A pot experiment has been conducted to evaluate the growth of the Dyah Suci, a lowland rice variety, in an SRI (System of Rice Intensification) planting system. The phosphorus-32 ( 32 P) isotope technique was used to evaluate the growth of plants in relation with their phosphorus uptake. The uptake was assumed to vary in the same direction as the growth of the plant. The 32 P uptake is assumed to vary in the opposite direction to the plant's total phosphorus uptake. Here the 32 P uptake is expressed in count per minutes (cpm) which is then transformed to disintegration per minute (dpm). The results show that, in terms of promoting the plant's uptake of phosphorus, the SRI planting system is superior to the conventional planting system, and it is manifested in the higher dry weight of straw and grain. From this experiment it is concluded that the 32 P method can be used satisfactorily as a tool for explaining the relation between P-uptake and plant growth.

The use of phosphorus and potassium-solubilizing microbes as biofertilizers is an alternative method to increase the availability of phosphorus and potassium in soils. This study aimed to explore the effectiveness of phosphorus (P) and potassium (K)-solubilizing multifunctional microbes (Aspergillus costaricaensis and Staphylococcus pasteuri mutants) on maize growth. The stages of this study consisted of viability test of P and K solubilizing A. costaricaensis and S. pasteuri mutants in peat and effectiveness test of P and K solubilizing A. costaricaensis and S. pasteuri mutants on maize growth. The results showed that peat carriers could keep the fungi population stable until 18 weeks of storage times. While the bacteria at 6 and 8 weeks storage times showed a slight decrease and stable in the 10 to 12 weeks storage time. The addition of P and K-solubilizing multifunctional microbes could reduce the use of fertilizer up to 50% in the treatment with a combination of easily soluble P or K sources with not-easily soluble P or K sources, as well as a combination of treatments of not-easily soluble P and K sources. This tended to occur in the treatment with the addition of A. costaricaensis mutant.

Carrier is one of the important factor to determine the quality of biofertilizer. The inoculant carriers should contain no or less microbial contaminant. The purpose of this research was to investigate viability of Azospirillum, Azotobacter and Phosphate Solubilizing Fungi inoculants in carrier material that were sterilized by Gamma Irradiation Co-60 and Electron Beam Machine (EBM). Each inoculants was injected to the sterilized peat, compost, coconut shell charcoal and zeolite. Viability of inoculants in steriled carrier was evaluated at 0, 7, 14, 42 and 70 days after preparation. The stirage was done in incubator at 25ºC. The result of viability of Azospirillum, Azotobacter and Phosphate Solubilizing Fungi inoculants on sterilized carrier material by Gamma Irradiation Co-60, EBM and autoclave tended to decline during storage 70 days at room temperature (250C). Viability of Azospirillum inoculants in zeolite sterilized by Gamma Irradiation Co-60 and autoclave gave the highest numbres of viable cells. Storage of these inoculants at 25ºC for 70 days only reduce the number of viable cells by 11.1%. Viability of Phosphate Solubilizing Fungi inoculants in coconut shell charcoal or compost sterilized by Gamma Irradiation Co-60 went down by 99.8% after 70 days. The sterilization of carriers by using autoclave or Gamma Irradiation Co-60 were better than EBM sterilization. . Keywords: Carrier, Electron Beam Machine, Gamma Irradiation Co-60, sterilization, viability

