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CARBON DIOXIDE EMISSION IN LAND USE TRANSITIONS TO PLANTATION

Fahmuddin Agus1, Eleonora Runtunuwu1, Tania June2, Erni Susanti1, Herna Komara3,
Haris Syahbuddin1, Irsal Las1, and Meine van Noordwijk4

1Indonesian Center for Agricultural Land Resources Research and Development, Jalan Ir. H. Juanda No. 98, Bogor 16123 Telp. (0251) 8323012, 8327215, Faks. (0251) 8311256, E-mail: This e-mail address is being protected from spambots, you need JavaScript enabled to view it
2Bogor Agricultural University, Kampus IPB Dramaga, Bogor 16002
3Directorate General of Plantation, Ministry of Agriculture, Jalan Harsono R.M. No. 3 Ragunan, Jakarta 12250
4World Agroforestry Centre (ICRAF), Southeast Asia Regional Office, Jalan CIFOR, Sindangbarang, PO Box 161 Bogor 16001

ABSTRACT

Carbon dioxide emission assessment associated with land use transitions to agriculture is important for designing strategies in reducing green house gas emission. Net CO2 emissions is the sum of 1) the above ground biomass C loss of the initial land use because of land clearing, 2) the above ground C accumulation by the subsequent plantation crops, 3) soil organic matter decomposition, and 4) soil organic C burning if land management or land clearing involves fire. For mineral soils, in most cases, conversion of primary and secondary forests with time average C stocks of about 300 and 132 t/ha, respectively, results in a net C emission. However, if shrub or Imperata grassland, with respective C stocks of 15 and 2 t/ha is rehabilitated to plantation, it generally results in a net C sequestration. For peat soil, CO2 emission is caused by peat decomposition, peat burning (if any), and the aboveground C decomposition and/or burning. Rehabilitating peat shrub (with assumed C stock of about 15 t/ha and average drainage depth of 40 cm) instead of clearing peat forest (with assumed C stock of about 200 t/ha and drainage depth of 0) for agriculture reduces CO2 emissions of about 862 t CO2-e/ha/25 year (34 t CO2-e/ha/year) because of substantial reduction in the plant biomass and possible peat soil carbon loss due to burning. Peat shrub remains as peat shrub emits about 22 t CO2-e/ha/year. If peat shrub is rehabilitated to paddy field, rubber plantation or oil palm plantation, the emission levels become 11, 7, and 30 t CO2-e/ha/year, respectively. This means that rehabilitating peat shrub to paddy field or rubber plantation, results in net emission reduction of 11 and 15 t CO2-e/ha/year, respectively, whereas rehabilitating it to oil palm plantation increases net emission of only 8 t CO2-e/ha/year, relative to leaving the peat shrub as is. Therefore, new plantation development should be prioritized on mineral soils shrub and Imperata grasslands or on peat shrub as these conversions, in most cases, result in the net CO2 sequestration and potentially improve the livelihood of the communities.

Keywords: Carbon dioxide emission, carbon sequestration, land use transition, plantations, peatlands, mineral soils

 

 

ANALISIS FINANSIAL DAN KEUNTUNGAN YANG HILANG DARI PENGURANGAN EMISI KARBON DIOKSIDA
PADA PERKEBUNAN KELAPA SAWIT

Herman1, Fahmuddin Agus2, dan Irsal Las2

1Lembaga Riset Perkebunan Indonesia, Jalan Salak No. 1A, Bogor 16151
Telp. (0251) 8333382, Faks. (0251) 8315985, E-mail: This e-mail address is being protected from spambots, you need JavaScript enabled to view it
2Balai Besar Penelitian dan Pengembangan Sumberdaya Lahan Pertanian, Jalan Ir. H. Juanda No. 98, Bogor 16123
Telp.
(0251) 8323012, Faks. (0251) 8311256, E-mail: This e-mail address is being protected from spambots, you need JavaScript enabled to view it

