BAHAN KAJIAN MK. STELA FPUB APRIL 2014. AGROEKOSISTEM SAWAH Diunduh dari sumber:

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1 BAHAN KAJIAN MK. STELA FPUB APRIL 2014

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3 AGROEKOSISTEM SAWAH Diunduh dari sumber: http://www.agr.nagoya-u.ac.jp/~soil/Soil_Biology_and_Chemistry-e/Researches.html …….. 28/10/2012

4 AGROEKOSISTEM SAWAH Paddy field ecosystem is composed of surface water, plowed soil layer and subsoil, and the plowed soil layer is divided into two layers; thin oxidized soil layer and reduced soil layer. These soil layers are connected by percolating water. In addition, rice roots are developed and plant residues such as rice straw and stubble after rice harvest are incorporated into the plowed soil layer. These microsites are different habitats for microorganisms, and unique microbial communities inhabit depending on the microsites. Diunduh dari sumber: http://www.agr.nagoya-u.ac.jp/~soil/Soil_Biology_and_Chemistry-e/Researches.html …….. 28/10/2012

5 SAWAH Sawah adalah lahan usaha pertanian yang secara fisik permukaan BIDANG OLAHNYA rata, dibatasi oleh pematang, serta dapat ditanami padi, palawija atau tanaman budidaya lainnya.paditanaman budidaya Biasanya sawah digunakan untuk bercocok tanam padi. Untuk keperluan ini, sawah harus mampu menyangga genangan air karena padi memerlukan penggenangan pada periode tertentu dalam pertumbuhannya. Untuk mengairi sawah digunakan sistem irigasi dari mata air, sungai atau air hujan.padiirigasimata airsungai hujan Sawah yang airnya berasal dari hujan dikenal sebagai sawah tadah hujan, sementara yang lainnya adalah sawah irigasi. Padi yang ditanam di sawah dikenal sebagai padi lahan basah (lowland rice).

6 EKOSISTEM SWAH Dalam usaha budidaya padi harus diketahui faktor-faktor yang mempengaruhi pertumbuhan tanaman secara ekologi, baik faktor biotik dan abiotik di lingkungan tumbuh tanaman tersebut. Pertanaman padi sawah adalah monokultur, selain itu terdapat beberapa flora dan fauna di sekitar pertanaman yang akan mempengaruhi pertumbuhan tanaman padi. Organisme yang ada di sekitar tanaman padi adalah mikrofauna dalam tanah, mesofauna, makrofauna dan vegetasi (gulma) yang ada di sekitar persawahan.

7 Kesesuaian Lahan untuk Padi sawah Untuk penilaian kesesuaian lahan tanaman padi sawah ini digunakan modifikasi dari sistem Steele dan Robinson (1972). Pada sistem ini aslinya dikenal lima kelas : 1.P-I: Lahan sangat sesuai untuk tanaman padi sawah (Setara dengan S1) 2.P-II: Lahan cukup sesuai untuk tanaman padi sawah (Setara dengan S2) 3.P-III: Lahan hampir sesuai untuk tanaman padi sawah (Setara dengan S3) 4.P-IV: Lahan kurang sesuai untuk tanaman padi sawah (Setara dengan N1) 5.P-V: Lahan tidak sesuai untuk tanaman padi sawah (Setara dengan N2)

8 Kesesuaian Lahan Sawah pada tingkat kelas (1). Kelas S1 : Lahan sangat sesuai untuk tanaman padi sawah. Pada umumnya lahan ini sedikit sekali pembatasnya dengan sifat-sifat : Kedalaman efektif tanah 75 cm, teksturnya lebih halus dari berlempung halus (fine loamy), permeabilitas lambat, hampir datar dan drainase agak terhambat hingga terhambat. Tingkat kesuburan tanah sangat tinggi atau sedang dan tidak mempunyai atau mengandung kadar garam atau bahan-bahan beracun dalam jumlah yang membahayakan. Air mudah ditahan pada tanah-tanah ini dengan alat pengontrol air yang biasa dipakai. Air irigasi cukup, paling tidak untuk satu kali tanam selama setahun tanpa adanya resiko kerusakan oleh kekeringan atau banjir. 21

