Judul: Evaluation of Soil Fertility in Some Farmlands in the North and South of Brebes District, Central Java
Abstrak: Brebes merupakan salah satu kabupaten dengan komoditas pertanian yang beragam. Budidaya pertanian yang diterapkan sebagian besar merupakan pertanian intensif yang menggunakan pupuk sintetik anorganik yang digunakan secara berlebihan dan terus-menerus. Perbedaan lokasi dan ketinggian memiliki pengaruh dalam tingkat kesuburan tanah. Evaluasi kesuburan tanah sangat penting untuk dilakukan guna menilai, memantau, dan mengatasi kendala hara tanah. Penelitian ini bertujuan untuk mengevaluasi kesuburan tanah di 39 lokasi yang terdiri dari tanah di Kabupaten Brebes bagian utara dan selatan. Penelitian ini dilakukan melalui beberapa tahapan yaitu pengambilan contoh tanah dan analisis sifat kimia tanah, penilaian sifat kimia tanah, analisis perbandingan kation berdasarkan Base Cation Saturation Ratio (BCSR), evaluasi kesuburan tanah, pembuatan peta sebaran hara N, P, K, dan status kesuburan tanah, serta analisis data. Hasil menunjukkan bahwa rata-rata status kesuburan tanah di Brebes bagian utara sedang, dengan C-organik sebagai faktor pembatas. Brebes bagian selatan memiliki rata-rata status kesuburan tanah tinggi. Berdasarkan uji t bahwa, pH, C-Organik, N-total, P2O5 HCl 25%, K2O HCl 25%, KTK, KB, Ca dd, dan Mg-dd tanah di bagian utara berbeda sangat nyata dan nyata pada parameter Na-dd dengan tanah di bagian selatan, kecuali P2O5 dan K-dd. Meskipun demikian, P2O5 dan K-dd tanah di bagian utara relatif lebih tinggi dibandingkan di bagian selatan. Pengelolaan tanah yang intensif oleh petani menyebabkan ketidakseimbangan hara kation basa tanah di bagian utara dan selatan. Rasio kation basa yang didapatkan menunjukan tingkat kation yang jauh dari proporsi ideal. Ketidakseimbangan hara teridentifikasi melalui tingginya konsentrasi Ca dan Mg, yang dapat mempengaruhi pergerakan kation K, yang berpotensi menghambat penyerapan K oleh tanaman., Brebes are districts with a diverse range of agricultural commodities. Agricultural cultivation is mostly intensive farming using synthetic inorganic fertilizers used excessively and continuously. Differences in location and altitude influenced the soil fertility. Soil fertility evaluation is essential to assess, monitor, and overcome soil nutrient constraints. This study aimed to evaluate soil fertility in 39 locations consisting of soils in northern and southern Brebes Districts. This research was conducted through several stages, namely soil sampling and analysis of soil chemical properties; assessment of soil chemical properties; analysis of cation ratio based on Base Cation Saturation Ratio (BCSR); soil fertility evaluation; mapping of N, P, and K nutrient distribution and soil fertility status; and data analysis. The results showed that the average soil fertility status of northern Brebes was moderate, with organic C as the limiting factor. Southern Brebes has a high average soil fertility status. Based on the t-test pH, Organic C, total N, P2O5 HCl 25%, K2O HCl 25%, CEC, Base Saturation, exchangeable Ca, and exchangeable Mg of soils in the northern part differed significantly and significantly on exchangeable Na parameters to soils in the southern part, except for P2O5 and Exchangeable K. Intensive soil management by farmers causes an imbalance in the soil base cation nutrients in the north and south regions. The base cation ratios obtained showed cation levels far from ideal proportions. Nutrient imbalance was identified through high concentrations of Ca and Mg, which can affect the movement of K cations and potentially inhibit K uptake by plants.
