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PENGELOLAAN EKOSISTEM SAWAH Diabstraksikan oleh: Soemarno, PSL-PPSUB 2013 KOMPENDIUM KAJIAN LINGKUNGAN DAN PEMBANGUNAN.

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Presentation on theme: "PENGELOLAAN EKOSISTEM SAWAH Diabstraksikan oleh: Soemarno, PSL-PPSUB 2013 KOMPENDIUM KAJIAN LINGKUNGAN DAN PEMBANGUNAN."— Presentation transcript:

1 PENGELOLAAN EKOSISTEM SAWAH Diabstraksikan oleh: Soemarno, PSL-PPSUB 2013 KOMPENDIUM KAJIAN LINGKUNGAN DAN PEMBANGUNAN

2 Kekeringan di Serang, Banten. Minggu, 5 Agustus :22 Beberapa petani membuat sumur bor di tengah sawah untuk menyelamatkan padi yang kekeringan di Kampung Astana, Ds Walikukun, Kec Carenang, Serang, Banten. Puluhan hektar sawah di lokasi itu terancam gagal panen akibat dilanda kekeringan sementara untuk membuat sumur bor tak semua petani mampu melakukannya karena harus mengeluarkan biaya tambahan. Diunduh dari: ….. 31/10/2012

3 Kekeringan Landa Pemalang, Lahan Sawah Jadi Retak-retak Sabtu, 21 Juli :57 WIB Diunduh dari: pemalang-lahan-sawah-jadi-retak-retak.html ….. 31/10/2012 Para petani tanaman padi di daerah Pantura (Pantai Utara), Jawa Tengah, kesulitan mendapatkan air irigasi di musim kemarau. Akibatnya, ribuan hektar tanaman padi di daerah Pemalang terancam gagal panen. Untuk menyelamatkan tanamannya, petani terpaksa harus membuat sumur bor yang disedot dengan mesin pompa air diesel. Kondisi ini menyebabkan biaya produksi meningkat. Bahkan, akibat kurangnya air irigasi ke sawah para petani, tanah sawah mengering dan retak-retak, membuat kondisi tanaman padi tidak maksimal. Jika tanah sawahnya tidak mendapatkan air, dikhawatirkan petani mengalami gagal panen.

4 Dampak kekeringan pada tanaman padi muda Irigasi Kering, Puluhan Hektar Sawah Kekeringan (Post date: 05/07/ :19 REPORTER: ab. EDITOR: mdika Lebak - Sedikitnya 30 hektar lahan persawan di desa Talaga Hiang, Kecamatan Cipanas, Kabupaten Lebak, kekeringan. Dinas Pertanian Kabupaten Lebak masih terus melakukan upaya mengairi sawah warga tersebut dengan cara melakukan penyedotan air di Leuwi Herang untuk disalurkan ke saluran irigasi Leuwi Dolog. Kepala Bidang Sarana Dinas Pertanian Lebak, Rahmat Yuniar didampingi Kabid Produksi, Yuntani, mengatakan, saat ini lahan tanam petani di Desa Talaga Hiang yang luasnya mencapai 30 HA dilanda kekeringan akibat kemarau, bahkan sarana irigasi yang ada di daerah setempat yaitu Irigasi Leuwi Dolog tidak jalan sehingga tidak dapat membantu memenuhi kebutuhan air yang dibutuhkan para petani desa setempat DIUNDUH DARI: puluhan-hektar-sawah-kekeringan ….. 31/10/2012http://mediabanten.com/content/irigasi-kering- puluhan-hektar-sawah-kekeringan

5 Hektare Sawah di Bekasi Terancam Kekeringan Posted by korantrans pada Agustus 22, 2009 Diunduh dari: sawah-di-bekasi-terancam-kekeringan/….. 31/10/2012. Trans, Bekasi : Akibat bencana alam yang menimpa bangunan bagi sadap (BKG/4) di daerah irigasi (DI) Kedung Gede, Desa Cipayung, Bekasi, maka seluas 5100 dari hektare lahan sawah di daerah itu akan terncam kekeringan. Apabila tidak diatasi segera maka sejumlah petani di daerah tersebut, atau yang berada di saluran Rengas Bandung tidak bisa menggarap sawahnya karena tidak tersedianya air. Menurut Kusmana, untuk mengantisipasi agar tidak terjadinya kekeringan, maka pihaknya bekerjasama dengan Perusahaan Jasa Tirta Jatiluhur akan membuat saluran pengelak (kisdam) dengan cara pemasangan cerucuk bambu dan karung pasir. Hal ini dalakukan untuk menaikan debit ar pada saluran. Sementara untuk penanganan jangka panjangnya harus dilaksanakan pembangunan baru yang biaya fisiknya saja diperkirakan antara Rp 1 sampai Rp 2 miliar. Masalah bencana alam di BKG/4 ini sudah dilaporkan ke pusat melalui Balai Pengelola Wilayah Sungai (BPWS) Citarum di Bandung. Selain itu pihak PPK Irigasi 1 sekarang sedang melakukan koordinasi dengan pihak kecamatan dan Pemkab Bekasi, terutama dalam masalah jika ada pembebasan lahan apabila adanya pembangunan saluran baru. “ Akibaat bencana alam itu, BKG/4 ini memang perlu segera diatasi dengan pembangunan baru. Namun sebagai orang lapangan, saya usulkan pembangunannya lebih baik dilaksanakan dalam dua tahap. Hal ini mengingat waktu yang sudah mepet ke akhir tahun anggaran,” (Kusmana).

6 SMJ Dampak kekeringan parah pada tanaman padi sawah

7 PENANAMAN PADI SISTEM LEGOWO Pola Tanam Pada areal beririgasi, lahan dapat ditanami padi 3 x setahun, tetapi pada sawah tadah hujan harus dilakukan pergiliran tanaman dengan palawija. Pergiliran tanaman ini juga dilakukan pada lahan beririgasi, biasanya setelah satu tahun menanam padi. Untuk meningkatkan produktivitas lahan, seringkali dilakukan tumpang sari dengan tanaman semusim lainnya, misalnya padi gogo dengan jagung atau padi gogo di antara ubi kayu dan kacang tanah. Pada pertanaman padi sawah, tanaman tumpang sari ditanam di pematang sawah, biasanya berupa kacang-kacangan.

8 SAWAH BER-TERAS-BANGKU Analysis of percolation and seepage through paddy bunds Han-Chen Huang, Chen-Wuing Liu, Shih-Kai Chen, Jui-Sheng Chen. Journal of Hydrology. Volume 284, Issues 1–4, 22 December 2003, Pages 13–25. Diunduh dari sumber: 29/10/2012 This study investigates percolation and seepage through the bunds of flat and terraced paddies. Field experiments were conducted in Hsin-Pu of Hsin-Chu County, Taiwan, to measure the soil water content of various types of bund. Measurements revealed that the soil was unsaturated along the sloped surface of the terrace. Experimental results also indicated that seepage face flow did not develop even after 2 days of heavy rainfall. A three-dimensional model, FEMWATER, was adopted to simulate percolation and lateral seepage under various bund conditions. In a flat paddy, the rate of percolation of bunds under which a plow sole was located, was 0.40 cm d −1, close to the average infiltration rate of a flooded paddy. The percolation of the bund without plow sole was 0.85 cm d −1, or double the average infiltration rate of a flooded paddy. Infiltration in the central area of a terraced paddy is mainly vertically downward, whereas flow near the bund is predominantly lateral. The paddy field near the bund has a high hydraulic gradient. The simulated infiltration flux into the bund (1.47 cm d −1 ) after 85 days of rice cultivation exceeded that into the central area (0.54 cm d −1 ) by a factor of The final percolation flux from the bund (1.24 cm d −1 ) also exceeded the final percolation from the plow sole (0.68 cm d −1 ) by a factor of The lateral seepage fluxes through the bund, downward and upward along the slope surface, are 2.01 and −2.12 cm d −1, respectively. However, the lateral seepage flux does not fully saturate the surface of the hillside soil. A simulation clearly shows that the seepage upstream of the paddy field does not move water downstream and is reused as subsurface return flow. Both experimental and simulation results clarify the mechanisms of water movement in the terraced paddy and reveal the existence of an unsaturated seepage face along the sloping surface of the terraced field.

9 SAWAH BER-TERAS-BANGKU Analysis of percolation and seepage through paddy bunds Han-Chen Huang, Chen-Wuing Liu, Shih-Kai Chen, Jui-Sheng Chen. Journal of Hydrology. Volume 284, Issues 1–4, 22 December 2003, Pages 13–25. Diunduh dari sumber: 29/10/2012 Two types of lateral seepage flow through bunds

10 SAWAH BER-TERAS-BANGKU Analysis of percolation and seepage through paddy bunds Han-Chen Huang, Chen-Wuing Liu, Shih-Kai Chen, Jui-Sheng Chen. Journal of Hydrology. Volume 284, Issues 1–4, 22 December 2003, Pages 13–25. Diunduh dari sumber: 29/10/2012 Schematic representation of a cross-sectional view of terraced rice field and the terminology used herein. Open arrows indicate soil water sampling locations and directions

11 SAWAH BER-TERAS-BANGKU Analysis of percolation and seepage through paddy bunds Han-Chen Huang, Chen-Wuing Liu, Shih-Kai Chen, Jui-Sheng Chen. Journal of Hydrology. Volume 284, Issues 1–4, 22 December 2003, Pages 13–25. Diunduh dari sumber: 29/10/2012 Cross-section in the vicinity of the bund of a typical flooded rice field

12 SAWAH BER-TERAS-BANGKU Analysis of percolation and seepage through paddy bunds Han-Chen Huang, Chen-Wuing Liu, Shih-Kai Chen, Jui-Sheng Chen. Journal of Hydrology. Volume 284, Issues 1–4, 22 December 2003, Pages 13–25. Diunduh dari sumber: 29/10/2012 Model of terraced rice paddy Darcy velocity flow field for lateral seepage in the terraced paddy (cm d −1 ).

