Kajian upaya meningkatkan daya penyediaan fosfat dalam gambut oligotrofik

MASGANTI, Promotor Prof.Dr.Ir. KPH. Tejoyuwono Notohadikusumo

2003 | Disertasi | S3 Ilmu Pertanian

Penelitian bahan gambut berskala laboratorium dan rumah kaca telah dilaksanakan di laboratorium dan rumah kaca Jurusan Tanah, Fakultas Pertanian UGM. Penelitian bertujuan untuk menentukan (1) macam senyawa penjerap P, sumber pupuk P, waktu memulai pelindian, lama periode pelindian, takaran amelioran, formulasi amelioran, waktu pemupukan P dan pemberian amelioran, dan jenis bahan gambut yang efektif meningkatkan daya penyimpanan P dalam bahan gambut, (2) macam senyawa penjerap P, takaran pupuk P, lama inkubasi, sumber pupuk P, takaran amelioran, formulasi amelioran, waktu pemupukan P dan pemberian amelioran, dan jenis bahan gambut yang efektif meningkatkan daya penyediaan P dalam bahan gambut, dan (3) formulasi amelioran, waktu pemupukan P dan pemberian amelioran, sumber pupuk P, jenis pot, dan jenis bahan gambut yang dapat memperbaiki pertumbuhan dan serapan hara tanaman jagung yang ditanam pada bahan gambut oligotrofik. Takaran efektif pupuk P diketahui melalui pengujian faktor perlakuan (a) takaran pupuk P, (b) lama inkubasi, dan (c) jenis bahan gambut. Perlakuan ditata dalam rancangan acak lengkap (RAL) dengan tiga ulangan. Pengamatan dilakukan terhadap pH(H2O), kadar P-tersedia, dan efisiensi penyediaan P bahan gambut. Metode pelindian bahan gambut ditentukan melalui penelitian (1) penentuan waktu memulai pelindian, dan (2) penentuan lama periode pelindian. Penelitian waktu memulai pelindian menguji faktor-faktor perlakuan (a) waktu memulai pelindian, (b) sumber pupuk P, dan (c) jenis bahan gambut, sedang dalam penelitian lama periode pelindian diuji faktor-faktor perlakuan (a) lama periode pelindian, (b) sumber pupuk P, dan (c) jenis bahan gambut. Perlakuan ditata dalam RAL dengan tiga ulangan. Pengamatan dilakukan terhadap total P dalam air lindian bahan gambut. Penelitian senyawa penjerap P menguji faktor perlakuan (a) macam kation dan anion, dan (2) sumber pupuk P. Perlakuan ditata dalam RAL dengan tiga ulangan. Pengamatan dilakukan terhadap total P, pH, dan daya hantar listrik (DHL) air lindian, dan kadar P-tersedia dalam bahan gambut. Takaran efektif CaCO3 ditentukan melalui pengujian faktor perlakuan (a) takaran CaCO3, (b) sumber pupuk P, dan (c) jenis bahan gambut. Perlakuan ditata dalam RAL dengan tiga ulangan. Pengamatan dilakukan terhadap air lindian meliputi total P, pH, dan DHL; dan bahan gambut meliputi pH(H2O), DHL, kadar Ptersedia, dan daya penyediaan P dalam bahan gambut. Penelitian penentuan formulasi efektif amelioran (CaCO3, abu gambut dan lumpur laut) menguji perlakuan formulasi amelioran, sumber pupuk P, dan jenis bahan gambut. Perlakuan ditata dalam RAL dengan tiga ulangan . Parameter air lindian yang diamati meliputi total P, pH, dan DHL, sedang parameter bahan gambut yang diukur adalah pH(H2O), DHL, kadar P-tersedia, dan daya penyediaan P dalam bahan gambut. Penelitian penentuan waktu pemupukan P dan pemberian amelioran menguji faktor perlakuan (a) waktu pemupukan P dan pemberian amelioran, (b) formulasi amelioran, (c) sumber pupuk P, dan (d) jenis bahan gambut. Perlakuan ditata dalam RAL dengan tiga ulangan. Pengamatan dilakukan terhadap total P, pH, dan DHL air lindian, sedang terhadap bahan gambut dilakukan pengamatan pH(H2O), DHL, kadar P-tersedia, dan daya penyediaan P dalam bahan gambut. Penelitian perbaikan pertumbuhan dan serapan hara tanaman jagung menguji faktor perlakuan (a) formulasi amelioran, (b) waktu pemupukan P dan pemberian amelioran, (c) sumber pupuk P, (d) jenis pot, dan (e) jenis bahan gambut. Perlakuan ditata dalam RAL. Pengamatan dilakukan terhadap pertumbuhan tanaman, serapan hara dan sifat kimia bahan gambut setelah panen. Hasil penelitian menunjukkan bahwa kadar P-tersedia dan efisiensi penyediaan P bahan gambut pada minggu pertama inkubasi nilainya paling rendah, akan tetapi meningkat pada