Assessing Soil Acidity

By  Richard Fisher, E. M Hutton, Avilio A. Franco, Anthony Juo, Donald Kass, and Dale Evans

What Is an acid soil? 

Soil scientists use ranges of pH values to describe the acidity of soils. Soils in the pH range of 6.8 to 7.2 are considered neutral. Any soil with a pH of less than 6.8 is considered acidic, and any soil with a pH of more than 7.2 is considered alkaline. Soils with a pH of less than 35 or more than 10 rarely support plant growth Acid soils are described as "mildly acidic," "moderately acidic," and "strongly acidic" as pH values decrease. Mildly and moderately acid soils may not be detrimental to the growth of most plants.

Regions in the tropics in which soils are likely to be acid or low in bases such as calcium and magnesium.

Source: Caudle (1991).

The term "acid soil" is usually reserved for soils in which many types of plants have difficulty growing. This manual is concerned with these strongly acidic soils. They are characterized by a pH of less than 5.5 and one or more chemical problems that limit plant growth. Such problems may include (1) toxic levels of available aluminum, (2) toxic levels of available manganese, and (3) infertility due to insufficient levels of other elements important for plant growth, particularly calcium and phosphorus. Strongly acidic soil conditions limit the kinds of plants that can grow, the productivity of those plants, and the efficiency of fertilizers applied to increase plant productivity.

What is pH? 

The acidity of a soil is assessed in terms of the acidity or alkalinity of the soil solution - the moisture in the soil - as measured in units of pH. The soil solution contains chemical elements in dissolved ionic form. Many of these function as essential plant nutrients, taken up from the soil solution by the roots of plants.

The acidity of a soil results from the relative presence or absence of acidic ions, such as hydrogen (H+), in the soil solution. Soil acidity increases with the increased presence of these ions and decreases with the increased presence of basic ions such as calcium (Ca++) and magnesium (Mg++).

The acidity of a soil solution is expressed on the pH scale as the negative logarithm of the hydrogen ion (H+) concentration. Because the pH scale is mathematically logarithmic, a pH change of one unit represents a ten-fold change in the acidity or alkalinity of the solution being measured. Thus a soil with pH 5 is ten times more acidic than a soil with pH 6. A soil with pH 4 is ten times more acidic than one with pH 5 and 100 times more acidic than a soil with pH 6.

How do soils become acidic?

Soils become acidic through the normal leaching action of rainfall over long periods of time. As rainwater moves down through the soil, it absorbs carbon dioxide from the soil atmosphere and forms weak carbonic acid. It also acquires weak organic acids as it encounters soil organic matter. This acidic solution attracts basic ions, such as calcium (Ca++), magnesium (Mg++), potassium (K+), and sodium (Na+), detaches them from the soil exchange complex, and leaches them from the rooting zone. As these basic ions are leached, they are replaced by acidic ions of hydrogen (H+) and aluminum (Al+++). Over long geologic periods, soils in warm climates with high rainfall become severely depleted of basic ions and strongly acidified. Many of these acid soils also have levels of available aluminum or other ions that limit plant growth.

At a pH of 5.5, a soil generally does not inhibit the growth of crops or trees because it contains little available (exchangeable) aluminum. As pH decreases to 5.1 or lower, the amount of available aluminum increases and begins to interfere with the uptake of calcium and phosphorus, adversely affecting plant growth.

The soil taxonomy classification of the United States Department of Agriculture labels most tropical soils with a pH of less than 5.5 as Oxisols or Ultisols. The Food and Agriculture Organization (FAO) calls these Ferralsols and Acrisols. The Oxisols, with aluminum saturations of 79 to 89 percent, are more harmful to leguminous trees and crops than are the Ultisols, with aluminum saturations of 49 to 64 percent. There are also some strongly acidic Entisols (called Arenosols by FAO), Inceptisols (classified as Cambisols, Plinthosols, and Gleysols by FAO), and Andisols (Andosols).

How does soil acidity affect the availability of nutrients? 

Plant roots obtain nutrients from the soil solution, and that solution's chemical composition is affected by its pH. Nutrient availability is greatest in soils with a pH between 55 and 65. When the soil solution falls outside this range, plants often show signs of nutrient deficiencies.