13 Jaring-jaring Makanan dalam Ekosistem Sawah Trophic relationships in a rice ecosystem showing the importance of detritivores and non crop vegetation components. Source: The three planks for ecological engineering (Heong et al 2012) Diunduh dari sumber: field-edges.html …….. 28/10/2012

14 Ecological Sustainability of the Paddy Soil-Rice System in Asia Kazutake Kyuma Department of Environmental Science The University of Shiga Prefecture 2500 Hassaka-cho, Hikone City Japan 522, Nutrient Status of Paddy Soils General Redox Transformations under Waterlogged Conditions The most characteristic management practice in paddy rice cultivation is waterlogging, or submergence of the land surface. This brings about anaerobic conditions in the soil, due to the very slow diffusion rate of oxygen through water. Biologically, after the oxygen reserve in the soil is exhausted and aerobic microorganisms have all died, facultative anaerobes dominate for some time. As the anaerobioc conditions continue, these microorganisms are gradually replaced by obligate or strict anaerobes. The biological changes are accompanied by a very characteristic succession of chemical transformations of materials. Following the disappearance of molecular oxygen, nitrate is used as a substrate for denitrifiers. Manganic oxides are solubilized as a result of reduction to manganous ions, likewise orange yellow to reddish colored iron oxides are reduced to soluble ferrous ions, decolorizing the soil. Many fermentation reactions based on various organic substrates proceed along with these mineral transformations, producing carbon dioxide, ammoniacal nitrogen, low molecular weight organic acids, and so forth. As the soil becomes even more reductive, sulfate reducers, which are strict anaerobes, produce sulfides; and methanobacteria, also strict anaerobes, produce methane. Diunduh dari sumber: …….. 28/10/2012

15 Ecological Sustainability of the Paddy Soil-Rice System in Asia Kazutake Kyuma Department of Environmental Science The University of Shiga Prefecture 2500 Hassaka-cho, Hikone City Japan 522, All these biochemical changes occur vigorously for the first month after submergence, when readily decomposable organic matter, the energy source for microorganisms, is abundantly available. Past this stage, there will be a period when the supply of oxygen by diffusion, though extremely slow, exceeds its consumption at the soil/water interface. As all the oxygen is trapped by such reduced substances as ferrous and manganous ions at the interface, a thin oxidized, orange colored layer (normally a few millimeters thick) is differentiated from the underlying bulk of the strongly reduced, bluish-gray plow layer. Diunduh dari sumber: …….. 28/10/2012 Successive Chemical Transformations in Submerged Soils

16 Ecological Sustainability of the Paddy Soil-Rice System in Asia Kazutake Kyuma Department of Environmental Science The University of Shiga Prefecture 2500 Hassaka-cho, Hikone City Japan 522, Supply of Basic Cations through Irrigation Water At least 1000 to 1500 mm of water is used to irrigate paddy fields during one rice cropping season. Nutrients dissolved in water, particularly basic cations such as calcium, magnesium and potassium, as well as silica, are supplied to rice in the water. If we assume that 1000 mm of water is used for one crop of rice, 1 mg kg -1 or 1 ppm of a substance dissolved in water amounts to 10 kg/ha. According to the mean water quality of Japanese rivers, irrigation of 1000 mm of water brings to a paddy field 88 kg/ha of Ca, 19 kg/ha of Mg, 12 kg/ha of K, and 190 kg/ha of SiO 2. Usually more than 1000 mm of water is used for irrigation, so the amount of nutrients supplied to rice is larger. Diunduh dari sumber: …….. 28/10/2012 Water Quality of Japanese and Thai Rivers

17 Ecological Sustainability of the Paddy Soil-Rice System in Asia Kazutake Kyuma Department of Environmental Science The University of Shiga Prefecture 2500 Hassaka-cho, Hikone City Japan 522, Supply of Nitrogen through Biological Nitrogen Fixation There are paddy areas where rice has been cultivated for hundreds of years without receiving any fertilizer, but where yields are sustained at 1.5 to 2 mt/ha. It is estimated that about 20 kg of N is required to harvest 1 mt of paddy. Thus, it is difficult to explain how rice yields can be sustained for so long without any application of N. The greater part of N in paddy soils exists in soil organic matter. This tends to be conserved more in paddy soils than in upland soils, because of the anaerobic conditions. Microbial decomposition of the organic matter gradually releases ammoniacal N (NH 4 + -N). As NH N is stable under anaerobic conditions, it is retained as a cation on negatively charged soil mineral and organic particles, until the time when rice roots take it up. Thus, the leaching of NH 4 + -N from paddy fields into the environment is not significant. Besides soil organic matter, there is another important source of N, i.e. biological N fixation. In paddy soils there are many microbes that are capable of fixing atmospheric N, such as blue-green algae, Clostridia, photosynthetic bacteria, and many of the heterotrophic bacteria in the rice rhizosphere. Estimates of the amount of biologically fixed N per crop of rice vary quite widely, but 30 to 40 kg/ha would be a reasonable figure. This amount of N is two or three times higher than the amount of N fixed in ordinary upland soils planted in non-leguminous crops. Interestingly enough, this amount of fixed N can explain the average yields of paddy obtained in unfertilized fields in southeast Asia (1.5 to 2 mt/ha) on the basis of 20 kg of N for 1 mt of paddy. Diunduh dari sumber: …….. 28/10/2012

18 Ecological Sustainability of the Paddy Soil-Rice System in Asia Kazutake Kyuma Department of Environmental Science The University of Shiga Prefecture 2500 Hassaka-cho, Hikone City Japan 522, Paddy soils are equipped with an excellent N cycling mechanism, with an input through biological N fixation and an output through denitrification. This appears to set the basis for sustainability of rice cultivation as an efficient food production system. Schematic Diagram of Nitrogen Cycle in Paddy Soil Ecosystem Diunduh dari sumber: …….. 28/10/2012

19 Ecological Sustainability of the Paddy Soil-Rice System in Asia Kazutake Kyuma Department of Environmental Science The University of Shiga Prefecture 2500 Hassaka-cho, Hikone City Japan 522, Negative Aspects of Soil Reduction Rice is known to suffer some physiological disorders under strongly reduced conditions. The best known is a root rot, caused by hydrogen sulfide evolved in soils that are poor in readily reducible iron oxides. These soils are often derived from pale colored, sandy, granitic sediments. They are poor, not only in iron oxides, but also in some other plant nutrients such as Mg, K and SiO 2. It is now known that root rot due to hydrogen sulfide is an acute case of the more general "akiochi" phenomenon observed in these "degraded paddy soils", as characterized above. In Japan, a nationwide project was carried out during the post-war period to ameliorate degraded paddy soils by dressing the soil with Fe-rich, more juvenile materials. With the aid of a government subsidy, the project was successfully completed, so that "akiochi" is no longer seen in Japan. There are large areas of paddy fields in southeast Asian countries that are characterized by the very low inherent potentiality of the soil. In fact, some of these deserve the name of "degraded" paddy soils. However, because of the generally low levels of both fertilizer inputs and rice yields, at present they may not be clearly differentiated from "normal" soils. Diunduh dari sumber: …….. 28/10/2012

20 Ecological Sustainability of the Paddy Soil-Rice System in Asia Kazutake Kyuma Department of Environmental Science The University of Shiga Prefecture 2500 Hassaka-cho, Hikone City Japan 522, Advantages of Paddy Rice Cultivation Comparison of Paddy Soils and Upland Soils The high level of resistance of paddy soils to erosive forces is even more important, from the viewpoint of sustainability. Upland soils tend to be eroded away unless they are properly protected. This is particularly true in the tropics, where the erosivity of rainfall is very high, and where upland soils usually have poor resistance to erosion. Paddy soils are most resistant to erosion when they are terraced and there are ridges around the field, as measures to retain surface water. In addition, paddy fields in the lowlands receive new sediments deposited from run-off that carries eroded topsoil down from the uplands, thus perpetuating soil fertility and productivity. Paddy soils have other advantages. In upland farming, crop rotation is a necessity to avoid a decline in yield due to diseases and pests that arise from a monoculture situation (soil sickness). In paddy fields, on the other hand, rice can be grown year after year without any clear sign of yield decline, over a considerable length of time. The alternation from aerobic to anaerobic conditions in a yearly cycle of rice farming is the best measure to remove the causes of soil sickness. No pathogens or soil-borne animals can survive such a drastic change in the redox environment. Diunduh dari sumber: …….. 28/10/2012

21 Ecological Sustainability of the Paddy Soil-Rice System in Asia Kazutake Kyuma Department of Environmental Science The University of Shiga Prefecture 2500 Hassaka-cho, Hikone City Japan 522, Intensification of Paddy Rice Cultivation and the Environment Rice is the staple food for more than two billion people, most of whom live in developing countries where the population is still rapidly increasing. A study conducted by the International Rice Research Institute (IRRI 1989) reveals that to meet the projected growth in the demand for rice, the world's annual rough rice production must increase from 458 million mt in 1987 to 556 million mt by 2000 and to 758 million tons by This represents a 65% increase. For the leading rice-growing countries of south and southeast Asia, the same study indicates that the increase needed in rice production by 2020 is even higher, at about double the present level. The potential for expanding the area planted in rice seems to have become very restricted in south and southeast Asia. Most land resources have already been exploited to their fullest extent, and most of the readily manageable water resources also have been developed to irrigate paddy fields. Therefore, any further increase in the production of rice depends heavily on intensification in existing rice lands. Diunduh dari sumber: …….. 28/10/2012

22 Ecological Sustainability of the Paddy Soil-Rice System in Asia Kazutake Kyuma Department of Environmental Science The University of Shiga Prefecture 2500 Hassaka-cho, Hikone City Japan 522, Impact of Irrigation/Drainage and Chemical Inputs Intensifying rice cultivation could have various impacts on the environment. If good irrigation and drainage are provided, improved rice cultivars may be introduced, along with better management of fertilizer, weeds and pests. The construction of dams, and of irrigation and drainage canals, would normally bring more benefits than disadvantages to the regional environment, as long as they are properly planned and implemented. It improves water use efficiency, regulates floods and droughts, and, through these, improves the environmental quality. Increased use of chemical preparations, such as fertilizers, pesticides and herbicides, could be more hazardous. It is possible that they might pollute irrigation water and soil, and sometimes cause human health problems. This must, however, also be evaluated in comparison with the upland cultivation of other crops. Generally speaking, paddy rice cultivation could be less hazardous to the environment if it is intensified, with a high level of chemical inputs, than upland crop cultivation. Diunduh dari sumber: …….. 28/10/2012

23 Ecological Sustainability of the Paddy Soil-Rice System in Asia Kazutake Kyuma Department of Environmental Science The University of Shiga Prefecture 2500 Hassaka-cho, Hikone City Japan 522, Impact of Gas Emissions from Paddy Fields In relation to the global environment, air pollution from soil emissions is receiving more and more attention. The production of nitrous oxide (N 2 O) from N fertilizers and manures is now considered to have an environmental impact. The gas is evolved in both nitrification and denitrification processes. The former is considered more important at present. It affects the destruction of ozone to oxygen, and also acts as a greenhouse gas. However, N 2 O emissions from paddy fields are considered to be very low (De Datta and Buresh 1989). Paddy fields have been emitting methane since time immemorial. Therefore, the issue at the present time is the reason for the recent rapid increase in the atmospheric methane concentration of about 1% annually. Certainly, there was a large increase in the area planted in rice during the early postwar period, but if we take the most recent decade, 1980 to 1990, the world-wide annual rate of increase in rice area has been only 0.23% (IRRI 1993). Diunduh dari sumber: …….. 28/10/2012

24 .. Methane emission from a simulated rice field ecosystem as influenced by hydroquinone and dicyandiamide Xingkai Xu, Yuesi Wang, Xunhua Zheng, Mingxing Wang, Zijian Wang, Likai Zhou, Oswald Van Cleemput. Science of The Total Environment, Volume 263, Issues 1–3, 18 December 2000, Pages 243–253. A simple apparatus for collecting methane emission from a simulated rice field ecosystem was formed. With no wheat straw powder amended all treatments with inhibitor(s) had so much lower methane emission during rice growth than the treatment with urea alone (control), which was contrary to methane emission from the cut rice–soil system. Especially for treatments with dicyandiamide (DCD) and with DCD plus hydroquinone (HQ), the total amount of methane emission from the soil system and intact rice–soil system was 68.25–46.64% and 46.89–41.78% of the control, respectively. Hence, DCD, especially in combination with HQ, not only increased methane oxidation in the floodwater–soil interface following application of urea, but also significantly enhanced methane oxidation in rice root rhizosphere, particularly from its tillering to booting stage. Wheat straw powder incorporated into flooded surface layer soil significantly weakened the above-mentioned simulating effects. Regression analysis indicated that methane emission from the rice field ecosystem was related to the turnover of ammonium-N in flooded surface layer soil. Diminishing methane emissions from the rice field ecosystem was significantly beneficial to the growth of rice. Diunduh dari sumber: 28/10/2012

25 .. Methane emission from a simulated rice field ecosystem as influenced by hydroquinone and dicyandiamide Xingkai Xu, Yuesi Wang, Xunhua Zheng, Mingxing Wang, Zijian Wang, Likai Zhou, Oswald Van Cleemput. Science of The Total Environment, Volume 263, Issues 1–3, 18 December 2000, Pages 243–253. Relationship between CH 4 emission from rice field ecosystem amended with wheat straw and NH 4 + -N concentration in the floodwater (mg N l −1 ). Diunduh dari sumber: 28/10/2012

26 .. Methane emission from a simulated rice field ecosystem as influenced by hydroquinone and dicyandiamide Xingkai Xu, Yuesi Wang, Xunhua Zheng, Mingxing Wang, Zijian Wang, Likai Zhou, Oswald Van Cleemput. Science of The Total Environment, Volume 263, Issues 1–3, 18 December 2000, Pages 243–253. Relationship between CH 4 emission from rice field ecosystem without applying wheat straw and NH 4 + -N concentration in the floodwater. Diunduh dari sumber: 28/10/2012

27 SAWAH = WETLANDS Atmospheric methane (CH 4 ) is an important greenhouse gas. On a scale of 100 years, it is approximately 20 times more effective than carbon dioxide (CO 2 ). The total annual CH 4 emission both from natural and anthropogenic terrestrial sources to the atmosphere is about 580 Tg (CH 4 ) yr -1. The contribution of natural and man-made wetlands (e.g. rice paddy) to this global total varies between 20 and 40%. Thereby, natural wetlands are the major non-anthropogenic source of methane at present and rice agriculture accounts for some 17% of the anthropogenic CH 4 emissions. This is because of the prevailing anaerobic conditions in these ecosystems, their high organic matter contents and their global distribution. Northern wetlands (>30° N) for example constitute about 60% of the global wetland area and emit a quarter to a third of the total CH 4 originating from wet soils. Microbial turnover of methane and transport pathways of gases in wetlands. Diunduh dari sumber: …….. 28/10/2012

28 Valuating ecosystem services is crucial for making the importance of ecosystem functioning explicit to the public and decision makers as well as scientists. Investigations of the value of agricultural ecosystems have focused mainly on value food and fibre production and been carried out at relatively coarse scales. However, such studies may have underestimated services provided by agricultural ecosystems because they did not consider additional services such as gas regulation, pollination control, nutrient transformation, and landscape aesthetics. We present the results of a field experimental study of gas regulation services and their economic values provided by rice paddy ecosystems in suburban Shanghai, China. Two major components of gas regulation by paddy fields are O 2 emissions and greenhouse gases (GHGs) regulation (including the uptake of CO 2 and emissions of CH 4 and N 2 O). Seasonal emissions of O 2 from experimental plots with different urea application rates ranged from 25,365 to 32,612 kg ha −1 year −1, with an economic value of 9549–12,277 RMB ha −1 year −1 (Chinese currency; 1 euro = RMB, Jan 18, 2005). The net GHGs regulation ranged from 705 to 2656 kg CO 2 C ha −1 year −1, with an economic value ranging from 531 to 2000 RMB ha −1 year −1. Thus, the overall economic value of gas regulation provided by the rice paddy ecosystems ranged from 10,080 to 14,277 RMB ha −1 year −1. Our results refined, and in some cases, modified previous estimates of agricultural ecosystem services based mainly on coarse-scale studies. Our study also demonstrated a systematic method to valuate the gas regulation services provided by rice paddy ecosystems, which will be useful for understanding regulation of atmospheric chemistry and greenhouse effects by other agriculture ecosystems.. The value of gas exchange as a service by rice paddies in suburban Shanghai, PR China Yu Xiao, Gaodi Xie, Chunxia Lu, Xianzhong Ding, Yao Lu. Agriculture, Ecosystems & Environment. Volume 109, Issues 3–4, 1 September 2005, Pages 273–283 Diunduh dari sumber: 28/10/2012

29 . Illustration of the static chamber used to measure gas fluxes in the rice paddy fields.. The value of gas exchange as a service by rice paddies in suburban Shanghai, PR China Yu Xiao, Gaodi Xie, Chunxia Lu, Xianzhong Ding, Yao Lu. Agriculture, Ecosystems & Environment. Volume 109, Issues 3–4, 1 September 2005, Pages 273–283 Diunduh dari sumber: 28/10/2012

30 The estimated economic values of CO 2 uptake, CH 4 emission, N 2 O emission, and overall GHGs regulation from the rice paddy ecosystems during the growing season with different urea application rates in suburban Shanghai, China. The bars are the means of eight measurements ± S.D., each of which is the average of three reduplicate plots. Letters a, b, and c beside the same legend denote the significant difference in Duncan's multiple range test (at the 5% significant level) across four N treatments for CH 4 emissions, or N 2 O emissions, or CO 2 uptake or integrated CHGs regulation. The value of gas exchange as a service by rice paddies in suburban Shanghai, PR China Yu Xiao, Gaodi Xie, Chunxia Lu, Xianzhong Ding, Yao Lu. Agriculture, Ecosystems & Environment. Volume 109, Issues 3–4, 1 September 2005, Pages 273–283 Diunduh dari sumber: 28/10/2012

31 DINAMIKA NITROGEN EKOSISTEM SAWAH A coupled soil water and nitrogen balance model for flooded rice fields in India V.M. Chowdary, N.H. Rao, P.B.S. Sarma. Agriculture, Ecosystems & Environment. Volume 103, Issue 3, August 2004, Pages 425–441. Diunduh dari sumber: …….. 29/10/2012 In the present study a simple model for assessing concentration of nitrate in water percolating out of the flooded rice (Oryza Sativa) fields is presented. The model considers all the important nitrogen (N) transformation processes that take place in flooded rice fields such as urea hydrolysis, volatilization, nitrification, mineralization, immobilization, denitrification, crop uptake and leaching. It is based on coupling of soil water and N-balance models. The coupled model also accounts for weather, and timings and amounts of water and fertilizer applications. All the N-transformations except plant uptake and leaching are considered to follow first-order kinetics. The simulation results show that urea hydrolysis is completed within 7 days of fertilizer application. It was also observed that the volatilization loss of N varies from 25 to 33% of the applied fertilizer and 75% of the total volatilization loss occurs within 7 days of urea application. The modeled leaching losses from the field experiments varied from 20 to 30% of the applied N. The N-uptake by the crop increased immediately after the application of fertilizer and decreased at 60 days after transplanting. The model is sufficiently general to be used in a wide range of conditions for quantification of nutrient losses by leaching and developing water and fertilizer management strategies for rice in irrigated areas.

