Visual Evaluation Soil Structure (VESS) di Lahan Tambang Silika, Semak Belukar, Agroforestri, dan Hutan Tanaman

Abstract

Alih fungsi kawasan hutan menjadi areal pertambangan dan bentuk penggunaan lahan lainnya merupakan salah satu penyebab utama degradasi tanah di Indonesia. Kegiatan penambangan, khususnya penambangan silika, berdampak pada rusaknya sifat fisik tanah, terutama struktur tanah, akibat hilangnya vegetasi penutup dan bahan organik tanah. Struktur tanah merupakan indikator penting kualitas tanah karena berpengaruh langsung terhadap porositas, infiltrasi air, dan pertumbuhan akar tanaman. Evaluasi kualitas tanah umumnya dilakukan melalui analisis laboratorium yang membutuhkan waktu dan biaya relatif besar, sehingga diperlukan metode alternatif yang lebih cepat dan efisien. Visual Evaluation Soil Structure (VESS) merupakan metode penilaian struktur tanah secara visual yang sederhana dan berpotensi menggambarkan kualitas tanah secara menyeluruh. Penelitian ini bertujuan untuk menganalisis perbedaan nilai VESS, sifat fisik dan kimia tanah, serta hubungan antara nilai VESS dengan sifat fisik dan kimia tanah pada empat jenis tutupan lahan, yaitu lahan tambang silika, semak belukar, agroforestri, dan hutan tanaman. Penelitian dilaksanakan pada bulan Desember 2024 hingga Januari 2025 di PT Gunung Walat Perkasa dan Hutan Pendidikan Gunung Walat, Kabupaten Sukabumi, Jawa Barat. Penelitian dirancang menggunakan rancangan acak lengkap faktor tunggal dengan jenis tutupan lahan sebagai perlakuan. Pada setiap tutupan lahan dibuat satu petak contoh dengan lima subpetak pengambilan sampel. Penilaian struktur tanah dilakukan menggunakan metode VESS, sedangkan analisis sifat fisik tanah meliputi bobot isi, porositas, dan kadar air tanah. Analisis sifat kimia tanah meliputi pH tanah dan kandungan C-organik. Data dianalisis menggunakan uji sidik ragam (ANOVA), uji lanjut Duncan’s Multiple Range Test (DMRT), serta uji korelasi Pearson. Hasil penelitian menunjukkan bahwa jenis tutupan lahan memberikan pengaruh nyata terhadap nilai VESS, sifat fisik, dan sifat kimia tanah, kecuali pada beberapa parameter antara tutupan lahan hutan tanaman dan agroforestri. Nilai VESS tertinggi diperoleh pada lahan tambang silika yang dikategorikan memiliki kualitas struktur tanah buruk, sedangkan nilai VESS terendah diperoleh pada lahan agroforestri dan hutan tanaman yang memiliki kualitas struktur tanah baik. Lahan tambang silika dicirikan oleh bobot isi tinggi, porositas rendah, kadar air rendah, pH sangat masam, dan kandungan C-organik rendah. Sebaliknya, lahan agroforestri dan hutan tanaman memiliki bobot isi rendah, porositas dan kadar air tinggi, pH relatif lebih tinggi, serta kandungan C-organik tinggi. Hasil uji korelasi menunjukkan bahwa nilai VESS memiliki hubungan yang sangat kuat dan signifikan dengan seluruh parameter sifat fisik dan kimia tanah. Penelitian ini menyimpulkan bahwa metode VESS efektif dan efisien sebagai alat evaluasi kualitas struktur tanah serta dapat digunakan sebagai metode pendugaan awal kualitas tanah pada berbagai tutupan lahan, khususnya pada lahan pascatambang dan lahan terdegradasi.

The conversion of forest areas into mining sites and other land uses is one of the main causes of soil degradation in Indonesia. Mining activities, particularly silica mining, negatively affect soil physical properties, especially soil structure, due to the loss of vegetation cover and soil organic matter. Soil structure is an important indicator of soil quality because it directly influences porosity, water infiltration, and root growth. Soil quality evaluation is commonly conducted through laboratory analyses that require considerable time and cost; therefore, alternative methods that are faster and more efficient are needed. Visual Evaluation of Soil Structure (VESS) is a simple visual assessment method that has the potential to represent overall soil quality. This study aimed to analyze differences in VESS scores, soil physical and chemical properties, and the relationships between VESS scores and soil physical and chemical properties across four land cover types silica mining land, shrubland, agroforestry, and plantation forest. The research was conducted from December 2024 to January 2025 at PT Gunung Walat Perkasa and the Gunung Walat Educational Forest, Sukabumi Regency, West Java, Indonesia. The study was designed using a single-factor completely randomized design, with land cover type as the treatment. One sampling plot was established for each land cover type, consisting of five subplots for soil sampling. Soil structure was evaluated using the VESS method, while soil physical properties analyzed included bulk density, porosity, and soil moisture content. Soil chemical properties analyzed included soil pH and organic carbon content. Data were analyzed using analysis of variance (ANOVA), Duncan’s Multiple Range Test (DMRT), and Pearson correlation analysis. The results showed that land cover type had a significant effect on VESS scores, soil physical properties, and soil chemical properties, except for several parameters between plantation forest and agroforestry land covers. The highest VESS scores, indicating poor soil structural quality, were observed in silica mining land, while the lowest VESS scores, indicating good soil structural quality, were found in agroforestry and plantation forest land. Silica mining land was characterized by high bulk density, low porosity, low soil moisture content, very acidic pH, and low organic carbon content. In contrast, agroforestry and plantation forest lands exhibited lower bulk density, higher porosity and soil moisture content, relatively higher pH, and higher organic carbon content. Correlation analysis revealed that VESS scores had very strong and significant relationships with all measured soil physical and chemical parameters. This study concludes that the VESS method is effective and efficient for evaluating soil structural quality and can be used as a preliminary assessment tool for soil quality across various land cover types, particularly in post-mining and degraded lands.