In alkaline soils at a pH above 7.0, phosphorus, iron, zinc, boron, and copper become less available to plants. In acid soils at a pH below 5.0, phosphorus and molybdenum become less available and soil nitrification slows down. Some nutrients - such as calcium, magnesium, and potassium - may be lost, and high levels of available iron or aluminum may lead to the formation of insoluble phosphate compounds, dramatically reducing the level of phosphate available to plants.

The two most important indicators of acid soil conditions that are severe enough to limit plant growth are low pH and high levels of available aluminum. Indeed, aluminum toxicity and soil infertility are often associated. In soils with a pH of 5.1 or lower, aluminum levels often constitute more than 50 percent of the cation exchange complex. Manganese toxicity can also occur in a soil with a pH of less than about 5.5, but manganese toxicity is not as common as aluminum toxicity.

How do you measure soil acidity? 

The best way to determine whether a soil is strongly acid is to consult a soil scientist. Failing this, a general soil survey map may be useful. Such a map may include specific information on soil pH and the degree of aluminum saturation. Otherwise, as a general "rule of thumb," soils classified as Oxisols or Ultisols are likely to be strongly acidic in tropical climates.

If you cannot consult a soil scientist or a reliable soil map, you may need to collect soil samples and have them analyzed. Take separate samples at depths of 0 to 20 cm, 20 to 50 cm, and 50 to 100 cm below the soil surface. The subsoil is normally the best indicator of acidity because the surface soil (at 0 to 20 cm) is often affected by recent management. Altogether, you will need about 10 separate samples at each depth for each distinct soil area in your site. Mix together the 10 samples for a specific area and depth and take a small subsample of the mixture.

You may be able to send your samples to a soil laboratory for analysis of pH and available aluminum levels. Alternatively, you can analyze the pH levels of your soil samples using a portable pH meter, colorimetric test kit, or test strips. Mix each subsample with an equal volume of pure water (rain water is preferable to tap water if deionized water is not available). After mixing, allow the soil particles to settle for a few minutes and then measure the pH of the solution above the soil particles.

Equipment for measuring pH is available by mail order or from retail outlets that specialize in agricultural or scientific supplies. Colorimetric pH test kits are fairly inexpensive but are less precise than electrochemical instruments. There is no simple field test for available aluminum, but if the pH is below 5.0, then available aluminum is likely to be high.

An alternative to analyzing the soil is to observe plant growth as an indicator of soil conditions. What kinds of plants are growing in the soil? The presence of plants that tolerate acid soils such as imperata grass, bracken ferns, and Stylosanthes species-is an indication of acid soil conditions. If crops are growing well, the soil is probably not highly acid. If, on the other hand, there are problems with beans, cotton, or maize crops, then soil acidity may be the culprit. Phaseolus beans (not cowpea types) are particularly sensitive to aluminum toxicity if they are growing well, aluminum may not be a problem.

How do you Interpret the results of a soil analysis? 

An analysis of soil nutrients is often expressed in terms of milliequivalents per 100 g of soil (meq/100 g). An equivalent expression is cmol charge/kg. Values given as milliequivalents per 100 g of soil may be converted to parts per million (ppm) as follows:
1 meq/100 g of K+ (potassium) = 391 ppm
1 meq/100 g of Al+++ (aluminum) = 90 ppm
1 meq/100 g of Mg++ (magnesium) = 122 ppm
1 meq/100 g of Ca++ (calcium) = 200 ppm
1 meq/100 g of Na+ (sodium) = 230 ppm.

 Phosphorus content is usually expressed as parts per million. Most field and vegetable crops will respond to additions of phosphorus and potassium fertilizers when soil phosphorus (sodium bicarbonate [NaHCO3]-extractable) is in the range of 8 to 15 ppm and exchangeable soil potassium is in the range of 60 to 100 ppm. Soil phosphorus above 25 ppm is considered adequate for maize. One important measure that can be obtained from soil test results is the percent of aluminum saturation. This value compares the amount of exchangeable aluminum in the soil with the sum of aluminum plus exchangeable bases, as in the formula:

 Al / (Ca + Mg + K + Na + Al) x 100 = % Al saturation

In most cases, not all of these elements need to be analyzed. As a minimum for calculating percent aluminum saturation, the content of aluminum, calcium, and magnesium should be determined.

Plant species and varieties differ in the amount of aluminum saturation they can tolerate: above that limit, plant growth is reduced. Generally, cowpea-type beans, males, rice, and cassava have high tolerance to aluminum (70-100% saturation), whereas phaseolus-type beans, sorghum, soybeans, and wheat have low to moderate tolerance (0-70%), and cotton and maize have low tolerance (0-40%). Some nitrogen fixing tree species are known to tolerate high levels of aluminum in the soil, but the critical level for many species is not known. Controlled experiments are required to provide this information for a number of tree species and, in some cases, for particular varieties and provenances.

If plants show stunting, crinkled leaves, or leaves with small brown spots, manganese toxicity may be suspected. To determine manganese toxicity, apply a 5 percent hydrogen peroxide solution to a soil sample: if the solution fizzes (makes bubbles), manganese toxicity may be a problem.

Source : http://www.fastonline.org

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Peningkatan Produksi Tanaman Pangan Dengan Zeolit

Peningkatan Produksi Tanaman Pangan Dengan Pembenah Tanah Zeolit

Meskipun pengembangan pembenah tanah zeolit sudah lama dipromosikan oleh swasta di bidang pertanian, tetapi penggunaannya belum banyak diketahui petani. Sehubungan dengan pengetahuan petani terhadap zeolit masih rendah, maka hal ini mengakibatkan pemasaran zeolit masih terhambat.

Di samping itu, masalah lambatnya pengembangan pembenah tanah zeolit di bidang pertanian disebabkan kurangnya koordinasi antara pemerintah dan swasta dalam melakukan upaya tindak lanjut untuk mencapai sasaran yang dituju. Pada situasi dan kondisi seperti itu akhirnya zeolit sebagai “mineral masa depan multi guna” banyak diekspor. Penyebab masalah kesulitan pengembangan zeolit masa lalu tidak hanya harus diungkap, tetapi juga harus dicari solusi pemecahan masalahnya dengan mencari informasi langsung dari petani.

Pengembangan pembenah tanah zeolit di bidang pertanian selama ini banyak dilakukan swasta. Apa yang dilakukan swasta tersebut sangat baik jika ada informasi yang lengkap tentang dimana dan berapa luas (calon lokasi) lahan pertanian yang terdegradasi. Sebenarnya yang mempunyai informasi calon lokasi lahan pertanian yang terdegradasi adalah pemerintah. Keterlambatan pemerintah untuk merumuskan kebijakan tentang pengembangan pembenah tanah dijadikan alasan swasta untuk mempromosikan produknya langsung ke petani. Sebagai contoh, jenis pembenah tanah zeolit yang dikenal dan digunakan petani antara lain adalah ........ di Lampung, ...... di Jawa Barat, dan ....... di Jawa Timur. Sumber informasi pembenah tanah zeolit yang diperoleh petani terutama berasal dari agen distributor zeolit/pedagang, sedangkan informasi yang diperoleh dari penyuluh pertanian sangat kecil. Fakta di lapang membuktikan bahwa ada agen distributor zeolit yang memberi subsidi zeolit kepada petani untuk satu kali musim tanam.

Langkah swasta tersebut perlu disambut dengan baik, namun harus dipastikan terlebih dahulu mutunya. Zeolit yang bermutu baik dipastikan sudah lolos uji mutu (LUM) dan lolos uji efektivitas (LUE) dan mendapatkan Nomor Registrasi dari Pusat Perijinan dan Investasi (PPI) di Departemen Pertanian. Jika zeolit sudah lolos LUM dan LUE maka pada saat dilakukan demonstrasi plot (demplot), petugas PPL mengawal pelaksanaannya dengan sungguh-sungguh agar teknik demplot dilakukan dengan baik dan benar.

Jika tidak dilakukan pengawalan maka petani menentukan keinginannya sendiri, misal takaran pupuknya dikurangi disebabkan kekeliruan informasi bahwa zeolit dapat menggantikan peranan pupuk. Fakta menunjukkan bahwa hasil demonstrasi plot pembenah tanah zeolit yang dilakukan pada lahan pertanian milik petani ada yang menaikkan dan ada juga yang menurunkan gabah kering panen (GKP). Aplikasi Zeolit menaikkan hasil GKP, hal ini disebabkan ada petani yang memberikan pupuk kandang sebanyak 5 ton/ha, sehingga produksi GKP dapat mencapai 8.5 ton/ha. Peningkatan produksi GKP tidak hanya dipengaruhi pemberian pupuk kandang saja, tetapi jika dikombinasikan dengan zeolit maka efisiensi serapan hara yang berasal dari pupuk kandang dan pupuk anorganik lebih tinggi lagi. Aplikasi zeolit menurunkan hasil GKP, hal ini disebabkan takaran zeolit yang diberikan masih rendah, dan takaran pupuk SP-36 dan KCL dikurangi atau sama sekali tidak diberikan karena kelangkaan pupuk atau harganya mahal, dan agen distributor zeolit tidak memberi subsidi pupuk anorganik karena alasan keterbatasan dana.

Pupuk organik dan zeolit yang diberikan secara bersamaan dengan dosis yang tepat dapat mempertahankan kelembaban tanah yang lebih lama, sehingga fluktuasi suhu di sekitar perakaran sangat kecil dan suhu tidak naik drastis (suhu tanah relatif stabil) setelah air diberikan ke tanah. Tanpa pemberian zeolit maka suhu tanah di sekitar perakaran meningkat drastis yang mengakibatkan kandungan C-organik cepat teoksidasi dan ketersediaannya di dalam tanah tidak dapat dipertahankan lebih lama lagi.

Pengalaman membuktikan jika 100 ton pupuk kandang diberikan pada lahan masam yang didominasi mineral kaolinit untuk budidaya tanaman nenas dengan teknologi tinggi, maka dalam waktu kurang dari 6 bulan kandungan C-organik di dalam tanah turun kembali pada nilai sebelum pemberiannya yaitu 1%, hal ini disebabkan tingkat degradasi lahannya sudah berat. Pengelolaan lahan tergradasi dengan teknologi tinggi mulai dari pengolahan lahan dengan traktor, pemberian pupuk anorganik cair tidak akan pernah menyelesaikan masalah. Fakta membuktikan bahwa setelah tanah diolah maka begitu turun hujan tanah menjadi padat lagi, dan pupuk cair yang diberikan banyak hilang tercuci, sehingga efisiensi pemupukan sangat sulit ditingkatkan dan indikatornya adalah penurunan produktivitas lahan sampai 50%. Formulasi pemberian zeolit dan bahan organik serta pupuk anorganik dengan takaran yang relatif berimbang berdasarkan uji tanah spesifik lokasi dapat memperbaiki sifat fisika, kimia, dan biologi tanah. Hasil penelitian pengaruh zeolit dengan merek tertentu terhadap produktivitas lahan sawah dan pertumbuhan serta hasil padi varietas IR-64 di 3 tempat dengan kondisi sawah yang berbeda (sawah tadah hujan, sawah berpengairan teknis, sawah berpengairan desa) bahwa takaran zeolit masing-masing adalah 150 kg/ha untuk lahan sawah berpengairan teknis di Desa Sukadana (Subang), 200 kg/ha untuk lahan sawah tadah hujan di Desa Bangle (Karawang), 250 kg/ha untuk lahan sawah berpengairan desa di Desa Cacuban (Sumedang). Tingkat efisiensi pemberian zeolit meningkat dengan meningkatnya kandungan pasir+debu, dimana tingkat efisiensi dari tinggi sampai rendah, yaitu 56% di Sumedang, 35% di Karawang, dan 31% di Subang. Peningkatan efisiensi pemberian zeolit cenderung berkorelasi dengan kandungan pasir + debu, dimana tingkat efisiensi pemberian zeolit 35% di Karawang dengan kandungan (pasir + debu) 44% dengan pendapatan bersih Rp. 2.820,- dan tingkat efisiensi 31% di Subang dengan kandungan (pasir+debu) 14% dengan pendapatan bersih Rp. 2.315,- untuk setiap I (satu) kg zeolit (Sumber: Balai Pengkajian Teknologi Pertanian Lembang, 1997). Selama teknis pelaksanaan inovasi teknologi yang diterapkan oleh petani sudah baik dan benar, maka pemberian pembenah tanah zeolit dapat meningkatkan produksi GPK > 25%. Perbedaan peningkatan produksi GKP sangat ditentukan perbedaan faktor teknis panca usahatani, yaitu: (1) sempurna dan tidak sempurnanya pelumpuran tanah setelah tanah diolah dua kali, (2) potensi daya hasil dari varietas padi yang ditanam tinggi atau rendah, (3) takaran pupuk yang diberikan berimbang atau tidak, (4) cara pemberian air teratur atau tidak, (5) pencegahan hama dan penyakit tanaman teratur atau tidak. Sebaliknya, pembenahan tanah tidak berpengaruh terhadap peningkatan produksi GKP, hal ini disebabkan teknis pelaksanaan inovasi teknologi pembenahan tanah yang diterapkan petani tidak mengikuti petunjuk, misal pembenahan tanah dan pupuk tidak dicampur rata, apalagi panca usahatani tidak dilakukan dengan baik.
Aplikasi pembenah tanah zeolit sebaiknya tidak dilakukan pada tipologi lahan yang mempunyai kapasitas tukar kation (KTK) rendah (sekitar 5 cmol (+) kg-1) seperti pada jenis tanah regosol, podsolik merah kuning, letosol cokelat kemerahan.

Prospek penggunaan dan pengembangan pembenah tanah zeolit sangat baik, sebab kenyataanya sudah terjadi kerusakan tanah yang ditandai dengan fenomena levelling-off, dan hasil penelitian membuktikan bahwa pemberian zeolit berpengaruh terhadap peningkatan produksi tanaman.


Oleh karena itu, pemerintah secepatnya menyusun strategi ke depan tentang kebijakan revitalisasi pembenah tanah untuk memperbaiki lahan kritis, sehingga produktivitas lahan dan peningkatan kesejahteraan petani dipertahankan secara berkelanjutan, dan swasembada pangan dapat dicapai dalam kurun waktu yang tidak terlalu lama.

M. Al - Jabri
Penulis adalah Peneliti Utama – Balai Penelitian Tanah, Badan Litbang Pertanian
Dimuat dalam Tabloid Sinar Tani, 7 Januari 2009

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Controlled-Release Fertilizers Using Zeolites

Controlled-Release Fertilizers Using Zeolites

The U.S. Geological Survey (USGS) has experimented with zeolites to help control the release of fertilizer nutrients in soil. The use of soluble fertilizers can lead to water pollution and to wasted nutrients. Nitrogen, for example, can leach into ground and surface waters, especially in sandy soils, and phosphate may become fixed and unavailable to plants, especially in tropical soils. Zeolites are porous minerals with high cation-exchange capacity that can help control the release of plant nutrients in agricultural systems. Zeolites can free soluble plant nutrients already in soil, and may improve soil fertility and water retention. Because zeolites are common, these unique minerals could be useful on a large-scale in agriculture.

USGS research has experimented with zeolites applied to several different fertilizers including controlled-release nitrogen, controlled-release phosphorous fertilizers, and in the release of trace nutrients.

Controlled-Release Nitrogen Fertilizer

Urea is one of the most common nitrogen fertilizers. It is very soluble in water, and can be leached through the root zone. In addition, urea is converted into ammonium ions by an enzyme found in most soils. Soil bacteria then convert these ammonium ions into readily leachable nitrate ions. Using zeolitic rocks in fertilizer can help prevent these nutrient losses.



A controlled-release nitrogen (N) fertilizer can be produced by heating zeolite rock chips to about 400oC to drive out all zeolite and pore water, which is replaced with molten urea. The urea crystallizes at about 132oC. The rate of nitrogen release from the zeolitic rock is slowed in three ways: (1) by containing urea in the rock pores and zeolite crystals, thus preventing the leaching of urea from the root zone; (2) by slowing the conversion of urea by soil enzymes, thus delaying the formation of ammonium ions; and (3) by taking up ammonium ions onto exchange sites in the zeolite, thus protecting them from nitrifying bacteria. Potassium-saturated zeolite prepared by the above method contains approximately 17 wt. percent elemental N. The rate of N release can be controlled by changing the size of the rock chips.

Controlled-Release Phosphorous Fertilizers

Phosphate (H2PO4) can be released to plants from phosphate rock (P-rock) composed largely of the calcium phosphate mineral apatite by mixing the rock with zeolite having an exchange ion such as ammonium. The approximate reaction in soil solution is as follows: (P-rock) + (NH4-zeolite) = (Ca-zeolite) + (NH4+) + (H2PO4-).

The zeolite takes up Ca2+ from the phosphate rock, thereby releasing both phosphate and ammonium ions. Unlike the leaching of very soluble phosphate fertilizers (for example, super-phosphate), the controlled-release phosphate is released as a result of a specific chemical reaction in the soil. As phosphate is taken up by plants or by soil fixation, thechemical reaction releases more phosphate and ammonium in the attempt to reestablish equilibrium. The rate of phosphate release is controlled by varying the ratio of P-rock to zeolite. Phosphorus is also released from the rock by the lowering of soil pH as ammonium ions are converted to nitrate.



Controlled-release fertilizers were tested in greenhouse pot experiments with sorghum-sudangrass using NH4-saturated zeolite (clinoptilolite) and P-rock with a phosphate application rate of 340 mg P per kg soil, and zeolite/P-rock ratios ranging from 0 to 6. Total phosphate uptake and phosphate concentration measured for the grass were related linearly to the zeolite/P-rock ratio, and yields summed over four cuttings were as much as four times larger than control experiments.

Release of Trace Nutrients

Experiments indicate that zeolite in soil can aid in the release of some trace nutrients and in their uptake by plants. The release of phosphorus, potassium (K), manganese (Mn), zinc (Zn), iron (Fe), and copper (Cu) was enhanced by the presence of zeolite in a neutral soil. The concentration of Cu and Mn in sudangrass (in mg/kg) was significantly related to the zeolite/P-rock (x) in experimental systems that used two different NH4-saturated clinoptilolites, two different soils, and two different forms of P-rock.

Potential Harmful Effects

Zeolites can be harmful as well as helpful to plant growth. For example, zeolites with sodium as the chief exchange ion can be toxic to plants, and K-, Ca-, and NH4-poor zeoIites can scavenge these ions from soil solutions and thereby limit plant growth when used in soils that are deficient in these nutrients. These negative results emphasize the need to use appropriate zeolites during agricultural experimentation.

Source : http://www.usgs.gov

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ZEO Health Zeolite

The Cleaning Process of ZEO Health Zeolite

We start with the cleanest zeolite on earth mined specifically for human consumption (the only mine in the world that does this). The zeolite is then intensely washed with purified water and prepared to ensure a standardized cat-ion capacity and clean cage. The zeolite is then put through rigorous quality control tests to ensure its quality and safety is maintained for human consumption. It is thoroughly dried and then MICRONIZED to the smallest powdered particle size thus allowing it to penetrate throughout the body and even through the blood brain barrier to safely remove disease causing toxic heavy metals that include lead, mercury, cadmium, arsenic, nickel, barium and other toxic chemicals.

Milled vs. Micronized Zeolite

Another characteristic of a low grade zeolite has to do with the way it is processed. When zeolite rocks are “milled”, they are grinded to powder. This is normally takes place at the mine and it the cheaper way to create powder. The problem with the milling process is that it crushes the zeolite cage structure rendering the zeolite un-absorbable in the body and largely ineffective for human consumption. “Micronization” is the only way to make powdered zeolite and maintain the benefits of the cage structure.



The micronization process is an expensive quality control. When faced with the choice of milling the zeolite at the mine or shipping it out to a specialty micronization plant, many zeolite companies choose to mill the zeolite. All Zeo Health Ltd. zeolite is micronized with the strictest quality controls and highest standards for human consumption.

Refference : http://www.zeolite.com

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Use Zeolite for Water Treatment

The high cation exchange capacity (C.E.C.) of GSA zeolites combined with their selective affinity for specific cations make them uniquely suited to various applications in water treatment. These natural zeolites have been shown to be effective in industrial and municipal waste water systems. The following is a listing of those cations which can be removed from various effluents by GSA zeolites under the proper conditions:

Rb+ Li+ K+ Cs+ NH+4

Na+ Ag+ Cd+2 Pb+2 Zn+2

Ba+2 Sr+2 Cu+2 Ca+2 Hg+2

Mg+2 Fe+3 Co+3 Al+3 Cr+3

One of the first full scale projects to incorporate natural zeolites in a municipal tertiary water treatment system was built for the Tahoe Truckee Sanitation Agency. This system, designed by CH2M Hill, utilizes zeolite as an ion exchange medium for the removal of ammonium (NH+4). The municipal effluent containing ammonium is passed through the natural zeolite which adsorbs the ammonium ion. The efficiency of ammonium removal is dependent upon temperature, water quality, and rate of flow. Regeneration of the natural zeolite bed for reuse is achieved by passing a brine solution through it. The regenerant then is passed through a stripping unit and the ammonium is converted into ammonium sulfate, and sold as a fertilizer.


A pilot project near Denver, Colorado, is now using natural zeolites for the removal of ammonium in a potable water system. Similar systems are now in production which remove various pollutants including heavy metals and radioactive ions from industrial effluents.

One alternative to a typical tertiary water treatment plant is to apply effluents over natural soils. The soil filters the pollutants from the water as it gradually percolates to the natural ground-water table which may be recovered from wells for reuse. The soil, as an ion exchange medium, is regenerated by way of crop production capable of removing many of the pollutants. A major limitation of such systems is the requirement for percolation which typically necessitates the use of a sandy soil type not ideal for ion exchange. The low cation exchange capacity of these sandy soil can then be enhanced through the addition of GSA zeolites which will not impede percolation. Tests of such a system were carried out by Dr. Ian Pepper of the University of Arizona. In these tests, a turf grass was used to regenerate the system and adequate efficiencies of pollutant removal were found to be attainable. Additions of natural zeolites in these systems may be found to favorably improve the sequestering of heavy metals. Further testing is required to fully demonstrate this possibility.

Systems for the specific removal of cations from industrial wastes utilizing natural zeolites as a component of the filter medium have been commercialized. These systems have successfully recovered precious metals from plating operations as well as basic industrial pollutants from effluents.

Reference : http://www.gsaresources.com

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Pupuk Zeolit, Si Murah Berkhasiat Tinggi untuk Kebun Sawit (bagian 2)

Dadang Gusyana - Information Officer, Indonesian Biotechnology Information Centre (Indo BIC) - member of ISAAA SEAsia Centre, 2005

Areal pertanaman sawit paling banyak mengalami degradasi tingkat kesuburan, baik kesuburan secara fisika, kimia ataupun biologi. Journal of Oil Palm Research mengemuka bahwa degradasi kesuburan lahan selain faktor produktivitas sawit yang tinggi juga disebabkan oleh hilangnya nutrisi pupuk karena terlarut melalui resapan air, perubahan cuaca, tidak ada perawatan tanah, tidak memperbaiki aerasi tanah dan tanah tidak lagi mengandung unsur mikro. Dari penelitian di Malaysia melalui studi kelayakan pada perkebunan sawit dengan menggunakan campuran pupuk dan zeolit di dapatkan perbandingan terbaik adalah NPK : Zeolit = 3 : 2. Hasil penelitian tersebut juga menyimpulkan bahwa zeolit dapat menghemat pupuk dan dapat meningkatkan hasil panen.


Gambar 1: Pada pemupukan tanaman dengan pupuk urea, dalam tanah urea akan membentuk ion amonium (NH4+), ion ini apabila tidak diikat oleh tanah (zeolit) maka akan terbuang percuma lewat air irigasi. Dengan demikian unsur hara yang diberikan lewat pemupukan akan lebih efisien apabila tanah pertanian diberi zeolit. Zeolit tidak hanya mengawetkan unsur N saja, tetapi juga K, Ca dan Mg.

Zeolit mempunyai kemampuan untuk mengawetkan pupuk. Kemampuan ini berarti akan menghemat biaya pemupukan, tetapi perlu diingat bahwa zeolit adalah bahan pedamping pupuk Urea, SP-36 dan KCI, bukan pengganti pupuk tersebut. Zeolit juga digunakan untuk mengurangi tingkat pencemaran logam berat seperti Pb, Cd, Zn, Cu2+, Mn2+, Ni2+ pada lingkungan. Modifikasi zeolit sebagai adsorben anion seperti NO3-, Cl-, dan SO4- telah dikembangkan melalui proses kalsinasi zeolit-H pada suhu 5500C.

Secara kimia kandungan zeolit yang utama adalah: Si02 = 62,75%; Al203 =12,71 %; K20 = 1,28 %; CaO = 3,39 %; Na2O = 1,29 %; MnO = 5,58 %; Fe203 = 2,01 %; MgO = 0,85 %; Clinoptilotit = 30 %; Mordernit = 49 %. Sedangkan nilai KPK antara 80 - 120 me/100 gr, nilai yang tergolong tinggi untuk penilaian tingkat kesuburan tanah. Nilai KPK ini akan menentukan kemampuan bahan tersebut untuk menyimpan pupuk yang diberikan sebelum diserap tanaman. Penelitian lainnya dilakukan oleh Winana, ES dkk, yang berjudul Perbaikain Medium Tanam dan Pertumbuhan Melalui Aplikasi Zeolit, Zeolit diketahui dapat memperbaiki kesuburan tanah antara lain melalui peningkatan kapasitas tukar kation.

