Effect of Organic Fertilizer and Biochar on Seedling Media Quality and Growth of Cacao Seedling

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Using acid soil as a cacao seedling medium limits the seedling growth due to low fertility, thus necessitating soil ameliorant treatment to improve its chemical, physical, and biological quality. This study aimed to investigate the effect of cacao husks as organic fertilizer and biochar on chemical and biological properties of seedling media and cacao seedling growth, was conducted in Soil Biotechnology Laboratory and Soil Fertility Laboratory, Bogor Agricultural University and Pakuwon Experimental Station at Indonesian Industrial and Beverage Crops Research Institute (IIBCRI), Sukabumi, from June 2014 until February 2015. Completely randomized design (CRD) was used in the factorial treatment with three factors: (1) organic fertilizer treatment (without organic fertilizer and with organic fertilizer 10% of the weight of seedling media), (2) the types of biochar (rice husk and white albizia wood), and (3) the doses of biochar (0%, 1%, 2%, 4%, 6% of the weight of seedling media), with three replications respectively. Observation was on chemical and biological properties of the soil and seedling growth.  The results showed that organic fertilizer or albizia wood biochar application significantly improved C-organic and  C/N ratio. Increasing the dose of biochar or organic fertilizer application raised the pH, total N, and microbes respiration, whereas  without organic fertilizer was linearly able to improve total population of microbes but not the dry weight of cacao seedling. The combination of biochar and organic fertilizers increased the stem diameter and dry weight of cacao seedling.
Pemanfaatan tanah masam Ultisol untuk media pembibitan kakao dihadapkan pada kendala rendahnya tingkat kesuburan. Oleh karena itu, perlu penambahan amelioran agar kualitas kimia, fisika, dan biologi tanah menjadi lebih baik. Tujuan penelitian adalah mengkaji pengaruh pupuk organik kulit buah kakao dan arang hayati terhadap sifat kimia dan biologi tanah media pembibitan dan dampaknya terhadap pertumbuhan bibit kakao. Penelitian dilaksanakan di Laboratorium Bioteknologi Tanah dan Laboratorium Kesuburan Tanah, Institut Pertanian Bogor dan Kebun Percobaan Pakuwon, Balai Penelitian Tanaman Industri dan Penyegar (Balittri), Sukabumi, mulai Juni 2014 sampai Februari 2015. Rancangan yang digunakan adalah acak lengkap (RAL) dengan susunan perlakuan faktorial tiga faktor yang diulang tiga kali. Faktor pertama adalah pemberian pupuk organik (tanpa pupuk organik dan dengan pupuk organik 10%). Faktor kedua adalah jenis arang hayati (sekam padi dan kayu sengon). Faktor ketiga adalah dosis arang hayati (0%, 1%, 2%, 4%, dan 6% dari bobot media pembibitan). Pengamatan dilakukan terhadap sifat kimia dan biologi media pembibitan, serta pertumbuhan bibit kakao. Hasil penelitian menunjukkan bahwa pemberian pupuk organik atau arang kayu sengon nyata meningkatkan C-organik dan nisbah C/N. Peningkatan dosis arang hayati atau pemberian pupuk organik dapat meningkatkan pH, N total, dan respirasi mikrob, sedangkan tanpa pupuk organik dapat meningkatkan populasi jamur, tetapi tidak dapat meningkatkan bobot kering bibit. Kombinasi arang hayati dan pupuk organik memperbesar diameter batang dan bobot kering tajuk bibit kakao.
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