Inaktivasi pirit dan jarosit terlapuk melalui pelindian dan penggunaan biofilter di tanah sulfat masam

Abstract

Salah satu areal alternatif yang memiliki prospek dan potensi besar untuk dijadikan areal produksi padi adalah lahan rawa pasang surut. Pengembangan sistem usahatani di lahan rawa, khususnya lahan pasang surut tanah sulfat masam perlu kehati-hatian mengingat sifat tanahnya yang rapuh. Kesalahan dalam reklamasi dan pengelolaan lahan dapat berakibat pada rusaknya lahan dan pencemaran lingkungan, sedang untuk memperbaikinya diperlukan biaya tinggi. Oleh karena itu, pengembangan sistem usahatani di lahan ini hendaknya memenuhi tiga syarat, yaitu: (1) secara teknis bisa dilaksanakan dan diterima masyarakat, (2) secara ekonomi layak dan menguntungkan, dan (3) dari aspek ekologis tidak merusak lingkungan baik setempat maupun lingkungan di tempat lain, sehingga sumberdaya alam tetap terpelihara baik dan pengembangan pertanian dapat berkelanjutan.

The experiments were conducted in the Laboratory of Soil Chemistry and Fertility, Faculty of Agriculture, IPB from March to July 2009, and greenhouse of Indonesian Research Institute for Swampland Agriculture (IRISA), Banjarbaru, South Kalimantan, from October until May 2010. The study was aimed to: (1) investigate the effectiveness of leaching water sources for reducing Fe2+, total-Fe, SO4 2-, and Al3+ concentration in leachate and soil at Eh values of -100 to 400 mV, (2) study the effect of leaching water source (fresh water, brackish water, and peat water) on concentrations of Fe2+, total-Fe, and SO4 2- in leached and soil of acid sulphate soil, and (3) study the effect of leaching water source, root volume (biofilter plant area/pot) and kind of biofilter plants on reducing concentration of Fe2+, total-Fe, and SO4 2- in leached and soil. The results showed that brackish water increased concentration of Fe2+, total-Fe, and Al3+ in leachate, while peat water increased concentration of SO4 2- in leachate. The higher concentration of Fe2+ was found at Eh condition of 100 mV in leachate, while the higher concentration of total-Fe, SO4 2-, and Al3+ was found at Eh condition of 400 mV. Chemical analysis of soil after leaching for eight weeks showed that brackish water decreased concentration of Fe2+ and Al 3+ in soil, while peat water decreased concentration of total-Fe and SO4 2- in soil. Eh condition at 200-300 mV reduced lower concentration of Fe2+ in soil, while at 400 mV reduced concentration of total-Fe, SO4 2-, and Al3+ in soil. During the leaching process, the concentration of Fe2+, total-Fe, and SO4 2- in leachate were decreased. The decrease of that concentrations in the first period was greater than that in the second period. Leaching by brackish water was more effective than by fresh water or peat water in lowering the concentration of Fe2+ and total-Fe in leached. Whereas, leaching by using peat water was more effective to decrease the concentration of SO4 2- compared other treatments. Leaching water sources had no significant effect in improving growth and yield components of Margasari rice variety, but significantly increased dry weight and yield of rice. Dry weight and yield of rice were higher on soil leached by peat water and fresh water than those on soil leached by brackish water. Eliocharis dulcis showed greater ability than Eleocharis retroflaxa to decrease the concentration Fe2+, total-Fe, dan SO4 2- in leachate. Increasing root volume (biofilter plant area/pot) of biofilter plants increased the plant ability in reducing the concentration of those ions in leachate. The leaching water sources had no consistent effect on the difference of Fe2+, total-Fe, and SO4 2- concentration in leachate.