Penelitian aplikasi zeolit dilakukan pada pembibitan kelapa sawit untuk mengetahui pengaruhnya terhadap medium tanam dan pertumbuhan serta serapan hara bibit kelapa sawit telah dilakukan di areal pembibitan kelapa sawit kebun percobaan Aek Pancur dengan menggunakan rancangan acak lengkap. Medium yang digunakan adalah tanah Typic Paleudults, Typic Udipsamments, dan Typic Hapludults. Perlakuan aplikasi zeolit terdiri dari 4 taraf dosis yaitu 0, 50, 100, dan 150 g/ polybag. Hasil penelitian menunjukkan bahwa pemberian zeolit ke dalam tanah umumnya mampu meningkatkan kandungan hara dalam tanah dan kapasitas tukar kation tanah.

Aplikasi zeolit sebagai bahan pembenah tanah pada pembibitan kelapa sawit tidak menunjukkan pengaruh yang nyata terhadap pertumbuhan dan serapan hara bibit hingga umur 11 bulan. Namun demikian, secara umum aplikasi zeolit hingga dosis 100 g/polybag cenderung dapat meningkatkan pertumbuhan dan serapan hara bibit dibandingkan dengan perlakuan tanpa aplikasi zeolit, sedangkan aplikasi dengan dosis hingga 150 g/ polybag cenderung menurunkan pertumbuhan dan serapan hara.

Asal Usul Zeolit

Penemuan zeolit di dunia dimulai dengan ditemukannya Stilbit pada tahun 1756 oleh seorang ilmuwan bernama A. F. Constedt. Constedt menggambarkan kekhasan mineral ini ketika berada dalam pemanasan terlihat seperti mendidih karena molekulnya kehilangan air dengan sangat cepat. Sesuai dengan sifatnya tersebut maka mineral ini diberi nama zeolit yang berasal dari kata ‘zein’ yang berarti mendidih dan ‘lithos’ yang berarti batuan. Pada tahun 1784, Barthelemy Faujas de Saint seorang profesor geologi Perancis menemukan sebuah formulasi yang cantik hasil penelitiannya tentang zeolit yang dipublikasikan dalam bukunya “Mineralogie des Volcans”. Akhirnya berkat jasanya, pada tahun 1842 zeolit baru tersebut dinamai Faujasit.

Zeolit telah dipelajari oleh para ahli mineral selama lebih dari 250 tahun. Berikut ini diberikan tahun ditemukannya mineral zeolit .Semenjak awal tahun 1940-an, ilmuwan Union Carbide telah memulai penelitiannya untuk mensintesis zeolit dan mereka berhasil mensintesis zeolit A dan X murni pada tahun 1950, dan setelah itu banyak ditemukan zeolit sintesis jenis baru. Zeolit merupakan senyawa aluminosilikat terhidrasi yang memiliki kerangka struktur tiga dimensi (3D), mikroporous, dan merupakan padatan kristalin dengan kandungan utama silikon, aluminium, dan oksigen serta mengikat sejumlah tertentu molekul air di dalam porinya.

Karena sifat unik dari zeolit, maka zeolit banyak digunakan untuk berbagai aplikasi di industri diantaranya zeolit digunakan di industri minyak bumi sebagai ‘cracking’, di industri deterjen sebagai penukar ion, pelunak air sadah dan di industri pemurnian air, serta berbagai aplikasi lain.

Dalam bidang pertanian, secara umum zeolit fungsi zeolit adalah: (1) Meningkatkan kadar oksigen terlarut dalam air irigasi lahan persawahan, (2) Menjaga keseimbangan pH tanah, (3) Mampu mengikat logam berat yang bersifat meracun tanaman misalnya Pb dan Cd, (4) Mengikat kation dari unsur dalam pupuk misalnya NH4+ dari urea K+ dari KC1, sehingga penyerapan pupuk menjadi effisien, (5) Ramah lingkungan karena menetralkan unsur yang mencemari lingkungan. (6) Memperbaiki struktur tanah (sifat fisik) karena kandungan Ca dan Na, (7) Meningkatkan KPK tanah (sifat kimia), dan (8) Meningkatkan hasil tanaman.

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