minggu berikutnya dan mencapai puncaknya pada minggu keenam. Peningkatan takaran P meningkatkan efisiensi penyediaan P dimana pada takaran 30 mg.g-1 P efisiensi penyediaan P menjadi maksimal. Efisiensi penyediaan P tertinggi (96,33%) diperoleh pada bahan gambut saprik yang dipupuk dengan takaran 30 mg.g-1 P, sedang efisiensi penyediaan P bahan gambut saprik (80,46%) lebih tinggi dari bahan gambut fibrik (74,89%). Dalam pelindian bahan gambut, semakin cepat bahan gambut dilindi setelah pemupukan P semakin rendah daya penyimpanan P bahan gambut. Akan tetapi daya penyimpanan P dalam bahan gambut antara tujuh hari dan 14 hari setelah pemupukan P tidak berbeda. Demikian juga semakin sering bahan gambut dilindi, maka semakin rendah daya penyimpanan P bahan gambut. Akan tetapi lama pelindian melebihi lima minggu secara signifikan sudah tidak menurunkan daya penyimpanan P bahan gambut. Daya penyimpanan P dan daya penyediaan P dalam bahan gambut sangat ditentukan oleh macam kation dan anion yang digunakan sebagai senyawa penjerap P. Diantara kation yang diuji, Ca menyebabkan daya menyimpan P dan daya menyediakan P bahan gambut paling tinggi diikuti Mg, K, Na dan NH4, sedang kation yang bersenyawa dengan karbonat menyebabkan daya penyimpanan P dan daya penyediaan P dalam bahan gambut lebih tinggi dibanding menggunakan senyawa sulfat dan klorida. Oleh karena itu penggunaan CaCO3 merupakan senyawa yang paling efektif meningkatkan daya menyimpan P dan daya menyediakan P bahan gambut. Takaran CaCO3 menentukan total P dalam air lindian, daya penyimpanan P, kadar P-tersedia dan daya penyediaan P dalam bahan gambut. Takaran CaCO3 berpengaruh kuadratik terhadap perbaikan daya menyimpan P dan daya menyediakan P bahan gambut. Daya penyimpanan P dan daya penyediaan P dalam bahan gambut tertinggi diperoleh pada takaran 0,75 kemasaman tertukar. Penggunaan amelioran tunggal berupa abu gambut atau lumpur laut meningkatkan daya penyimpanan P dan daya penyediaan P dalam bahan gambut dibanding menggunakan amelioran tunggal CaCO3. Formulasi amelioran ganda berupa campuran 43,8% CaCO3; 43,8% abu gambut, dan 12,5% lumpur laut atau 37,5% CaCO3; 37,5% abu gambut, dan 25,0% lumpur laut meningkatkan daya penyimpanan P dan daya penyediaan P dalam bahan gambut sama baiknya dengan amelioran tunggal abu gambut atau lumpur laut. Semakin lama kontak antara bahan amelioran dengan bahan gambut, maka semakin tinggi daya penyimpanan P dan daya penyediaan P dalam bahan gambut. Daya penyimpanan P dan daya penyediaan P tertinggi diperoleh pada pemberian amelioran dua minggu sebelum pemupukan P, diikuti pemberian amelioran dan pupuk P secara bersamaan dan terendah pada bahan gambut yang diberi pupuk P dua minggu lebih awal dari amelioran. Pertumbuhan dan serapan hara P, Ca, Mg, K, dan Cu tanaman jagung yang media tumbuhnya diameliorasi dengan amelioran ganda 43,8% CaCO3; 43,8% abu gambut, dan 12,5% lumpur laut lebih baik dibanding jika media tumbuhnya diameliorasi dengan amelioran tunggal CaCO3. Demikian juga tanaman yang ditanam dalam pot yang diberi amelioran dua minggu lebih awal dari pemupukan P tumbuh lebih baik dan menyerap hara P, Ca, Mg, K, dan Cu lebih banyak dibandingkan dengan tanaman yang ditanam dalam pot yang diberi amelioran dan pupuk P secara bersamaan. Keadaan yang sama juga terjadi jika tanaman dibudidayakan dalam pot yang dipupuk dengan fosfat alam dibandingkan dengan tanaman yang dibudidayakan dalam pot yang dipupuk dengan SP36, tanaman jagung ditanam dalam pot tertutup dibandingkan dengan tanaman yang ditanaman dalam pot terbuka, dan tanaman yang menggunakan media tumbuh bahan gambut saprik dibanding tanaman yang ditanam pada media tumbuh bahan gambut fibrik.

