Judul: Analysis of the distribution of soil organic-C in PT Perkebunan Buah Subang
Abstrak: Lahan pertanian yang digunakan secara terus-menerus dapat menurunkan kesuburan tanah. Salah satu indikator kesuburan tanah adalah bahan organik tanah. Pengukuran kadar bahan organik dapat ditentukan dengan menganalisis kandungan C-organik tanah. Penelitian ini bertujuan mempelajari sebaran kandungan Corganik dalam tanah di PT Perkebunan Buah Subang dan faktor-faktor yang mempengaruhinya, meliputi kondisi lingkungan dan karakteristik tanah. Pengambilan contoh tanah dilakukan secara komposit dengan memperhatikan perbedaan kemiringan lereng dan tipe penggunaan lahan. Hasil penelitian menunjukkan kandungan C-organik tertinggi yaitu 3.13% terdapat pada penggunaan lahan hutan bambu, kemiringan 30–45% sedangkan kadar C-organik terendah yaitu 1.36% terdapat pada lahan terbuka, kemiringan 30-45%. Nilai pH tanah di lokasi penelitian termasuk sangat masam sampai agak masam (3.4 – 5.69), nilai KTK tanah sangat rendah sampai rendah (3.81 me/100 g –16.4 me/100 g). Hasil uji korelasi menunjukkan bahwa tipe penggunaan lahan memiliki korelasi kuat dengan C-organik tanah dengan nilai konstanta korelasi 0.729 . Selanjutnya, dengan menggunakan analisis regresi berganda diperoleh hasil bahwa tipe penggunaan lahan dan lereng memiliki keterkaitan dengan kandungan C organik tanah dengan nilai konstanta masing-masing adalah 0.119 dan 0.015., Agricultural land used continuously can reduce soil fertility. One of the indicators of soil fertility is soil organic matter. Organic matter content is measured by analyzing the soil organic-C content. The objective of this study was to determine the distribution of soil organic-C content in PT. Perkebunan Buah Subang and the factors that affect it, including environmental conditions and soil characteristics. Soil sampling was carried out in a composite with notice the differences in slope and land use types. The results showed that the highest organic- C content was 3.13% in bamboo forest land use, a slope of 30-45%, while the lowest organic-C content was 1.36% in bare land, a slope of 30-45%. Soil pH values at the research location were very acid to slightly acid (3.4 - 5.69), the soil cation exchange capacity values were very low to low (3.81 me/100 g – 16.4 me /100 g). The correlation test showed that the land use type had a strong correlation with soil organic-C, with a constant correlation value of 0.729. Furthermore, using multiple regression analysis, the result is that the land use type and slope were related to soil organic-C content with constant values of 0.119 and 0.015.
Keyword: correlation test, organic-C, multiple regression test, land use type

Judul: The Chemical Properties of Soil in Taliwang Distric, West Sumbawa Regency on Land Use of Teakwood Plantation, Dryland, and Paddy Soils.