ABSTRAK

Areal perkebunan kelapa sawit meningkat tajam dengan laju rata-rata 12,30%/tahun sejak 1980. Perluasan perkebunan kelapa sawit, terutama bila mengonversi hutan primer, berpotensi menyebabkan peningkatan emisi gas rumah kaca (GRK). Emisi GRK akibat penggundulan hutan dapat dikurangi melalui kebijakan nasional dipadukan dengan mekanisme perdagangan karbon internasional, seperti Reducing Emissions from Deforestation and Degradation (REDD). Biaya investasi satu unit perkebunan sawit dengan luas efektif 6.000 ha dengan model PIR adalah sekitar Rp256,86 miliar pada tanah mineral dan Rp276,82 miliar pada lahan gambut. Untuk perkebunan besar, biaya investasinya Rp265,72 miliar pada tanah mineral dan Rp286,30 miliar pada lahan gambut. Bila harga minyak sawit mentah (CPO) Rp8.000/kg dan harga inti sawit Rp5.500/kg, pada suku bunga 15% perkebunan meraup keuntungan bersih Rp1.957.000/ha/tahun dengan model PIR dan Rp1.615.000/ha/tahun dengan model perkebunan besar pada lahan bertanah mineral. Apabila emisi dari perubahan penggunaan lahan hutan primer sampai satu siklus produksi perkebunan sawit pada lahan bertanah mineral adalah 41 t CO2/ha/tahun maka keuntungan yang hilang karena konservasi hutan untuk pengurangan emisi CO2 adalah US$5,19/t CO2 pada sistem PIR dan US$4,28/t CO2 pada perkebunan besar. Pada lahan gambut, keuntungan bersih menjadi Rp1.797.000/ha/ tahun dengan sistem PIR dan Rp1.468.000/ha/tahun pada perkebunan besar. Dengan perkiraan emisi pada lahan gambut rata-rata sebanyak 64 t CO2/ha/tahun maka keuntungan yang hilang berturut-turut adalah US$3,05 dan 2,49/t CO2 pada sistem PIR dan perkebunan besar. Hasil perkiraan keuntungan yang hilang dapat dijadikan acuan dasar perkiraan besaran kompensasi yang berhak diterima pemilik/penguasa hutan yang mengkonservasi hutannya.

Kata kunci: Kelapa sawit, lahan mineral, lahan gambut, keuntungan yang hilang, gas rumah kaca

ABSTRACT

Financial analysis and opportunity cost of carbon dioxide emission reduction in oil palm plantation

The area of oil palm plantation rapidly increases at a rate of 12.30% annually since early 1980s. Expansion of oil palm plantation, especially from forest conversion, entails a significant green house gas (GHG) emission. GHG emission from deforestation can be reduced through national policy in combination with the international carbon trading scheme such as Reducing Emissions from Deforestation and Degradation (REDD). A unit of oil palm plantation of 6,000 ha effective area under the Nucleus Estate Smallholder (NES) model requires an investment of about IDR256.86 billion on the mineral land and IDR276.82 billion on peatland. Under the large estate plantation, the total investment is IDR265.72 billion on the mineral land and IDR286.30 billion on the peatland. If the price of crude palm oil (CPO) is IDR8,000/kg and kernel palm oil price is IDR5,500/kg, at 15% interest rate, the estate company gained a Net Present Value (NPV) of IDR1,957,000/ha/year from the NES model and IDR1,615,000/ha/ year from large plantation on the mineral land. If the average emission from primary forest conversion to one cycle of oil palm is about 41 t CO2/ha/year, then the opportunity cost from land conservation for emission reduction is US$5.19/t CO2 under NES and US$4.28/t CO2 under the estate plantation. For peatland, the NPV becomes IDR1,797,000/ha/year under NES and IDR1,468,000/ha/year under the estate plantation. With the estimated average emission rate of about 64 t CO2/ha/year, the opportunity costs become US$3.05 and 2.49/t CO2 under the NES and estate, respectively. The estimated opportunity cost can be used as a basis for negotiating the amount of compensation that the land owners deserve for conserving the forest lands.

Keywords: Oil palms, mineral lands, peatlands, opportunity costs, greenhouse gases

 

 

PROSPEK PENGEMBANGAN RICE ESTATE DI KABUPATEN MERAUKE :
TINJAUAN DARI ASPEK PENGELOLAAN TANAH DAN AIR

Prospect of Rice Estate Development in Merauke Regency:
A View from Soil and Water Management Aspects

I G.M. Subiksa

Balai Penelitian Tanah, Jl. Ir. H. Juanda No. 98, Bogor 16123

ABSTRAK

Pengembangan rice estate sebagai instrumen untuk mewujudkan Kabupaten Merauke sebagai lumbung pangan di Kawasan Timur Indonesia telah dimulai dengan disusunnya master plan pengembangan rice estate. Dalam master plan tersebut, telah didelineasi 206 unit kawasan pengembangan yang tiap unitnya meliputi areal seluas 5.000 ha. Pengembangan rice estate memerlukan perencanaan pengelolaan tanah dan air yang cermat untuk mencapai produktivitas lahan yang tinggi dan berkelanjutan tanpa merusak lingkungan. Teknologi pengelolaan tanah dan air yang tepat diyakini menjadi kunci keberhasilan pengembangan kawasan. Hal ini mengingat sebagian besar lahan yang berpotensi untuk dikembangkan merupakan lahan rawa. Kondisi topografi lahan yang datar dan karakteristik iklim serta hidrologi yang spesifik dan beragam, menyebabkan sistem pengelolaan tanah dan air akan sangat spesifik lokasi. Model rancang bangun rice estate yang dikembangkan sebaiknya sistem integrasi tanaman ternak berbasis padi, karena ternak ruminansia dapat saling bersinergi dengan padi mewujudkan sistem pertanian berkelanjutan dengan input luar rendah. Ameliorasi, pemupukan berimbang dan pengelolaan bahan organik menjadi komponen teknologi yang sangat menentukan keberhasilan pengembangan rice estate. Tulisan ini mengulas prospek pengembangan rice estate ditinjau dari aspek pengolahan tanah dan air, pengelolaan bahan organik dan pemupukan berimbang di Kabupaten Merauke Papua.

Kata kunci : Rice estate, pengelolaan tanah dan air, ameliorasi, pemupukan berimbang


NUTRIENT BALANCE AND VEGETABLE CROP PRODUCTION AS AFFECTEDBY DIFFERENT SOURCES OF ORGANIC FERTILIZERS

Fahmuddin Agus
1*, Diah Setyorini1, Wiwik Hartatik1, Sang-Min Lee2,
Jwa-Kyung Sung2, and Jae-Hoon Shin2
1Indonesian Soil Research Institute, Jln. Juanda 98, Bogor 16123, Indonesia
2National Academy of Agricultural Science (NAAS) RDA, Suwon 441-707, Korea

ABSTRAK

Understanding the net nutrient balance in a farming system is crucial in assessing the system sustainability. We quantified N, P and K balances under vegetable organic farming in a Eutric Hapludand in West Java, Indonesia in five planting seasons from 2005 to 2007. The ten treatments and three replications, arranged in a completely randomized block design, included single or combined sources of organic fertilizers: barnyard manure, composts or green manures. The organic matter rates were adjusted every planting season depending on the previous crop responses. The results showed that the application of 20 t ha-1 barnyard manure per crop resulted in positive balances of N, P, and K, except in the second crops of 2006 where potassium balance were -25 to -11 kg ha-1 under the treatments involving cattle barnyard manure, because of low K content of these treatments and high K uptake by Chinese cabbage. Application of 20 to 25 t ha-1 of plant residue or 5 t ha-1 of Tithonia compost also resulted in a negative K balance. Soil available P increased significantly under 25 t ha-1 barnyard manure and that under chicken manure had the highest available P. Accordingly, chicken barnyard manure gave the highest crop yield because of relatively higher N, P and K contents. Plant residues gave the lowest yield due to the lowest nutrient content among all sources. Reducing the use of barnyard manure to 12.5 t ha-1 and substituting it with Tithonia compost, Tithonia green manure or vegetable plant residue compost gave insignificantly different yield compared to the application of 25 t ha-1 barnyard manure singly. In the long run, application of 25 t ha-1 cattle, goat, and horse manure or about 20 t ha-1 chicken manure is recommendable for sustaining the fertility of this Andisol for vegetable production.

Key words: Nutrient balance, vegetable crops, barnyard manure, organic farming, Andisol
Makalah diterbitkan pada Korean Journal of Soil Science Fertilizer. 42(1). 1-13 (2009)

 

DISSOLVED SILICA DYNAMICS AND PHYTOPLANKTON POPULATION IN CITARUM WATERSHED, INDONESIA

 

Husnain 1*, Toshiyuki Wakatsuki 2 and Tsugiyuki Masunaga 3
1
Laboratory of Soils and Ecological Engineering, Faculty of Life and Environmental Sciences, Shimane University, Matsue 690-8504, Japan.
3
Faculty of Life and Environmental Sciences, Shimane University,
Matsue 690- 8504, Japan.
2
Faculty of Agriculture, Kinki University, Nakamachi, Nara 631-8505, Japan.
*e-mail: This e-mail address is being protected from spambots, you need JavaScript enabled to view it , This e-mail address is being protected from spambots, you need JavaScript enabled to view it , This e-mail address is being protected from spambots, you need JavaScript enabled to view it

 

 

 

