phosphate bacteria and P1 = application of solubilizing phosphate bacteria. The results showed doses of azolla 90 g/pot increased the growth of paddy, however the highest was found at treatment azolla with dosage 30 g/pot. Application of solubilizing phosphate bacteria increased the growth and production of paddy. Application 60 g fresh azolla/pot and inoculation of solubilizing P bacteria was the best treatment treatment that is (number of tiller 4 tiller, number of panicle 8,25 panicles, total grain amount 272,5 grain, dry weight of dry grain 6,75 g, dry straw weight 18, 27 g).