Keyword: BCSR, Brebes, Kesuburan Tanah, Pertanian, Klasterisasi Lokasi

Judul: Comparison of Methods for Assessing Soil Fertility Status  on Toposequence Transect in Sandai Subdistrict, Ketapang District, West  Kalimantan
Abstrak: Penilaian status kesuburan tanah penting dalam pengembangan pertanian terutama untuk menghadapi tantangan krisis pangan dan potensi degradasi lahan. Penelitian ini mengkaji status kesuburan tanah pada transek toposekuen di Kecamatan Sandai, Kabupaten Ketapang, Kalimantan Barat. Contoh tanah yang diambil dari kedalaman 0-30 dan 30-60 cm pada tujuh titik pengamatan (TP1, TP2, TP3, TK1, TK2, TK3, dan TK4) kemudian dianalisis kapasitas tukar kation (KTK), kejenuhan basa (KB), P2O5 ekstrak HCl 25%, K2O ekstrak HCl 25%, dan karbon organik (C-organik) serta basa-basa dapat ditukar (Ca, Mg, dan K). Analisis ini didukung dengan Principal Component Analysis (PCA) melalui perangkat lunak statistik R Studio. Penilaian kesuburan tanah didasarkan pada kriteria Five Major Soil Chemical Properties (FMSCP), Basic Cation Saturation Ratio (BCSR) dan Sufficiency Level of Available Nutrients (SLAN). Status kesuburan tanah berdasarkan metode FMSCP berkisar antara sangat rendah (SR) hingga rendah (R). Terdapat variasi yang tinggi pada status kesuburan tanah (defisiensi hingga berlebih) berdasarkan kriteria BCSR dan SLAN, yang memiliki hubungan erat dengan keragaman bahan induk tanah dan kemiringan lereng. Tanah-tanah pada titik pengamatan TP1, TP2, dan TP3 berstatus defisiensi hingga seimbang, sedangkan TK1, TK2, TK3, dan TK4 didominasi oleh status seimbang hingga berlebih pada metode BCSR. Kriteria SLAN nasional mengindikasikan Ca, Mg, dan K tanah berstatus defisiensi. Status defisiensi juga terdapat hanya pada unsur K berdasarkan kriteria SLAN internasional. Hasil penelitian ini merekomendasikan implementasi dari metode penilaian status kesuburan tanah berbasis kriteria FMSCP pada tanah-tanah tropis di Indonesia., Assessment of soil fertility status is important in agricultural development, especially to face the challenges of the food crisis and potential land degradation. This research examines the status of soil fertility on topose sequence transects in Sandai Subdistrict, Ketapang District, West Kalimantan. Soil samples taken from depths of 0-30 and 30-60 cm at seven observation points (TP1, TP2, TP3, TK1, TK2, TK3, and TK4) were then analyzed for cation exchange capacity (CEC), base saturation (BS), P2O5 extract HCl 25%, K2O extract HCl 25%, and organic carbon (C-organics) as well as exchangeable bases (Ca, Mg, and K). This analysis was supported by Principal Component Analysis (PCA) via R Studio statistical software. Soil fertility assessment is based on the Five Major Soil Chemical Properties (FMSCP), Basic Cation Saturation Ratio (BCSR) and Sufficiency Level of Available Nutrients (SLAN) criteria. Soil fertility status based on the FMSCP method ranges from very low (VL) to low (L). There is high variation in soil fertility status (deficient to excessive) based on the BCSR and SLAN criteria, which is closely related to the diversity of soil parent materials and slope. The soils at observation points TP1, TP2, and TP3 have deficiency to balance status, while TK1, TK2, TK3, and TK4 are dominated by balance to excess status using the BCSR method. National SLAN criteria indicate soil Ca, Mg and K have deficiency status. Deficiency status also exists only for element K based on international SLAN criteria. The results of this research recommend the implementation of a soil fertility status assessment method based on FMSCP criteria on tropical soils in Indonesia.
Keyword: BCSR, FMSCP, SLAN, soil fertility, toposequence

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.
Keyword: