Judul: Evaluasi Kesuburan Andisol pada Beberapa Kabupaten di Sumatera Utara
Abstrak: Kabupaten Humbang Hasundutan, Dairi, dan Karo merupakan daerah dataran tinggi yang berpotensi untuk pengembangan hortikultura. Akan tetapi, tingkat kesuburan tanah menjadi permasalahan utama. Penelitian bertujuan mengevaluasi tingkat kesuburan tanah serta membandingkan Andisol di Humbang Hasundutan, Dairi, dan Karo. Contoh tanah pada kedalaman 0-20cm di setiap daerah dilakukan analisis sifat kimia tanah, kemudian dilakukan perbandingan berdasarkan kriteria PPT Tahun 1995. Hasil penelitian menunjukkan terdapat variasi hasil akibat adanya perbedaan pengelolaan tanah serta jenis penggunaan lahan. Kabupaten Humbang Hasundutan memiliki rata-rata nilai C-organik tinggi, P total rendah, K total sangat tinggi, KTK rendah serta KB sedang. Kabupaten Dairi memiliki ratarata C-organik, P total serta K total yang sangat tinggi, serta KTK dan KB yang sedang. Kabupaten Karo memiliki rata-rata C-organik yang tinggi, P total dan K total sangat tinggi, KTK sedang, serta KB yang tinggi. Berdasarkan evaluasi status kesuburan tanahnya, Kabupaten Dairi dan Karo memiliki tingkat kesuburan tanah sedang, sedangkan Kabupaten Humbang Hasundutan memiliki status kesuburan rendah., Humbang Hasundutan, Dairi, and Karo regencies are highland areas with the potential for horticultural development. However, the level of soil fertility becomes the main problem. The study aimed to evaluate soil fertility levels and compare Andisol in Humbang Hasundutan, Dairi, and Karo. Soil samples at a depth of 0-20 cm in each area were analyzed regarding the soil chemical characteristics, then a comparison was made based on the soil fertility criteria PPT 1995. The results showed that there were variations in results due to differences in soil management and types of land use. Humbang Hasundutan Regency had an average of high organic carbon (C) values, low total phosphorus (P), very high total potassium (K), low cation exchange capacity (CEC) and medium base saturation. Dairi Regency had a very high average of organic C, total P and K total, as well as moderate CEC and base saturation. Karo Regency had a high average of organic C, very high total P and total K, medium CEC, and high base saturation. Based on the evaluation of the soil fertility status, Dairi and Karo Regencies had moderate soil fertility, while Humbang Hasundutan Regency had a low fertility status.
Keyword: base saturation, cation exchange capacity, organic carbon, total potassium, total phosphorus

Judul: The Effect of Changes in Soil  Organic Carbon Levels on the Phosphorus Sorption Characteristics in Andisol  Humbang Hasundutan, North Sumatera
Abstrak: Kawasan Humbang Hasundutan Provinsi Sumatera Utara merupakan salah satu daerah pengembangan kawasan lumbung pangan (Food Estate). Jenis tanah pada kawasan ini termasuk Andisol yang memiliki permasalahan pada ketersediaan hara fosfor (P). Andisol merupakan tanah yang berkembang dari bahan vulkanik yang memiliki mineral-mineral klei amorf yang mengerap P sangat tinggi. Penelitian ini bertujuan untuk menganalisis dan mengevaluasi beberapa sifat kimia tanah dan karakteristik erapan P pada Andisol yang belum terganggu dan Andisol yang mendapat penambahan bahan organik sebanyak 20 t ha-1 di Humbang Hasundutan Sumatera Utara. Contoh tanah yang dianalisis adalah berasal dari tiap horizon masing-masing profil tanahnya. Contoh tanah Andisol yang belum terganggu diambil pada kedalaman 0-19 cm dan 19-40 cm, dan contoh tanah Andisol yang sudah diberi bahan organik 20 t ha-1 diambil pada kedalaman 0-17 cm, 17-27 cm, dan 27-50 cm. Hasil penelitian menunjukkan bahwa pemberian bahan organik sebesar 20 t ha-1 meningkatkan kadar karbon (C)- Organik, P-tersedia, dan pH, serta menurunkan aluminium yang dapat dipertukarkan (Al-dd) pada lapisan atas (kedalaman 0-17 cm dan 17-27 cm). Pemberian bahan organik sebesar 20 t ha-1 tidak berpengaruh secara statistik terhadap erapan P maksimum, tetapi nyata menurunkan konstanta energi erapan P (k) dan standar kebutuhan P (P0.2). Nilai k berkorelasi negatif secara nyata dengan C-Organik. Penelitian ini menunjukkan bahwa pemberian bahan organik 20 t ha-1 meningkatkan kadar C-organik tanah, P-tersedia, pH dan menurunkan nilai Al-dd. Untuk parameter erapan P, pemberian bahan organik tanah 20 t ha-1 menurunkan nilai k dan P0.2 dimana nilai k berkorelasi negatif dengan kadar C-organik tanah. Semakin tinggi kadar C organik tanah maka semakin rendah nilai k erapan P sebagai konstanta energi ikatan erapan P., Humbang Hasundutan area of North Sumatera Province is one of the development areas for the food estate area. Soil types in this area was Andisol which have problem with phosphorus (P) availability. Andisol is a soil that develops from volcanic material that has amorphous clay minerals that sorbs very high P. This study aimed to analyze and evaluate some soil chemical properties and P sorption characteristics in Andisol that has not been disturbed and Andisol which received the addition of organic matter as much as 20 t ha-1 in Humbang Hasundutan North Sumatra. The soil samples analyzed were derived from each horizon of each soil profile. Undisturbed Andisol soil samples were collected at a depth of 0-19 cm and 19-40 cm, and Andisol soil samples that have been applied with organic matter 20 t ha-1 collected at a depth of 0-17 cm, 1 7-27 cm, and 27-50 cm.The results showed that soil samples which was applied with organic matter increased organic carbon (C) levels, available P, soil pH, and lower exchangeable aluminium (exch Al) at the depth of 0-17 cm and 17-27 cm. The application of 20 t ha-1 did not statistically affect the P sorption maximum but significantly decreased the P bonding energy constant (k) and standard P requirement (P0.2) . The k value significantly negatively correlated with organic C. This study suggested that the application of organic matter 20 t ha-1 increased soil organic C levels, available P, soil pH and lower
Keyword: correlation, organic matter, bonding energy, soil organic C

Judul: Simulasi Protokol Autentikasi Pelanggan pada Voice Privacy
Abstrak: Existing design of the telephone public network is susceptible to eavesdropping on its voice stream. Consequently, any wire taper can listen to supposedly private conversation. In order to prevent such eavesdropping, we propose a protocols and its implementation for end-to-end voice privacy authenticate as a service available for interested subscribers. Our protocols consist of customer enrollment system, customer authentication system and simulation voice privacy. Protocols that we made are adaptation from Sharif and Wijekesera journal with the title Providing Voice Privacy as a Service over the Public Telephone Network. The result of the process shows how the customer enrolls and how the system process the password, how the system authenticate customer simulate voice privacy.
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