Judul: Dynamics of Nitrogen Release by Four Types of Urea in Flooded Conditions
Abstrak: Nitrogen (N) merupakan salah satu unsur hara esensial bagi tanaman. Salah satu penyebab rendahnya ketersediaan N adalah pencucian. Pupuk urea merupakan sumber hara N yang paling banyak digunakan di Indonesia, termasuk pada lahan sawah. Urea merupakan pupuk N yang larut air sehingga penggunaan urea di sawah perlu dikaji dalam hubungannya dengan pelepasan pupuk. Di dalam penelitian ini digunakan urea dengan formulasi berbeda yaitu urea kujang dan pusri yang merupakan urea konvensional dan urea prill dan granul yang merupakan urea modifikasi yang mengandung formaldehida masing-masing 0,10 dan 0,50 %. Metode yang digunakan adalah inkubasi dan pencucian. Inkubasi dilakukan selama 7, 14, 28, 45, 60, dan 90 hari dan dilakukan pencucian pada setiap akhir masa inkubasi. Hasil pencucian ditetapkan kandungan amonium dan nitrat. Hasil penelitian menunjukkan bahwa pelepasan N dalam bentuk amonium dan nitrat antar perlakuan pupuk urea tidak berbeda nyata. Hasil total N tercuci menunjukkan nilai paling tinggi diperoleh oleh urea granul sebesar 78,0 mg tabung-1, kemudian disusul oleh urea prill 75,2 mg tabung-1, urea kujang sebesar 71,5 mg tabung-1, dan urea pusri sebesar 68,4 mg tabung-1. Berdasarkan hasil persamaan first order kinetic, diperoleh nilai pelepasan maksimum dan konstanta kecepatan. Nilai pelepasan maksimum tertinggi dimiliki oleh urea granul sebesar 94,6 mg tabung-1, kemudian urea prill sebesar 88,3 mg tabung-1, urea pusri sebesar 82,3 mg tabung-1, dan urea kujang sebesar 79,2 mg tabung-1. Sementara untuk nilai konstanta kecepatan, konstanta kecepatan tertinggi diperoleh pada urea kujang sebesar 0,0349 hari-1, kemudian dilanjutkan oleh urea prill dan pusri sebesar 0,0256 hari-1, dan urea granul sebesar 0,0253 hari-1. Hasil penelitian menunjukkan bahwa urea yang diperlakukan dengan formaldehida terutama dalam bentuk granul cenderung memiliki kemampuan untuk memperlambat proses pelepasan N yang ditunjukkan dengan nilai konstanta kecepatan yang paling rendah., Nitrogen (N) is one of the essential nutrients for plants. One of the causes of the low availability of N is leaching. Urea fertilizer is the most widely used source of N in Indonesia, including in paddy fields. Urea is a water-soluble N fertilizer, so the use of urea in paddy fields needs to be studied in relation to the release of fertilizer. In this study, urea with different formulations was used those were urea kujang and pusri as conventional urea, while urea prill and granule as modified urea containing 0,10 and 0,50 % formaldehyde, respectively. The method in this study was the incubation and washing method. Incubation was carried out for 7, 14, 28, 45, 60, and 90 days and washing was conducted at the end of each incubation period. The results of washing were determined for the content of ammonium and nitrate. The results showed that the release of N in the form of ammonium and nitrate among urea fertilizer types were not significantly different. The results of total leached N showed that the highest value was obtained by granul urea at 78,0 mg tube-1, then followed by prill urea at 75,2 mg tube-1, kujang urea at 71,5 mg tube-1, and pusri urea at 68,4 mg tube-1. Based on the results of the first-order kinetic equation, it was revealed the maximum release and constant rate. The highest value
Keyword: anaerobic, conventional, granul, Latosol

Judul: Comparison of nitrogen absorption by corn (Zea mays L.) from four urea fertilizers
