Kajian Kualitas Tanah pada Lahan Gambut Terbakar di Kota Pontianak Provinsi Kalimantan Barat

Abstract

Kebakaran lahan gambut menyebabkan terjadinya perubahan sifat fisika, kimia dan biologi tanah gambut sehingga secara otomatis mempengaruhi kualitas tanah yang dinyatakan dengan Indeks Kualitas Tanah (IKT). Tujuan penelitian ini adalah menentukan indeks kualitas tanah dan faktor penentunya pada lahan gambut terbakar (GT) dan tidak terbakar (GTT). Penelitian dilakukan di Kelurahan Bansir Darat Kecamatan Pontianak Tenggara Kota Pontianak pada GTT  dan GT. Tahapan penelitian meliputi pengambilan sampel tanah pada masing-masing lahan, pengamatan dan pengukuran kedalaman gambut, ketebalan lapisan gambut dan kematangan gambut serta perhitungan jumlah cacing. Analisis sifat fisika tanah meliputi bobot isi, kadar air kapasitas lapang, porositas total; sifat kimia tanah terdiri dari reaksi tanah (pH), karbon organik (C-organik), Nitrogen total (N-total), rasio CN, posfor tersedia (P-tersedia), natrium, kalium, kalsium dan magnesium dapat dipertukarkan (Na-dd, K-dd, Ca-dd dan Mg-dd), kapasitas tukar kation (KTK), kejenuhan basa (KB), kadar abu; dan jumlah cacing tanah untuk sifat biologi tanah. Hasil penelitian menunjukkan GT dengan kematangan saprik memiliki kedalaman gambut lebih dangkal dibandingkan GTT dengan kematangan hemik. Kadar air dan porositas pada GT juga lebih rendah dibandingkan GTT. Kation basa GT lebih tinggi dibandingkan GTT meskipun kriteria keduanya sangat rendah. Parameter penentu kualitas tanah yaitu C-organik, CN rasio, N-total, P-tersedia, kalsium, natrium, kalium, kejenuhan basa, bobot isi, kadar air dan porositas. Kedua lahan memiliki kriteria IKT rendah namun GT memiliki nilai yang lebih tinggi (0,34) daripada GTT (0,27). Meskipun nilai IKT pada GT lebih tinggi, banyak dampak negatif yang ditimbulkan dari pembakaran lahan gambut. Karena itu pemerintah melarang pembakaran lahan dengan mengeluarkan kebijakan-kebijakan tentang pelarangan pembakaran hutan dan lahan gambut.

Abstract

Peatland fires cause changes in the physical, chemical and biological characteristics of the peat soil. It automatically affects the quality of the soil as stated by the Soil Quality Index (IKT). The purpose of this study was to determine the soil quality index and its determinants in burnt (GT) and unburnt (GTT) peatlands. The research was conducted in Bansir Darat Village, Southeast Pontianak District, Pontianak City on GT and GTT. The research stages included taking soil samples from each land, observing and measuring the depth of the peat, the thickness of the peat layer, the maturity of the peat and counting the number of worms as well. Analysis of soil physical characteristics including bulk density, moisture content of field capacity, total porosity; soil chemistry consists of C-organic, total nitrogen (N-total), CN ratio, available phosphorus (P-available), exchangeable sodium (Na-dd), potassium (K-dd), calcium-dd (Ca-dd)dan magnesium (Mg-dd), cation exchange capacity (CEC), base saturation (KB), content of ash; and the number of earth worms for soil biology property. The results showed that the physical characteristics of peat on GT had a shallower peat depth with sapric compared to GTT with hemic. The water content and porosity on GT are lower than GTT as well. The base cation of GT is higher than GTT even though the criteria for both are very low. The determinants of soil quality were C-organic, CN ratio, N-total, P-available, calcium, sodium, potassium, base saturation, content weight, moisture content and porosity. The Soil Quality Index of both lands have low criteria but GT has a higher value (0.34) than GTT (0.27). Even though the IKT value in GT is higher, there are many negative impacts caused by burning peatlands. Therefore, the government forbids burning of land by issuing policies to prohibit the burning of forests and peatlands.