Judul: Ambang Batas Fe dalam Pupuk Organik yang Berpotensi Menyebabkan Keracunan Fe Pada Tanaman Padi Sawah
Abstrak: Many scientists reported that intensive agricultural using a high rate of in anorganic NPK fertilizer and pesticide, caused declining in soil productivity, soil degradation, and increased environmental pollution. Organic content of these soils are mostly very low, while it is widely know that organic matter is very important to keep physical, chemical, and biological properties of soil as well as soil productivity. However, the quality and quantity of organic matter to be used are important factor determining the impact on the soil. In Ministry of Agriculture Decree (Permentan) No. 28, 2009, a maximum limit of total iron content in organic fertilizer is 8.000 mg kg-1 while most of the current organic fertilizers available in the market exceed this limit. The objectives of the study were to know the quality of organic fertilizer currently available in the market in Java Island and to determine the threshold level of iron that potentially cause iron toxicity in rice. The survey was conducted on May to July 2011 in java Island for survey and collecting a number of organic fertilizer currently marketed and the pot experiment was conducted on May to November 2011 in green house. This experiment using a randomized complete block design with two factors; the types of soil (Endoaquert, Tropaquept, and Hapludult) and organic fertilizer enriched with Fe (FeCl3) in various level. Each treatment was replicated three times. Survey results from 60 samples of granule organic fertilizer taken from several areas in Java Island with 11 parameters, there was indicated two samples (3 % from the total samples) that fulfilled several criteria following of Permentan No. 28, 2009 and no sample (0%) that fulfilled several criteria following of Permentan No. 70, 2011. The pot experiment results showed that the threshold of total iron content in granule organic fertilizer potentially cause iron toxicity for Endoaquert, Tropaquept, and Hapludult were 62.900, 37.300, and 61.100 mg kg-1 respectively. The threshold of total iron content in granule organic fertilizer potentially cause iron toxicity in rice of IR 64 variety with dose 1 ton/ha is 59.500 mg kg-1.
Keyword: Iron, threshold, organic fertilizer, iron toxicity, wetland rice

Judul: Increased Rice Yield (Oryza sativa L.) with Application of Organic Fertilizer Enriched with Microbes
Abstrak: Produktivitas padi Indonesia beberapa tahun terakhir mengalami penurunan. Pemupukan yang sesuai dengan kondisi tanah dan kebutuhan tanaman mampu meningkatkan produksi tanaman. Aplikasi pupuk organik diperkaya dapat meningkatkan kesuburan tanah. Mikroba yang hidup di perakaran tanaman atau PGPR dalam pupuk dapat meningkatkan ketersediaan hara dalam tanah dan mensintesis hormon pertumbuhan tanaman melalui aktivitas biologisnya. Penelitian ini bertujuan untuk mempelajari pengaruh aplikasi pupuk organik diperkaya terhadap peningkatan hasil padi sawah dan pengurangan dosis pupuk anorganik. Rancangan yang digunakan adalah rancangan kelompok lengkap teracak satu faktor yaitu dosis pupuk dengan 4 ulangan. Penelitian dilaksanakan di Kebun Pendidikan Sawah Baru IPB. Analisis tanah dan analisis kandungan pupuk dilaksanakan di Laboratorium Kimia dan Kesuburan Tanah, Departemen Ilmu Tanah dan Sumber Daya Lahan, Laboratorium Pengujian Departemen Agronomi dan Hortikultura, serta Laboratorium Tanah, Tanaman, Pupuk, Air, Balai Penelitian dan Pengembangan Pertanian. Pelaksanaan penelitian dimulai pada November 2020 hingga April 2021. Pengamatan dilakukan terhadap pertumbuhan, hasil, dan komponen hasil padi sawah. Hasil penelitian ini menunjukkan aplikasi pupuk organik diperkaya secara umum tidak meningkatkan pertumbuhan dan hasil per tanaman maupun hasil per hektar padi sawah. Aplikasi pupuk organik diperkaya dapat mengurangi 25% penggunaan pupuk anorganik dengan nilai efektivitas agronomi relatif sebesar 108,8%., Rice productivity in Indonesia has decreased in recent years. Fertilization that is suitable for soil conditions and plant needs can increase crop yield. The application of bioorganic fertilizer would be able to increase soil fertility. Microbes that live in plant roots could increase the availability of nutrients in the soil and synthesize plant growth hormones through their biological activities. The research aims to study the effect of the application of organic fertilizer enriched with microbes on increasing growth, yield, and yield components of lowland rice and the reduction of the dose of inorganic fertilizer. The experimental design used was a randomized complete group design with one factor, namely the dose of fertilizer with 4 replications. The research was carried out at the Sawah Baru Teaching Farm, IPB. Soil analysis and analysis of fertilizer content were carried out at the Laboratory of Chemistry and Soil Fertility, Department of Soil Science and Land Resources, Testing Laboratory of the Department of Agronomy and Horticulture, and the Laboratory of Soil, Plants, Fertilizer, Water, Agricultural Research and Development Center. The experiment was conducted from November 2020 until April 2021. The observations made were observations of vegetative and generative characters, as well as yields. Results shows, the application of enriched organic fertilizers did not increase growth and yield per plant or yield per hectare of lowland rice. Application of enriched organic fertilizers, however, could reduce 25% of inorganic fertilizers usage with a relative agronomic effectiveness value of 108.8%.
Keyword: effectiveness, organic fertilizer, PGPR, rice, yield

Judul: Invers dari Matriks Tridiagonal Jacobi
Abstrak: Suatu matriks berukuran n×n dinamakan matriks tridiagonal jika untuk . Karya ilmiah ini memberikan algoritma yang mudah untuk menemukan invers ( dari matriks tridiagonal Jacobi yang simetrik dan nonsimetrik. Setiap elemen pada matriks tridiagonal ini adalah bilangan real. Terdapat 3 lema dan 2 teorema untuk menentukan . Lema pertama menunjukkan persamaan utama dalam membuktikan lema-lema dan teorema-teorema selanjutnya. Invers dari matriks yang simetrik dibuktikan oleh lema kedua yang menunjukkan elemen-elemen baris ke- dari . Selanjutnya, lema kedua dilengkapi dengan teorema pertama yang menunjukkan elemen-elemen dengan . Invers dari matriks yang nonsimetrik dibuktikan oleh lema ketiga yang menunjukkan elemen-elemen dengan dan elemen-elemen dengan dibuktikankan oleh teorema kedua.
Keyword: symmetric, nonsymmetric, matrix