Abstrak: Jagung merupakan salah satu komoditas pangan utama di Indonesia. Peningkatan produktivitas jagung umumnya menggunakan pupuk urea untuk memenuhi kebutuhan nitrogennya. Masalah utama terkait penggunaan urea yaitu tingginya jumlah nitrogen tercuci. Salah satu upaya mencegah pencucian N yaitu dengan mengubah senyawa urea menjadi senyawa urea lambat tersedia (slow release), diantaranya dengan mengubah sebagian senyawa urea menjadi urea-formaldehida yang bersifat lambat tersedia. Penelitian ini bertujuan untuk mempelajari pengaruh empat jenis pupuk urea terhadap bobot biomassa kering, serapan nitrogen, dan efisiensi serapan nitrogen. Penelitian menggunakan rancangan acak lengkap satu perlakuan dengan empat ulangan. Penelitian dilaksanakan di rumah kaca dengan media tanah seberat 15 kg (Bobot Kering Mutlak) dengan polybag. Perlakuan terdiri atas perlakuan tanpa pemupukan N (kontrol), pemupukan urea konvensional yang terdiri dari urea kujang dan urea pusri dan urea slow-release berupa urea urea granul (0,5% formaldehida) dan urea prill (0,1% formaldehida). Biomassa bagian atas tanaman untuk keperluan analisis dipanen tiap minggu selama 10 minggu dari satuan percobaan yang terpisah. Analisis kadar N jaringan jagung dilakukan setiap minggu panen dengan metode mikro Kjehdahl. Hasil percobaan menunjukkan pemberian urea slow-release, khususnya urea granul, meningkatkan bobot biomassa jagung dibandingkan dengan penggunaan urea konvensional. Selain itu, penggunaan urea slow-release memiliki tingkat efisiensi lebih tinggi dibandingkan dengan urea konvensional. Faktor yang menyebabkan urea granul memiliki serapan dan efisiensi yang lebih tinggi adalah pelapisan butir dengan senyawa urea-formaldehid pada urea slow-release., Corn is one of the main foods commodities in Indonesia. To increase corn productivity, urea fertilizer is commonly used to supply its nitrogen (N) needs. The main problem related to the use of urea fertilizer is the high amount of nitrogen leached. One way to prevent nitrogen leaching is by forming a urea compound to a slow-release compound, one of them is changing part of the urea compound to urea-formaldehyde. This research was aimed to study the effect of four different urea fertilizers on corn’s biomass production, nitrogen absorption, and nitrogen absorption efficiency. This research used a completely randomized design of one factor with four repetitions. The research was carried out in a greenhouse with 15 kg soil as plant’s media in a polybag. The treatments consisted of treatment without N fertilization (control), conventional urea fertilizers (kujang urea and pusri urea), and slow-release ureas which is granule urea (0.5% formaldehyde) and prill urea (0.1% formaldehyde). Upper plant biomass for analysis was harvested every week for 10 weeks from separated experimental uni. Total N analysis was determined by mikro Kjeldahl method. The result showed that the application of slow-release urea, especially granulated urea, increased nitrogen absorption and biomass weight compared to the application of conventional urea fertilizers. Factors that cause the granule slow-release urea has higher absorption and efficiency is the coating of the grain with urea-formaldehyde
Keyword: conventional urea, granulated urea, nitrogen efficiency, slow-release, urea-formaldehyde

Judul: Pengembangan Model Codebook untuk Identifikasi Chord Gitar
Abstrak: Acoustic guitar can produce sound waves with different types of tones. High-low tone is determined by the fundamental frequency of the sound wave. Human sense of hearing can distinguish high-and low tones, but can not know for sure what kind of tone is heard by him. This study developed a guitar chord recognition system. This study uses MFCC as feature extraction methods and the codebook as pattern recognition method for identification of the guitar chord. Cluster technique used in this study is the K-means clustering. Data obtained from MFCC are clustered using the K-Means method, and the model for classification is constructed using the codebook method. The parameters used in MFCC is the number of cepstral coefficients, overlap, and the time frame, while an important parameter in the K-Means is the number of clusters. This study uses 8640 guitar chord sounds from 24 classes. Each of the data is made up of two chords which will be tested. Simulation results show that the maximum accuracy obtained is 98.89% obtained on 26 cepstral coefficients, overlap 0.4, time frame is 30 ms, on 100 clusters.
Keyword: chord, codebook, k-means, mel frequency cepstral coefficients (MFCC)