Judul: Consistency and Shrink-Swell Soils in Shallot Field, Brebes Regency, Central Java
Abstrak: Bawang merah merupakan salah satu komoditas yang sangat dibutuhkan dalam kehidupan sehari-hari. Sentra produsen bawang merah terbesar di Indonesia adalah Kabupaten Brebes. Namun pada kenyataannya produktivitas bawang merah di Kabupaten Brebes mengalami penurunan. Salah satu upaya untuk meningkatkan produktivitas bawang merah yaitu dengan melakukan pengolahan tanah yang baik, misalnya dengan mengkaji konsistensi tanah di lahan tersebut. Kemampuan mengembang dan mengerut tanah yang tinggi dapat beresiko terhadap pertumbuhan umbi bawang merah. Resiko tersebut dapat diminimalisir dengan cara memperhatikan nilai COLE (Coeficient Of Linear Extensibility) yang merupakan indikator dalam penetapan sifat mengembang dan mengerut tanah. Penelitian ini bertujuan menganalisis konsistensi dan nilai COLE serta kaitannya dengan sifat fisik dan kimia tanah pada lahan bawang merah di Kabupaten Brebes, Jawa Tengah. Hasil penelitian menunjukkan bahwa Konsistensi dan Nilai COLE tanah berbeda antar jenis tanah. Indeks plastisitas, jangka olah, dan nilai COLE memiliki korelasi terhadap kadar klei dan bahan organik. Ketiga jenis tanah memiliki Indeks plastisitas yang tinggi, jangka olah yang sempit, dan nilai COLE yang baik. Hal ini menunjukkan kualitas tanah pada lahan ini masih perlu diperbaiki untuk memperoleh kondisi yang lebih baik bagi pertumbuhan bawang merah., Shallots are one of the commodities needed in everyday life. The largest shallot producing center in Indonesia is Brebes Regency. But in reality, shallot productivity in Brebes Regency has decreased. One of the efforts to increase shallot productivity is by doing good tillage, for example by assessing the consistency of the soil. The high ability of soil to swell and shrink can be a risk to the growth of shallot bulbs. This risk can be minimized by paying attention to the COLE (Coeficient Of Linear Extensibility) value which is an indicator in determining the soil swelling and shrinking. This study aims to analyze the consistency and value of shrink-swell soil and its relation to the soil physical and chemical properties on shallot fields in Brebes Regency, Central Java. The results showed that soil consistency and shrink-swell value were different among soil types. Plasticity index, tillage period, and shrink-swell value have a correlation with clay and organic matter content. All three soil types have high plasticity index, narrow tillage period, and good shrink-swell value. This shows that the quality of the soil on this land still needs to be improved to obtain better conditions for the growth of shallots.
Keyword: gleisol, cambisol, mediteran, productivity

Judul: Plant Spacing Modelling Analysis Towards Shallot Productivity (Field Study: Brebes Regency)
Abstrak: Kondisi cuaca dan penggunaan sumber daya mempengaruhi produktivitas bawang merah. Analisis ini mengkaji hubungan antara pertumbuhan bawang merah dengan kondisi iklim sekitar untuk mengoptimalkan produktivitas dengan menggunakan perlakuan jarak tanam. Penelitian ini bertujuan untuk mengetahui pengaruh jarak tanam terhadap produktivitas bawang merah dalam respon kondisi cuaca harian yang dapat dimodelkan menggunakan model simulasi untuk menentukan jarak tanam yang optimal. Penelitian lapang dilakukan di Desa Karangbale, Brebes, Jawa Tengah, yang merupakan salah satu sentra produksi bawang merah. Model simulasi dapat menggambarkan proses pertumbuhan bawang merah dengan uji t berpasangan dengan p value lebih besar dari 0,05 untuk semua variabel pertumbuhan seperti hari panen, produktivitas, dan LAI pada semua perlakuan. Hasil analisis menunjukkan jarak tanam JT3TG (16x16 cm) lebih optimal dibandingkan dengan JT1TG (14x14 cm), JT2TG (18x18 cm), JT1JL (14x16 cm), dan JT2JL (14x18 cm) ditinjau dari produktivitas, efisiensi penerimaan radiasi, dan serangan hama dan penyakit tanaman, Weather conditions and resource use affect shallot productivity. This analysis examines the relation between the growth of shallot plants and the surrounding climatic conditions to optimize productivity using plant spacing treatment. This study aims to determine the effect of spacing on shallot productivity in response to daily weather conditions which can be modelled using a simulation model to determine optimal planting space. Field research was conducted in Karangbale Village, Brebes, Central Java, which is one of the shallot production centres. The simulation model can predict the shallot growth process with paired t-test with p-value greater than 0.05 for all growth variables such as harvest days, productivity, and LAI in all treatments. The results of the analysis showed that JT3TG (16x16 cm) was more optimal spacing rather than JT1TG (14x14 cm), JT2TG (18x18 cm), JT1JL (16x14 cm), and JT2JL (16x18 cm) in terms of productivity, radiation reception efficiency, and the lowest pests and crop diseases infestation.
Keyword: crop model simulation, growth, plant spacing, productivity, radiation use efficiency

Judul: Comparison of HIV Model with and without Time Delay
Abstrak: Acquired immunodeficiency syndrome (AIDS) is the reduction of the human immune system. AIDS is caused by human immunodeficiency virus (HIV). No medicine has been found for this desease until recently. An AIDS therapy is usually performed with highly active antiretroviral therapy, namely reverse transcriptase inhibitors, protease inhibitors and combination of both. Various models have been developed to explain the immune system of patients with AIDS, namely the HIV, response and the time delay model. This paper discusses the comparison between the dynamics of the HIV virus, the dynamic response of protease inhibitors and dynamics of time delay. The dynamics model of HIV is influenced by the level of white blood cells produced and the rate of its death. Dynamics of protease inhibitors on the response and the time delay model is influenced by the death rate of infected white blood cells and the failure rate of treatment.
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