GATRA FISIOLOGIS DAN AGRONOMIS PENGARUH PENGENDALIAN KERACUNAN BESI PADI SAWAH DI LAHAN RAWA PASANG SURUT SULFAT MASAM

Izhar Khairullah, Prof. Dr. Ir. Didik Indradewa, Dip.Agr.St.

2012 | Disertasi | S3 Agronomi

Keracunan besi merupakan masalah utama dalam pengembangan padi di lahan rawa pasang surut sulfat masam. Untuk mengatasi hal tersebut telah dilakukan tiga penelitian pada Januari 2010 sampai Agustus 2011. Penelitian 1 di rumah kaca bertujuan untuk mempelajari pengaruh konsentrasi Fe tanah terhadap Fe tanaman, pertumbuhan, dan hasil padi serta memilih varietas yang tahan, menghindar, dan tahan keracunan besi. Penelitian 2 di rumah kaca untuk mempelajari serapan Fe, karakter fisiologis dan agronomis akibat pemberian bahan organik serta menentukan aras optimum kompos jerami dan purun tikus dalam mengendalikan keracunan besi dan meningkatkan hasil padi. Penelitian 3 di sawah pasang surut sulfat masam untuk mempelajari pengaruh bahan amelioran dalam mengendalikan keracunan besi, meningkatkan proses fisiologis, pertumbuhan, dan hasil serta menentukan teknologi ameliorasi terbaik dalam mengendalikan keracunan besi dan meningkatkan hasil padi di lahan rawa pasang surut sulfat masam. Variabel pengamatan meliputi karakter fisiologis dan agronomis, pertumbuhan dan hasil, Fe tanah dan Fe tanaman, indeks bronzing daun, indeks ketahanan akar dan tajuk, dan gejala keracunan besi. Hasil penelitian menunjukkan bahwa peningkatan konsentrasi Fe tanah meningkatkan kadar Fe akar dan Fe daun Inpara-2 dan Inpara-1 (padi rawa) paling kecil, sedangkan IR64 (padi sawah beririgasi) paling besar. Penurunan pertumbuhan dan hasil gabah Inpara-1 paling kecil diikuti Inpara-2, sedangkan IR64 paling besar. Inpara-1 tergolong varietas tahan, Inpara-2 varietas menghindar, dan IR64 varietas rentan keracunan besi. Inpara-2 mampu menekan konsentrasi Fe di daerah perakaran, menyerap Fe dalam jumlah sedikit, proses fisiologis dan pertumbuhan baik, dan hasil per rumpun tinggi (19,56 g). Inpara-1 cukup mampu menekan konsentrasi Fe di daerah perakaran, menyerap Fe dalam jumlah banyak, proses fisiologis dan pertumbuhan baik, dan hasil tinggi (21,59 g). IR64 tidak mampu menekan konsentrasi Fe di daerah perakaran, menyerap Fe dalam jumlah banyak, proses fisiologis dan pertumbuhan kurang baik, dan hasil rendah (13,57 g). Aras optimum kompos purun tikus yang ditambahkan pada jerami 5 t ha-1 untuk mengendalikan keracunan besi dan meningkatkan hasil Inpara-1, Inpara-2, dan IR64 adalah 5,14 t ha-1, 5,29 t ha-1, 5,31 t ha-1. Bahan amelioran kompos aerob dan anaerob jerami dan purun tikus serta dolomit mampu menurunkan gejala keracunan besi, indeks bronzing daun, konsentrasi Fe tanah, kadar Fe akar, Fe batang, dan Fe daun, serta meningkatkan proses fisiologis, pertumbuhan, komponen hasil, dan hasil Inpara-1, Inpara-2, dan IR64. Hasil gabah Inpara-1 (4,45 t ha-1) sebanding dengan Inpara-2 dan lebih tinggi 42,6% dibanding IR64 (3,12 t ha-1), tetapi IR64 lebih tanggap terhadap pemberian bahan amelioran tersebut dibanding Inpara-1 dan Inpara-2. Kompos aerob jerami 5 t ha-1 dan purun tikus 5 t ha-1 merupakan teknologi ameliorasi terbaik dalam mengendalikan keracunan besi, meningkatkan proses fisiologis, pertumbuhan, dan hasil. Hasil gabah pada aras kombinasi tersebut sebesar 4,83 t ha-1 dan meningkat 73,7%, 34,5%, dan 16,4 % dibanding tanpa pemberian amelioran, pemberian kompos jerami dan purun tikus secara anaerob, dan pemberian dolomit 2 t ha-1.

Iron toxicity is a major problem in increasing rice production at acid sulfate soils of tidal swamplands. To solve the problem has been conducted three experiments in January 2010 up to August 2011. The first experiment in a greenhouse aimed to study the effects of Fe concentration to Fe of plants, growth and yield of rice, and to select resistant, avoidant, and susceptible varieties to iron toxicity. The second experiment in the greenhouse was to study Fe uptake, physiological and agronomic characters due to application of organic matter, and to determine optimum rate of straw and purun tikus (Eleocharis dulcis) compost in controlling iron toxicity and increasing rice yield. The third experiment at rice field was to study the effect of ameliorant in controlling iron toxicity, increasing physiological processes, growth and yield, and to determine the best amelioration technology in controlling iron toxicity and increasing rice yields at acid sulfate soils of tidal swamplands. Observations were done on physiological and agronomic characters, growth and yield, soil Fe and Fe of plants, leaf bronzing index, root and shoot resistance index, and iron toxicity symptoms. The results showed that increasing concentrations of soil Fe increased the smallest of Fe content in roots and leaves of Inpara-2 and Inpara-1 (swamp rice), those of IR64 (irrigated rice) was the most value. Decreasing in growth and yield of Inpara-1 was the smallest followed by Inpara-2, whereas IR64 was the greatest. Inpara-1, Inpara-2, and IR64 were tolerant, avoidant and susceptible varieties to iron toxicity, respectively. Inpara-2 could have reduced Fe concentration in root zone, absorbed Fe in relatively small quantities, good physiological processes and plant growth, and produced high yield per hill (19.56 g). Inpara-1 was quite capable to suppress Fe concentration in the root zone, in absorbed Fe relatively large amounts, very good physiological processes and plant growth, and produced high yield per hill (21.59 g). IR64 was not able to suppress Fe concentration in the root zone, absorbed large amounts of Fe, poor physiological processes and plant growth, and produced low grain yield per hill (13.57 g). Optimum rate of purun tikus compost had been added to straw 5 t ha-1 in controlling iron toxicity and increasing grain yield for Inpara-1, Inpara-2, and IR64 were 5.14 t ha-1, 5.29 t ha-1, 5.31 t ha-1, respectively. Organic matter in the form of aerobic and anaerobic composting of straw and purun tikus, and dolomite could have reduced iron toxicity symptoms, leaf bronzing index, Fe concentrations in soil, Fe content in roots, stems and leafves and increased physiological processes, growth, yield components, and grain yield of Inpara-1, Inpara-2, and IR64. Grain yield of Inpara-1 (4.45 t ha-1) was not significantly different with Inpara-2, but it was higher about 42.6% than IR64 (3.12 t ha-1). IR64 was greater responsive to application of these ameliorant than Inpara-1 and Inpara-2. Aerobic compost of straw 5 t ha-1 which was added to purun tikus 5 t ha-1 was the best amelioration technology in controlling iron toxicity, increasing physiological processes, growth and yield of rice. The grain yield at the rate was 4.83 t ha-1 and increased 73.7%, 34.5%, and 16.4%, respectively compared to no ameliorant, application of straw and purun tikus anaerobic compost and application of dolomite 2 t ha-1.

Kata Kunci : Padi, fisiologis, agronomis, keracunan besi, lahan rawa, pasang surut, sulfat masam.