ABSTRACT
Silicon is an essential and a beneficial nutrient for aquatic and terrestrial primary producers, respectively. Previous research reported that low silica available in lowland sawahs (a leveled and bounded rice field with an inlet and outlet for irrigation and drainage) in the Citarum watershed was partially associated with low dissolved silica (DSi) concentrations in irrigation water. DSi dynamics and the effect of phytoplankton were studied in the reservoirs of three major dams on Citarum River. The concentrations of DSi and other essential nutrients, as well as phytoplankton diversity and density, were monitored at several sites in the Citarum basin from September 2006 to November 2007. DSi concentrations were highest in the upstream reaches, including the furthest upstream reservoir (Saguling), and decreased downstream. Dams contributed to a decrease of approximately 49-58% in DSi concentrations. The DSi reduction is associated with rising diatom densities (P<0.05), which utilize silica in the construction of frustules. The lowest DSi concentration was measured in Jatiluhur reservoir where diatoms were very abundant. High NO3-N and PO4-P concentrations in upstream and reservoirs which ranged from 1.3 to 18.3 mg L-1 and 0.06 to 2.3 mg L-1, respectively, were probably derived from drainage of industries and houses in upstream and feeding materials used for fish culture in the reservoirs. This condition may enhance the growth of phytoplankton including diatom. Diatom was a major species in the reservoirs, while Cyanophyceae was dominant in all segments of Citarum River. Increasing diatom population could retain more DSi as diatom accumulate abundant silica in its cell wall and depleted Si supply from irrigation water into sawah in lowland.
Key words: dam, diatom, DSi, phytoplankton, reservoir, silica retention.
Makalah diterbitkan pada Journal of Food, Agriculture & Environment Vol.7 (3&4) : - . 2009

 

 


HUSNAIN1,3, Toshiyuki WAKATSUKI2, Diah SETYORINI3, HERMANSAH4, Kuniaki SATO1 and Tsugiyuki MASUNAGA1
1Faculty of Life and Environmental Sciences, Shimane University, Matsue 690-8504, 2Faculty of Agriculture, Kinki University, Nara 631-8505, Japan, 3Indonesian Soil Research Institute, Bogor 16123, and 4Faculty of Agriculture, Andalas University, Padang 25163, Indonesia

ABSTRACT

Silicon is a beneficial element for rice plants and is one of the major factors affecting the sustainability of rice production. We investigated silica (Si) availability and dynamics in soils of sawah, other land uses, and also in river and canal water in two watersheds in Citarum and Kaligarang, Java Island, Indonesia. The term sawah refers to a leveled and bounded rice field with an inlet and an outlet for irrigation and drainage, respectively. In the present study, we examined Si content in soils, plants and river water in relation to factors influencing the Si content, such as parent material and land use. The available Si content in sawah was found to be deficient at two sites and low at 10 sites out of 16 sites investigated in the Citarum watershed. In the Kaligarang watershed, no sawah site was classified as deficient and nine out of the 15 sawah sites were determined to be low for rice plant growth. A survey of Si content in rice flag leaves in some selected rice fields showed that seven out of 12 samples had contents less than 125 g SiO2 kg1; these rice samples with low Si contents were those in sawah classified as low in Si contents. In the Citarum watershed, sawah soils developed from the accumulation of lake and clay sediment contained relatively little available Si, while sawah soils in the Kaligarang watershed that were mainly developed from tuff and volcanic ash contained relatively more available Si. In the Citarum watershed, the type of land use influenced Si availability in the soils via a large amount of litter accumulation of pine trees in the case of pine plantations, and acidification in the soils in the case of tea plantations and maize fields. In general, the Si content in river and canal water was higher in the Kaligarang watershed than in the Citarum watershed, and this appears to be affected by the type of parent material. In addition to the type of parent material, Si depletion occurring in dams might also influence Si content in the lower stream of river or canal water in the Citarum watershed.
Key words: available silica, parent material, rice, sawah, silica deficiency.
Makalah diterbitkan pada Journal of Soil Science and Plant Nutrition (2008) 54, 916927


ENVIRONMENTAL MULTIFUNCTIONALITY OF INDONESIAN AGRICULTURE


F. Agus, Irawan, H. Suganda, Wahyunto, A. Setiyanto, M. Kundarto
e: 10pt; color: #141314; font-family: Arial">F. Agus, Irawan, H. Suganda, Wahyunto: Indonesian Soil Research Institute, Jln. Juanda 98, Bogor 16123, Indonesia;
e-mail: This e-mail address is being protected from spambots, you need JavaScript enabled to view it
A. Setiyanto: Center for Agricultural Socio-Economic Research, Bogor, Indonesia
M. Kundarto: UPN Veteran, Yogyakarta, Indonesia

 

ABSTRACT

 