Pupuk organik penting untuk memperbaiki sifat kimia, fisika, dan biologi tanah. Penelitian ini dilakukan untuk mempelajari peran pupuk kandang sapi dalam menyumbangkan nitrogen (N) pada tanaman padi sawah dengan teknik isotop 15N. Penelitian dilakukan di tanah sawah Jayamukti, Karawang Jawa Barat. Penelitian ini menggunakan rancangan acak lengkap dengan 6 perlakuan dan 3 ulangan. Perlakuan yang diberikan adalah pupuk kandang dengan dosis 0 t ha-1, 0 t ha-1 + 300 kg N ha-1, 5 t ha-1 + 300 kg N ha-1, 10 t ha-1 + 300 kg N ha-1, 15 t ha-1 + 300 kg N ha-1, 20 t ha-1 + 300 kg N ha-1. Hasil penelitian menunjukkan bahwa aplikasi pupuk organik dengan dosis 20 t/ha disertai dengan urea 300 kg N ha-1 dapat meningkatkan hasil berat kering gabah secara nyata sebanyak 64,75% dari perlakuan kontrol tanpa pupuk kandang dan tanpa N. Aplikasi pupuk kandang sebesar 15 t ha-1 ditambah N rekomendasi berpengaruh nyata dalam meningkatkan sumbangan N berasal dari tanah pada jerami sebesar 19,98% dari perlakuan tanpa pupuk kandang + N. Penelitian ini menunjukkan bahwa pemberian pupuk kandang mampu meningkatkan sumbangan atau kontribusi hara terutama N yang berasal dari tanah pada tanaman padi sawah.

Rice husk biochar and compost application are expected to improve soil chemical properties such as pH, organic carbon, and available P in Ultisol, which in turn improves crop growth and P uptake by plants. The purpose of this research was to analyze the effect of the combination of rice husk biochar and compost on the soil chemical properties (pH, organic carbon, and available P), maize growth, and P uptake by maize in an Ultisol. The research used a Randomized Block Design with six treatments (P0: control; P1: 4 t biochar ha-1; P2: 30 t compost ha-1; P3: 4 t biochar ha-1 and 30 t compost ha-1; P4: 8 t biochar ha-1 and 30 t compost ha-1; P5: 4 t biochar ha-1 and 60 t compost ha-1) and four replications. The result showed that the combination of 8 t rice husk biochar ha-1 and 30 t compost ha-1 showed a significant effect on increasing pH, organic carbon, and available P in an Ultisol, increasing the height of maize crops at 4 and 6 WAP (weeks after planting). However, it had no effect on the number of leaves and showed an effect on the increase in P uptake of maize crop.

ABSTRAKProduktivitas tanah ditentukan oleh karakteristik tanah, yang terdiri dari sifat fisik, kimia dan biologi tanah. Keterkaitan di antara ketiga sifat tersebut dapat diwakili oleh satu indikator yaitu kandungan karbon dalam tanah.Salah satu dampak dari pemenuhan kebutuhan bahan organik tanah adalah terpenuhinya kebutuhan unsur hara, terutama hara utama yang menjadi pembatas pada pertanaman padi sawah. Dalam hal ini unsur hara P menjadi faktor pembatas, karena seringkali berada dalam jumlah berlimpah namun dalam bentuk yang tidak dapat dimanfaatkan oleh tanaman. Percobaan dilakukan dengan tujuan mempelajari dampak aplikasi bahan organik kompos jerami yang diintegrasikan dengan Biochar, terhadap ketersediaan hara P pada tanah sawah. Interaksi kompos jerami+Biochar dengan inokulan BPF dan sumber-sumber P menjadi rancangan perlakuan yang diujikan dalam percobaan. Disain percobaan menerapkan rancangan acak kelompok dengan pola faktorial, menetapkan dosis aplikasi kompos jerami+Biochar sebagai taraf pertama yang terdiri dari 5 taraf level : 0; 1; 2; 3; 4 t ha -1. Faktor kedua adalah sumber P, yang terdiri dari 5 taraf level : tanpa fosfat (p 0 ); 100 kg ha -1 pupuk SP-36 (p 1 ); fosfat alam pada dosis 163 kg ha -1 (p 2 ); inokulan BPF pada dosis 2 kg ha -1 (p 3 ); dan fosfat alam berinokulan BPF (p 4 ). Percobaan dilaksanakan di rumah kaca kebun percobaan PAIR -BATAN, Jakarta, pada bulan Maret 2014. Dinamika P akibat perlakuan yang diujikan, digambarkan dari hasil penelusuran menggunakan radioisotop 32 P aktivitas 30 mCi melalui serapan P pada tanaman padi varietas Sidenuk. Hasil percobaan menunjukkan perlakuan yang diberikan menyebabkan perbedaan signifikan pada respons kandungan C-organik tanah, jumlah populasi BPF, cacahan 32 P tanaman dan serapan P dari berbagai sumber di dalam tanaman padi.Kata kunci : Biochar,BPF, fosfat alam, isotop 32 P, kompos jerami ABSTRACTSoil productivity is determined by soil characteristics itself, which consist of physical, chemical and biological character.The linkage between these three properties can be represented by a single indicator, namely the carbon content in the soil. One of the effects of soil organic matter fulfillment is the availability of soil nutrients, especially to the nutrient that limits the lowland rice production. In this case, P (phospohorus) nutrient become a limiting factor because their numbers are often in abundance but in a form that can not be used by plants.Experiments were carried out with the aim of studying the impact of straw compost application that integrates with Biochar, to the availability of P in lowland soil. The interaction of straw compost+Biochar with PSB inoculant and P sources, become the treatment that being tested in the experiment. Randomized Block Design with factorial pattern is applied as design experiment. Asthe first factor is the application dose of straw compost+Biochar, consistsof 5 levels of treatment : 0; 1; 2; 3; 4 t ha -1 . Second factor is several sources of P, consist of 5 levels of treatment : without P sources (p 0 )...

