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BAHAN KAJIAN MK. DASAR ILMU TANAH TANAH VERTISOLS.

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Presentasi berjudul: "BAHAN KAJIAN MK. DASAR ILMU TANAH TANAH VERTISOLS."— Transcript presentasi:

1 BAHAN KAJIAN MK. DASAR ILMU TANAH TANAH VERTISOLS

2 TANAH VERTISOLS RINGKASAN 1.Vegetasi: lahan-berumput, pohon yg perakarannya dalam 2.Iklim: variasi musiman hujan dan suhu; beracam resim suhu tanah, kecuali pergelic 3.Rezim lengas tanah: Rezim lengas-tanah erratik 4.Ciri tanah: kaya liat (dominais liat mengembang tipe 2:1 type ---> montmorillonit, smectite), KTK tinggi, permeabilitas rendah, bidang geser (slickensides), mikro relief gilgai, warna gelap khroma rendah, BOT medium hingga rendah ( %) 5.Diagnostic horizons: cambic (argillic, natric) 6.Epipedon: mollic 7.Major processes: shrinking and swelling, pedoturbation 8.Characteristics: stage of weathering relatively unadvanced or minimal, lack in horizon differentiation VERTISOLS: Tanah-tanah liat warna gelap yang mengembang-mengkerut 1.Beragam bahan induk, termasuk alluvial, colluvial dan deposit lacustrine 2.Marl and other calcareaous rocks, limestone, shales, igneous, metamorphic and volcanic rocks of basic nature 3.Unconsolidated sediments which are dominantely basic in character and low in quartz 4.The parent material although variable in origin, are rich in feldspars and ferro-magnesian minerals and yield clay residues on weathering 5.Vertisols may develop in situ from the parent materials. The smectites in these soils could be derived from the original rock or form as a result of neogenesis or transformations from primary minerals. 6.Ciri utama: kaya liat (dominasi liat mengembang tipe 2:1 -> montmorillonite, smectite) Diunduh dari: ………….. 25/2/2013

3 TANAH VERTISOLS KONDISI LINGKUNGAN IKLIM: Vertisols ditemukan di hampir setiap zone iklim utama. Di Australia, Vertisols berkembang di daerah-daerah dengan rezim air aridik, dan ada juga di zone Ustik dan Xerik. Generally, the seasonal variations in precipitation and temperature, which favor the formation of smectitic clays as well as provide many of the physical attributes of these soils, would be considered as prerequisites for the formation of Vertisols. The variation in climatic conditions result in weathering of primary and secondary minerals during wet season, but encourage the accumulation of basic cations in the dry season. Areas where Vertisols are found are characterized by a period when the potential evapotranspiration exceeds precipitation (fry period). During periods with sufficient moisture deficit cracking occurs, although the intensity in cold temperature regions, is much lower than in the warmer regions. Umumnya, curah hujan tinggi menghasilkan retakan-retakan yang intensif, peningkatan kandungan BOT, dan peningkatan pencucian karbonat dan garam-garam. Diunduh dari: ………….. 25/2/2013

4 TANAH VERTISOLS KONDISI LINGKUNGAN VEGETASI: Vegetasi alamiah yang berasisoasi dnegan ordo tanah ini sangat beragam. Tipe-tipe vegetasi alamiah, hingga batas tertentu, dibatasi oleh sifat-sifat tanah, seperti kandungan liat yg tinggi, sifat mengembang-mengkerut, dan struktur tanah. Sifat-sifat tanah dan iklim membatasi tipe-tipe vegetasi seperti rumput dan pohon yang tumbuhnya lambat dna perakarannya dalam (mis. Acacia). The main features of the natural vegetation in these soils are tolerance to drought, as well as development of deep roots to overcome root damage by a consequence of the annual cracking. Most Vertisols have has grassland or savanna vegetation as the native vegetation, but some had formed under forest. Present use of Vertisols comprise wheat, rice, cotton, and sorghum, pastureland in the the south of the United States. Vertisols in India are used for grain legume, oil seed crops, and cotton cultivated in a ridge and furrow system. In Australia most Vertisols are used for grazing by sheep and cattle or dry land agriculture. Large areas of Vertisols in Africa are largely un-utilized except for extensive grazing. Diunduh dari: ………….. 25/2/2013

5 TANAH VERTISOLS KONDISI RELIEF Ada dua sekala yang berbeda, yaitu (i) makro, dan (ii) mikro. 1.Relief Makro : Vertisols umumnya ditemukan di daerah-daerah dengan kemiringan tidak lebih dari 5 %, karena akan terjadi erosi tanah yang intensif.. Sering kali daerah yang datar kekurangan jaringan drainage, infiltration lambat, mengakibatkan genangan air di permukaan. 2.Micro relief: Gilgai-relief. The development of gilgai-relief is due to shrinking and swelling of Vertisols and soil movement, i.e., the soil mass cannot re-occupy the original volume since surficial material has fallen into the cracks during dry season. As such, part of the soil mass is forced upwards forming the mounds (or knolls). The formation of a mound provides a locally preferred site for the further release of pressure, thereby perpetuating the formation of other mounds and depressions in an area. Diunduh dari: ………….. 25/2/2013

6 TANAH VERTISOLS BAHAN INDUK TANAH Vertisols berkembang dari beragam bahan induk, termasuk alluvial, colluvial dan deposit lacustrine, batuan marl dan batuan berkapur lainnya, limestone, shales, igneous, batuan metamorf dan batuan vulkanik yang bersifat basis (alkalis). Bahan induk vertisols ini dapat berasal dari allochtonous ataur autochthonous. Dalam banyak kasus, bahan induk tanah merupakan endapan muda dan pembentukan tanah masih pada fase awal. Vertisols may develop in situ from the parent materials. The smectites (clay minerals) in these soils could be derived from the original rock or form as a result of neogenesis or transformations from primary minerals. A high pH and high potentials of Si as well as Mg smectites develop, a process which is also favored by poor drainage conditions. Calcareous parent material or unconsolidated sediments which are dominantely basic in character and low in quartz favor the formation of Vertisols. Anah-tanah ini berkembang di daerah dataran dengan bahan induk liat berkapur atau calcareous atau residu pelapukan dari batuan sedimen yang lunak dan berkapur. Vertisols di Australia berkembang dari bahan induk batuan basalt, di India vertisols berkembang dari bahan induk gneisses daan sandstones. The parent material although variable in origin, are rich in feldspars and ferro-magnesian minerals and yield clay residues on weathering. Where parent materials are not basic, alkaline earth elements can be added by seepage or by flood water. Diunduh dari: ………….. 25/2/2013

7 TANAH VERTISOLS KONDISI LINGKUNGAN Waktu - Time: Kebanyakan Vertisols berkembang pada lanskap muda, tetapi juga ditemukan pada permukaan geomorfik tua. It is believed that the stage of weathering in Vertisols is relatively unadvanced or minimal. Diunduh dari: 1/3/2013 Sketch showing the kinematics of mass movement in Vertisols that result in gilgai microrelief (after Beinroth, 1965)

8 TANAH VERTISOLS Mikro-relief Gilgai. Diunduh dari: ………….. 1/3/2013

9 TANAH VERTISOLS Microphological differentiation of a sequence of soils (generalised). Diunduh dari: ………….. 1/3/2013

10 TANAH VERTISOLS PROSES GENESIS TANAH Vertisols form under multiple genetic pathways which are complex. In general, soil forming processes that lead to the formation of Vertisols are those which control the formation and stability of smectites in the soil. However, subsidiary processes, such as fluctuations in the moisture status, accumulation of organic matter, carbonates, gypsum or soluble salts and acidification processes through leaching, result in the differences within the Vertisols. The development of Vertisols requires conditions that ensure the formation and preservation of smectites. These clay minerals may form either in situ through the weathering and development of a solum (autochtonous Vertisols) or from a sediment which is composed of materials that can produce vertic properties (allochtonous Vertisols). The latter is geographically more extensive and occupies the lower parts of the landscape. The development of smectitic clays is favored by a high pH with sufficient Ca 2+ and Mg 2+ in the soil system. The presence of a relatively impermeable layer at some depth within the soil prevents the leaching of the various components needed to form smectites. Diunduh dari: ………….. 25/2/2013