Industrial and urban developments in Indonesia focus on the economic merits, but neglect agricultural services that, when disappear, will destabilize the environmental and livelihood systems. A series of 5-year study has evaluated various aspects of multifunctionality and implications of paddy field conversion on the disappearance of multifunctionality. Soil loss from a series of 18 terraced paddy fields in central Java is negligible. Only a few terraces located along the streams directly caused sedimentation. The functions of flood mitigation, water-resource conservation, erosion reduction, organic waste disposal, heat mitigation, and rural amenity of paddy fields in Citarum watershed in West Java were significant. The replacement cost of such functions was about 51% ($92.67 million yr-1) of the total price of rice of $181.34 million y-1 produced in the 156,000 ha paddy field. This amount could be considered as free services by the farmers to the society. However, because of society negligence and unawareness, conversion has been accelerating while development of newpaddy fields has been decelerating in the last few years. Low and fluctuating price of agricultural products, unavailability or non-affordability of agricultural supplies and inaccessibility to market are among the major disincentives faced by farmers. Because of appreciable multifunctionality they produce, farmers deserve various incentives for the sake of environmental sustainability and other services.
Keywords Flood mitigation; Water-resource conservation; Erosion reduction; Organic waste disposal; Heat mitigation . Rural amenity
Makalah diterbitkan pada Paddy Water Environ (2006) 4:181-188

 

 

 

PREDICTING RUNOFF AND SEDIMENT YIELD FROM A STIFF‐STEMMED GRASS HEDGE
SYSTEM FOR A SMALL WATERSHED


A. Rachman, S. H. Anderson, E. E. Alberts, A. L. Thompson, C. J. Gantzer

ABSTRACT

Grass hedges planted at regular intervals on the landscape offer many opportunities to reduce runoff and sediment from leaving fields. Objectives of this study were (1) to evaluate the ability of the WEPP watershed model to simulate grass hedge system effects of sediment trapping (TE), bench terracing (BT), and variable effective soil hydraulic conductivity (HC) on simulated hillslope runoff and sediment yield, and (2) to model the effects of measured effective hydraulic conductivity (Keff) values from a grass hedge management system by comparing predicted runoff and sediment yield values to those measured in a small watershed over an 11‐year period. The study was conducted on a 6.6 ha watershed located in the deep loess hills region of southwestern Iowa. Narrow grass hedges of predominantly switchgrass (Panicum virgatum) were planted at 15.4 m intervals in 1991. The WEPP model simulated greater reductions in runoff (9%) and sediment yield (58%) from BT compared to TE and HC effects. Combination of all three effects gave the highest reductions in runoff (22%) and sediment yield (79%) compared to individual effects or any combination of two effects. The watershed model did not adequately simulate slope length reduction effects from the grass hedges. Runoff (r2 = 0.78) and sediment yield (r2 = 0.75) were comparable to observed data when measured Keff values for grass hedge, row crop, and channel areas were used as input data. Measured Keff data from grass hedge, row crop, and channel areas should be used for improved runoff and sediment yield predictions.

Keywords. Bench terracing, Effective hydraulic conductivity, Sediment trapping, Switchgrass hedges, WEPP model.
Makalah diterbitkan pada American Society of Agricultural and Biological Engineers, Vol. 51(2): 425-432 2008

 

 

KAJIAN METODE PENETAPAN KAPASITAS TUKAR KATION ZEOLIT SEBAGAI PEMBENAH
TANAH UNTUK LAHAN PERTANIAN TERDEGRADASI


Al-Jabri

 

 

 

ABSTRACT

Cation exchangeable capacity (CEC) of zeolite could be determined not only based on SNI 13-3494 1994, but also Permentan No. 02/Pert/HK060/2/2006. Procedure of CEC determination based on SNI 13-3494 1994 and Permentan No. 02/Pert/HK060/2/2006 were not the same, so that CEC of zeolite from one sample of zeolite which is determined with both procedure could be different, and its CEC will definitely different. Generally, CEC of zeolite which is determined based on Permentan No. 02/Pert/HK060/2/2006 lower compare to SNI 13-3494 1994. Possible sources of error in these steps include the following: (1) in the saturation step, neither narrow ratios nor wide ratios between zeolite and ammonium acetate solution will be influential to the amount more or less ion NH4+ to enter the exchange sites, and duration of percolation, (2) the washing step, to remove ion NH4+ excess on the exchange sites with etanol 96%, (3) ion NH4+ cation exchange with NaCl or KCl. The results of this study have been found that CEC zeolite sample No. 13, 15, 19, and 21 were 83, 84, 95, and 94 cmol(+) kg-1 respectively were greater than Permentan No. 02/Pert/HK.060/2/2006 (80 cmol(+) kg-1). CEC Zeolite Agro 2000 SNI 13-3496-1994 (119 cmol(+) kg-1) was greater if compare to CEC Permentan No. 02/Pert/HK.060/2/2006 (25 cmol(+) kg-1). CEC Zeolite Agro 88 SNI 13-3496-1994 (193 cmol(+) kg-1) greater if compare to CEC Permentan No. 02/Pert/HK.060/2/2006 (25 cmol(+) kg-1). Although CEC zeolite which is determined based on SNI 13-3496-1994 always high value, but in the saturation step, the washing step and removal ion NH4+ excess on the exchange sites with etanol 96%, (3) ion NH4+ cation exchange with NaCl or KCl were constitute a critical steps for CEC determination. CEC zeolite SNI 13-3496-1994 be suggested to revised, and CEC procedure either for soil conditioner for rehabilitation soil degradation or industry must be the same procedure.