32 DINAMIKA NITROGEN EKOSISTEM SAWAH A coupled soil water and nitrogen balance model for flooded rice fields in India V.M. Chowdary, N.H. Rao, P.B.S. Sarma. Agriculture, Ecosystems & Environment. Volume 103, Issue 3, August 2004, Pages 425–441. Diunduh dari sumber: …….. 29/10/2012. Schematic representation of the N-transformations in flooded rice field.

33 DINAMIKA NITROGEN EKOSISTEM SAWAH A coupled soil water and nitrogen balance model for flooded rice fields in India V.M. Chowdary, N.H. Rao, P.B.S. Sarma. Agriculture, Ecosystems & Environment. Volume 103, Issue 3, August 2004, Pages 425–441. Diunduh dari sumber: …….. 29/10/2012. Zoning of ideal paddy field for N-balance studies.

34 DINAMIKA NITROGEN EKOSISTEM SAWAH A coupled soil water and nitrogen balance model for flooded rice fields in India V.M. Chowdary, N.H. Rao, P.B.S. Sarma. Agriculture, Ecosystems & Environment. Volume 103, Issue 3, August 2004, Pages 425–441. Diunduh dari sumber: …….. 29/10/2012 Schematic representation of nitrogen balance model.

35 DINAMIKA NITROGEN EKOSISTEM SAWAH A coupled soil water and nitrogen balance model for flooded rice fields in India V.M. Chowdary, N.H. Rao, P.B.S. Sarma. Agriculture, Ecosystems & Environment. Volume 103, Issue 3, August 2004, Pages 425–441. Diunduh dari sumber: …….. 29/10/2012 Nitrogen uptake in rice at Pantnagar, Uttar Pradesh, India. (a) Basal application (80 kg N ha −1 ) and (b) split application ( kg N ha −1 ).

36 AIR DAN PADI SAWAH Rice and Water B.A.M. Bouman, E. Humphreys, T.P. Tuong, R. Barker. Advances in Agronomy. Volume 92, 2007, Pages 187–237. Diunduh dari sumber: …….. 29/10/2012. Rice environments also provide unique—but as yet poorly understood— ecosystem services such as the regulation of water and the preservation of aquatic and terrestrial biodiversity. Rice production under flooded conditions is highly sustainable. In comparison with other field crops, flooded rice fields produce more of the greenhouse gas methane but less nitrous oxide, have no to very little nitrate pollution of the groundwater, and use relatively little to no herbicides. Flooded rice can locally raise groundwater tables with subsequent risk of salinization if the groundwater carries salts, but is also an effective restoration crop to leach accumulated salts from the soil in combination with drainage. Water scarcity is expected to shift rice production to more water ‐ abundant delta areas, and to lead to crop diversification and more aerobic (nonflooded) soil conditions in rice fields in water ‐ short areas. In these latter areas, investments should target the adoption of water ‐ saving technologies, the reuse of drainage and percolation water, and the improvement of irrigation supply systems. A suite of water ‐ saving technologies can help farmers reduce percolation, drainage, and evaporation losses from their fields by 15–20% without a yield decline. However, greater understanding of the adverse effects of increasingly aerobic field conditions on the sustainability of rice production, environment, and ecosystem services is needed. In drought ‐, salinity ‐, and flood ‐ prone environments, the combination of improved varieties with specific management packages has the potential to increase on ‐ farm yields by 50– 100% in the coming 10 years, provided that investment in research and extension is intensified.

37 AIR DAN PADI SAWAH Rice and Water B.A.M. Bouman, E. Humphreys, T.P. Tuong, R. Barker. Advances in Agronomy. Volume 92, 2007, Pages 187–237. Diunduh dari sumber: …….. 29/10/2012. Water balance of a lowland (paddy) rice field. C, capillary rise; E, evaporation; I, irrigation; O, overbund flow; P, percolation; R, rainfall; S, seepage; T, transpiration.

38 AIR DAN PADI SAWAH Rice and Water B.A.M. Bouman, E. Humphreys, T.P. Tuong, R. Barker. Advances in Agronomy. Volume 92, 2007, Pages 187–237. Diunduh dari sumber: …….. 29/10/2012. Emissions of CH 4 (A) and N 2 O (B), and combined global warming potential (C) of rice fields under continuous flooding (control), under plastic film with unsaturated soil underneath, and under straw mulch with aerobic soil conditions underneath, at three sites in China. Source: Dittert et al. (2002).Dittert et al. (2002)

39 AIR DAN PADI SAWAH Rice and Water B.A.M. Bouman, E. Humphreys, T.P. Tuong, R. Barker. Advances in Agronomy. Volume 92, 2007, Pages 187–237. Diunduh dari sumber: …….. 29/10/2012 Surface and subsurface water flows across lowland rice fields. D, drainage (overbund flow); I, irrigation; P, percolation; S, seepage.

40 HEMAT AIR PADI SAWAH. On-farm strategies for reducing water input in irrigated rice; case studies in the Philippines D.F. Tabbal, B.A.M. Bouman, S.I. Bhuiyan, E.B. Sibayan, M.A. Sattar. Agricultural Water Management. Volume 56, Issue 2, 30 July 2002, Pages 93–112. Diunduh dari sumber: …….. 29/10/2012 This paper reports results of on-farm experiments in the Philippines to reduce water input by water-saving irrigation techniques and alternative crop establishment methods, such as wet and dry seeding. With continuous standing water, direct wet-seeded rice yielded higher than traditional transplanted rice by 3–17%, required 19% less water during the crop growth period and increased water productivity by 25–48%. Direct dry-seeded rice yielded the same as transplanted and wet-seeded rice, but can make more effective use of early season rainfall in the wet season and save irrigation water for the subsequent dry season. Direct seeding can further reduce water input by shortening the land preparation period. In transplanted and wet-seeded rice, keeping the soil continuously around saturation reduced yields on average by 5% and water inputs by 35% and increased water productivity by 45% compared with flooded conditions. Intermittent irrigation further reduced water inputs but at the expense of increased yield loss. Under water-saving irrigation, wet-seeded rice out-yielded transplanted rice by 6–36% and was a suitable establishment method to save water and retain high yields. Groundwater depth greatly affected water use and the possibilities of saving water. With shallow groundwater tables of 10–20 cm depth, irrigation water requirements and potential water savings were low but yield reductions were relatively small. The introduction of water-saving technologies at the field level can have implications for the hydrology and water use at larger spatial scale levels.

41 HEMAT AIR PADI SAWAH. On-farm strategies for reducing water input in irrigated rice; case studies in the Philippines D.F. Tabbal, B.A.M. Bouman, S.I. Bhuiyan, E.B. Sibayan, M.A. Sattar. Agricultural Water Management. Volume 56, Issue 2, 30 July 2002, Pages 93–112. Diunduh dari sumber: …….. 29/10/2012. Schematic presentation of rice growth under four establishment systems: transplanting with seedbed in main field (A), transplanting with separate seedbed (B), direct wet seeding (C) and direct dry seeding (D).

42 HEMAT AIR PADI SAWAH. On-farm strategies for reducing water input in irrigated rice; case studies in the Philippines D.F. Tabbal, B.A.M. Bouman, S.I. Bhuiyan, E.B. Sibayan, M.A. Sattar. Agricultural Water Management. Volume 56, Issue 2, 30 July 2002, Pages 93–112. Diunduh dari sumber: …….. 29/10/2012 Components of the water balance of a flooded, puddled rice field.

43 HEMAT AIR PADI SAWAH. On-farm strategies for reducing water input in irrigated rice; case studies in the Philippines D.F. Tabbal, B.A.M. Bouman, S.I. Bhuiyan, E.B. Sibayan, M.A. Sattar. Agricultural Water Management. Volume 56, Issue 2, 30 July 2002, Pages 93–112. Diunduh dari sumber: …….. 29/10/2012 Graphical presentation of the water-saving irrigation treatments of experiment 1.

44 NERACA AIR SAWAH TADAH-HUJAN Water balance simulation model for optimal sizing of on-farm reservoir in rainfed farming system Dipankar Roy, Sudhindra N. Panda, B. Panigrahi. Computers and Electronics in Agriculture. Volume 65, Issue 1, January 2009, Pages 114–124. Diunduh dari sumber: 29/10/2012. The on-farm reservoir (OFR) is used to harvest the surplus water from the diked crop field and recycle the stored water as supplemental irrigation to rice in monsoon (rainy) and non-rice (dry) crops in winter season under rainfed farming system. A user-friendly software, using Visual Basic 6.0 program, is developed to find out the optimal size of the OFR in terms of percentage of field area (here in called as OFR sizes throughout the manuscript) by simulating the water balance model parameters of the crop field and the OFR. The software is meant for all the concerned including the engineers, planners and farming community for any monsoon influenced cropping area, which uses rainfed agriculture. The menu driven system is flexible enough to simulate the OFR sizes for various combinations of the OFR geometry, field sizes, and the cropping systems. The user has to specify the crops to be grown in the fields, irrigation management practices of the crops, types of OFR (lined or unlined), side slope, depth of OFR, and field sizes. Evapotranspiration sub-model is embedded with the main model to compute the ET from the meteorological data. As model application, the developed model is used to simulate the OFR sizes for the rice–mustard and rice–groundnut cropping systems using the experimental observed and meteorological data of the study area located at Indian Institute of Technology, Kharagpur in eastern India. The water balance model parameters of the crop field are validated with 2 years of observed data from the experimental field of above mentioned study area. The study reveals that rice–groundnut cropping system requires higher OFR sizes than rice–mustard cropping systems. Moreover, it is observed that as the field areas increase, the OFR sizes for each cropping systems is found to decrease.