11 TANAH VERTISOLS PROSES GENESIS TANAH Pengkerutan dan pemuaian menyebabkan terjadinya “shearing” sehingga menghasilkan pembentukan “slickensides”. Proses ini disebabkan oleh adanya mineral liat “smectitic” dan alterasi musim basah dan musim kering. Akibat dari proses ini, Vertisols membentuk retakan-retakan yang dalam dan lebar dengan pola POLIGONAL. Pedoturbation (churning) is a process which homogenizes the soil profile due to the infilling of the cracks by surficial material during dry season. The process in Vertisols is also called self-mulching or self-swallowing. Diunduh dari: ………….. 25/2/2013

12 TANAH VERTISOLS PROSES GENESIS TANAH Selama siklus pengeringan terbentuklah retakan-retakan, sedangkan pada saat pembasahan terbentuk “tekanan geser” yang menghasilkan pembentukan “slickensides” dan/atau penghalusan permukaan “sphenoids”. Kedua sifat ini memerlukan material yang bersifat plastis. Tekanan lateral yang berkembang dalam tanah-tanah ini jauh lebih besar dibandingkan dg tekanan vertikal akibat pembengkakan (swelling). Di dalam tanah, komponen vertikal dari tekanan “swelling” mencakup “bobot /berat” dari material di sebelah atasnya. The moisture conditions above and below a point within the soil determines the net pressure and angle of shear. As such, the near surface horizon develop cracks and may have only a few slickensides since both the horizontal and vertical pressures are small (the net pressure being much lower than the sheat strength of the material). In deeper horizons, typically from 50 to about 125 cm below the surface, slickensides development is maximum. In these deeper layers, the net pressure is much greater than the shear strength of the material and soil movement occurs with swelling. Sphenoids develop as a result of the existence of much lower vertical and horizontal pressures in comparison to that needed for the development of slickensides. In the typical case, sphenoids would be found in between the surface horizon with cracks and deeper horizons with slickensides. Their development has been related to lower clay contents, as well as smaller proportions of smectitic clays in the colloidal fractions.

13 TANAH VERTISOLS PROSES GENESIS TANAH Tranlokasi liat pada vertisols tidak fenomenal, namun dmeikian, adanya liat-liat “smectitic” mempunyai semua kondisi yang diperlukan untuk proses dispersi, translokasi, dan akumulasi liat pada horison bawah-permukaan. In some Vertisols there is some evidence of illuviated clays in the lower soil profile, which is subjected to the least amount of pedoturbation. This process tends to obliterate all evidence of the illuviation process and it is unlikely that well-defined clay skins will be preserved, instead any translocated clay is probably engulfed in the matrix and/or slickensides as a result of shrink- swell processes. Diunduh dari: ………….. 25/2/2013

14 TANAH VERTISOLS MODEL PEDOGENIK PEMBENTUKAN VERTISOLS (I). Model Pedoturbasi (Self-Swallowing Model) Persyaratan bagi pembentukan Vertisols adalah adanya mineral liat tipe “mengembang” (smectites). Adanya mineral liat ini menyebabkan terjadinya proses mengembang-mengkerut pada tanah. Selama musim kering tanah retak-retak. Selama retakan ini membuka, material tanah permukaan jatuh masuk ke dalam retakan oleh adanaya gaya angin, aktivitas binatang atau erosi oleh air. On rewetting the clays hydrate and expand. As expansion takes place, the cracks close, but because of the 'additional' material now present in the lower parts of the profile, a greater volume is required and the expanding material presses and slides the aggregates against each other developing slickensides. Diunduh dari: ………….. 25/2/2013

15 TANAH VERTISOLS MODEL PEDOGENIK PEMBENTUKAN VERTISOLS (II). Model Mekanistik This model is based on the failure along shear planes (slickensides) of plastic soil material when swelling pressures generated by hydration of clays exceed the shear strength of the soil material. Stress is relieved by an upward movement that is constrained by the weight of the overlying soil material, resulting in a failure shear plane that is usually inclined at ° above the horizontal. This model does not require that surface material falls into cracks. Instead, surface material is transported upward along the slickensides to produce the microknolls of the gilgai-relief. Once microrelief is established, soil processes are driven largely by small-scale variations in hydrology and microclimate, and less so by pedoturbation. Diunduh dari: ………….. 25/2/2013

16 TANAH VERTISOLS SIFAT DAN CIRI VERTISOLS Lima zone atau horizons dengan penciri strukturalnya dapat ditemukan pada Vertisols, meskipun tidak selalu semuanya ditemukan bersama dalam satu profil tanah, dan urutannya mungkin juga beragam. Zone 1: Zone ini dari permukaan hingga kedalaman sekitar 25 cm atau lapisan olah bajak kalau ada. Zone ini dicirikan oleh adanya agregat prismatik yang berukuran besar, hingga 30 cm lebarnya, yang dihasilkan dari proses retakan-retakan. Materialnya keras atau sangat keras kalau kering dan agregat prismatik dapat memisahkan diri manjadi gumpal bersudut yang kasar ukurannya. Zone 2: This zone is typically 10 to 30 cm thick and characterized by coarse angular blocky elements that may occur aggregated into discernable prisms. If overlain by a plow zone, it may represent a root restricting layer for agricultural crops. Zone 3: This zone may vary in thickness from 10 to over 100cm. Soil Taxonomy refers to the structural elements in this zone as 'wedge-shaped natural structural aggregates that have their long axis tilted 10 to 60 degrees from the horizontal'. These structural aggregates have an orthorhombic form, are generally 5 to 10 cm long along their long axis; and smooth or striated ped faces. Their mode of formation is related to the slickensides, which are characteristic of zone 4. Diunduh dari: ………….. 25/2/2013

17 TANAH VERTISOLS SIFAT DAN CIRI VERTISOLS Zone 4: Zone ini menjadi tempat pembentukan bidang-geser dan tebalnya berkisar from cm. Istilah “bidang geser” menunjukkan “permukaan” halus dan mengkilap yang juga dapat “be grooved or striated”. Dalam zone ini, bidang geser menempati luasan sekitar cm 2. Their surface topography is not flat, but curved or slightly undulating. The net result of the inclined arrangement is to produce a set of intersecting slickensides arranged in a synclinal form. The deepest part of the syncline is between 50 and 125 cm below the surface, while the shallower arms may reach within 25 cm of the surface. The amplitude of the two arms represents the amplitude of the gilgai and may vary from about 3 m to more than 25 m. The thickness and expression of zones 2 &3 are a function of the depth at which the arms of the slickensides approach the surface. Diunduh dari: ………….. 25/2/2013

18 TANAH VERTISOLS SIFAT DAN CIRI VERTISOLS Zone 5: Zone ini berada di bawah zone 4 atau langsung di bawah zone 3. Zone ini mengalami variasi kelengasan sedikit saja, bersifat masif, dan menunjukkan akumulasi gipsum, carbonates dan garam-garam larut lainnya.. Variations from the model profile is the rule rather than the exception. One or more of zones 2, 3 or 4 may be absent, but 'conceptually zone 3, 4 or both must be present for recognition as a Vertisol. The expression of zones 2, 3 and 4 will show considerable variation as a function of soil moisture content and variation in intrinsic soil attributes (variation in clay type and content), however their relative positions are usually sequential. Generally, the clay content is very high in Vertisols and the dominant clay minerals are 2:1 type minerals (smectites, montmorillonites). These clay minerals have the outstanding feature to expand (swell) when wet and shrink when dry. Therefore, pronounced changes in volumes with changes in soil moisture result in deep cracks in the dry season and very plastic and sticky soil consistency when wet. Due to the high clay content of expanding character the cation exchange capacity of the whole soil is high. A high clay content is also associated with slow permeability but the water adsorption is high. Diunduh dari: ………….. 25/2/2013