 

 

 

 

 

 


Keywords: cation exchangeable capacity (CEC), zeolite, soil degradation
Makalah diterbitkan dalam Jurnal Standardisasi Volume 10 No.2 Tahun 2008. Badan Standardisasi Nasional.

 

 

 

PENGARUH ASAM OKSALAT Na+, NH4+, DAN Fe3+ TERHADAP KETERSEDIAAN K TANAH, SERAPAN N, P, DAN K TANAMAN, SERTA PRODUKSI JAGUNG PADA TANAH-TANAH YANG DIDOMINASI SMEKTIT


D. Nursyamsi, K. Idris, S. Sabiham, D.A. Rachim, dan A. Sofyan

ABSTRAK

Tanah-tanah yang didominasi mineral liat smektit mempunyai prospek yang cukup besar untuk dikembangkan menjadi lahan pertanian, asal disertai dengan pengelolaan tanah dan tanaman yang tepat. Walaupun kadar K total tanah tinggi, tapi ketersediaan kalium bagi tanaman sering menjadi masalah, karena K difiksasi oleh mineral liat smektit. Penelitian yang bertujuan untuk mempelajari pengaruh pemberian asam oksalat, Na+, NH4+, dan Fe3+ terhadap ketersediaan K tanah, serapan N, P, dan K, serta produksi tanaman jagung (Zea mays, L.) pada tanah-tanah yang didominasi mineral liat smektit telah dilaksanakan di Laboratorium Penelitian dan Uji Tanah dan Rumah Kaca Balai Penelitian Tanah, Bogor. Percobaan menggunakan empat contoh tanah bulk yang diambil dari Bogor (Hapludalf Tipik), Cilacap (Endoaquert Kromik), Ngawi (Endoaquert Tipik), dan Blora (Haplustalf Tipik). Percobaan inkubasi di laboratorium dan pot di rumah kaca menggunakan Rancangan Faktorial dalam Rancangan Acak Kelompok, ulangan tiga kali, dan percobaan pot menggunakan jagung varietas Pioneer 21 sebagai tanaman indikator. Faktor pertama adalah takaran asam oksalat, yaitu: 0, 1.000, 2.000, dan 4.000 ppm, sedangkan faktor kedua adalah penambahan kation, yaitu: tanpa kation, Na+, NH4+, dan Fe3+ masing-masing dari NaCl, NH4Cl, dan FeCl3 dengan takaran 50% jerapan maksimum. Takaran Fe3+ 50% jerapan maksimum menyebabkan tanaman mati sehingga percobaan diulang di musim berikutnya dengan takaran Fe3+: 0, 125, 250, 375, dan 500 ppm. Hasil penelitian menunjukkan bahwa asam oksalat, Na+, NH4+, dan Fe3+ nyata meningkatkan K tersedia baik di Alfisols maupun Vertisols, dimana pengaruhnya di Vertisols lebih tinggi dibandingkan Alfisols. Tingkat kekuatan perlakuan dalam melepaskan K dari bentuk tidak tersedia menjadi tersedia adalah Fe3+ > NH4+ > Na+ > asam oksalat. Asam oksalat nyata meningkatkan serapan N, P dan K tanaman di Vertisols, sedangkan Fe3+ takaran 125 ppm nyata meningkatkan serapan K tanaman di Alfisols serta N, P, dan K tanaman di Vertisols. Asam oksalat nyata meningkatkan bobot brangkasan kering jagung umur 4 minggu setelah tanam (MST) pada Hapludalf Tipik dan Endoaquert Tipik, sedangkan Fe3+ takaran 125 ppm nyata meningkatkan hasil brangkasan kering pada Endoaquert Kromik dan Endoaquert Tipik.


Kata kunci : Asam oksalat, Na+, NH4+, Fe3+, K tersedia, Jagung, Tanah yang didominasi smektit.
Makalah diterbitkan dalam Jurnal Tanah dan Iklim (Indonesian Soil and Climate Journal) Nomor 28, Desember 2008. Balai Besar Penelitian dan Pengembangan Sumberdaya Lahan Pertanian, Badan Penelitian dan Pengembangan Pertanian, Departemen Pertanian.