45 NERACA AIR SAWAH TADAH-HUJAN Water balance simulation model for optimal sizing of on-farm reservoir in rainfed farming system Dipankar Roy, Sudhindra N. Panda, B. Panigrahi. Computers and Electronics in Agriculture. Volume 65, Issue 1, January 2009, Pages 114–124. Diunduh dari sumber: 29/10/2012 Schematic presentation of water balance parameters of the rice field and the OFR with their respective control volumes.

46 NERACA AIR SAWAH TADAH-HUJAN Water balance simulation model for optimal sizing of on-farm reservoir in rainfed farming system Dipankar Roy, Sudhindra N. Panda, B. Panigrahi. Computers and Electronics in Agriculture. Volume 65, Issue 1, January 2009, Pages 114–124. Diunduh dari sumber: 29/10/2012 Flow chart for computation of OFR size.

47 NERACA AIR SAWAH TADAH-HUJAN Water balance simulation model for optimal sizing of on-farm reservoir in rainfed farming system Dipankar Roy, Sudhindra N. Panda, B. Panigrahi. Computers and Electronics in Agriculture. Volume 65, Issue 1, January 2009, Pages 114–124. Diunduh dari sumber: 29/10/2012 Variation of actual evapotranspiration, AET in rice field.

48 NERACA AIR SAWAH TADAH-HUJAN Water balance simulation model for optimal sizing of on-farm reservoir in rainfed farming system Dipankar Roy, Sudhindra N. Panda, B. Panigrahi. Computers and Electronics in Agriculture. Volume 65, Issue 1, January 2009, Pages 114–124. Diunduh dari sumber: 29/10/2012 Variation of deep percolation in rice field.

49 KEHILANGAN AIR DARI SAWAH. Causes of high water losses from irrigated rice fields: field measurements and results from analogue and digital models S.H. Walker. Agricultural Water Management. Volume 40, Issue 1, 1 March 1999, Pages 123–127. Diunduh dari sumber: 29/10/2012 In places where rice is grown in paddy fields with permanent bunds, considerable quantities of water are lost through lateral seepage of water into the bund and from there vertically to the groundwater. Lateral percolation losses increase with increases in field water depth, bund width, aquifer thickness and depth to groundwater. These losses do not occur in systems where the bunds are reformed every year. The paper discusses the areas of research required to quantify the magnitude of these `losses' at a scheme level and suggests management interventions to improve the efficiency of water use.

50 KEHILANGAN AIR DARI SAWAH. Causes of high water losses from irrigated rice fields: field measurements and results from analogue and digital models S.H. Walker. Agricultural Water Management. Volume 40, Issue 1, 1 March 1999, Pages 123–127. Diunduh dari sumber: 29/10/2012 Hypothesis: lateral percolation into and down through the bunds greatly exceeds vertical percolation through the impermeable bed of the rice fields.

51 KEHILANGAN AIR DARI SAWAH. Causes of high water losses from irrigated rice fields: field measurements and results from analogue and digital models S.H. Walker. Agricultural Water Management. Volume 40, Issue 1, 1 March 1999, Pages 123–127. Diunduh dari sumber: 29/10/2012 Field observations verify inflow to the bund from both the adjacent fields.

52 KEHILANGAN AIR DARI SAWAH. Causes of high water losses from irrigated rice fields: field measurements and results from analogue and digital models S.H. Walker. Agricultural Water Management. Volume 40, Issue 1, 1 March 1999, Pages 123–127. Diunduh dari sumber: 29/10/2012 Analogue model result for flows in vertical section.

53 CO2 & PANAS PADA EKOSISTEM SAWAH. CO 2 /heat fluxes in rice fields: Comparative assessment of flooded and non-flooded fields in the Philippines Ma. Carmelita R. Alberto, Reiner Wassmann, Takashi Hirano, Akira Miyata, Arvind Kumar, Agnes Padre, Modesto Amante. Agricultural and Forest Meteorology. Volume 149, Issue 10, 1 October 2009, Pages 1737–1750. Diunduh dari sumber: 29/10/2012 The seasonal fluxes of heat, moisture and CO 2 were investigated under two different rice environments: flooded and aerobic soil conditions, using the eddy covariance technique during 2008 dry season. This study was intended to monitor the environmental impact, in terms of C budget and heat exchange, of shifting from lowland rice production to aerobic rice cultivation as an alternative to maintain crop productivity under water scarcity. The aerobic rice fields had higher sensible heat flux (H) and lower latent heat flux (LE) compared to flooded fields. On seasonal average, aerobic rice fields had 48% more sensible heat flux while flooded rice fields had 20% more latent heat flux. Consequently, the aerobic rice fields had significantly higher Bowen ratio (0.25) than flooded fields (0.14), indicating that a larger proportion of the available net radiation was used for sensible heat transfer or for warming the surrounding air. The total C budget integrated over the cropping period showed that the net ecosystem exchange (NEE) in flooded rice fields was about three times higher than in aerobic fields while gross primary production (GPP) and ecosystem respiration (R e ) were 1.5 and 1.2 times higher, respectively. The high GPP of flooded rice ecosystem was evident because the photosynthetic capacity of lowland rice is naturally large. The R e of flooded rice fields was also relatively high because it was enhanced by the high photosynthetic activities of lowland rice as manifested by larger above-ground plant biomass. The NEE, GPP, and R e values for flooded rice fields were −258, 778, and 521 g C m −2, respectively. For aerobic rice fields, values were −85, 515, and 430 g C m −2 for NEE, GPP, and R e, respectively. The ratio of R e /GPP in flooded fields was 0.67 while it was 0.83 for aerobic rice fields.

54 CO2 & PANAS PADA EKOSISTEM SAWAH. CO 2 /heat fluxes in rice fields: Comparative assessment of flooded and non-flooded fields in the Philippines Ma. Carmelita R. Alberto, Reiner Wassmann, Takashi Hirano, Akira Miyata, Arvind Kumar, Agnes Padre, Modesto Amante. Agricultural and Forest Meteorology. Volume 149, Issue 10, 1 October 2009, Pages 1737–1750. Diunduh dari sumber: 29/10/2012 Solar radiation (SR), rainfall, and ambient temperature during the 2008 dry season from 11 January to 15 May.

55 CO2 & PANAS PADA EKOSISTEM SAWAH. CO 2 /heat fluxes in rice fields: Comparative assessment of flooded and non-flooded fields in the Philippines Ma. Carmelita R. Alberto, Reiner Wassmann, Takashi Hirano, Akira Miyata, Arvind Kumar, Agnes Padre, Modesto Amante. Agricultural and Forest Meteorology. Volume 149, Issue 10, 1 October 2009, Pages 1737–1750. Diunduh dari sumber: 29/10/2012. Mean diurnal variations of air temperature, T air, in the rice canopy (0.75 m above the soil) during 2008 dry season. Student's t-test was applied to compare the difference in the average daily means of flooded and aerobic rice fields. Values were averaged over the growth stage. (DAT—Days after Transplanting; DAS—Days after Sowing).

56 CO2 & PANAS PADA EKOSISTEM SAWAH. CO 2 /heat fluxes in rice fields: Comparative assessment of flooded and non-flooded fields in the Philippines Ma. Carmelita R. Alberto, Reiner Wassmann, Takashi Hirano, Akira Miyata, Arvind Kumar, Agnes Padre, Modesto Amante. Agricultural and Forest Meteorology. Volume 149, Issue 10, 1 October 2009, Pages 1737–1750. Diunduh dari sumber: 29/10/2012 Mean diurnal variations of soil temperature, T soil, in the rice canopy (0.75 m above the soil) during 2008 dry season. Student's t-test was applied to compare the difference in the average daily means of flooded and aerobic rice fields. Values were averaged over the growth stage. (DAT—Days after Transplanting; DAS—Days after Sowing).

57 CO2 & PANAS PADA EKOSISTEM SAWAH. CO 2 /heat fluxes in rice fields: Comparative assessment of flooded and non-flooded fields in the Philippines Ma. Carmelita R. Alberto, Reiner Wassmann, Takashi Hirano, Akira Miyata, Arvind Kumar, Agnes Padre, Modesto Amante. Agricultural and Forest Meteorology. Volume 149, Issue 10, 1 October 2009, Pages 1737–1750. Diunduh dari sumber: 29/10/2012 Mean diurnal variations of vapor pressure deficit, VPD, in the rice canopy (0.75 m above the soil) during 2008 dry season. Student's t-test was applied to compare the difference in the average daily means of flooded and aerobic rice fields. Values were averaged over the growth stage. (DAT—Days after Transplanting; DAS—Days after Sowing).

58 CO2 & PANAS PADA EKOSISTEM SAWAH. CO 2 /heat fluxes in rice fields: Comparative assessment of flooded and non-flooded fields in the Philippines Ma. Carmelita R. Alberto, Reiner Wassmann, Takashi Hirano, Akira Miyata, Arvind Kumar, Agnes Padre, Modesto Amante. Agricultural and Forest Meteorology. Volume 149, Issue 10, 1 October 2009, Pages 1737–1750. Diunduh dari sumber: 29/10/2012 Mean diurnal variations of half-hourly net ecosystem CO 2 exchange, NEE, during 2008 dry season. Student's t-test was applied to compare the difference in the average daily means of flooded and aerobic rice fields. Values were averaged over the growth stage. (DAT—Days after Transplanting; DAS—Days after Sowing).

