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.
Keyword: 

Judul: Hubungan antara beberapa sifat fisik, kimia dan biologi tanah dengan air tanah pada berbagai tekstur tanah
Abstrak: Penelitian ini dilakukan di Laboratorium Fisika, Kimia den Kesuburan, Mineralogi, dan Biologi Tanah, Jurusan Tanah, Fakultas Pertanian, Institut Pertanian Bogor dan Laboratorium Agronomi Balai Penelitian Tanaman Pangan Cimanggu Во- gor mulai bulan Maret sampai dengan bulan September 1987. Tujuan Penelitian melihat hubungan antara beberapa sifat fisik, kimia dan biologi tanah dengan retensi air tanah pada berbagai tekstur tanah serta menduga parameter sifat fisik, kimia dan biologi tanah yang paling berperanan dalam menentukan retensi air tanah. Sebagai bahan penelitian digunakan Grumusol Cihea, Podsolik Jasinga, Andosol Sukamantri, Regosol Sindang Barang dan Latosol Darmaga, masing-masing diambil pada kedalaman 20 cm dan 40 - 60 cm. Contoh tanah berupa tanah utuh, agregat utuh dan tanah terganggu. Selain bahan di atas ju- ga digunakan berbagai macam bahan analisis sifat-sifat fisik, kimia dan biologi tanah yang ditetapkan. Analisis retensi air tanah dilakukan dengan metode kurva pF (plate dan membrane apparatus). Sedangkan parameter-parameter yang dianalisis, yang diduga mempunyai hubuzgan erat dengan retensi air tanah diantaranya: tekstur, selisih pH H2O dan pH KCl (APH), bobot isi, porositas total, indeks stabilitas agregat (ISA), sodium adsorption ratio (SAR) dan aktivitas mikroorganisme…dst
Keyword: 

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.
Keyword: