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: Evaluation of Essential Micronutrients (Fe,  Mn, Cu, and Zn) and Toxic Heavy Metals (Pb and Cd) in Soils of Brebes District, Central Java
Abstrak: Praktik pertanian intensif yang beragam dengan penggunaan pupuk dan pestisida melebihi dosis pada wilayah utara dan selatan di Kabupaten Brebes dapat mengakibatkan disproporsi hara tanah seperti hara mikro esensial Fe, Mn, Cu, dan Zn serta akumulasi logam berat beracun Pb dan Cd yang berpotensi merugikan kesehatan tanaman, lingkungan, hingga manusia. Penelitian ini bertujuan menganalisis kondisi tanah melalui evaluasi hara mikro esensial seperti Fe, Mn, Cu, dan Zn serta logam berat beracun seperti Pb dan Cd pada tanah wilayah utara dan selatan di 39 lokasi pengambilan sampel tanah dengan penggunaan lahan pertanian dan hutan di Kabupaten Brebes, Jawa Tengah. Metode penelitian dilakukan melalui pengambilan dan persiapan sampel tanah, analisis sampel tanah di laboratorium, penilaian bioavailabilitas logam berat, dan analisis data. Keseluruhan hara mikro esensial yaitu Fe, Mn, Cu, dan Zn pada wilayah utara dan selatan memiliki kriteria cukup, namun terdapat 2 lokasi mengalami defisiensi Zn. Hara mikro esensial tanah di wilayah utara relatif lebih rendah dibandingkan dengan wilayah selatan. Hara mikro esensial memiliki korelasi dengan pH H2O, KTK, C-organik, N-total, P2O5 HCl 25%, Ca-dd, dan Na-dd. Kadar Pb dan Cd total dan Pb serta Cd tersedia tanah baik di wilayah utara maupun selatan termasuk dalam kategori normal. Kadar Pb dan Cd total tanah di wilayah utara relatif lebih rendah dibandingkan dengan wilayah selatan. Sementara itu, Pb-tersedia di tanah wilayah utara cenderung lebih tinggi dibandingkan di wilayah selatan, sedangkan Cd-tersedia di wilayah utara relatif lebih rendah daripada wilayah selatan. Logam berat beracun Pb dan Cd berkorelasi dengan N-total, KTK, dan Mg-dd. Bioavailabilitas Pb dan Cd di wilayah utara cenderung lebih tinggi daripada di wilayah selatan. Bioavailabilitas Cd lebih tinggi dibandingkan dengan Pb. Semakin tinggi bioavailabilitas logam berat maka semakin besar peluang terserapnya logam berat pada tanaman sehingga menyebabkan logam akan terakumulasi pada bagian-bagian tanaman., Intensive agricultural practices that vary with the use of fertilizers and pesticides exceeding doses in the northern and southern regions of Brebes Regency can result in soil nutrient disproportions, such as essential micronutrients Fe, Mn, Cu, and Zn, and the accumulation of toxic heavy metals Pb and Cd, which have the potential to harm plants, the environment, and human health. This study aims to analyze soil conditions through the evaluation of essential micronutrients, such as Fe, Mn, Cu, and Zn, and toxic heavy metals, such as Pb and Cd, in northern and southern soils in 39 soil sampling locations with agricultural and forest land uses in Brebes Regency, Central Java. The research was conducted through the collection and preparation of soil samples, analysis of soil samples in the laboratory, assessment of heavy metal bioavailability, and data analysis. The overall essential micronutrients of Fe, Mn, Cu, and Zn in the north and south have sufficient criteria, but the two locations experience Zn deficiency. Essential soil micronutrients in the northern region were lower than those in the southern region. Essential micronutrients were correlated with pH H2O, CEC, organic C, total N, P2O5 HCl 25%, exchangeable Ca and Na. The total Pb and Cd and soil available Pb and Cd in both the northern and southern regions were in the normal category. The
Keyword: hara mikro, Bioavailabilitas Logam Berat, Pb dan Cd

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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