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10 (2).Kelas S2: Lahan cukup sesuai untuk tanaman padi sawah Pembatas adalah kecil dan termasuk satu atau lebih dari faktor pembatas : 1.Kedalaman efektif 50-75 cm 2.Sebaran besar butir berliat, berlempung halus atau berdebu halus 3.Permeabilitas 0.5 - 2.0 cm/jam 4.Tingkat kesuburan tanah rendah 5.Salinitas 1500-2500 mmhos/cm 6. pH tanah sedikit membatasi produksi (pH pada lapisan 0-30 cm adalah 4.5-5.0 atau 7.5-8.0) 7.Kemiringan 1-3% 8.Sedikit berkerikil yang menghambat pertumbuhan tanaman 9.Kadang-kadang ada sedikit kekurangan air 10.Kadang-kadang ada kerusakan sedang yang disebabkan oleh banjir/genangan Air pada lahan ini dapat ditahan di tempat tanpa kesulitan. Air irigasi cukup tersdia untuk satu kali tanam dalam setahun. Dapat mengalami sedikit /sebentar menderita kekurangan air tanah tetapi produksi tidak begitu banyak berpengaruh oleh adanya kekeringan. Kadar hara dapat menjadi faktor pembatas akan tetapi biasanya masih dapat diatasi dengan pemupukan.

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12 (3).Kelas S3: Lahan hampir sesuai untuk tanaman padi sawah. Lahan ini mempunyai satu atau lebih dari pembataspembatas berikut: 1.Kedalaman efektif 25-50 cm 2.Permeabilitas 2.0 - 6.5 cm/jam 3.Tingkat kemasaman yang ekstrim (pH lapisan 0.30 cm adalah 4.0-4.5) 4.Sebaran besar butir (tekstur) berdebu kasar dan berlem­pung kasar 5.Lereng 3-5% 6.50-80% wilayah rata tanpa mikro relief 7.Sedikit berkerikil dan berbatu 8.Resiko ”SEDANG” dalam periode < 4 tahun, dalam 10 tahun yang disebabkan oleh sedikit kekurangan air 9.Drainase sangat terhambat atau sedang 10. ”Sedang” (tapi sering) kerusakan oleh banjir/genangan sewaktu-waktu kerusakan dapat menjadi hebat. Perlengkapan dan fasilitas pengendali air mungkin diperlukan untuk menahan air. Air irigasi cukup tersedia untuk satu kali tanam pada kebanyakan tahun, tetapi periode kering dapat menyebabkan kerusakan sedang pada tanah yang mempunyai kapasitas memegang air rendah. Dalam beberapa hal pemupukan diperlukan untuk mempertinggi hasil tanaman.

13 (4).Kelas N1: Lahan tidak sesuai pada saat ini. Lahan mempunyai pembatas satu atau lebih dari faktor-faktor berikut ini: 1.Kedalaman efektif 10-25 cm 2.Sebaran besar butir (tekstur) berskeletal 3.Permeabilitas 6.5-25 cm/jam 4.Kesuburan tanah sangat rendah 5.Reaksi tanah pada kedalaman 0-30 cm adalah 3.5-4.0 atau 8.0-8.5 6.Salinitas 2500-4000 mmhos/cm 7.Kemiringan 5-8% 8.Relief mikro: 40-50% pada wilayah datar 9.Adanya resiko yang serius disebabkan oleh adanya keku­rangan air 10.Drainase cepat 11.Banjir/genangan sering terjadi dan mem-bahayakan

14 (5).Kelas N2: Lahan tidak sesuai untuk tanaman padi sawah Lahan mempunyai banyak pembatas yang sukar diatasi, sehingga membuatnya tidak sesuai untuk tanaman padi sawah. Pembatasnya termasuk lereng terjal, dan keadaan topografi yang tidak memungkinkan untuk mengumpulkan atau menahan air, kedalaman efektif dangkal sekali dan sangat berbatu, teksturnya berpasir dan berskeletal, permeabilitas sangat cepat, salinitas tinggi dan bahay banjir/genangan yang sangat membahayakan. Kebanyakan lahan-lahan dari kelas ini pada daerah tinggi atau bergunung. Lahan ini mungkin sesuai untuk padangrumput atau hutan.

