PERANAN BAHAN ORGANIK DAN UREA DALAM MENINGKATKAN KETERSEDIAAN HARA N DAN PERTUMBUHAN PADI SAWAH DI LAHAN SULFAT MASAM POTENSIAL KABUPATEN BARITO KUALA

AFIAH HAYATI,SP.,MP., Dr. Ir. Abdul Syukur, SU.,

2013 | Disertasi | S3 Ilmu Tanah

Lahan sulfat masam potensial yang mempunyai potensi untuk dikembangkan menjadi lahan pertanian mempunyai banyak kendala salah satunya memiliki kandungan hara N yang rendah. Pertumbuhan dan kualitas hasil tanaman sangat dipengaruhi oleh ketersediaan unsur hara dalam tanah. Pemanfaatan bahan organik yang ada disekitar lahan pasang surut (insitu) diharapkan dapat menambah unsur hara terutama N sehingga efisiensi pemupukan N menjadi meningkat. Penggunaan pupuk N sintetis dapat dikurangi, dengan demikian biaya pemupukan juga jadi berkurang selain itu kerusakan lingkungan dapat ditekan. Penelitian bertujuan mengetahui pengaruh pengelolaan tanah di lahan pasang surut untuk tanaman padi dengan pemberian bahan organik yang di padukan dengan pemupukan nitrogen terhadap ketersediaan hara nitrogen, serapan nitrogen oleh padi serta produksinya di lahan pasang surut. Tahapan penelitian untuk mencapai tujuan tersebut adalah sebagai berikut : 1) Karakterisasi lahan sulfat masam potensial dan bahan organik insitu yang digunakan, 2) Pengaruh pemberian bahan organik insitu dan pemupukan urea terhadap ketersedian nitrogen tanah, pertumbuhan dan serapan nitrogen oleh tanaman padi di lahan sulfat masam potensial dan 3) Efisiensi pemupukan nitrogen dalam pengelolaan lahan sulfat masam potensial dengan penggunaan kombinasi antara bahan organik insitu dan urea pada tanaman padi. Percobaan dilaksanakan di laboratorium dan rumah kaca Jurusan Tanah Fakultas Pertanian Universitas Lambung Mangkurat. Percobaan lapangan dilakukan di Kebun Percobaan Balittra Desa Tanjung Harapan Kecamatan Alalak Kabupaten Barito Kuala. Semua penelitian berlangsung dari bulan April 2010 sampai Desember 2011. Hasil penelitian menunjukkan bahwa: Pemberian urea dengan beberapa takaran, jenis bahan organik dan waktu inkubasi bahan organik di lahan sulfat masam potensial dapat meningkatkan kandungan NH4 + dan NO3 - tanah. Pemberian urea dengan beberapa takaran, jenis bahan organik dan waktu inkubasi bahan organik di lahan sulfat masam potensial dapat meningkatkan jumlah anakan dan serapan nitrogen tanaman padi di lahan sulfat masam potensial. Pemberian urea yang dikombinasikan dengan jenis bahan organik dapat meningkatkan jumlah N termineralisasi di lahan sulfat masam potensial. Jumlah N termineralisasi pada 6 MST paling banyak terdapat pada kombinasi pemberian 75 kg urea/ha dengan jerami padi-purun tikus yaitu 1028,94 ppm dan jumlah N termineralisasi paling sedikit terdapat pada kombinasi perlakuan tanpa diberi urea dengan jerami padi-kayu apu yaitu sebesar 720,61 ppm. Pemberian 75 kg urea/ha ditambah dengan jerami padi-kayuapu di lahan sulfat masam potensial dapat meningkatkan efisiensi serapan N hingga 80,10 %, dan Pemberian 75 kg/ha yang ditambah kayuapu-purun tikus dapat meningkatkan hasil padi di lahan sulfat masam potensial menjadi 5,35 ton/ha.

Development of potential acid sulphate soils for agricultural areas encounters several problems; one of them is that these soils contain low nitrogen. The growth and quality of crops was essentially influenced by the availability of nutrients in the soils. Utilization of organic matter found on tidal-swamp lands (insitu) is expected to improve nutrient availability especially nitrogen, and thereby increasing the efficiency of nitrogen fertilization. The reduction in the amount of N fertilizer applied to soils will result in decreases in the cost paid by farmers and reduce environmental degradation. This research aims to study the effect of organic matter and urea application on the availability of nitrogen, nitrogen uptake by paddy and paddy yield in potential acid sulphate soils. The experiment consisted of several stages : (1) Characterization of potential acid sulphate soils and insitu organic matter that is used, (2) An experiment to study the effect of insitu organic matter and urea application on nitrogen availability, paddy growth and the efficiency of nitrogen uptake by paddy in potential acid sulphate soils, and (3) Determination of the efficiency of nitrogen fertilization in acid sulphate soils treated with insitu organic matter application in conjunction with urea applications. The research was conducted in the laboratory and greenhouse of Soil Science Department, Faculty of Agriculture, Lambung Mangkurat University. Field experiments were carried out on the Field Experiment Site of Research Centre for Swampland Agriculture in the Village of TanjungHarapan, Alalak Sub-district, Barito Kuala Regency. All these experiment were carried out in the period of April 2010 – December 2011. Results of the experiments have been shown that urea application at different amounts, application of different types of organic matter and different incubation periods to potential acid sulphate soils improved the concentration of ammonium and nitrate in soils. These treatments also increased the number of paddy tiller and nitrogen uptake by paddy. Urea application in combination with organic matter application enhanced the amount of mineralized N in the potential acid sulphate soils. The highest amount of mineralised N (1028,94 ppm) at 6 weeks after planting was observed at the treatment of 75 kg urea ha-1 and the organic matter of paddy straw-purun tikus while the lowest amount of mineralized N (720,61 ppm) was found when paddy straw-puruntikus was applied without urea addition. Application of 75 kg urea to soils in combination with application of paddy straw-kayuapu improved the efficiency of nitrogen uptake up to 80,10%. In addition, application of 75 kg urea ha-1 in conjunction with application of kayuapu-purun tikus enlarged the paddy production in potential acid sulphate soils from 3,85 ton ha-1 to 5,35 ton/ha.

Kata Kunci : Lahan sulfat masam potensial, Kayuapu, Purun tikus, Jerami padi, Efisiensi serapan N