 

DAMPAK TSUNAMI TERHADAP SIFAT-SIFAT TANAH PERTANIAN
DI NAD DAN STRATEGI REHABILITASINYA


Achmad Rachman, Deddy Erfandi, dan M. Nasil

 

ABSTRAK

Gelombang tsunami yang terjadi akibat gempa bumi di pantai barat Sumatera pada tanggal 26 Desember 2004 telah menyebabkan terjadinya peningkatan salinitas lahan-lahan pertanian dan rusaknya sistem irigasi dan drainase di sepanjang pantai Provinsi Nanggroe Aceh Darussalam (NAD). Tujuan penelitian ini adalah untuk memonitor perubahan salinitas tanah di daerah yang terkena tsunami. Pengambilan contoh tanah pada beberapa kedalaman dan pengukuran salinitas menggunakan electromagnetic induction technique (EM38) telah dilakukan di beberapa tempat. Tingkat salinitas tanah dipengaruhi oleh karakteristik lumpur yang terbawa oleh tsunami ke lahan pertanian dan tingkat permeabilitas tanah. Garam-garam telah bergerak ke dalam lapisan tanah yang lebih dalam, khsusunya pada tanah yang teksturnya lebih kasar, dimana umumnya petani menanam kacang tanah pada musim kemarau. Pada lahan persawahan yang teksturnya lebih berat, garam-garam terakumulasi di dekat permukaan tanah, mungkin disebabkan oleh genangan air yang lebih lama pada saat tsunami dan terdapatnya lapisan tapak bajak yang menghambat pergerakan air ke dalam tanah. Beberapa rekomendasi telah diberikan kepada petugas dan petani sehingga mereka dapat mengurangi kehilangan hasil sebagai akibat dari tsunami. Rekomendasi tersebut di antaranya adalah menghindari menanam pada bagian lahan yang salinitasnya masih tinggi, meningkatkan laju pencucian horizontal dan vertikal, memperbaiki kesuburan tanah, dan menanam tanaman yang toleran terhadap salinitas yang relatif tinggi.


Kata kunci : Tsunami, Salinitas, Pencucian, Rehabilitasi
Makalah diterbitkan dalam Jurnal Tanah dan Iklim (Indonesian Soil and Climate Journal) Nomor 28, Desember 2008. Balai Besar Penelitian dan Pengembangan Sumberdaya Lahan Pertanian, Badan Penelitian dan Pengembangan Pertanian, Departemen Pertanian.

 

 

MOBILITAS SEDIMEN DAN HARA PADA SISTEM SAWAH BERTERAS DENGAN IRIGASI TRADISIONAL

Sukristiyonubowo

 

 

 

 

 

 

 

ABSTRAK

Mobilitas sedimen dan hara pada sistem sawah berteras dengan irigasi tradisional telah diteliti di Desa Keji, Kabupaten Semarang pada Musim Hujan 2003-2004. Tujuan penelitian adalah mengevaluasi sedimen dan hara tanaman yang terbawa masuk melalui air irigasi dan yang terangkut keluar oleh larutan sedimen selama pertumbuhan tanaman padi dan mempelajari mobilitas sedimen dan hara tanaman pada musim hujan Perlakuan yang diuji, meliputi Praktek Petani, Praktek Petani + Jerami, Perbaikan Teknologi, dan Perbaikan Teknologi + Jerami. Debit air irigasi saat pelumpuran adalah yang tertinggi, dan bervariasi mulai 2,55 ± 1,23 sampai 3,10 ± 0,55 l detik-1. Sebaliknya, pada stadia vegetatif debit air irigasi adalah yang terkecil, yaitu antara 0,33 ± 0,15 dan 0,54 ± 0,15 l detik-1, dan pada stadia generatif antara 1,38 ± 0,28 dan 1,60 ± 0,06 l detik-1. Selanjutnya, debit larutan sedimen saat pelumpuran berkisar mulai 0,89 ± 0,20 sampai 1,31 ± 0,34 l detik-1. Pada stadia vegetatif debit larutan sedimen adalah yang terkecil, yaitu antara 0,21 ± 0,07 dan 0,78 ± 0,52 l detik-1, sedangkan pada stadia generatif antara 1,13 ± 0,06 dan 1,32 ± 0,09 l detik-1. Hanya pada saat pelumpuran sedimen yang terbawa masuk oleh air irigasi lebih kecil dari pada sedimen yang terangkut keluar oleh larutan sedimen. Banyaknya sedimen yang tersimpan adalah antara 647 sampai 1.589 kg ha-1 musim-1 dari total sedimen yang terbawa masuk oleh air irigasi antara 2.715 sampai 5.521 kg ha-1 musim-1. Sebaliknya, hara terlarut (nitrogen, fosfor dan kalium) yang terbawa masuk oleh air irigasi tersimpan di persawahan, yang bervariasi antara 7,20 - 13,62 kg N; 0,13 - 0,20 kg P; dan 7,25 - 13,42 kg K ha-1 musim-1. Secara statistik, antar perlakuan tidak menunjukkan perbedaan yang nyata, baik untuk jumlah sedimen maupun hara yang tersimpan. Hasil penelitian ini mendemonstrasikan adanya fungsi lain (external services) yang diberikan oleh sistem sawah berteras, selain sebagai tempat memproduksi beras

Kata kunci : Debit, Sedimen, Nitrogen, Fosfor, Kalium, Sawah berteras
Makalah diterbitkan dalam Jurnal Tanah dan Iklim (Indonesian Soil and Climate Journal) Nomor 28, Desember 2008. Balai Besar Penelitian dan Pengembangan Sumberdaya Lahan Pertanian, Badan Penelitian dan Pengembangan Pertanian, Departemen Pertanian.

 

KELARUTAN FOSFAT ALAM DAN SP-36 DALAM GAMBUT
YANG DIBERI BAHAN AMELIORAN TANAH MINERAL

W. Hartatik dan K. Idris

ABSTRAK

Pemupukan fosfat alam pada gambut mempunyai prospek yang baik karena mudah larut dalam kondisi masam. Namun penelitian penggunaan fosfat alam pada tanah gambut, masih sangat terbatas. Tujuan penelitian ini adalah untuk mempelajari kelarutan fosfat alam dan SP-36 dalam gambut yang diberi bahan amelioran tanah mineral. Penelitian dilaksanakan di laboratorium Balai Penelitian Tanah Bogor. Penelitian terdiri atas dua kegiatan: 1) Kelarutan fosfat alam pada gambut. Bahan tanah gambut oligotropik dari Air Sugihan, Sumatera Selatan setara 100 g bobot kering oven 105oC diinkubasi selama 12 minggu dengan fosfat alam dari Maroko, Christmas, dan Ciamis. Perlakuan berupa 11 tingkat takaran fosfat alam, yaitu 0, 10, 20, 30, 40, 50, 60, 75, 100, 125, dan 150 ppm P. Analisis P larut dengan metode biru molibdat dilaksanakan pada 2, 4, 8 dan 12 minggu setelah inkubasi. Kegiatan 2) Pemberian beberapa jenis fosfat alam atau SP-36 pada tanah gambut yang diberi bahan ameliorant tanah mineral. Takaran P yang dicoba sebanyak 4 taraf (25, 50, 75, dan 100% erapan P) ditambah perlakuan kontrol parsial dan kontrol lengkap, diulang dua kali. Bahan tanah gambut yang digunakan setara 200 g bobot kering oven 105oC kemudian diberi bahan amelioran tanah mineral dengan takaran 7,5% erapan maksimum Fe, diinkubasi 12 minggu. P larut diukur dengan metode biru molibdat pada 1, 2, 4, 6, 8, 10, dan 12 minggu. Hasil percobaan menunjukkan bahwa dalam gambut, kelarutan fosfat alam Maroko lebih tinggi dari fosfat alam Ciamis, sementara kelarutan yang terendah ditunjukkan oleh fosfat alam Christmas. Kelarutan sumber P dalam tanah gambut yang telah diberi perlakuan bahan amelioran tanah mineral memberikan hasil yang sejalan dengan kelarutan fosfat alam dalam gambut, yaitu: SP-36 > fosfat alam Maroko > fosfat alam Ciamis > fosfat alam Christmas. Kelarutan P meningkat sampai minggu ke-8 dan selanjutnya menurun. Konsentrasi P larut akibat perlakuan pemberian fosfat alam atau SP-36 pada pengamatan 12 minggu setelah inkubasi berkisar 15,7-34,2 ppm P. Fosfat alam yang mempunyai reaktivitas tinggi memberikan kelarutan yang cukuptinggi dalam gambut, sehingga dapat digunakan sebagai sumber P pada tanah gambut.

Kata kunci : Gambut, Ameliorasi, Pemupukan P, Kelarutan P.
Makalah diterbitkan dalam Jurnal Tanah dan Iklim (Indonesian Soil and Climate Journal) Nomor 27, Desember 2008. Balai Besar Penelitian dan Pengembangan Sumberdaya Lahan Pertanian, Badan Penelitian dan Pengembangan Pertanian, Departemen Pertanian

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