ABSTRAK
Penelitian survei yang mengkaji karakteristik tanah pada satuan lahan volkan tua. Penelitian dilakukan pada dua areal lahan, yaitu kaki lereng Gunung Sipiso-piso dan kaki lereng Gunung Simbolon. Analisis tanah di Laboratorium Riset dan Teknologi, Fakultas Pertanian, Universitas Sumatera Utara. Pada masing-masing areal dibuat profil pewakil kemudian diamati morfologi dan karakteristik serta diklasifikasikan menurut klasifikasi taksonomi tanah dan klasifikasi nasional. Analisis tanah meliputi Bulk densiti, tekstur, pH H2O, pH KCl, pH NaF, ZPC, KTK, KB, Basa-basa tukar, C-organik, P-tersedia, Retensi P, P-total, Al Fe Si ekstrak oksalat, Al dan Fe ekstrak pirofosfat. Hasil penelitian menunjukkan bahwa satuan lahan volkan tua yang berada di kaki lereng Gunung Sipiso-piso memiliki BD < 0.90 gcm-3,muatan tanah permanen negatif, retensi P sedang, kadar P tersedia sangat rendah, pH NaF ≥ 9.2, nilai KTK sedang dan ZPC tidak terdeteksi. Lahan ini masih mempunyai sifat tanah andik dan diklasifikasikan menurut taksonomi tanah (Ultic Hapludand) dan klasifikasi nasional (Andosol Distrik). Sedangkan lahan volkan tua yang terdapat di kaki lereng Gunung Simbolon memiliki BD < 0.90 gcm-3, muatan tanah permanen negatif, retensi P rendah, kadar P tersedia sedang, pH NaF ≥ 9.2, nilai KTK rendah, dan ZPC tidak terdeteksi. Klasifikasi tanah pada areal ini berdasarkan taksonomi tanah (Andic Dystrudept) dan klasifikasi nasional (Kambisol Kromik). Volkan tua memiliki perbedaan dengan tanah di lahan volkan muda dalam hal muatan tanah, ZPC, retensi P dan KTK tanah.
Kata kunci : karakteristik tanah, klasifikasi tanah, lahan volkan tua
ABSTRACT
The survey research was aimed to review the character of soil on old volcan land units. This study was conducted in two area, i.e the Mt.Sipiso-piso and Mt.Simbolon footslope. Soil analysis was held in Research and Technology Laboratory, Agriculture Faculty, University of North Sumatera. The representative pedon in each area was observed morphologcally and the properties as well, then classified according to soil taxonomy and national
classification. Soil properties measured were bulkdensity, soil texture, pH H2O,
pH KCl, pH NaF, ZPC (Zero Point of Charge), Cation Exchange Capacity (CEC), Base saturation, C-Organic content, P-available (Bray II), P-retention, Al-oxsalate extracted (Alo) Fe-Al-oxsalate extracted (Feo), Al-pyrophosphate extracted (Alp) and Fe-pyrophosphate extracted (Fep). The result showed that the footslope
Mt.Sipiso-piso old volcan land unit has BD < 0.90 gcm-3, negative permanent
charge, moderate P-retention, low P-available (Bray II), pH NaF ≥ 9.2, moderate
CEC and ZPC was undetected. This land had andic soil features and classified into Ultic Hapludand (according to Soil Taxonomy) and Andosol Distrik (according to national classification). Meanwhile, the footslope Mt.Simbolon old
volcan land unit has BD < 0.90 gcm-3, negative permanent charge, low
P-retention, moderate P-available (Bray II), pH NaF ≥ 9.2, low CEC and ZPC was
undetected. This land was classified into Andic Dystrudept (according to Soil Taxonomy) and Kambisol Kromik (according to national classification). Old and young volcan soil have the differentiation in term of soil charge, ZPC, P-retention and CEC.
Keyword : Soil characteristic, soil classification, an old volcan land
