Pengaruh Perubahan Kadar Karbon Organik Tanah Terhadap Karakteristik Erapan Fosfor Andisol Humbang Hasundutan Sumatera Utara

Abstract

Kawasan Humbang Hasundutan Provinsi Sumatera Utara merupakan salah satu daerah pengembangan kawasan lumbung pangan (Food Estate). Jenis tanah pada kawasan ini termasuk Andisol yang memiliki permasalahan pada ketersediaan hara fosfor (P). Andisol merupakan tanah yang berkembang dari bahan vulkanik yang memiliki mineral-mineral klei amorf yang mengerap P sangat tinggi. Penelitian ini bertujuan untuk menganalisis dan mengevaluasi beberapa sifat kimia tanah dan karakteristik erapan P pada Andisol yang belum terganggu dan Andisol yang mendapat penambahan bahan organik sebanyak 20 t ha-1 di Humbang Hasundutan Sumatera Utara. Contoh tanah yang dianalisis adalah berasal dari tiap horizon masing-masing profil tanahnya. Contoh tanah Andisol yang belum terganggu diambil pada kedalaman 0-19 cm dan 19-40 cm, dan contoh tanah Andisol yang sudah diberi bahan organik 20 t ha-1 diambil pada kedalaman 0-17 cm, 17-27 cm, dan 27-50 cm. Hasil penelitian menunjukkan bahwa pemberian bahan organik sebesar 20 t ha-1 meningkatkan kadar karbon (C)- Organik, P-tersedia, dan pH, serta menurunkan aluminium yang dapat dipertukarkan (Al-dd) pada lapisan atas (kedalaman 0-17 cm dan 17-27 cm). Pemberian bahan organik sebesar 20 t ha-1 tidak berpengaruh secara statistik terhadap erapan P maksimum, tetapi nyata menurunkan konstanta energi erapan P (k) dan standar kebutuhan P (P0.2). Nilai k berkorelasi negatif secara nyata dengan C-Organik. Penelitian ini menunjukkan bahwa pemberian bahan organik 20 t ha-1 meningkatkan kadar C-organik tanah, P-tersedia, pH dan menurunkan nilai Al-dd. Untuk parameter erapan P, pemberian bahan organik tanah 20 t ha-1 menurunkan nilai k dan P0.2 dimana nilai k berkorelasi negatif dengan kadar C-organik tanah. Semakin tinggi kadar C organik tanah maka semakin rendah nilai k erapan P sebagai konstanta energi ikatan erapan P.

Humbang Hasundutan area of North Sumatera Province is one of the development areas for the food estate area. Soil types in this area was Andisol which have problem with phosphorus (P) availability. Andisol is a soil that develops from volcanic material that has amorphous clay minerals that sorbs very high P. This study aimed to analyze and evaluate some soil chemical properties and P sorption characteristics in Andisol that has not been disturbed and Andisol which received the addition of organic matter as much as 20 t ha-1 in Humbang Hasundutan North Sumatra. The soil samples analyzed were derived from each horizon of each soil profile. Undisturbed Andisol soil samples were collected at a depth of 0-19 cm and 19-40 cm, and Andisol soil samples that have been applied with organic matter 20 t ha-1 collected at a depth of 0-17 cm, 1 7-27 cm, and 27-50 cm.The results showed that soil samples which was applied with organic matter increased organic carbon (C) levels, available P, soil pH, and lower exchangeable aluminium (exch Al) at the depth of 0-17 cm and 17-27 cm. The application of 20 t ha-1 did not statistically affect the P sorption maximum but significantly decreased the P bonding energy constant (k) and standard P requirement (P0.2) . The k value significantly negatively correlated with organic C. This study suggested that the application of organic matter 20 t ha-1 increased soil organic C levels, available P, soil pH and lower exch Al. As for the P sorption parameters, the application of soil organic matter 20 t ha-1 decreased the k value and P0.2 where the k value was negatively correlated with the soil organic C content. The higher the organic C content of the soil, the lower the value of k value as P bonding energy constant.