Abstrak: Sifat kimia tanah berperan besar dalam menentukan kesuburan tanah. Kesuburan tanah secara kimia dinilai dari kandungan nitrogen, fosfor, basa dapat ditukar (K, Ca, Mg, dan Na), pH tanah, karbon organik, dan kapasitas tukar kation. Penelitian ini bertujuan mengkaji sifat kimia tanah di Kecamatan Taliwang, Kabupaten Sumbawa Barat pada tiga penggunaan lahan berbeda yaitu Kebun Jati (L1), Ladang (L2), dan Sawah (L3). Penelitian ini dilaksanakan pada September 2020 hingga Maret 2021. Contoh tanah diambil pada L1 dan L2 masing-masing empat lapisan, sedangkan pada L3 tiga lapisan. Analisis kimia tanah dilakukan di Laboratorium Kimia dan Kesuburan Tanah, IPB University. Hasil penelitian menunjukkan bahwa pH tanah umumnya berkisar agak masam hingga netral (6,4- 7,3), nilai pH tanah sawah cenderung nertral sedangkan nilai pH tanah kebun jati dan ladang tergolong agak masam. Kandungan C-organik tergolong rendah hingga tinggi (0,93% - 4,09%), kandungan N-total tergolong sangat rendah hingga sedang (0,07%-0,21%). Nilai P-tersedia tergolong sangat rendah pada semua contoh tanah (0,09 ppm-1,31 ppm). Rendahnya nilai P-tersedia pada lokasi penelitian diduga karena P diikat menjadi bentuk tidak larut oleh basa-basa seperti Ca dan Mg yang kandungannya tinggi di dalam tanah yang diamati. Di samping itu karena tanah yang diamati merupakan tanah yang berkembang dari bahan induk yang miskin akan unsur P. Nilai KTK tanah berkisar dari 13,9 cmol(+)/kg sampai 30,4 cmol(+)/kg. Nilai KB tanah yang diamati tergolong sangat tinggi yaitu lebih dari 100% dan tergolong tinggi sampai sangat tinggi. Kebun jati memiliki kandungan karbon organik, N-total, P-tersedia, basa dapat ditukar dan KTK lebih tinggi dibandingkan dengan ladang dan sawah. Kandungan karbon organik, N-total, dan P-tersedia yang termasuk kategori rendah pada penggunaan lahan kebun jati, ladang, dan sawah harus menjadi perhatian utama dalam pengelolaan tanah di Kecamatan Taliwang, Kabupaten Sumbawa Barat. Kata kunci: Basa dapat ditukar, Karbon organik, Kapasitas tukar kation, N-total, pH tanah, P tersedia., The soil chemical properties play a major role in determining soil fertility. Soil fertility is characterized chemically by the nitrogen and phosphorus content, exchangeable bases (K, Ca, Mg, and Na), soil pH, organic carbon, and cation exchange capacity (CEC). This research was aimed to examine the chemical properties of soil in Taliwang District, West Sumbawa Regency on three different land uses, namely teakwood plantation (L1), dryland (L2), and paddy soil (L3). The study was conducted from September 2020 to March 2021. Soil samples were taken at L1 and L2 each from four layers (horizons), while in L3 soil samples were taken from three layers. Soil chemical properties analysis was conducted at the Laboratory of Soil Chemistry and Fertility, IPB University. The results showed that the pH of the soil were generally ranged from slightly acidic to neutral (6.4-7.3), the pH value of paddy soil is neutral while the pH value of teakwood plantation soil and dryland soil is relatively slightly acidic. Organic carbon of soil samples of three landuse observed is relatively low to high (0.93%-4.09%), the total nitrogen content is classified as very low to moderate (0.07%-0.21%). The available-P value is very low in all soil samples (0.09 ppm-1.31 ppm). The low value of available-P at the research site due to the high
Keyword: Available-P, Carbon organic, Cation exchange capacity, Exchangeable bases, Soil pH, Total-N

Judul: Hamiltonian formulation for linear waves motion in two layers fluid
Abstrak: The surface wave could be considered as a wave that separates two fluids, namely water and air. Based on this assumption, it is introduced the interfacial wave, a wave between two layers of fluid with different density. The formulation of interfacial waves motion begins with deriving the base equation of irrotational ideal fluid. Furthermore, according to irrotational fluid assumption, the base equation can be stated in velocity potential. In this derivation, the fluids domain is assumed to be restricted by rigid lid boundary conditions, both at the upper and lower limit. Therefore, the interfacial waves motion can be explained in a hamiltonian formulation. In the hamiltonian formulation, total energy is defined as the sum of kinetic and potential energy. The hamiltonian system is obtained from reduction of kinetic energy by using the Dirichlet Neumann Operator. The resulted kinetic energy equation is nonlinear. Therefore, this form is linearized by first part of the Taylor expansion. This linearization gives a dispersion relation of linear wave. Based on this dispersion relation, the phase speed of the linear wave depends on the density ratio of the two layers fluid.
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