Laboratory and greenhouse peat material experiments were conducted at soil laboratory, and greenhouse, Department of Soil Science, Faculty of Agriculture, Gadjah Mada University in Sekip and Kuningan, Yogyakarta. The aims of this study are : to determine (1) the types of P adsorbent compounds, source of P fertilizer, starting time of leaching, leaching period duration, rate of ameliorant, ameliorant formulation, time of P fertilization and ameliorant application, and kind of peat material which effectively increasing of P retention capacity in the oligotrophic peat material, (2) the types of P adsorbent compounds, rate of P fertilizer, incubation length, source of P fertilizer, rate of ameliorant, ameliorant formulation, time of P fertilization and ameliorant application, and kind of peat material which effectively increasing of P supplying capacity in the oligotrophic peat material, and (3) the ameliorant formulation, time of P fertilization and ameliorant application, source of P fertilizer, the kinds of pot and peat material that can improve the growth, and nutrients uptake of maize plant grown on the oligotrophic peat material. Effective rates of P fertilizer was found out through the examination of the treatments (a) rates of P fertilizer, (b) incubation length, and (c) kind of peat material. The treatments were arranged in a completely randomized design (CRD) with three replications. The parameters observed were pH(H2O), available P, and efficiency of P supply of the peat material. The treatment factors imposed of leaching methods studies on peat material were (1) starting time of leaching, and (2) leaching period duration. The study of starting time of leaching on peat material tested the treatments (a) starting time of leaching, (b) source of P fertilizer, and (c) kind of peat material, whereas study of leaching period tested the treatments (a) leaching period duration, (b) source of P fertilizer, and (c) kind of peat material. The treatments were arranged in CRD with three replications. Total of P leachate water of the peat material was determined. The study of effectively of P adsorbent compounds on peat material tested the treatments (a) cations and anions, and (b) source of P fertilizer. The treatments were arranged in CRD with three replications. Some properties of leachate water like total of P, pH, and electric conductivity (EC), and available P of the peat material were determined. The treatment factors imposed on determine of effective rates of CaCO3 study was determined through the examination of treatments (a) rate of CaCO3, (b) source of P fertilizer, and (c) kind of peat material. The treatments were arranged in CRD with three replications. The leachate water parameter observed were total of P, pH, and EC, whereas the peat material parameter observed were pH(H2O), EC, available P, and P supplying capacity of the peat material. The study of the determination of effective ameliorant formulation (CaCO3 : peat ash : marine sediment) treatments were ameliorant formulation, source of P fertilizer, and kind of peat material. The treatments were arranged in CRD with three replications. Some properties of leachate water like P content, pH, and EC, and the peat material parameter like pH(H2O), EC, available P, and P supplying capacity of the peat material were determined. Defined of time of P fertilization and ameliorant application research examined the treatments of (a) time of P fertilization and ameliorant application, (b) ameliorant formulation, (c) source of P fertilizer, and (d) kind of peat material. The treatments were arranged in CRD with three replications. Some properties of leachate water of the peat material like P content, pH, and EC, whereas peat material parameter like pH(H2O), EC, available P, and P supplying capacity of the peat material were determined. The study of growth improvement and nutrients uptake of maize tested the treatments (a) ameliorant formulation, (b) time of P fertilization and ameliorant application, (c) source of P fertilizer, (d) kind of pot, and (e) kind of peat material. The treatments were arranged in CRD with three replications. The parameter observed were plant growth, nutrients uptake by maize, and some chemical characteristics of the peat material after