EVALUASI KESESUAIAN LAHAN JATI PLUS PERHUTANI STUDI KASUS DI KPH NGAWI DAN KPH PEMALANG

ERLANGGA ABDILLAH, Prof. Dr. Ir. Mohammad Na'iem, M.Agr.Sc; Dr.Ir. Haryono Supriyo, M.Agr.Sc

2015 | Tesis | S2 Ilmu Kehutanan

Tanah merupakan salah satu sumber daya lahan yang berfungsi sebagai media pertumbuhan tanaman, habitat bagi organisme tanah, media rekayasa, sistem daur ulang bagi unsur hara dan sisa-sisa organik serta sistem pasokan air. Setiap tanah mempunyai kualitas dan karakteristik masing-masing yang akan menentukan kemampuanya sebagai sumber daya lahan yang setiap saat bisa berubah. Evaluasi kesesuaian lahan dan kesuburan tanah yang dilakukan dengan survei tanah ditujukan untuk menilai karakteristik lahan dan menentukan faktor kendala utama kesesuaian lahan dan kesuburan tanah serta alternatif pengelolaannya untuk meningkatkan produktivitas lahan. Penelitian ini bertujuan untuk menentukan karakteristik lahan, klasifikasi kesesuaian lahan dan kesuburan tanah, menentukan faktor pembatas kesesuaian lahan dan kesuburan tanah, serta memberikan arahan strategis pengembangan tanaman JPP dilokasi penelitian KPH Ngawi dan KPH Pemalang. Total lahan yang dievaluasi, 12 satuan peta tanah (SPT) masing-masing didasarkan pada satu profil pewakil pada tingkat semidetail. Penilaian klasifikasi dan penentuan kendala kesesuaian lahan menggunakan Limitasi Sederhana LPT Bogor (1983) dan pada kesuburan tanah mengunakan Klasifikasi Kapabilitas Kesuburan Tanah (Sanchez et al., 2003). Pengamatan lapangan dan pengambilan data kesuburan tanah dilakukan berdasarkan panduan Balai Penelitian Tanah (2004) dan National Soil Survey Center (2002). Analisis tanah di laboratorium berupa tekstur tanah dengan metode pipet, pH tanah, C-organik metode Walkley dan Black, N dengan metode Kjeldahl, P dengan metode Olsen, K Ekstraksi NH4Oac pH 7, Basa tertukar Ca, Mg, Na, K, Kejenuhan Basa dan KTK ekstrak NH4Oac pH 7, kemasaman tertukar Al-dd dan H-dd ekstrak KCl 1M. Metode analisis laboratorium didasarkan pada buku Petunjuk Teknis Analisis Kimia Tanah, Tanaman, Air dan Pupuk (Balai Penelitian Tanah, 2009). Penentuan sub-ordo tanah diklasifikasikan berdasarkan kunci taksonomi tanah (Soil Survey Staff, 1999). Hasil evaluasi lahan terhadap beberapa sifat fisik dan kimia tanah serta faktor fisik lingkungan menunjukkan adanya 4 sub-ordo tanah di lokasi penelitian, yakni Ustert (SPT Walikukun 67k, Watutinatah 108d, Sidowayah 65a, Sidulaju 63a, dan Gladang 68d), Orthent (SPT Begal 25g, dan Ngasem 24b), Ustept (SPT Dukuhrandu 12c) dan Ustalf (SPT Kijene 103f, Kramat 35d, Klapanunggal 7b, dan Klapanunggal 46a) yang terbentuk dibawah curah hujan 2.072-2.231 mm/tahun dengan regim suhu tanah isohipertermik dan regim kelembaban tanah ustik. Kesesuian lahan aktual pada SPT di lokasi penelitian mempunyai faktor pembatas sesuai marginal (S3) hingga tidak sesuai permanen (N2). Kesesuaian lahan potensial yang bisa dikembangkan untuk pengelolaan JPP di lokasi penelitian adalah SPT Gladang 68d dengan kelas kesesuaian lahan potensial S2 (cukup sesuai), selanjutnya SPT KIjene 103f, Klapanunggal 46a, Klapanunggal 7b, Dukuhrandu 12c dan SPT Sidowayah 65a dengan kelas kesesuaian lahan potensaial S3 (sesuai marginal). Hasil klasifikasi kesuburan tanah di lokasi penelitian menunjukkan bahwa tanah didominasi oleh tekstur lempungan baik di lapisan olah maupun lapisan bawah dan mempunyai kelerengan datar (<3%) hingga agak curam (15-30%). Tanah di lokasi penelitian mempunyai laju infiltrasi rendah, kemampuan menahan air tinggi, tanah sulit diolah, dan pada lahan yang miring mempunyai potensi run-off tinggi. Penilaian status kesuburan tanah dengan menggunakan PPT (1983) menunjukkan KPK tinggi (>24-40 cmol(+)kg-1) hingga sangat tinggi (>40 cmol(+)kg-1), kejenuhan basa tinggi (>60-80%) hingga sangat tinggi (>80%), kandungan C-organik sangat rendah (<1%) hingga rendah (>1-2%), P2O5 sangat rendah (<5 ppm) hingga rendah (>5-10 ppm) dan K2O sangat rendah (<10 ppm) hingga rendah (>10-20 ppm). Arahan strategsi untuk pengelolaan tanah di pertanaman JPP di kedua lokasi penelitian adalah dengan penerapan bahan organik, pengelolaan tanah secara intensif dan penerapan konservasi tanah.