: Phosphor 32 P-isotopic method P-contribution P-fertilizer Organic manure P-fertilizer other than chemical fertilizers has been used extensively in agriculture. However, the extent to which P-fertilizer contributes to the growth of plants has only been discussed a few, meanwhile the information will be very helpful to the use of P-fertilizer efficiently. The 32 P method was used to distinguish P contribution from several sources, i.e soil, chemical fertilizer (Sp) and manure/organic fertilizer (Pk). The isotope carrier free solution of KH 2 32 PO 4 , which is contained of 98% 32 P, was applied to the soil and thus making it as the only source of labeled-P. Radioactivity counting of soil samples will lead to the measurement of P-contribution from several sources of P given. The experiment result showed that most of the P taken up by the plants was from soil. Thus, the P from Sp (P-Sp) and Pk (P-Pk) became un-significantly support the plant growth expressed in lesser dry weight of straw, grain and plants compared to those who taken its P from soil. Although soil contributed most of its available P to straw and grain of lowland rice, but Sp and Pk still contributed P to both plant parts. It was obtained that in straw 64 -82% P was derived from soil; 12 -21% P was derived from Pk; and 18 -29% P was derived from Sp. For grain 49 -89% P was derived from soil; 11 -15% P was derived from Pk; and19 -45% P was derived from Sp.

Metode jatuhan radioisotop (Fallout Radio Nuclides) telah lama dimanfaatkan dan dikembangkan untuk mempelajari dan mengukur erosi tanah. Penelitian ini bertujuan menduga erosi/deposisi tanah di Sub DAS Ciesek, DAS Ciliwung Hulu menggunakan jatuhan radioisotop 137Cs dan 210Pb excess di alam. Pengambilan sampel tanah dilakukan menggunakan soil core pada empat transek penggunaan lahan yang berbeda. Sampel tanah dianalisis menggunakan Multi Channel Analyzer (MCA) untuk mendapatkan nilai inventori kedua radioisotop tersebut. Hasil penelitian menunjukkan perbedaan pola distribusi erosi/deposisi antara isotop 137Cs dan 210Pb excess. Penggunaan isotop 137Cs menunjukkan proses erosi tanah terjadi pada lahan kebun campuran dan tegalan, tapi proses deposisi terjadi di lahan terbuka. Penggunaan 210Pb excess menunjukkan erosi tanah terjadi di lahan terbuka, namun deposisi terjadi di lahan kebun campuran dan tegalan. Penggunaan 210Pb excess pada penelitian ini lebih dapat diandalkan dibandingkan dengan 137Cs, dalam hal pendugaan erosi tanah