19 TANAH VERTISOLS SIFAT DAN CIRI VERTISOLS Bidang geser “Slickensides” menjadi ciri khas dari Vertisols. They are defined as polished and grooved surfaces produced by one soil mass sliding past another. The formation of slickenside features is related to swelling pressures which exceed the shear strength of the soil under overburden-pressure confinement. The shear strength of a soil is a function of cohesion plus the angle of internal friction, which is low in clay soils. The cohesion is a function of bulk density, clay content, clay mineralogy, and is inversely related to moisture content. Generally, lateral swelling pressures in soils are much larger than vertical swelling pressures, as the latter is substantially reduced by the overburden pressure. Maximum slickensides are between 50 and 125 cm depth, however, fewer slickensides are found at depths between 25 and 50 cm. At such depths both vertical and horizontal pressures are small. As the moisture changes become limited at 125 cm depth, slickensides become scarce below this depth. Shearing occurs at an angle of 30 to 50 degrees from the horizontal and it is dependent on moisture and the swelling pressures, which vary vertically, horizontally, and temporally. Diunduh dari: ………….. 25/2/2013

20 TANAH VERTISOLS SIFAT DAN CIRI VERTISOLS Slickensides hanya dapat terbentuk kalau materialnya plastis. Bidang geser (slickensides, stress cutans) sangat berbeda dengan selimut- liat (argillans) yang ditemukan pada permukaan agregat dan dihasilkan dari proses translokasi liat. The latter have sharp outer and inner boundaries with distinct extinction patterns and are often finely layered (laminar fabric). The relatively small slickensides developed by pedogenesis must not be confuse with large slickensides of the substratum which in alluvial and lacustrine sediments is a feature of the parent material. Diunduh dari: ………….. 25/2/2013

21 TANAH VERTISOLS SIFAT DAN CIRI VERTISOLS The organic matter content is generally low ( %) in spite of the usual dark soil color. Complexation or chelation of organic colloids to clay minerals of the smectite group probably darkens the mineral. Some of the dark color may also be related to presence of manganese oxides. The dark black color may be also due to the parent material (e.g. Vertisols derived from basalt). The Chrom great groups of Vertisols are brownish in color and typically have small amounts of montmorillonites. These great groups typically have large amounts of iron oxyhydroxides and are well-drained. Kankars (carbonate glaebules or nodules) are basically lime concretions that are found in Vertisols. Many Vertisols are formed in calcareous parent material and have kankars throughout the profile. In deeper horizons, it is also common to find calcic horizons. Drying, in the presence of Fe and Mn, results in the formation of hard concretions. Diunduh dari: ………….. 25/2/2013

22 TANAH VERTISOLS SIFAT DAN CIRI VERTISOLS Struktur tanah Vertisols bersifat temporer. Ukuran struktur, bentuk, grade dan konsistensi semuanya berhubungan dnegan kondisi lengas tanah. The depth at which the different structural elements are expressed may also be a function of moisture conditions in different parts of the profile. Ideally, structural assessments should be made under different moisture conditions. Seringkali Vertisols menunjukkan struktur gumpal bersudut (agregat yang berbentuk baji “wedge”). Diunduh dari: ………….. 25/2/2013

23 TANAH VERTISOLS SIFAT DAN CIRI VERTISOLS Ciri mikro-relief yang khas adalah knolls (gundukan) dan basins (cekungan) pada lanskap Vertisol. Cekungan lebih basah daripada gundukan, karena adanya pelepasan air melalui retakan-retakan dan genangan air selama periode basah. They exhibit higher organic matter contents and are often more saline than the microknolls. The knolls are drier, have a higher calcium carbonate content and are in the erosional positions. Minibasins and microknolls show a repetitive but irregular pattern within a Vertisol landscape with distances of about 3 to 10 m between the knolls. The topography related to Vertisols is called 'Gilgai micro-topography'. Various forms of gilgai have been reported: round, mushroom, tank, wavy, lattice, stony, and depressional. The form is related to landscape shape, clay content and type, and soil moisture regime. A fine, angular blocky structure, described by some as 'nutty' may develop in surfaces that have a very high montmorillonitic clay content. In the dry season they show a very hard consistence and appear as loose gravel strewn on the surface. In previous classification systems these soils were called Grumosols. Kebanyakan Vertisols mempunyai epipedon mollic dan horison penciri cambic, tetapi beberapa lainnya mempunyai horison penciri bawah permukaan, termausk argillic atau natrik. Diunduh dari: ………….. 25/2/2013

