Judul: Karakteristik fiska dan mekanika pada berbagai  jenis tanah
Abstrak: Soil physical properties, as well as biologrcal and chemical propwties, affect crop production and growth in relation with water availability and physical environment for plant g~owth. Also, mechanical properties of soil become important in agriculture for learning the soil carrying capacity for agricultural machinery and its effect toward rooting environment. This reseacl~ was conducted with the objective of learning the basic physical, hydraulic and mechanical properties of various types of soil and studying their interrelations with soil colloid. Research method comprise soii sampling in the'fie!d &om various locations in West Java, Central Java and South Sumatra. Analysis of physical, chemical, mineralogical and rnechanicai properties of soil with standard rnethd, was conducted in laboratory of Department of Soil Science, Faculty of Agriculture and Department of Agricultural Engineering Faculty of Agricultural Technology, Bogor Agricultural University fiom January to September 2003 Result of this research show that physical and mechanical properties of each soil type studied, differ from each other. The studied soils have textural classes sandy loam. loamy sand, clay, silty clay and clay loam. Soil with coarse textural class (sandy loam and loamy sand) had buld density ( I . 18 - 1.30 gr/crn3) higher than those of clay textured soit, lower total porosity (5 1.73 - 52.24%), very low Coefficient of Linear Extensibility (COLE) (0.005 - 0.001), Index of aggregate stability (IS A) ranging from very unstable to stable (39.55 - 54.47) and permeability ranging from rapid to very rapid (12.56 - 25.18 d o u r ) . Content of available water in this soil is very low (2.5 - 3.0%) Soil with medium textural class (clay loam) had lower bulk density (0.53 - 0.66 gr/cm3) as compared with bulk density of common m i n d soil, h&er tad porosity (74.30 - 78.58%) as ascompared with clay textured mil (24.5 1 - 68.16%), very high values of COLE (0.268 - 0.353). aggregate stability with ranged from very unstable to stable (32.56 - 4830) an permeability class with was somewhat rapid ( 8.87 - 10.23 cm/hour) . Content of available water in this soil is vw high (32.6 - 35.4%). Soils with clay textural class clay, silty clay and silty clay i loam) had higher bulk density (0.83 - 2.02 gr/cm ) as cumpared with medium textured soils (0.53 - 0.66 gr/cm3). COLE values ranging b m low to very high (0.020 - 0.366), aggregate stab&@ ranging fiom very unstable to very stable (3 1.44 129.551, and permeability ranging h m very slow to modemrely rapid (0.04 - 1 1 -39 cmm0ur)- Available soil water ranged liom very low to very high (3.0 - 26.5%). Most of the mils studied, had kaolinitic clay mineral. Podsolik soil of Jamga and Grumusols had smdte clay miad w h m other types of soil had mixed clay minerd (Planowl of Serang, Alluvial of Kmwang, Muvial of Brebes and Medireran of Ciampea). Soil with medium textural class (Andosd) were dominated by Allophane mineral.
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Judul: Karakterisasi kelembaban tanah dalam kaitannya dengan sifat fisika tanah pada berbagai tekstur dan jenis tanah
Abstrak: Karakteristik tanah yang berbeda sangat dipengaruhi oleh kelas tekstur tanah. Salah satu karakteristik tersebut adalah kelembaban tanah. Penelitian ini bertujuan untuk (a) menelaah secara mendalam karakter kelembaban tanah dan sifat-sifat fisika pada berbagai tekstur dan jenis tanah, (b) menganalisis hubungan antara berbagai sifat fisik dan kimia tanah dengan parameter kelembaban tanah. Metode yang dilakukan pada penelitian ini meliputi pengambilan contoh tanah di lapang dan analisis tanah di laboratorium yang berlangsung sejak bulan Januari sampai dengan Juni 2003. Pengambilan contoh tanah dilakukan pada berbagai tempat di Jawa Tengah, Jawa Barat dan Sumatera Selatan. Analisis tanah dilakukan di Laboratorium Departemen Tanah, Fakultas Pertanian, Institut Pertanian Bogor meliputi analisis tekstur 10 fraksi, bobot isi, bobot jenis partikel, kadar C-organik dan pengukuran retensi air tanah pada pF 1, 2, 2.54 dan 4.2 dengan menggunakan alat Pressure Plate. Peubah-peubah yang diamati dalam penelitian ini adalah kadar air kapasitas lapang, kadar air titik layu permanen, air tersedia dan pori air drainase sebagai peubah tak bebas, sedangkan bobot isi, porositas total, tekstur, indeks stabilitas agregat dan kadar bahan organik sebagai peubah bebas. Analisis statistik yang digunakan dalam penelitian ini adalah analisis regresi linear sederhana. Hasil penelitian menunjukkan bahwa tanah yang bertekstur liat (halus) mempunyai bentuk kurva pF yang agak tegak antara pF 1 sampai pF 2.54, kemudian agak mendatar antara pF 2.54 sampai pF 4.2. Tanah yang bertekstur kasar (pasir) mempunyai bentuk kurva pF yang agak mendatar antara pF 1 sampai pF 2.54, kemudian agak tegak antara pF 2.54 sampai 4.2. Tanah yang bertekstur sedang (lempung) mempunyai bentuk kurva pF di antara tanah yang bertekstur liat dan pasir. Persen pasir mempunyai pengaruh nyata terhadap kadar air pF 2, kadar air kapasitas lapang, kadar air titik layu permanen dan pori air drainase (r² = 0.496, r²= 0.588, r² 0.594 dan r²= 0.422). Persen liat mempunyai pengaruh nyata terhadap kadar air pF 2, kadar air kapasitas lapang, kadar air titik layu permanen dan pori air drainase (r² = 0.619, r² = 0.785, r²= 0.645 dan r²= 0.437). Bobot isi, porositas total dan bahan organik mempunyai pengaruh nyata terhadap air tersedia (r²= 0.627, r²= 0.609 dan r²= 0.598). Persen debu dan indeks stabilitas agregat (ISA) tidak berpengaruh nyata terhadap parameter-parameter kelembaban tanah.
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Judul: A Continuous Vaccination Strategy in the SVIR Epidemic Model
Abstrak: Vaccination is conducted to minimize the spread of a disease. The vaccination is usually done several times within a fixed time interval. In the SVIR model, it is assumed that individuals do not get immediate immunity following a vaccination program. So according to process of vaccination on SVIR model, there are two strategies, i.e. the continuous vaccination strategy (CVS) and the pulse vaccination strategy (PVS). In this study, only the CVS strategy in epidemic model SVIR is considered. Results of the study indicate that dynamics of the CVS system depends on the basic reproductive number. If the basic reproductive number is less than one, then the disease-free fixed point is asymptotically stable. It means that the disease will eventually disappear from the population. Conversely, if the basic reproductive number is greater than one, then the endemic fixed point is asymptotically stable, which means that the disease will remain exist in the population. Simulation result shows that the vaccination would minimize the spread of disease by reducing the basic reproductive number. If the time for the vaccinated recipients to obtain the immunity, as well as a possibility of vaccinated recipients to be infected are neglected, then the disease will be eradicated. This condition is called an over-evaluating effect of vaccination.
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