Judul: Peranan arang batang kelapa sawit dalam peningkatan produksi tanaman jagung (Zea mays, L.)
Abstrak: The main problem of continuously cultivated land is decreasing land productivity. Improvement of land productivity can be done by application of suitable soil ameliorant. Charcoal is one of soil ameliorants that can be used for improving soil properties such as to stimulate plant growth by providing and maintaining nutrients in the soil due to improving soil physical and biological properties. Abundant availability of oil palm trunks when oil palm replanting is an opportunity to utilize oil palm trunks as charcoal raw material. This research aimed to study the effect of charcoal from oil palm trunks on corn growth and production as well as to study tendency of the movement and development of roots grown on media with and without of charcoal from oil palm trunks. Soil material was taken from Latosol at a depth of 0-20 cm. The soil material was treated by charcoal from oil palm trunks as much as 0%, 4%, 8%, 12%, 16% and 20% (w/w) of the soil. The soil also was addded by basic N, P, and K fertilizers and then corn was planted. The results showed that soil treated by 4% of charcoal from oil palm trunks increased significantly corn growth and production. Application of higher charcoal rates did not increase the growth and production of corn, and moreover tended to decrease at 20% charcoal treatment. Biomass production of corn increased significantly compared to untreated charcoal. The porous structure of charcoal improve the structure of soils which allows roots capable to utilize more available nutrients as indicated by the evidence of more roots in the soil containing charcoal and increasing corn production.
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Judul: Peranan Amelioran terhadap Perbaikan Sifat Kimia Tanah dan Hasil Jagung (Zea mays) di Lahan Bekas Tambang Timah
Abstrak: Peningkatan produksi pertanian dihadapkan pada masalah semakin menurunnya sumberdaya lahan pertanian, sehingga pemanfaatan lahan marginal dapat menjadi solusi. Lahan bekas tambang timah merupakan salah satu lahan marginal yang dapat dijadikan lahan pertanian dengan faktor pembatas fisik, kimia dan biologi tanah yang buruk seperti bentang alam yang tidak teratur, tekstur tanah berpasir, iklim mikro yang buruk, kemampuan menahan air dan hara yang rendah, kandungan nutrisi tanah rendah, dan penurunan keanekaragaman hayati organisme tanah. Penerapan teknologi tepat guna yang paling mendasar dalam memperbaiki lahan bekas tambang timah adalah pemberian bahan amelioran. Biochar dari bahan baku tandan kosong kelapa sawit (TKKS), pupuk kandang, dan kompos mucuna merupakan tiga bahan amelioran yang banyak tersedia dan mudah didapatkan di Kepulauan Bangka Belitung. Pengaruh amelioran terhadap perbaikan sifat kimia tanah, pertumbuhan, dan produksi tanaman tergantung pada karakteristik amelioran yang dipengaruhi oleh jenis bahan baku dan dosis aplikasi, sehingga penelitian peranan amelioran terhadap sifat kimia tanah dan hasil jagung di lahan bekas tambang timah penting untuk dilakukan. Penelitian bertujuan mengkarakterisasi sifat fisik biochar dan sifat kimia biochar, pupuk kandang, dan kompos mucuna serta mendapatkan jenis dan dosis amelioran terbaik untuk perbaikan sifat kimia dan hasil jagung di lahan bekas tambang timah. Penelitian menggunakan rancangan acak kelompok dengan tujuh perlakuan dan empat ulangan. Perlakuan yang diuji cobakan yaitu Kontrol (tanpa amelioran), Bio (20 t ha-1 biochar), PK (20 t ha-1 pupuk kandang), KM (20 t ha-1 kompos mucuna), Bio+PK (10 t ha-1 biochar + 10 t ha-1 pupuk kandang), Bio+KM (10 t ha-1 biochar + 10 t ha-1 kompos mucuna), dan PK+KM (10 t ha-1 kompos mucuna + 10 t ha-1 pupuk kandang). Hasil penelitian menunjukkan bahwa sifat fisik biochar dengan proses pendinginan tanpa menggunakan air lebih baik dibandingkan dengan biochar dengan proses pendinginan menggunakan air dengan nilai luas permukaan, total volume pori, dan volume mikropori lebih tinggi 5% hingga lebih dari 100%. Sifat kimia biochar dari TKKS memiliki C/N rasio, pH, P terlarut asam sitrat 2%, K-Ca-Mg total, Fe-Cu-Zn total tertinggi. Kandungan P total dan Na total tertinggi dimiliki oleh pupuk kandang, sedangkan C organik, N total dan, Mn total tertinggi dimiliki oleh kompos mucuna. Kandungan logam berat Pb dan Cd pada biochar, pupuk kandang dan kompos mucuna masih di bawah ambang batas kandungan Pb (maksimal 50 ppm) dan Cd (maksimal 2 ppm). Aplikasi biochar dengan dosis 20 t ha-1 memberikan efek terbaik dalam memperbaiki sifat kimia tanah yakni pH, K, Mg, dan KB. Selain itu, pemberian 20 t ha-1 amelioran biochar memberikan hasil jagung lebih tinggi dibandingkan dengan tanpa pemberian amelioran, namun tidak berbeda dengan perlakuan amelioran lainnya.
Keyword: ameliorant, corn yield, ex-tin mining land, soil chemical properties

Judul: Dynamical System of Hepatitis B in Three Groups with Vaccination
Abstrak: The aim of this study is to modify the hepatitis B transmission model in three age groups involving vaccination from the model conducted by Zhoe and Zhang.The method used is to analyze the stability of the fixed point and its basic reproduction number (R_0). Performed stability analysis and numerical simulation to see population dynamics. Next, a sensitivity analysis of the parameters was carried out to see its effect on R_0. From the analysis obtained two fixed points, namely non-endemic and endemic fixed points. Non-endemic fixed points are locally asymptotically stable if R_0 <1 Meanwhile, the endemic fixed point is locally asymptotically stable if R_0 > 1. Hepatitis vaccination affects the number of susceptible population, because the more successful the vaccination, the smaller the number of susceptible populations so that the smaller the population will be infected.
Keyword: Dynamic, Hepatitis B, Vaccine, Mathematical model