88 PEMBERIAN KOMPOS PADA TANAH BEKAS TAMBANG DENGAN INDIKATOR TANAMAN SAWI (Brassica chinensis L) THE EFFECTS OF COMPOST APPLICATION ON EX-MINING LAND WITH CHINESE CABBAGE (Brassica chinensis L) AS INDICATOR Karamoy Lientje Theffie, Wiesje J.N. Kumolontang dan Jenny Rondonuwu *) *) Fakultas Pertanian Unsrat Manado ABSTRACT This research aimed to determine the effects of compost applications on ex-mining lands by using chinese cabbage as indicator. The experiments were conducted at the Faculty of Agriculture greenhouse and the soil and compost analysis were done at the Soil Chemistry and Fertility Laboratory for a duration of two months. The research employed a Completely Randomized Design method with 5 treatments repeated 3 times to get 15 experimental units. The analysis on ex-mining soil revealed that it contained only trace amounts of soil nutrients N, P, and K. The laboratory analysis on the compost sample resulted in a C/N ratio of 11.87 which suggested that the compost was mature and ready to be used. The Analysis of Variance on research data showed that compost applications did not affect plant height between treatments at each weekly observation, and similarly did not affect leaf quantity and fresh weight at harvest time. However, the research found that the compost applications tended to improve plant height, leaf quantity, and fresh weight of plants at harvest time. The minimal effect of compost applications between treatments suggested that the plants did not utilized the nutrients supplied by the compost in their early stages of development. Moreover, it was also suspected that the compost applications had not been sufficient in supplying the soil nutrients needed by the plants to ensure proper growth which ultimately affected the fresh weight of the plants at harvest time. Keywords: compost, ex-mining land ABSTRAK Penelitian ini bertujuan menentukan pengaruh pemberian kompos pada tanah bekas tambang dengan indikator tanaman sawi. Penelitian ini dilakukan di Rumah Kaca Fakultas Pertanian dan analisis tanah serta kompos dilakukan di Laboratorium Kimia dan Kesuburan Tanah dengan lama penelitian 2 bulan. Penelitian dirancang menggunakan Rancangan Acak Lengkap (RAL) dengan 5 (lima) perlakuan serta diulang sebanyak 3 (tiga) kali sehingga diperoleh 15 satuan percobaan. Hasil penelitian kandungan hara N, P dan K tanah bekas tambang tergolong sangat rendah. Hasil analisis kompos diperoleh ratio C/N 11.87 hail ini menunjukkan pupuk kompos yang digunakan telah matang dan siap digunakan. Hasil analisis sidik ragam menunjukkan pemberian pupuk kompos tidak berpengaruh antar perlakuan terhadap tinggi tanaman pada setiap minggu pengamatan, demikian juga jumlah daun dan berat segar tanaman saat panen. Tetapi dari hasil penelitian dapat dilihat ada kecenderungan terjadi peningkatan tinggi tanaman, jumlah daun dan berat segar tanaman saat panen dengan adanya pemberian kompos. Tidak adanya pengaruh pemberian kompos antar perlakuan pada penelitian ini menunjukkan tanaman pada awal pertumbuhan belum seluruhnya menggunakan hara yang ada pada kompos. Selain itu kemungkinan pemberian kompos belum mampu menyediakan hara yang dibutuhkan tanaman untuk pertumbuhannya yang berpengaruh pada produksi tanaman dalam hal ini berat segar tanaman saat panen. Kata kunci: kompos, tanah tambang Eugenia Volume 21 No. 2 Juni 2015