Judul: Kekuatan Geser Tanah Pada Perlakuan Tanaman  Vetiver (Chrysopogon zizanioides L.) dan Tanaman Orok-Orok (Crotalaria juncea L.) di Latosol dan Regosol
Abstrak: Kekuatan geser tanah menunjukkan kemampuan tanah untuk bertahan terhadap keruntuhan. Sifat ini sampai tahap tertentu dipengaruhi oleh perakaran tanaman. Besarnya kekuatan geser tanah juga dipengaruhi oleh sifat fisik tanah lainnya seperti kelembaban, tekstur, dan porositas tanah. Penelitian mengenai kekuatan geser tanah serta keterkaitannya dengan sifat-sifat tanah dan perakaran tanaman telah dilakukan pada skala rumah kaca menggunakan Rancangan Acak Lengkap faktorial dengan dua faktor, yaitu tanah dan jenis tanaman. Hasil penelitian menunjukkan bahwa tekstur tanah mempengaruhi kekuatan geser tanah. Berdasarkan dua jenis tekstur yang digunakan didapatkan bahwa semakin tinggi kandungan klei maka kekuatan geser tanah semakin tinggi. Latosol memiliki nilai kekuatan geser tanah lebih tinggi dibandingkan Regosol. Nilai kekuatan geser tanah pada kadar air 30% lebih tinggi dibandingkan kadar air kapasitas lapang. Nilai kekuatan geser pada perlakuan tanaman vetiver lebih tinggi dibandingkan dengan pada perlakuan orok-orok. Kekuatan geser tanah tertinggi terdapat pada Latosol yang ditanami vetiver yaitu sebesar 59,07 kPa. Bobot akar vetiver lebih tinggi dibandingkan dengan bobot akar orok orok. Semakin besar nilai bobot kering akar maka nilai kekuatan geser tanah semakin tinggi., Soil shear strength indicates the soil's ability to withstand failure. Soil shear strength to some extent is influenced by plant roots. The magnitude of the soil shear strength is also influenced by other physical properties of the soil such as moisture, texture, and soil porosity. Research on soil shear strength and its relationship to soil properties and plant roothas been done at a greenhouse scale using a factorial completely randomized design with two factors, namely soil and plant species. The results showed that soil texture affect the shear strength of the soil. Based on the two texture classes used, it was found that the higher the clay content, the higher the shear strength of the soil. Latosol has a higher soil shear strength value than Regosol. The value of the soil shear strength at the moisture content of 30% higher than at the water content of the field capacity. The value of shear strength in soil planted with vetiver plants was higher than that of sun hemp plant. Latosol planted with vetiver plant has the highest soil shear strength of 59.07 kPa. The weight of the roots of vetiver was higher than the weight of the roots of the sun hemp plant. The greater the dry weight value of the roots, the higher the value of the soil shear strength.
Keyword: moisture content, rooting, shear strength, texture

Judul: Soil Strength of Latosol and Podzolik on Various Land Use and Slope
Abstrak: Kekuatan geser tanah merupakan faktor penentu tanah dalam menopang gaya yang bekerja terhadapnya. Kekuatan geser tanah dipengaruhi salah satunya oleh vegetasi melalui kehadiran perakaran yang berperan dalam penguatan mekanik tanah dan kekuatan geser tanah. Penelitian ini bertujuan mengkaji kekuatan geser Latosol dan Podsolik pada lahan perkebunan sawit dan karet dengan kemiringan lereng berbeda serta mempelajari hubungannya dengan sifat tanah lainnya. Hasil penelitian menunjukkan bahwa kekuatan geser di Podsolik lebih tinggi dari Latosol dan pada lahan karet lebih tinggi dari lahan sawit. Kekuatan geser tanah di lereng landai pada kadar air 40% lebih kuat, sementara pada sampel tanah remolded dengan kadar air jenuh menunjukkan sebaliknya yaitu kuat geser lahan di lereng lebih curam lebih tinggi. Sifat fisik tanah C-organik, bobot isi, dan stabilitas agregat memiliki korelasi positif terhadap kekuatan geser tanah dengan nilai korelasi tertinggi pada C-organik sebesar 0,48. Latosol memiliki nilai sensitivitas yang lebih rendah dibandingkan Podsolik, yang menandakan Latosol memiliki potensi kehilangan kekuatan geser yang lebih rendah. Nilai sensitivitas tanah berkorelasi negatif dengan kandungan liat dengan tingkat korelasi tinggi yakni 0,90., Soil shear strength determines the capability of soil in supporting the pressure working on it. Soil shear strength is affected by vegetation through the presence of roots which play a role in strengthening soil mechanics and soil shear strength. This study aims to examine the soil shear strength of Latosol and Podsolik on oil palm and rubber plantations on different slopes and to study their correlation with other soil properties. The results showed that the shear strength of Podsolik was higher than Latosol and in rubber land use has a higher than in oil palm land use. The soil shear strength on gentle slope at moisture 40% water content stronger, while the remolded soil sample at a saturated water content shows the opposite, land with steeper slope has a higher. Soil physical properties soil C-organic, bulk density, and aggregate stability have a positive correlation to the soil shear strength where the highest correlation value occured on C-organic of 0.48. Latosol has a lower sensitivity value than Podsolik which indicates that Latosol has a lower potential for shear strength loss. Soil sensitivity value was negatively correlated with clay content with a high correlation level of 0.90.
Keyword: kelas lereng, sensitivitas tanah, remolded, jenis vegetasi

Judul: Approximation of the Median of Poisson Distribution Using the Relation of Poisson-Gamma Distribution
Abstrak: A major drawback of median is that median cannot usually be defined in closed form, even in the cases where their distribution functions are known. This study gives an approximation of the closed form for the median of the Poisson distribution by using the relation of Poisson-Gamma distribution. The approximation uses elementary techniques based on the monotonicity of certain sequences involving tail probabilities of the Poisson distribution and the Central Limit Theorem. Furthermore, a closed form expression for the mean absolute deviation 􀜧|􀜰􀰒 􀵆 􀜯􀝁􀝀􁈺􀜰􀰒􁈻| is also studied. The median is relevant because of the fact that it minimizes the mean absolute deviation of a Poisson random variable (􀜰􀰒􁈻 by considering median as central tendency.
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