15 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 93–112Volume 56, Issue 2 Traditional transplanted rice with continuous standing water in Asia has relatively high water inputs. Because of increasing water scarcity, there is a need to develop alternative systems that require less water. 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. Diunduh dari sumber: http://www.sciencedirect.com/science/article/pii/S0378377402000070 …….. 13/1/2013http://www.sciencedirect.com/science/article/pii/S0378377402000070

16 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 93–112Volume 56, Issue 2 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. Diunduh dari sumber: http://www.sciencedirect.com/science/article/pii/S0378377402000070 …….. 13/1/2013http://www.sciencedirect.com/science/article/pii/S0378377402000070

17 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 93–112Volume 56, Issue 2 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). Diunduh dari sumber: http://www.sciencedirect.com/science/article/pii/S0378377402000070 …….. 13/1/2013http://www.sciencedirect.com/science/article/pii/S0378377402000070

18 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 93–112Volume 56, Issue 2 Components of the water balance of a flooded, puddled rice field. Diunduh dari sumber: http://www.sciencedirect.com/science/article/pii/S0378377402000070 …….. 13/1/2013http://www.sciencedirect.com/science/article/pii/S0378377402000070

19 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 93–112Volume 56, Issue 2 Graphical presentation of the water-saving irrigation treatments of experiment 1 Diunduh dari sumber: http://www.sciencedirect.com/science/article/pii/S0378377402000070 …….. 13/1/2013http://www.sciencedirect.com/science/article/pii/S0378377402000070

20 . 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 425–441Volume 103, Issue 3 Quantification of nitrate losses is important for devising measures to ensure sustainability of soil fertility and groundwater resources and for the development of crop nutrient management protocols. Hence, 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. A heuristic procedure is developed for selection of the rate constants of the transformation processes for different soil and environmental conditions. Diunduh dari sumber:.. http://www.sciencedirect.com/science/article/pii/S016788090300433X.…….. 13/1/2013

21 . 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 425–441Volume 103, Issue 3 The model is evaluated by comparing simulation results with published data of three field experiments conducted at two locations namely G.B. Pant University Farm, Pantnagar, UP and IARI Research Farm, New Delhi of India, respectively. 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. Diunduh dari sumber:.. http://www.sciencedirect.com/science/article/pii/S016788090300433X.…….. 13/1/2013

22 . 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 425–441Volume 103, Issue 3 Schematic representation of the N-transformations in flooded rice field. Diunduh dari sumber:.. http://www.sciencedirect.com/science/article/pii/S016788090300433X.…….. 13/1/2013

23 . 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 425–441Volume 103, Issue 3 Zoning of ideal paddy field for N-balance studies. Diunduh dari sumber:.. http://www.sciencedirect.com/science/article/pii/S016788090300433X.…….. 13/1/2013

24 . 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 425–441Volume 103, Issue 3 Nitrogen uptake in rice at Pantnagar, Uttar Pradesh, India. (a) Basal application (80 kg N ha −1 ) and (b) split application (40+20+20 kg N ha −1 ). Diunduh dari sumber:.. http://www.sciencedirect.com/science/article/pii/S016788090300433X.…….. 13/1/2013

25 Nutrient Management for Improving Lowland Rice Productivity and Sustainability N.K Fageria, N.A Slaton, V.C Baligar Advances in Agronomy. Volume 80, 2003, Pages 63–152Volume 80 Rice (Oryza sativa L.) is an important food crop for a large proportion of the world's population. Total rice production will need to increase to feed an increasing world population. Rice is produced under both upland and lowland ecosystems with about 76% of the global rice produced from irrigated-lowland rice systems. The anaerobic soil environment created by flood-irrigation of lowland rice creates a unique and challenging environment for the efficient management of soil and fertilizer nutrients. Supplying essential nutrients in adequate rates, sources, application methods, and application times are important factors that influence the productivity and sustainability of rice. This review emphasizes our current, research-based knowledge of N, P, K, Ca, Mg, S, B, Fe, Mn, and Zn management in regards to the efficiency and sustainability of lowland rice production and identifies where additional research is needed to bridge information gaps. Our goal is to provide a comprehensive review describing the nutritional problems, nutrient use efficiencies, and the production strategies used for efficient nutrient use and production of lowland rice. While the soils, climatic environments, cultivars, and degree of mechanization may vary considerably among the rice producing regions of the world, the basic principles governing efficient nutrient use by flood-irrigated rice are relatively constant. A summation of best management practices should help scientists develop practical, integrated recommendations that improve nutrient use efficiency in lowland rice production systems. Diunduh dari sumber:.. http://www.sciencedirect.com/science/article/pii/S0065211303800032.…….. 13/1/2013

