Pengaruh Biochar Bambu dan Biochar Limbah Ekstrak Bromelain terhadap Kadaar Bahan Organik Tanah Lapisan Olah Ultisol Lampung Tengah

Abstract

Ultisol di PT. Great Giant Pineapple (GGP) Lampung Tengah memiliki kadar bahan organik rendah (<1%) yang terus menurun akibat budidaya monokultur tanaman nanas sehingga menimbulkan masalah efisiensi pemupukan. Biochar, arang berpori hasil pirolisis biomassa, berpotensi memperbaiki sifat tanah yang berkaitan dengan bahan organik tanah (BOT) seperti porositas, kapasitas menahan air, pH, dan kemampuan memegang hara. Penelitian ini mengkaji dinamika BOT pada lapisan olah Ultisol PT. GGP setelah aplikasi biochar berbahan baku bambu dan biochar limbah ekstrak bromelain (LEB) sebanyak 4 ton/ha. Penelitian berlangsung pada Agustus 2024 hingga Juni 2025 di Plot 80A PT. GGP, dan analisis fraksionasi BOT di Laboratorium Departemen Ilmu Tanah dan Sumberdaya Lahan, IPB University. Sampel tanah diambil pada kedalaman 0–10 cm dan 10–20 cm, pada satu dan tiga bulan setelah aplikasi biochar, lalu difraksionasi menjadi BOT bebas, BOT terikat klei, dan BOT terikat seskuioksida. Satu bulan setelah aplikasi BOT total di 0–10 cm pada perlakuan biochar tidak lebih tinggi dari kontrol akibat adanya sebagian biochar yang hanyut, sedangkan di 10–20 cm lebih tinggi, menunjukkan mobilisasi vertikal partikel biochar. Setelah tiga bulan, BOT total di 0–10 cm menurun signifikan pada semua perlakuan, kemungkinan akibat aliran permukaan dan dekomposisi fraksi labil atau bebas. BOT bebas lebih tinggi pada perlakuan biochar satu bulan setelah aplikasi, menandakan biochar belum terdekomposisi atau berikatan dengan mineral, namun menurun setelah tiga bulan bersamaan dengan meningkatnya BOT terikat klei dan seskuioksida yang mengindikasikan transformasi fraksi bebas menjadi terikat. Biochar bambu lebih efektif membentuk kompleks organo-mineral dengan seskuioksida, sedangkan biochar LEB mempertahankan BOT bebas lebih tinggi dengan transformasi terbatas.

Kata kunci: fraksionasi, klei, kompleks organo-mineral, pirolisis, seskuioksida

Ultisols at PT. Great Giant Pineapple (GGP), Central Lampung, has a low organic matter content (<1%) that continues to decline due to pineapple monoculture cultivation, leading to problems in fertilization efficiency. Biochar, a porous charcoal produced through biomass pyrolysis, has the potential to improve soil properties related to soil organic matter (SOM), such as porosity, water-holding capacity, pH, and nutrient retention. This study examined the dynamics of SOM in the tillage layer of Ultisols at PT. GGP after the application of bamboo-based biochar and bromelain extract waste (BEW) biochar at a rate of 4 tons/ha. The research was conducted from August 2024 to June 2025 in Plot 80A of PT. GGP, and SOM fractionation analysis was carried out at the Laboratory of Soil Science and Land Resources, IPB University. Soil samples were collected at depths of 0–10 cm and 10–20 cm, at one and three months after biochar application, and then fractionated into free SOM, clay-bound SOM, and sesquioxide-bound SOM. One month after application, total SOM in the 0–10 cm layer of the biochar treatments was not higher than the control due to partial leaching of biochar, while in the 10–20 cm layer it was higher, indicating vertical mobilization of biochar particles. After three months, total SOM in the 0–10 cm layer decreased significantly across all treatments, possibly due to surface runoff and the decomposition of labile or free fractions. Free SOM was higher in the biochar treatments one month after application, indicating that biochar had not yet decomposed or bound with minerals, but decreased after three months in line with the increase in clay-bound and sesquioxide-bound SOM, suggesting the transformation of free fractions into bound ones. Bamboo biochar was more effective in forming organo-mineral complexes with sesquioxides, whereas BEW biochar maintained higher free SOM with limited transformation.

Keywords: clay, fractionation, organo-mineral complex, pyrolysis, sesquioxides