Sifat-Sifat Tanah pada Lahan Potensial untuk Pengembangan Pertanian di Provinsi Jambi dan Implikasi Pengelolaannya
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Date
2014-07-01
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Balai Besar Penelitian dan Pengembangan Sumberdaya Lahan Pertanian
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Abstrak. Hingga saat ini, lahan potensial tersedia di Indonesia mencapai 30 juta hektar, sekitar 633.338 ha (2,11%) terdapat di Provinsi Jambi. Dengan semakin terbatasnya lahan tersedia untuk pengembangan pertanian, maka strategi pemanfaatan lahan menjadi sangat penting. Identifikasi karakteristik lahan merupakan strategi awal upaya pemanfaatan lahan yang lebih terarah sesuai dengan karakteristik yang dimiliki. Untuk itu empat pedon pewakil, masing-masing UG2 dan UG6 dari tuf masam, UG3 dari batupasir dan UG5 dari batu granit telah dideskripsi di lapang, dan 16 contoh tanah dari keempat pedon pewakil tersebut telah dianalisis komposisi mineral pasir dan liat, sifat fisika dan kimianya di laboratorium. Hasil penelitian menunjukkan komposisi mineral pasir didominasi oleh kuarsa. Pada pedon dari tuf masam, selain kuarsa terdapat opak. Kandungan mineral mudah lapuk sangat rendah bahkan hampir tidak ada. pH tanah masam sampai sangat masam, P dan K serta basa-basa dapat ditukar sangat rendah, sedangkan unsur bersifat toksik (Al) tinggi sampai sangat tinggi. Mineral liat didominasi oleh kaolinit, selain gibsit dan goetit dalam jumlah bervariasi. Muatan permukaan koloid rendah sampai sangat rendah. Berbeda dengan pedon dari batuan granit, pada pedon tuf masam mineral liat terdiri atas kaolinit dan illit. Muatan permukaan lebih tinggi, dan sifat fisika lebih baik. Kemampuan menyimpan dan menyediakan air lebih tinggi. Bulk density lebih rendah (1,04-1,18 g cm-3), dibandingkan pedon dari batupasir (1,11-1,33 g cm-3), dan tuf masam (1,17-1,43 g cm-3). Total ruang pori (TRP) dan pori drainase cepat (PDC) lebih tinggi. Berdasarkan sifat-sifat tanah yang dimiliki, pengelolaan lahan potensial tersedia di Provinsi Jambi ditujukan pada peningkatan muatan permukaan koloid, peningkatan pH tanah dan basa-basa serta menurunkan kejenuhan Al. Abstract. Currently, the available potential land in Indonesia is about 30 Mha, 2.11% of which (633,338 ha) is in Jambi. With the limited available potential land for agriculture development, the strategy of land use is an important issue. The identification of land characteristics is the first strategy to determine direction of land use based on their characteristics. Four representative pedons (UG2 and UG 6, derived from acidic tuffs; UG3 derived from sandstone; UG5 derived from granitic rocks) were described in the field, and sixteen soil samples from four representatives pedon were collected and analyzed for mineralogy of sand and clay fractions, soil physical and chemical properties in the laboratory. The result showed that mineralogical composition of the sand fraction was dominated by quartz. For the pedon derived from acidic tuff, its mineralogy was quartz and opaque. The content of easily weathered mineral is very low. The soil pH is acid to very acid and the contents of P, K, and exchangeable bases were low. The Al content is high to very high. The clay mineralogy is dominated by kaolinite while, gibbsite and goethite varied. The colloidal surface charge was low to very low. Different with the granitic pedons, the clay mineralogy of acidic tuffs was dominated by kaolinite and illite. Colloidal surface charge was higher and the soil physical properties were better. Bulk density of the acidic tuff is lower (1.04-1.18 g cm-3), compared to sandstone pedons(1.11-1.33 g cm-3). The total pore space and rapid drainage pores are high. Based on soil properties, the management of the arable land in Jambi Province should be directed to improve colloidal surface charge, increase soil pH and basiccations, and to decrease Al saturation.