26 Nutrient Management for Improving Lowland Rice Productivity and Sustainability N.K Fageria, N.A Slaton, V.C Baligar Advances in Agronomy. Volume 80, 2003, Pages 63–152Volume 80 An illustration of the various N chemical forms, transformations and behavior in the flooded soil environment in which rice is grown. Nitrogen sources are in blocks, N chemical forms are in circles and the mechanisms responsible for the various N transformations or behavior are located on the arrowed lines. (R. J. Norman, C. E. Wilson, Jr. and N. A. Slaton). Diunduh dari sumber:.. http://www.sciencedirect.com/science/article/pii/S0065211303800032.…….. 13/1/2013

27 Nutrient Management for Improving Lowland Rice Productivity and Sustainability N.K Fageria, N.A Slaton, V.C Baligar Advances in Agronomy. Volume 80, 2003, Pages 63–152Volume 80 Influence of N fertilizer rate on panicle length, panicle number per square meter, spikelet sterility, and 1000-grain weight of lowand rice. Values are the average of 3 years of field experimentation. (Reproduced with permission from Fageria, N. K. and Baligar, V. C. 2001. Lowland rice response to nitrogen fertilization. Commun. Soil Sci. Plant Anal. 32: 1405–1429. (Copyright Marcel Dekker, New York).). Diunduh dari sumber:.. http://www.sciencedirect.com/science/article/pii/S0065211303800032.…….. 13/1/2013

28 Nutrient Management for Improving Lowland Rice Productivity and Sustainability N.K Fageria, N.A Slaton, V.C Baligar Advances in Agronomy. Volume 80, 2003, Pages 63–152Volume 80. Response of flooded lowland rice to N fertilizer rate on a Brazilian Inceptisol. (Reproduced with permission from Fageria, N. K. and Baligar, V. C. 2001. Lowland rice response to nitrogen fertilization. Commun. Soil Sci. Plant Anal. 32: 1405–1429. (Copyright Marcel Dekker, New York).). Diunduh dari sumber:.. http://www.sciencedirect.com/science/article/pii/S0065211303800032.…….. 13/1/2013

29 Nutrient Management for Improving Lowland Rice Productivity and Sustainability N.K Fageria, N.A Slaton, V.C Baligar Advances in Agronomy. Volume 80, 2003, Pages 63–152Volume 80 Phosphorus concentration in rice plant shoots at different growth stages in Brazil and Arkansas, USA. Diunduh dari sumber:.. http://www.sciencedirect.com/science/article/pii/S0065211303800032.…….. 13/1/2013

30 PENGELOLAAN AIR PADA TANAH SAWAH Produksi padi sawah akan menurun jika tanaman padi menderita cekaman air (water stress). Gejala umum akibat kekurangan air antara lain daun padi menggulung, daun terbakar (leaf scorching), anakan padi berkurang, tanaman kerdil, pembungaan tertunda, dan biji hampa. Tanaman padi membutuhkan air yang volumenya berbeda untuk setiap fase pertumbuhannya. Variasi kebutuhan air tergantung juga pada varietas padi dan sistem pengelolaan lahan sawah. Pengaturan air untuk sistem mina-padi berbeda dengan sistem sawah tanpa ikan. Pengelolaan air di lahan sawah tidak hanya menyangkut sistem irigasi, tetapi juga sistem drainase pada saat tertentu dibutuhkan, baik untuk mengurangi kuantitas air maupun untuk mengganti air yang lama dengan air irigasi baru sehingga memberikan peluang terjadinya sirkulasi oksigen dan hara.