harvest. The results show that the value of available P, and the efficiency of P available capacity in peat material one week after incubation is lowest, however increases in subsequent weeks and reaches its peak value in six weeks after incubation. An increase of rates of P fertilizer increases the efficiency of P availability in which on 30 mg.g-1 rates of P fertilizer, efficiency of P availability becomes maximal. The highest efficiency of P availability (96.33%) was obtained on sapric peat material fertilized with 30 mg.g-1 P, while the efficiency of P available capacity of sapric peat material (80.46%) is higher than fibric peat material (74.89%). In the study of peat material leaching, the faster of peat material leaching starting time after P fertilization, the lower of P retention capacity of the peat material. But P retention capacity of the peat material between days 7 and 14 after P fertilization, however, is not different. Also, the more often peat material is leached out, P retention capacity of the peat material becomes lower. But leaching periodical more than five weeks significantly do not decrease P retention capacity of the peat material. Phosphate retention capacity, and P supplying capacity of the peat material is strongly determined by type of cation and anion used as a P adsorbent compound. Amongst cation examined, Ca resulted in highest P retention capacity, and P supplying capacity of the peat material, followed by Mg, K, Na, and NH4, whereas using of cation becoming a compound with carbonate caused P retention capacity, and P supplying capacity of the peat material higher compared to cation using sulphate and chloride compounds. The use of CaCO3, therefore, formed compound that most effectively increases P retention capacity, and P supplying capacity of the peat material. Rates of CaCO3 determines total of P in leachate water, P retention capacity, available P, and the P supplying capacity of the peat material. Rates of CaCO3 have a quadratic effect on the increasing of P retention capacity, and P supplying capacity of the peat material. The highest of P retention capacity, and P supplying capacity were obtained on 0.75 exchangeable acidity. The use of single ameliorant in the form of peat ash or marine sediment increases better P retention capacity, and P supplying capacity of the peat material compared to using single ameliorant CaCO3. Double ameliorant formulation in form of the mixture of CaCO3 43.8%; peat ash 43.8%; and marine sediment 12.5% or CaCO3 37.5%; peat ash 37.5%; and marine sediment 25.0% increase P retention capacity, and P supplying capacity of peat material as better as single ameliorant of peat ash or marine sediment. The longer of contact between ameliorant material with peat material, the P retention capacity, and P supplying capacity of the peat material are higher. The highest of P retention capacity, and P supplying capacity were obtained on ameliorant application at two weeks before P fertilization, followed by ameliorant application and P fertilization at the same time, and the lowest was on peat material given with P fertilizer two weeks earlier from ameliorant. The growth and P, Ca, Mg, K, and Cu uptake of maize grown in pot ameliorated with double ameliorant 43.8% CaCO3; 43.8% peat ash; and 12.5% marine sediment is better compared to those being ameliorated withsingle ameliorant CaCO3. Also, the plant grown in media given with ameliorant two weeks earlier from P fertilizer grows much better and uptakes more P, Ca, Mg, K, and Cu compared to plant grown in growing media given with ameliorant and P fertilizer at the same time. The same condition also happen if maize fertilized with rock phosphate compared to SP36, maize plant grown in closed pot system compared to plant grown in open pot system, and plant using growth medium of sapric peat material compared to plant grown on growth medium of fibric peat material.

Kata Kunci : Tanah Gambut, Oligotrofik, Penyediaan Fosfat