Iswandi Anas

Is soil degradation unrelated to deforestation? Examining soil parameters of land use systems in upland Central Sulawesi, Indonesia

It is generally assumed that declining soil fertility during cultivation forces farmers to clear forest. We wanted to test this for a rainforest margin area in Central Sulawesi, Indonesia. We compared soil characteristics in different land-use systems and after different length of cultivation. 66 sites with four major land-use systems (maize, agroforestry, forest fallow and natural forest) were sampled. Soils were generally fertile, with high base cation saturation, high cation exchange capacity, moderate pH-values and moderate to high stocks of total nitrogen. Organic matter stocks were highest in natural forest, intermediate in forest fallow and lowest in maize and agroforestry sites. In maize fields soil organic matter decreased during continuous cultivation, whereas in agroforestry it was stable or had the tendency to increase in time. The effective cation exchange capacity (ECEC) was highest in natural forest and lowest in maize fields. Base cations saturation of ECEC did not change significantly during cultivation both maize and agroforestry, whereas the contribution of K cations decreased in maize and showed no changes in agroforestry sites. Our results indicate that maize cultivation tends to reduce soil fertility but agroforestry systems are able to stop this decline of soil fertility or even improve it. As most areas in this rain forest margin are converted into agroforestry systems it is unlikely that soil degradation causes deforestation in this case. On the contrary, the relatively high soil fertility may actually attract new immigrants who contribute to deforestation and start agriculture as smallholders.

Impact of forest disturbance and land use change on soil and litter arthropod assemblages in tropical rainforest margins

Land use intensification at rainforest margins increases the pressure on the primary rainforest ecosystem, known for its high biodiversity and important functional role in global climate and carbon balances. Studying this system at different levels of disturbance increases our knowledge about its stability and mechanisms of diversity changes. While most studies investigating the effects of disturbance on animal populations focus on canopy communities, the present study reviews the driving factors for soil and litter arthropod communities. In addition, results from a study along a land use gradient in Central Sulawesi (Indonesia) will be discussed.

Community Structure of Ammonia Oxidizing Bacteria and Their Potential to Produce Nitrous Oxide and Carbon Dioxide in Acid Tea Soils

The potentials of nitrous oxide (N 2 O) and carbon dioxide (CO 2 ) production in acid tea soils from Indonesia and Japan were investigated in a laboratory incubation experiment, and the community structures of ammonia-oxidizing bacteria in these soils were characterized using PCR-DGGE approaches. The soils used were sampled from tea plantations in Shizuoka, Japan and in Bogor and Malino, Indonesia. All of the soils were acidic (pH 3.45 to 4.00). The N 2 O and CO 2 production in Shizuoka was almost 5 times higher than in Bogor and Malino. All of the amoA gene sequences defined belong to the genus Nitrosospira sp. with cluster 2 and cluster 3a.

AKTIVITAS ENZIM SELULASE MIKROBA YANG DIISOLASI DARI JERAMI PADI DI PERSAWAHAN PASANG SURUT DI KALIMANTAN SELATAN

Enzim selulase terdiri dari tiga enzim ekstraselular yang bekerja secara sinergis dalam mendegredasi selulosa, yakni endoglukanase, eksoglukanase dan β-glukosidase. Tiga enzim tersebut berperan dalam mendegradasi selulosa menjadi gula sederhana. Penelitian ini bertujuan untuk mengisolasi dan menyeleksi mikroba (bakteri dan fungi) berdasarkan aktivitas enzim selulase dari mikroba tanah yang diisolasi dari persawahan pasang surut Kalimantan Selatan. Kemampuan mengekskresikan enzim endoglukanase dinilai berdasarkan nilai indeks selulolitik pada media CMC dan kemampuan mengekskresikan enzim eksoglukanase dan β-glukosidase diukur dari aktivitas kedua enzim tersebut menggunakan metode Mandel yang dimodifikasi. Hasil yang diperoleh menunjukkan bahwa kisaran nilai indeks selulolitik dari mikroba selulolitik di persawahan pasang surut tipe A sebesar 2.29-3.72, di lahan tipe B sebesar 2.66-5.41, dan di lahan tipe C sebesar 1.84-3.34. Aktivitas eksoglukanase dari mikroba selulolitik di persawahan pasang surut tipe A sebesar 0.27-1.65 nkat mL-1, lahan tipe B sebesar 0.37-1.85 nkat mL-1, dan lahan tipe C sebesar 0.31-1.85 nkat mL-1. Mikroba selulolitik dari persawahan pasang surut Kalimantan Selatan memiliki aktivitas β-glukosidase sebesar 0.05-1.52 nkat mL-1. Isolat- isolat mikroba selulolitik yang memiliki aktivitas selulase tertinggi adalah isolat bakteri selulolitik J11, J42, R23, BK12, C52, TB41, B82 dan SN123, dan isolat fungi selulolitik ST33, ST22, TB31, B52, GA22, TD11, PI52 dan P31.

KOMBINASI PUPUK ORGANIK HAYATI DAN PUPUK FOSFAT UNTUK PENINGKATAN KERAGAAN BIBIT KELAPA SAWIT (Elaeis guineensis Jacq)

Percobaan ini dilakukan untuk mengetahui pengaruh pupuk organik hayati diperkaya mikrob tanah terhadap keragaan tanaman, populasi total mikrob dan populasi mikrob pelarut fosfat di pembibitan kelapa sawit. Persiapan media tanam dilakukan dengan mengambil lapisan tanah atas (topsoil) dengan kedalaman maksimal 25 cm kemudian tanah tersebut dikering anginkan dan dimasukkan ke dalam setiap kantong plastik media tanam dengan volume masing-masing 5 kg. Pengukuran parameter keragaan tanaman bibit kelapa sawit dilakukan dari minggu ke-4 setelah tanam (MST) hingga ke-22 MST di rumah kaca kebun percobaan Cikabayan, Darmaga. Percobaan uji efektivitas mikrob pelarut fosfat (MPF) pada pupuk organik hayati menggunakan Rancangan Acak Kelompok (RAK), yang terdiri dari dua faktor dengan tiga ulangan. Hasil percobaan menunjukkan pengaruh penggunaan pupuk batuan fosfat terhadap tinggi tanaman memberikan hasil yang lebih baik dibandingan penggunaan SP-36 dan analisa statistik terhadap pengaruh tunggal pupuk organik hayati, pengaruh pupuk organik terhadap populasi total mikrob menunjukkan hasil terbaik.

Media Campuran Tanah-Pasir dan Pupuk Anorganik untuk Memproduksi Inokulan Cendawan Mikoriza Arbuskula (CMA)

AMF fungi are obligate biotroph, they can not be multiplied on artificial growth medium. The growth of AMF fungi depends on photosynthates of the host plant. The AMF inoculant production so far is done on special growth media such as vermicullite or zeolite and using a certain composition of fertilizer such as Hyponex (N: P: K = 25: 5:20). The aims of this experiment were (1) to study the possibility of using soil-sand mixture for growth medium in AMF inoculant production, and (2) to study the possibility of using Urea, SP-36 and KCI as fertilizers in AMF inoculant production. The results of the experiment showed that soil-sand mixture was a better growth medium for AMF inoculant production than zeolite. The number of AMF fungi spore, the root infection rate and the root biomass of the host plant (shorgum) were higher on soil-sand mixture growth medium compared to zeolite. Urea, SP-36 and KCI can be used as subtitute to Hyponex fertilizer in AMF inoculant production. Key words: CMA, Produksi inokulum, Entrophospora colombiana. Glomus manihotis