31 SAWAH IRIGASI Di Indonesia, sawah sering dikategorikan menjadi tiga yaitu (a)sawah beririgasi; (b)sawah tadah hujan; dan (c)sawah rawa (lebak dan pasang surut). Sistem pengelolaan air pada ketiga macam sawah tersebut sangat berbeda, karena perbedaan kondisi hidrologi dan kebutuhan air. Teknik pengelolaan air lahan sawah didasarkan pada kebutuhan air untuk tanaman (baik padi maupun palawija) dan sistem pengelolaan lahan sawah. Diunduh dari sumber: http://surososipil.files.wordpress.com/2008/10/irigasi1-bab-4-kebutuhan-irigasi.pdf………. 28/10/2012

32 KEBUTUHAN AIR IRIGASI Kebutuhan air tanaman didefinisikan sebagai jumlah air yang dibutuhkan oleh tanaman pada suatu periode untuk dapat tumbuh dan produksi secara normal. Kebutuhan air nyata untuk areal usaha pertanian meliputi evapotranspirasi (ET), sejumlah air yang dibutuhkan untuk pengoperasian secara khusus seperti penyiapan lahan dan penggantian air, serta kehilangan selama pemakaian. Sehingga kebutuhan air dapat dirumuskan sebagai berikut (Sudjarwadi 1990): KAI = ET + KA + KK Dimana: KAI = Kebutuhan Air Irigasi ET = Evapotranspirasi KA = Kehilangan air KK = Kebutuhan Khusus. Diunduh dari sumber: http://surososipil.files.wordpress.com/2008/10/irigasi1-bab-4-kebutuhan-irigasi.pdf………. 28/10/2012

33 Hidrologi lahan sawah Pengetahuan tentang hidrologi lahan sawah sangat diperlukan dalam merancang strategi pengelolaan air. Karakteristik hidrologi lahan sawah sangat ditentukan oleh kondisi biofisik lahan. Hidrologi sawah beririgasi berbeda dengan sawah tadah hujan maupun sawah rawa. Oleh karena itu strategi pengelolaan air pada lahan sawah beririgasi akan berbeda dengan pada lahan sawah tadah hujan maupun sawah rawa. Diunduh dari sumber: http://fftc.imita.org/library.php?func=view&id=20110722052543………. 30/10/2012 Types of Response to Water Scarcity Sumber: Irrigation Management in Rice-Based Cropping Systems: Issues and Challenges in Southeast Asia. Randolph Barker and Francois Molle.

34 Diunduh dari sumber: http://www.knowledgebank.irri.org/rkb/1-the-water-balance-of-lowland-rice.html ………. 30/10/2012 THE WATER BALANCE OF LOWLAND RICE Because of the flooded nature of lowland rice, its water balance and water productivity are different from those of other cereals such as wheat and maize. Water inputs to lowland rice fields are needed to match the outflows by seepage, percolation, evaporation, and transpiration (Figure 1).Figure 1

35 Diunduh dari sumber: http://www.knowledgebank.irri.org/rkb/1-the-water-balance-of-lowland-rice.html ………. 30/10/2012 THE WATER BALANCE OF LOWLAND RICE Seepage is the lateral subsurface flow of water and percolation is the down flow of water below the root zone. Typical combined values for seepage and percolation vary from 1-5 mm d-1 in heavy clay soils to 25-30 mm d-1 in sandy and sandy loam soils. Evaporation occurs from the ponded water layer and transpiration is water loss from the leaves of the plants. Typical combined evapotranspiration rates of rice fields are 4-5 mm d-1 in the wet season and 6-7 mm d-1 in the dry season, but can be as high as 10-11 mm d-1 in subtropical regions before the onset of the monsoon. Total seasonal water input to rice fields (rainfall plus irrigation) varies from as little as 400 mm in heavy clay soils with shallow groundwater tables to more than 2000 mm in coarse-textured (sandy or loamy) soils with deep groundwater tables. Around 1300-1500 mm is a typical value for irrigated rice in Asia. Outflows of water by seepage and percolation account for about 25-50% of all water inputs in heavy soils with shallow water tables of 20-50 cm depth, and for 50- 85% in coarse-textured soils with deep water tables of 150 cm depth or more.

36 KARAKTERISTIK HIDROLOGI LAHAN SAWAH Lahan sawah Pluvial 1.Sumber air berasal dari air hujan 2.Kelebihan air hilang melalui perkolasi dan aliran permukaan 3.Terdapat di daerah landai sampai lereng curam 4.Air tanah dalam, drainase baik, tidak ada gejala jenuh air dalam profil tanah 5.Padi ditanam sebagai padi gogo. Hydrological processes in a paddy field. (a) Hydrologic Characteristics of a paddy field. (b) Outline of runoff simulation model in paddies. Simulations of storm hydrographs in a mixed-landuse watershed using a modified TR-20 model T.I. Jang, H.K. Kim, S.J. Im, S.W. Park. Agricultural Water Management. Volume 97, Issue 2, February 2010, Pages 201–207.

37 KARAKTERISTIK HIDROLOGI LAHAN SAWAH Lahan sawah Phreatik 1.Sumber air berasal dari air hujan dan air tanah 2.Air tanah (phreatic) dangkal, paling tidak pada waktu musim tanam 3.Kelebihan air hilang melalui aliran permukaan 4.Tidak pernah tergenang lebih dari beberapa jam 5.Dalam profil tanah ada gejala jenuh air (gley motting) 6.Bila tanpa perataan (leveling) dan pembuatan pematang, akan lebih baik ditanami padi gogo 7.Bila dengan perataan dan pembuatan pematang dapat dikembangkan untuk padi sawah. Model development for nutrient loading from paddy rice fields Sang-Ok Chung, Hyeon-Soo Kim, Jin Soo Kim. Agricultural Water Management. Volume 62, Issue 1, 19 August 2003, Pages 1–17

38 KARAKTERISTIK HIDROLOGI LAHAN SAWAH Schematics of water balance components in a paddy field. Model development for nutrient loading from paddy rice fields Sang-Ok Chung, Hyeon-Soo Kim, Jin Soo Kim. Agricultural Water Management. Volume 62, Issue 1, 19 August 2003, Pages 1–17

39 Karakteristik hidrologi lahan sawah Lahan sawah fluxial 1.Sumber air seluruhnya atau sebagian berasal dari aliran permukaan, air sungai dan air hujan langsung 2.Dalam keadaan alami tergenang air selama beberapa bulan yaitu selama padi ditanam 3.Terdapat di daerah lembah, dataran aluvial sungai dan sebagainya 4.Drainase permukaan dan drainase dalam (perkolasi) lambat sehingga genangan air mudah terjadi 5.Padi ditanam sebagai padi sawah. Development and test of SWAT for modeling hydrological processes in irrigation districts with paddy rice Xianhong Xie, Yuanlai Cui. Journal of Hydrology. Volume 396, Issues 1–2, 5 January 2011, Pages 61–71.

40 Karakteristik hidrologi lahan sawah Schematic diagram of a paddy field. (h min, h max and H p denote the three critical depths; E can, E pot and E s denote the three kinds of evaporation from the free water in canopies, the water body surface and the soil water respectively; E p denotes the crop transpiration. Development and test of SWAT for modeling hydrological processes in irrigation districts with paddy rice Xianhong Xie, Yuanlai Cui. Journal of Hydrology. Volume 396, Issues 1–2, 5 January 2011, Pages 61–71.

41 GOOD WATER MANAGEMENT PRACTICES FOR RICEFIELD Diunduh dari sumber: http://www.knowledgebank.irri.org/factsheetsPDFs/watermanagement_FSWaterSavingGeneral.pdf ………. 30/10/2012 A few principles exist to “get the basics right” for good water management in paddy rice. Field channels In many paddy fields, water flows from one field to another through breaches in the bunds. Under such conditions, water in an individual field can not be controlled and field- specific water management is not possible - construction of channels to convey water to and from each field, or group of fields, greatly improves the irrigation and drainage of water. Land leveling A well-leveled field is a prerequisite for good water management. When a field is not level, water may stagnate in the depressions whereas higher parts may fall dry. This results in uneven crop emergence, uneven early growth, uneven fertilizer distribution, and weed problems. See the fact sheets on land leveling for more information.

42 GOOD WATER MANAGEMENT PRACTICES FOR RICEFIELD Diunduh dari sumber: http://www.knowledgebank.irri.org/factsheetsPDFs/watermanagement_FSWaterSavingGeneral.pdf ………. 30/10/2012 A few principles exist to “get the basics right” for good water management in paddy rice. Field channels In many paddy fields, water flows from one field to another through breaches in the bunds. Under such conditions, water in an individual field can not be controlled and field-specific water management is not possible - construction of channels to convey water to and from each field, or group of fields, greatly improves the irrigation and drainage of water. Land leveling A well-leveled field is a prerequisite for good water management. When a field is not level, water may stagnate in the depressions whereas higher parts may fall dry. This results in uneven crop emergence, uneven early growth, uneven fertilizer distribution, and weed problems. See the fact sheets on land leveling for more information. Tillage Wet land preparation can consume up to a third of the total water used in paddy rice. In large-scale irrigation systems, synchronizing operations and minimizing the duration of the land preparation period can reduce water use. Large amounts of water can be lost during soaking prior to puddling when large and deep cracks are present. A shallow tillage to fill the cracks before soaking can greatly reduce this water loss. After soaking, thorough puddling results in a compacted plow sole that reduces water losses by percolation. The efficacy of puddling depends on soil properties. Puddling may not be effective in coarse soils, whereas it is very efficient in clay soils that form cracks during the fallow period. Puddling may not be necessary in heavy clay soils with limited internal drainage. In such soils, direct dry seeding on land that is tilled in a dry state is possible with minimal percolation losses.

43 GOOD WATER MANAGEMENT PRACTICES FOR RICEFIELD Diunduh dari sumber: http://www.knowledgebank.irri.org/factsheetsPDFs/watermanagement_FSWaterSavingGeneral.pdf ………. 30/10/2012 Bund Good bunds are a prerequisite to limit water losses by seepage and under- bund flows. Bunds should be well compacted and any cracks or rat holes should be plastered with mud at the beginning of the crop season. Also, check for, and repair new rat holes, cracks, and porosity caused by earth worms throughout the growing season. Plastic sheets can be used to repair especially permeable parts of bunds. A few principles exist to “get the basics right” for good water management in paddy rice. Ponded water depth Keeping the depth of ponded water around 5 cm minimizes water losses by seepage and percolation. See the fact sheet on Alternate Wetting and Drying for more information on field water management.

44 THE SOUND WATER MANAGEMENT Diunduh dari sumber: http://www.knowledgebank.irri.org/rkb/2-sound-water-management.html………. 30/10/2012 Good water management in lowland rice focuses on practices that conserve water (by eliminating the unproductive water flows of seepage, percolation, and evaporation) while ensuring sufficient water for the crop. Water management practices are given for the different periods of the crop cycle from pre-planting activities to the ripening stage. It is assumed that farmers have access to sufficient irrigation to maintain flooded conditions. Water-saving technologies for conditions of insufficient water are described in subsequent paragraphs.

45 THE SOUND WATER MANAGEMENT Diunduh dari sumber: http://www.knowledgebank.irri.org/rkb/2-sound-water-management.html………. 30/10/2012 Pre-planting The amount of water used for wet land preparation of lowland rice can be as low as 100-150 mm but can go up to 900 mm in large-scale irrigation systems with a long land preparation period. Various options exist to minimize the amount of water used in the pre-planting period. Land preparation lays the foundation for the whole cropping season and it is important in any situation to “get the basics right” for good water management afterwards. Especially important for good water management are field channels, land leveling, and tillage operations (puddling, bund preparation and maintenance).

46 THE SOUND WATER MANAGEMENT Diunduh dari sumber: http://www.knowledgebank.irri.org/rkb/2-sound-water-management.html………. 30/10/2012 Field channels to manage water In many irrigation systems, there are no field channels (or ‘tertiary’ irrigation or drainage channels) and water flows from one field into the other through breaches in the bunds. This is called “plot-to-plot” irrigation. The amount of water flowing in and out of a rice field can not be controlled and field-specific water management is not possible. This means that farmers may not be able to drain their fields before harvest because water keeps flowing in from other fields. Also, they may not be able to have water flowing in if upstream farmers retain water in their fields or let their fields dry out to prepare for harvest. Moreover, a number of technologies to cope with water scarcity require good water control for individual fields. Finally, the water that continuously flows through the rice fields may remove valuable (fertilizer) nutrients. Constructing separate channels to convey water to (irrigation) and from (drainage) each field greatly improves the individual control of water, and is the recommended practice in any type of irrigation system. Alternatively, if field channels can not be constructed for individual fields, they should be constructed to serve a limited number of fields together.