59 CO2 & PANAS PADA EKOSISTEM SAWAH. CO 2 /heat fluxes in rice fields: Comparative assessment of flooded and non-flooded fields in the Philippines Ma. Carmelita R. Alberto, Reiner Wassmann, Takashi Hirano, Akira Miyata, Arvind Kumar, Agnes Padre, Modesto Amante. Agricultural and Forest Meteorology. Volume 149, Issue 10, 1 October 2009, Pages 1737–1750. Diunduh dari sumber: 29/10/2012 Relationship between daily sum of ecosystem respiration (R e ) and soil water potential (SWP) at 15 cm soil depth in aerobic rice fields during 2008 dry season. Daily R e was grouped into 24 bins and averaged with equal number of data points per bin. Vertical bars denote standard error. Triangles denote values during vegetative to panicle initiation stage; squares denote values during reproductive to ripening stage; circles denote values during harvest stage.

60 CO2 & PANAS PADA EKOSISTEM SAWAH. CO 2 /heat fluxes in rice fields: Comparative assessment of flooded and non-flooded fields in the Philippines Ma. Carmelita R. Alberto, Reiner Wassmann, Takashi Hirano, Akira Miyata, Arvind Kumar, Agnes Padre, Modesto Amante. Agricultural and Forest Meteorology. Volume 149, Issue 10, 1 October 2009, Pages 1737–1750. Diunduh dari sumber: 29/10/2012 Relationship between daily sum of gross primary production (GPP) and soil water potential (SWP) at 15 cm soil depth in aerobic rice fields during 2008 dry season. Daily GPP was grouped into 24 bins and averaged with equal number of data points per bin. Vertical bars denote standard error. Triangles denote values during vegetative to panicle initiation stage; squares denote values during reproductive to ripening stage; circles denote values during harvest stage.

61 CO2 & PANAS PADA EKOSISTEM SAWAH. CO 2 /heat fluxes in rice fields: Comparative assessment of flooded and non-flooded fields in the Philippines Ma. Carmelita R. Alberto, Reiner Wassmann, Takashi Hirano, Akira Miyata, Arvind Kumar, Agnes Padre, Modesto Amante. Agricultural and Forest Meteorology. Volume 149, Issue 10, 1 October 2009, Pages 1737–1750. Diunduh dari sumber: 29/10/2012 Relationship between net ecosystem CO 2 exchange (NEE) at photosynthetic active radiation (PAR) larger than 1000 μmol m −2 s −1 and vapor pressure deficit (VPD) in (a) aerobic fields when soil water potential (SWP) at 15 cm depth was <−100 kPa and (b) flooded rice fields during 2008 dry season. Half-hourly data were sorted by VPD and bin averaged with equal number of data per bin. Vertical bars denote standard error.

62 CO2 & PANAS PADA EKOSISTEM SAWAH. CO 2 /heat fluxes in rice fields: Comparative assessment of flooded and non-flooded fields in the Philippines Ma. Carmelita R. Alberto, Reiner Wassmann, Takashi Hirano, Akira Miyata, Arvind Kumar, Agnes Padre, Modesto Amante. Agricultural and Forest Meteorology. Volume 149, Issue 10, 1 October 2009, Pages 1737–1750. Diunduh dari sumber: 29/10/2012 Seasonal variations in daily NEE, R e, and GPP in flooded rice fields during the 2008 dry season from 21 January to 12 May. The vertical bars show the different growth stages of the flooded rice (vegetative, tillering to panicle initiation, reproductive, heading to flowering, ripening, and harvest). The shading of the horizontal bar denotes flooded (black), saturated (grey) and dry soil conditions (white).

63 CO2 & PANAS PADA EKOSISTEM SAWAH. CO 2 /heat fluxes in rice fields: Comparative assessment of flooded and non-flooded fields in the Philippines Ma. Carmelita R. Alberto, Reiner Wassmann, Takashi Hirano, Akira Miyata, Arvind Kumar, Agnes Padre, Modesto Amante. Agricultural and Forest Meteorology. Volume 149, Issue 10, 1 October 2009, Pages 1737–1750. Diunduh dari sumber: 29/10/2012 Seasonal variations in daily (a) NEE, R e, and GPP and (b) soil water potential (SWP) at 5 cm and 15 cm soil depths of aerobic rice fields during 2008 dry season from 21 January to 12 May. The vertical bars show the different growth stages of the aerobic rice (vegetative, tillering to panicle initiation, reproductive, heading to flowering, ripening, and harvest).

64 JASA-JASA EKOSISTEM SAWAH. Ecosystem services by paddy fields as substitutes of natural wetlands in Japan Yosihiro Natuhara Ecological Engineering. Available online 22 May Diunduh dari sumber: …….. 29/10/2012 Ecosystem services provided by paddy fields include; groundwater recharge, production of non-rice foods, flood control, soil erosion and landslide prevention, climate-change mitigation, water purification, culture and landscape, and support of ecosystems and biodiversity. Among these services, the value of services that regulate ecosystem functions was estimated to be US$ 72.8 billion in Japan. More than 5000 species have been recorded in paddy fields and the surrounding environment. Because paddy fields are artificially disturbed by water level management, plowing, and harvest, most species move between paddy fields and the surrounding environment. The linkage between paddy fields and the associated environment plays an important role in biodiversity. Two changes that have affected the ecosystem of paddy fields are modernization and abandonment of farming. Satoyama, a traditional socio- ecological production landscape, which provided a functional linkage between paddy fields and the associated environment has lost its functions. Biodiversity-conscious rice farming has been promoted by collaborations among farmers, consumers and governments. Biodiversity certification programs are successful examples of biodiversity-conscious framing. In these programs incentives include direct payments and/or premium prices paid by consumers, as well as farmers willingness to improve the safety of food and environment.

65 JASA-JASA EKOSISTEM SAWAH. Ecosystem services by paddy fields as substitutes of natural wetlands in Japan Yosihiro Natuhara Ecological Engineering. Available online 22 May Diunduh dari sumber: …….. 29/10/2012 Landscape of paddy fields and movement of species.

66 JASA-JASA EKOSISTEM SAWAH. Ecosystem services by paddy fields as substitutes of natural wetlands in Japan Yosihiro Natuhara Ecological Engineering. Available online 22 May Diunduh dari sumber: …….. 29/10/2012 Water management of paddy field and life cycle of species. Timing of flooding and drainage affects survival of aquatic species. O. albistylum is a multivoltine.

67 JASA-JASA EKOSISTEM SAWAH. Ecosystem services by paddy fields as substitutes of natural wetlands in Japan Yosihiro Natuhara Ecological Engineering. Available online 22 May Diunduh dari sumber: …….. 29/10/2012 Land consolidation and drainage improvement. Conversion to fields equipped with deeper ditches for rapid draining has almost eliminated wet winter paddy fields. The gap between paddy and drainage ditch prevents fish from migrating to the paddy.

68 JASA-JASA EKOSISTEM SAWAH. Ecosystem services by paddy fields as substitutes of natural wetlands in Japan Yosihiro Natuhara Ecological Engineering. Available online 22 May Diunduh dari sumber: …….. 29/10/2012 Impacts of changes in paddy field on fish. (Modified from Katano, 2000). Katano, 2000

69 JASA-JASA EKOSISTEM SAWAH. Ecosystem services by paddy fields as substitutes of natural wetlands in Japan Yosihiro Natuhara Ecological Engineering. Available online 22 May Diunduh dari sumber: …….. 29/10/2012 This irrigation and drainage ditch is designed for living things. Fish and tadpoles can survive in non-irrigation season.

70 NERACA KARBON EKOSISTEM SAWAH. Rice paddy fields are also one of the typical agricultural ecosystems in Monsoon Asia. Among them, single rice cropping paddies that dominates in northeastern Asia are characterized by two contrasting periods, a flooded growing period and dry fallowed period which lasts two thirds of a year. From the analyses using stable isotopes of water and carbon, the largest carbon input was CO 2 fixation by photosynthesis of rice, where 64-65% of the fixed carbon was harvested in autumn. Inflow and outflow of dissolved carbon accounted for 5-9% of the total input and output Diunduh dari sumber: …….. 29/10/2012

71 Management-induced organic carbon accumulation in paddy soils: The role of organo-mineral associations Livia Wissing, Angelika Kölbl, Werner Häusler, Peter Schad, Zhi-Hong Cao, Ingrid Kögel- Knabner. Soil and Tillage Research. Volume 126, January 2013, Pages 60–71. Iron (Fe) oxides strongly interact with organic matter in soil and play an important role in the stabilization of organic matter. These processes are often influenced by soil cultivation, including tillage, crop rotation and irrigation. We assessed the effect of Fe oxides on organic carbon (OC) accumulation during the development of soils used for paddy rice production in comparison to non-irrigated cropping systems. Soil samples were taken from two chronosequences derived from uniform parent material in the Zhejiang Province (PR China). Bulk soils and soil fractions were analyzed for OC concentrations, soil mineralogy and soil organic matter (SOM) composition was determined by solid-state 13 C NMR spectroscopy. Paddy soils were characterized by increasing OC concentrations, from 18 mg g −1 to 30 mg g −1, during 2000 years of rice cultivation, but OC concentrations of non-paddy soils were low in all age classes (11 mg g −1 ). SOM composition revealed from Solid- state 13 C NMR spectroscopy did not change during pedogenesis in either chronosequence. Selective enrichment of lignin-derived compounds, caused by long- term paddy rice management, could not be confirmed by the present study. The management of paddy soils creates an environment of Fe oxide formation which was different to those in non-paddy soils. Paddy soils are dominated by poorly crystalline Fe oxides (Fe o ) and significantly lower content of crystalline Fe oxides (Fe d − Fe o ). This was in contrast to non-paddy soils, which are characterized by high proportions of crystalline Fe oxides. The paddy-specific Fe oxide composition was effective after only 50 years of soil development and the proportion Fe oxides did not alter during further pedogenesis. This chronosequence study revealed that the potential for OC accumulation was higher in paddy versus non-paddy soils and was already reached at earliest stages of paddy soil development. Changes in paddy soil management associated with redox cycle changes will not only affect Fe oxide composition of paddy soils but most probably also OC storage potential. Diunduh dari sumber: …….. 31/10/2012

72 Management-induced organic carbon accumulation in paddy soils: The role of organo-mineral associations Livia Wissing, Angelika Kölbl, Werner Häusler, Peter Schad, Zhi-Hong Cao, Ingrid Kögel- Knabner. Soil and Tillage Research. Volume 126, January 2013, Pages 60–71. Relation between oxalate (Fe o ) extractable iron (Fe) oxides and the organic carbon (OC) concentrations of the paddy (P) and non-paddy (NP) soil fractions (20–6.3 μm = medium silt; 6.3–2 μm = fine silt; 2–0.2 μm = coarse clay; <0.2 μm = fine clay) with standard errors. Diunduh dari sumber: …….. 31/10/2012

73 PLoS One. 2012; 7(5): e Published online 2012 May 4. Effects of Tillage and Nitrogen Fertilizers on CH 4 and CO 2 Emissions and Soil Organic Carbon in Paddy Fields of Central China Li Cheng-Fang, Zhou Dan-Na, Kou Zhi-Kui, Zhang Zhi-Sheng, Wang Jin-Ping, Cai Ming-Li, and Cao Cou-Gui. Quantifying carbon (C) sequestration in paddy soils is necessary to help better understand the effect of agricultural practices on the C cycle. The objective of the present study was to assess the effects of tillage practices [conventional tillage (CT) and no-tillage (NT)] and the application of nitrogen (N) fertilizer (0 and 210 kg N ha −1 ) on fluxes of CH 4 and CO 2, and soil organic C (SOC) sequestration during the 2009 and 2010 rice growing seasons in central China. Application of N fertilizer significantly increased CH 4 emissions by 13%– 66% and SOC by 21%–94% irrespective of soil sampling depths, but had no effect on CO 2 emissions in either year. Tillage significantly affected CH 4 and CO 2 emissions, where NT significantly decreased CH 4 emissions by 10%– 36% but increased CO 2 emissions by 22%–40% in both years. The effects of tillage on the SOC varied with the depth of soil sampling. NT significantly increased the SOC by 7%–48% in the 0–5 cm layer compared with CT. However, there was no significant difference in the SOC between NT and CT across the entire 0–20 cm layer. Hence, our results suggest that the potential of SOC sequestration in NT paddy fields may be overestimated in central China if only surface soil samples are considered. Diunduh dari sumber: 31/10/2012

74 PLoS One. 2012; 7(5): e Published online 2012 May 4. Effects of Tillage and Nitrogen Fertilizers on CH 4 and CO 2 Emissions and Soil Organic Carbon in Paddy Fields of Central China Li Cheng-Fang, Zhou Dan-Na, Kou Zhi-Kui, Zhang Zhi-Sheng, Wang Jin-Ping, Cai Ming-Li, and Cao Cou-Gui. The entire process of CH 4 emission from rice fields, including production, oxidation, and transport into the atmosphere is influenced by agricultural management practices, such as tillage and N fertilizer use [1]–[3].[1][3] Tillage affects a range of biological, chemical, and physical properties, thereby affecting the release of CH 4 [4]. No-tillage (NT) has been reported to reduce CH 4 emissions from paddy soils because rice straw is placed on the soil surface under NT and the soil conditions are more oxidative than those of conventional tillage (CT) [3], [5].[4][3][5] CH 4 emissions from paddy fields are reportedly affected by the form and amount of N fertilizer applied [6].[6] 1.Chu H, Hosen Y, Yagi K. NO, N 2 O, CH 4 and CO 2 fluxes in winter barley field of Japanese Andisol as affected by N fertilizer management. Soil Biol Biochem. 2007;39:330– Guo J, Zhou C. Greenhouse gas emissions and mitigation measures in Chinese agroecosystems. Agric Forest Meteorol. 2007;142:270– Harada H, Kobayashi H, Shindo H. Reduction in greenhouse gas emissions by no-tilling rice cultivation in Hachirogata polder, northern Japan: life-cycle inventory analysis. Soil Sci Plant Nutr. 2007;53:668– Oorts K, Merckx R, Gréhan E, Labreuche J, Nicolardot B. Determinants of annual fluxes of CO 2 and N 2 O in long–term no–tillage and conventional tillage systems in northern France. Soil Till Res. 2007;95:133– Liang W, Shi Y, Zhang H, Yue J, Huang GH. Greenhouse gas emissions from northeast China rice fields in fallow season. Pedosphere. 2007;17(5):630– Minami K. The effect of nitrogen fertilizer use and other practices on methane emission from flooded rice. Fertil Res. 1995;40:71–84. Diunduh dari sumber: 31/10/2012

75 PLoS One. 2012; 7(5): e Published online 2012 May 4. Effects of Tillage and Nitrogen Fertilizers on CH 4 and CO 2 Emissions and Soil Organic Carbon in Paddy Fields of Central China Li Cheng-Fang, Zhou Dan-Na, Kou Zhi-Kui, Zhang Zhi-Sheng, Wang Jin-Ping, Cai Ming-Li, and Cao Cou-Gui. Tillage practices can affect soil biochemical and physical properties, consequently influencing the release of CO 2 [8]. However, there is no consensus on the differences in the soil CO 2 emissions between NT- and CT- treated paddy fields. Some authors have reported similar soil CO 2 fluxes from NT- and CT-treated paddy fields [7]. However, Liang et al. [9] reported higher soil CO 2 emissions from CT-treated paddy fields than from the NT paddy fields. Nitrogen supplied by commercial fertilizers can be expected to affect soil CO 2 flux by increasing the C input from enhanced plant productivity and crop residues returned to the soil [11]. However, studies on the effects of N fertilizer on soil CO 2 emissions reveal diverse results [12]. Within the past few years, Iqbal et al. [13] and Xiao et al. [14] observed increased CO 2 emissions from paddy soils because of a positive effect of N fertilization on plant biomass.[8][7][9][11][12][13][14] 1.[7]. Harada H, Kobayashi H, Shindo H. Reduction in greenhouse gas emissions by no-tilling rice cultivation in Hachirogata polder, northern Japan: life-cycle inventory analysis. Soil Sci Plant Nutr. 2007;53:668– [8]. Oorts K, Merckx R, Gréhan E, Labreuche J, Nicolardot B. Determinants of annual fluxes of CO 2 and N 2 O in long–term no–tillage and conventional tillage systems in northern France. Soil Till Res. 2007;95:133– [9]. Liang W, Shi Y, Zhang H, Yue J, Huang GH. Greenhouse gas emissions from northeast China rice fields in fallow season. Pedosphere. 2007;17(5):630– [11]. Paustian K, Collins HP, Paul EA. Management controls on soil carbon. In: Paul EA, Paustian K, Elliot ET, Cole CV (Eds.) Soil Organic Matter in Temperate Agroecosystems - Long-term Experiments in North America, CRC Press, Boca Raton, FL, 1997;15–49 5.[12]. Lee DK, Doolittle JJ, Owens VN. Soil carbon dioxide fluxes in established switch grass land managed for biomass production. Soil Biol Biochem. 2007;39:178– [13]. Iqbal J, Hu RG, Lin S, Hatano R, Feng ML, et al. CO 2 emission in a subtropical red paddy soil (Ultisol) as affected by straw and N fertilizer applications: a case study in Southern China. Agric Ecosyst Environ. 2009;131:292– [14]. Xiao Y, Xie G, Lu G, Ding X, Lu Y. The value of gas exchange as a service by rice paddies in suburban Shanghai, PR China. Agric Ecosyst Environ. 2005;109:273–283. Diunduh dari sumber: 31/10/2012

76 PLoS One. 2012; 7(5): e Published online 2012 May 4. Effects of Tillage and Nitrogen Fertilizers on CH 4 and CO 2 Emissions and Soil Organic Carbon in Paddy Fields of Central China Li Cheng-Fang, Zhou Dan-Na, Kou Zhi-Kui, Zhang Zhi-Sheng, Wang Jin-Ping, Cai Ming-Li, and Cao Cou-Gui. Land management practices are increasingly thought to affect soil carbon levels and may partially ameliorate CO 2 emissions and climate change [17], [18]. Studies have indicated that NT can increase C sequestration in paddy soils compared with CT [19]– [21]. In 2007, Tang et al. [20] indicated that the NT could sequester kg C ha −1 yr −1 in the top 20 cm of purple paddy soil in the Beipei district of Chongqing City, China. In a 12-year study, Gao et al. [21] reported that NT could sequester kg C ha −1 yr −1 in gray fluvoaguic paddy soils to a depth of 30 cm in Zhangjiagang City, Jiangsu Province, China.[17][18][19] [21][20][21] However, Six et al. [22] and Su [23] indicated that the effects of NT on SOC sequestration depend on the soil type. In a 5-year study, He et al. [24] indicated that NT did not increase the SOC sequestration of paddy fields in the 20 cm layer of sandy silty loam in Ningxiang country, Hunan Province.[22][23][24] 1.[17]. Lal R. Soil carbon sequestration impacts on global climate change and food security. Science. 2004;304:1623–1627. [PubMed]PubMed 2.[18]. DeLuca TH, Zabinski CA. Prairie ecosystems and the carbon problem. Front Ecol Environ. 2011;9:407– [19]. Lu F, Wang XK, Han B, Ouyang ZY, Duan XN, et al. Soil carbon sequestrations by nitrogen fertilizer application, straw return and no-tillage in China’s cropland. Global Change Biol. 2009;15:281– [20]. Tang XH, Shao JA, Gao M, Wei CF, Xie DT, et al. Chin J Appl Ecol 18: 1027–1032. (in Chinese); Effects of conservational tillage on aggregate composition and organic carbon storage in purple paddy soil. 5.[21]. Gao YJ, Zhu PL, Huang DM, Wang ZM. Soil Environ Sci 9: 27–30. (in Chinese); Long-term impact of different soil management on organic matter and total nitrogen in rice- based cropping system. 6.[22]. Six J, Feller C, Denef K, Ogle SM, Moraes Sa JC, et al. Soil organic matter, biota and aggregation in temperate and tropical soils – effects of no-tillage. Agronomie. 2002;22:755– [23]. Su YZ. Soil carbon and nitrogen sequestration following the conversion of cropland to alfalfa forage land in northwest China. Soil Till Res. 2007;92:181– [24]. He YY, Zhang HL, Sun GF, Tang WG, Li Y, et al. J Agro-Environ Sci 29(1): 200–204. (in Chinese); Effect of different tillage on soil organic carbon and the organic carbon storage in two-crop paddy field. Diunduh dari sumber: 31/10/2012

77 PLoS One. 2012; 7(5): e Published online 2012 May 4. Effects of Tillage and Nitrogen Fertilizers on CH 4 and CO 2 Emissions and Soil Organic Carbon in Paddy Fields of Central China Li Cheng-Fang, Zhou Dan-Na, Kou Zhi-Kui, Zhang Zhi-Sheng, Wang Jin-Ping, Cai Ming-Li, and Cao Cou-Gui. Changes in CH 4 emission fluxes from paddy fields under different management practices during the 2009 and 2010 rice growing seasons. Diunduh dari sumber: 31/10/2012 The pattern of seasonal CH 4 emission fluxes was similar across NT and CT treatments during the 2009 and 2010 rice growing seasons. In both years, the CH 4 emission fluxes in the four treatment groups were all initially low, increased gradually, and then peaked in mid-July (about 4–5 weeks after sowing). Thereafter, the CH 4 emission fluxes declined gradually and remained relatively low until harvesting when the CH 4 emission fluxes were lowest.

78 PLoS One. 2012; 7(5): e Published online 2012 May 4. Effects of Tillage and Nitrogen Fertilizers on CH 4 and CO 2 Emissions and Soil Organic Carbon in Paddy Fields of Central China Li Cheng-Fang, Zhou Dan-Na, Kou Zhi-Kui, Zhang Zhi-Sheng, Wang Jin-Ping, Cai Ming-Li, and Cao Cou-Gui. Changes in CO 2 emission fluxes from paddy fields under different management practices during the 2009 and 2010 rice growing seasons. Diunduh dari sumber: 31/10/2012 Tillage treatments exhibited clear seasonal variations in soil CO 2 fluxes in the 2009 and 2010 rice growing seasons. The soil CO 2 fluxes remained relatively low for the first two weeks after tillage, increased rapidly, stayed relatively high until about the middle 10 days of July, and then decreased to relatively low levels. Just one day after tillage (June 9, 2009 and June 13, 2010), the soil CO 2 fluxes from CT were 1.40–4.60 times higher than those from NT (P<0.05).

79 PLoS One. 2012; 7(5): e Published online 2012 May 4. Effects of Tillage and Nitrogen Fertilizers on CH 4 and CO 2 Emissions and Soil Organic Carbon in Paddy Fields of Central China Li Cheng-Fang, Zhou Dan-Na, Kou Zhi-Kui, Zhang Zhi-Sheng, Wang Jin-Ping, Cai Ming-Li, and Cao Cou-Gui. CH 4 Emission Application of N fertilizer in the present study increased CH 4 emissions from paddy fields because of the promotion of rice growth, providing additional C sources and emission pathways [32]. Lindau and Bollich [33], in a study on a Louisiana rice field, which also had a humid subtropical climate, reported similar results from silt loam soil. However, Wassmann et al. [34] and Lu et al. [35] indicated no significant effect of N fertilizer application on CH 4 emissions from paddy fields in Zhejiang Province, China. Schütz et al. [36] found that the application of urea significantly decreased CH 4 emissions from paddy fields in Italy. Results varied among studies because of the differences in soil texture or climate. These findings show that further study is needed to understand the functioning of these complex and dynamic systems.[32][33][34][35][36] The decrease in CH 4 emissions under NT may be attributed to the differences regarding the size and activity of the methanotrophic community between tillage treatments [37]. Tillage also affects gaseous diffusivity and the rate of supply of atmospheric CH 4 [38]. By contrast, NT improves macroporosity and maintains its continuity [39]. The improvement probably allows greater air diffusion, increasing CH 4 uptake and decreasing CH 4 emissions.[37][38][39] 1.[32]. Neue HU, Roger PA. Rice agriculture: factors controlling emissions. In: Khalil MAK (ed.), Atmospheric Methane. Its Role in the Global Environment, 2000;134–169 2.[33]. Lindau CW, Bollich PK. Methane emissions from Louisiana first and Ratoon crop rice. Soil Sci. 1993;156:42–48. 3.[34]. Wassmann R, Schüetz H, Papen H, Rennenberg H, Seiler W, et al. Quantification of methane emissions from Chinese rice fields (Zhejiang Province) influenced by fertilizer treatment. Biogeochemistry. 1993;20:83– [35]. Lu WF, Chen W, Duan WM, Lu Y, Lantin RS, et al. Methane emission and mitigation options in irrigated rice fields in southeast China. Nutr Cy Agroecosyst. 2000;58:65–73. 5.[36]. Schütz H, Holzapfel-Pschorn A, Conrad R, Rennenberg H, Seiler W. A 3–year continuous record on the influence of daytime, season and fertilizer treatment on methane emission rate from an Italian rice paddy. J Geophys Res. 1989;94:16406– [37]. Ussiri DAN, Lal R, Jarecki MK. Nitrous oxide and methane emissions from long–term tillage under a continuous corn cropping system in Ohio. Soil Till Res. 2009;104:247– [38]. Hütsch BW. Tillage and land use effects on methane oxidation rates and their vertical profiles in soil. Biol Fertil Soils. 1998;27:284– [39]. Ball BC, Scott A, Parker JP. Field N 2 O, CO 2 and CH 4 fluxes in relation to tillage, compaction and soil quality in Scotland. Soil Till Res. 1999;53:29–39. Diunduh dari sumber: 31/10/2012

80 PLoS One. 2012; 7(5): e Published online 2012 May 4. Effects of Tillage and Nitrogen Fertilizers on CH 4 and CO 2 Emissions and Soil Organic Carbon in Paddy Fields of Central China Li Cheng-Fang, Zhou Dan-Na, Kou Zhi-Kui, Zhang Zhi-Sheng, Wang Jin-Ping, Cai Ming-Li, and Cao Cou-Gui. CO 2 Emissions Application of N fertilizer increases plant biomass production, stimulating soil biological activity, and consequently, CO 2 emission [40]. Wilson and Al- Kaisi [41], as well as Iqbal et al. [13], observed increased CO 2 emissions caused by N fertilizer application. By contrast, Burton et al. [15] and DeForest et al. [16] indicated that reduced extracellular enzyme activities and fungal populations resulting from N fertilizer application resulted in decreased soil CO 2 emissions. We observed no significant effect of N fertilizer application on cumulative CO 2 emissions, consistent with the results reported by Almaraz et al. [42]. This finding may be due to the fact that CO 2 is reduced to CH 4 under anaerobic conditions, thus leading to significant differences in CH 4 emissions rather than in CO 2 emissions between fertilized and unfertilized treatment areas.[40][41][13][15][16][42] 1.[13]. Iqbal J, Hu RG, Lin S, Hatano R, Feng ML, et al. CO 2 emission in a subtropical red paddy soil (Ultisol) as affected by straw and N fertilizer applications: a case study in Southern China. Agric Ecosyst Environ. 2009;131:292– [14]. Xiao Y, Xie G, Lu G, Ding X, Lu Y. The value of gas exchange as a service by rice paddies in suburban Shanghai, PR China. Agric Ecosyst Environ. 2005;109:273– [15]. Burton AJ, Pregitzer KS, Crawford JN, Zogg GP, Zak DR. Simulated chronic NO 3 - deposition reduces soil respiration in Northern hardwood forests. Global Change Biol. 2004;10:1080– [16]. DeForest JL, Zak DR, Pregitzer KS, Burton AJ. Atmospheric nitrate deposition, microbial community composition, and enzyme activity in Northern hardwood forests. Soil Sci Soc Am J. 2004;68:132– [40]. Dick RP. A review: long term effects of agricultural systems on soil biochemical and microbial parameters. Agric Ecosyst Environ. 1992;40:25–36. 6.[41]. Wilson HM, Al-Kaisi MM. Crop rotation and nitrogen fertilization effect on soil CO 2 emissions in central Iowa. Appl Soil Ecol. 2008;39:264– [42]. Almaraz JJ, Zhou XM, Mabood F, Madramootoo C, Rochette P, et al. Greenhouse gas fluxes associated with soybean production under two tillage systems in southwestern Quebec. Soil Till Res. 2009;104:134–139. Diunduh dari sumber: 31/10/2012

81 Arsenic as a Food Chain Contaminant: Mechanisms of Plant Uptake and Metabolism and Mitigation Strategies Annual Review of Plant Biology. Vol. 61: (Volume publication date June 2010) Fang-Jie Zhao, Steve P. McGrath, and Andrew A. Meharg Rice is efficient at As accumulation owing to flooded paddy cultivation that leads to arsenite mobilization, and the inadvertent yet efficient uptake of arsenite through the silicon transport pathway. Diunduh dari sumber: ?journalCode=arplant …….. 31/10/2012


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