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: 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: Grup dan Homomorfisma Grup pada Rubik Revenge
Abstrak: Rubik cube is a kind of puzzle game. A player must arrange rubik sides, which have been disordered, back to the position where every side has the same colour. This paper does not focus on the settlement solution, but instead on proving the existence of a group homomorphism between rubik movement group and S96 symmetric permutation group in rubik revenge. Firstly, it has been proved that rubik movement set is a group. Then, it also has been proved that the M set, which contains numeric labels of 1 until 96 in cubinos sides, is S96 symmetric permutation group.
Keyword: