Judul: Water use efficiency on upland sugar cane
Abstrak: Low Indonesian sugar production is mainly due to low productivity and low sugar yield. The shift of sugarcane crop acreage from low land to upland was the major factor of low productivity. Cultivation of sugarcane in uplands faced many constraints, namely low availaibility of soil water, low soil nutrient and unavailability of appropriate varieties. Cane cultivation in upland is commonly done at the beginning of the wet season (in November) in order to avoid the plant from water stress at the beginning of growth period. This causes the sugarcane age of only 7 months and have not reach maturity at harvest time in June which leads to lower sugarcane productivity. Shifting planting season is an alternative that can be done to obtain plants with sufficient maturity at the harvest time. However, the consequences of shifting the planting season is that the planting occured on dry season and which means that watering is needed. The limited availability of water demands efficiency in water usage. The application of organic matter as filter cake compost is expected to reduce the frequency of irrigation. This aims of this study are (1) to study the effect of water supply on performance of several varieties of sugarcane, (2) to study the effect of filter cake compost on nutrient uptake by sugarcane at various irrigation levels, (3) to analyze the efficiency of water usage in connection with the provision of filter cake compost in some varieties of sugarcane, and (4) to develop recommendation of water supply efficiency in the field with the addition of filter cake compost. The study was conducted in three stages of the experiment, which were the performance of several varieties under water stress, the effect of filter cake compost and irrigation on plant nutrient uptake, and the application of filter cake compost and frequency of irrigation on upland sugar cane productivity. The sugarcane varieties used in the experiments of performance varieties under different moisture content were PS 851, PS 864, PS 862, PS 921, PS 951, PS 91-787 and BL. After 3 months observation, it appears that water stress began significantly affected plant growth at 50% of field capacity (FC). The results showed that seven varieties were able to grow well under soil water content up to 75% FC. Based on Drought Tolerance Index, varieties BL and PS 864 has DTI values close to tolerant, while others were considered as moderate tolerant. Although the DTI value of PS 921 was only classified as moderately tolerant, it has the highest biomass in all of the soil water content treatments. It shows that PS 921 has the highest potential among the other varieties as variety of sugarcane suitable for upland planting. To study the effect of filter cake compost and water supply on the nutrient uptake of sugarcane, the variety PS 921 was used. The dose of filter cake compost were 0, 5, 10, 15, and 20 tons per hectare and the soil water content were 100%, 75% and 50% FC, respectively. The results of this experiments show that the uptake of P by sugarcane was influenced
Keyword: Water use efficiency, Saccharum officinarum L., Saccharrum robustum L.

Judul: Growth and Production of Sugarcane (Saccharum officinarum L.) First Ratoon in Residual Filter Cake and Inorganic Fertilizer.
Abstrak: Intensifikasi tebu keprasan lahan kering merupakan salah satu cara dalam rangka meningkatkan produksi gula nasional. Penelitian dilakukan bulan Agustus 2019 - Juli 2020 pada tebu keprasan pertama di lahan percobaan PT Kebun Tebu Mas, Lamongan, Jawa Timur dengan rancangan split split plot. Perlakuan terdiri atas 3 faktor yaitu varietas (PS 881 dan PS 862) sebagai petak utama, residual kompos blotong (taraf residual pupuk blotong 0, 5, dan 10 ton ha-1) sebagai anak petak, dan residual pupuk anorganik (residual pupuk 25%, 50%, 75%, dan 100% dosis rekomendasi) sebagai anak-anak petak. Hasil penelitian menunjukkan bahwa pertumbuhan varietas PS 862 lebih baik daripada PS 881 pada keragaan tinggi tanaman, panjang ruas, diameter, panjang batang, dan jumlah batang. Residual kompos blotong memiliki pengaruh nyata lebih baik pada taraf 10 ton ha-1 pada panjang ruas. Residual pupuk anorganik taraf 75% memiliki respon yang lebih baik pada peubah jumlah daun, jumlah tunas, jumlah batang dan diameter. Varietas PS 862 dengan 5 ton ha-1 residual kompos blotong menghasilkan bobot batang terbaik sebesar 0,48 kg m-1. Varietas PS 862 dengan 75% residual pupuk anorganik menghasilkan hasil tebu sebesar 78,52 ton ha-1 dan tidak berbeda nyata dengan residual 100% pupuk anorganik., Intensification of upland sugarcane is one way to increase national sugar production. The research was conducted in August 2019-July 2020 on the experimental field of PT Kebun Tebu Mas, Lamongan on the first ratooncane with a split-split plot design. The treatment consisted of three factors, variety (PS 881 and PS 862 as main plots), residual filter cake (0, 5, and 10 tons ha-1) as subplots, and inorganic fertilizer residues (25, 50, 75, and 100% recommended doses) as subsubplots. The results showed that growth and yield of PS 862 was better than PS 881 in the performance of plant height, internode length, diameter, stem length, and number of stems. The residue of blotong compost had a significantly better effect at the level of 10 tons ha-1 on internode length. Residual inorganic fertilizer level 75% had a better response to the variables of number of leaves, number of shoots, number of stems and diameter. The PS 862 with 5 tons ha-1 residual blotong compost produced the best stem weight of 0.48 kg m-1. The PS 862 variety with 75% residual inorganic fertilizer produced sugarcane yields of 78.52 tons ha-1 and was not significantly different from the residual 100% inorganic fertilizer.
Keyword: intensification, PS 881, PS 862, sugar, upland

Judul: Invers dari Matriks Tridiagonal Jacobi
Abstrak: Suatu matriks berukuran n×n dinamakan matriks tridiagonal jika untuk . Karya ilmiah ini memberikan algoritma yang mudah untuk menemukan invers ( dari matriks tridiagonal Jacobi yang simetrik dan nonsimetrik. Setiap elemen pada matriks tridiagonal ini adalah bilangan real. Terdapat 3 lema dan 2 teorema untuk menentukan . Lema pertama menunjukkan persamaan utama dalam membuktikan lema-lema dan teorema-teorema selanjutnya. Invers dari matriks yang simetrik dibuktikan oleh lema kedua yang menunjukkan elemen-elemen baris ke- dari . Selanjutnya, lema kedua dilengkapi dengan teorema pertama yang menunjukkan elemen-elemen dengan . Invers dari matriks yang nonsimetrik dibuktikan oleh lema ketiga yang menunjukkan elemen-elemen dengan dan elemen-elemen dengan dibuktikankan oleh teorema kedua.
Keyword: symmetric, nonsymmetric, matrix