Soil is one of the land resources that serves as a medium for plant growth, habitat for soil organisms, utilization medium, recycling systems for nutrient and organic debris as well as water supply mechanism. Each soil has the qualities and characteristics that will determine their ability as a land resource that could change at any moment. Soil suitability and fertility evaluation are conducted with the soil survey which is aimed to assess the characteristics of the soil and determine the major constraint factors of land suitability and soil fertility as well as the alternatives of cultivation to improve its productivity. This research aims to determine the characteristics of the land, suitability classification and soil fertility, to figure the factors out that are limiting the land suitability and soil fertility, as well as providing strategic directives for Teak plus trees (JPP) cultivation on the research sites of Forest Development Unit (FDU) Ngawi and Pemalang. The total land to be evaluated, 12 soil map units (SMU) are each evaluated based on a representative profile at semi-detail level. Assessment classification and constraint factors determination of land suitability used simple limitation of LPT Bogor (1983) and on soil fertility evaluation, researcher is using Soil Fertility Capability Classification (Sanchez et al., 2003). Field observations and soil fertility data collection are conducted based on guide of Soil Research Institute (2004) and the National Soil Survey Center (2002). Soil analysis in the laboratory in the form of soil texture is done by using pipette method, soil pH, C-organic method of Walkley and Black, N by the Kjeldahl method, P by Olsen method, K Extraction NH4Oac pH 7, Alkali swapped Ca, Mg, Na, K, Alkali Saturation and CEC extracts NH4Oac pH 7, acidity swapped Al-dd and H-dd extract 1M KCl. Methods of laboratory analysis are based on books of Technical Guidelines for Chemical Analysis of Soil, Plant, Water and Fertilizer (Soil Research Institute, 2009). The determination of the soil sub-order classified based on key of soil taxonomic (Soil Survey Staff, 1999). Results of the land evaluation to some soil physical and chemical chaarcteristics and environment physical factors shows 4 soil sub-orders in the research sites, the Ustert (SMU Walikukun 67k, Watutinatah 108d, Sidowayah 65a, Sidulaju 63A, and Gladang 68d), Orthent (SMU Begal 25g and 24b Ngasem), Ustept (SMU Dukuhrandu 12c) and Ustalf (SMU Kijene 103F, Kramat 35d, Klapanunggal 7b, and Klapanunggal 46a) which formed under the rainfall rate of 2072-2231 mm/year with isohyperthermic soil temperature regime and ustic soil moisture regime. Actual Land Suitability on the SMU (Soil Map Units) at the researh sites has constraint factor correspond marginally (S3) to permanently unsuitable (N2). The suitability of potential land that can be developed for teak plus trees cultivation at the research sites is SMU Gladang 68d with S2 land suitability potential classes (quite appropriate), hereinafter SMU KIjene 103F, Klapanunggal 46a, Klapanunggal 7b, Dukuhrandu 12c and SMU Sidowayah 65a with S3 land suitability potential classes (according to marginal). Soil fertility classification results of the research sites show that the soil is dominated by silty texture in both topsoil and lower layers and has flat slope (<3%) to moderately steep rate (15-30%). Soils in the research sites has low infiltration rate, high rate of ability to restrain water, difficult to cultivate, and has high potential for run-off on the sloping land. Assessment of soil fertility status by using PPT (1983) shows a high (> 24-40 cmol (+) kg-1) to very high CEC level (> 40 cmol (+) kg-1), Alkali saturation is leveled high (> 60-80% ) to very high (> 80%), C-organic content is very low (<1%) to low (> 1-2%), P2O5 is very low (<5 ppm) to low level (> 5-10 ppm) and very low (<10 ppm) to low K2O (> 10-20 ppm). Strategic directives for the soil supervision in the Teak plus trees cultivation at both sites is the application of organic substances, intensive soil supervision and implementation of soil conservation.

Kata Kunci : Jati Plus Perhutani, evaluasi kesesuaian lahan, evaluasi kesuburan tanah, status kesuburan tanah, bahan organik.