24 TANAH VERTISOLS KLASIFIKASI VERTISOLS Persyaratan untuk memenuhi kualifikasi Vertisol adalah: 1.Clay content of at least 30 % to a depth of at least 50 cm, or a lithic or paralithic contact, duripan, or a petrocalcic horizon if shallower 2.Cracks that open and close periodically 3.Evidence of soil movement (e.g. slickensides, wedge-shaped aggregates) 4.Any soil temperature regime, except pergelic (i.e., Gelisols) 5.Soil moisture regime must be erratic to allow for cracking in dry season and swelling in wet season 6.Gilgai surface topography is not considered as a requirement to meet a Vertisol. Cultivation practice may erase gilgai microtopography. Ada enam subordo di dalam ordo Vertisol. They are differentiated by aquic conditions, soil moisture regime, and on the cracking characteristics of the soil. Note that although the formative elements for soil moisture regimes are used in naming Xererts, Torrerts, Usterts, and Uderts, the names do not necessarily mean that the soils have those soil moisture regimes. Diunduh dari: ………….. 25/2/2013

25 TANAH VERTISOLS KLASIFIKASI VERTISOLS Aquerts: Vertisols which are subdued aquic conditions for some time in most years and show redoximorphic features are grouped as Aquerts. Because of the high clay content the permeability is slowed down and aquic conditions are likely to occur. In general, when precipitation exceeds evapotranspiration ponding may occur. Under wet soil moisture conditions iron and manganese is mobilized and reduced. The manganese may be partly responsible for the dark color of the soil profile. Cryerts: They have a cryic soil temperature regime. Cryerts are most extensive in the grassland and forest-grassland transitions zones. Xererts: They have a thermic, mesic, or frigid soil temperature regime. They show cracks that are open at least 60 consecutive days during the summer, but are closed at least 60 consecutive days during winter. Diunduh dari: ………….. 25/2/2013

26 TANAH VERTISOLS KLASIFIKASI VERTISOLS Torrerts: Tanah-tanah ini mempunyai retakan-retakan yang menutup selama kurang dari 60 hari berturutan pada saat suhu lapisan tanah permukaan 50 cm lebih dari 8°C. Usterts: Tanah-tanah ini mempunyai retakan-retakan yang membuka selama minimal 90 hari kumulatif setiap tahun. Secara global, ordo tanah ini paling luas sebarannya, meliputi tanah-tanah Vertisols di daerah tropis dan iklim monsoon. Diunduh dari: ………….. 25/2/2013

27 TANAH VERTISOLS KLASIFIKASI VERTISOLS Uderts: Tanah-tanah ini mempunyai retakan yang membuka selama kurang dari 90 hari kumulatif per tahun, dan kurang dari 60 hari berturutan selama summer. Great groups are differentiated by subsurface diagnostic horizons (e.g. salic, calcic, natric, gypsic horizons), the presence of a duripan (e.g. Duraquerts, Durixererts), organic carbon content (e.g. Humicryerts), or reaction (electrical conductivity is less than 4 dS/m and pH in 1:1 water of 5 or less in 25 cm or more within top 50 cm - e.g. Dystrusters, Dystraquerts). Beberapa rezim lengas tanah pada tingkat sugroup beragam mulai dari kondisi kering hingga basah: 1.Xeric (e.g. Xeric Epiaquerts), 2.Aridic (e.g. Aridic Epiaquerts), 3.Udic (e.g Udic Haplusterts), 4.Ustic (e.g. Ustic Dystraquerts), and 5.Aquic (e.g. Aquic Dystrusterts, Aquic Salitorrerts). Diunduh dari: ………….. 25/2/2013

28 TANAH VERTISOLS KLASIFIKASI VERTISOLS Warna tanah digunakan untuk membedakan subgroup 'aeric' dari Vertisols. Soils that have in one or more horizons between either an Ap horizon or a depth of 25 cm from the mineral soil surface, whichever is deeper, 50 percent or more colors as follows: 1.Nilai HUE 2.5R atau lebih merah, dan/atau 2.Nilai VALUE, lembab, 6 atau lebih dan KHROMA 3 atau lebih; atau 3.Nilai VALUE, lembab, 5 atau kurang dan KHROMA 2 atau lebih; atau 4.Nilai HUE 5Y dan KHROMA 3 atau lebih; atau 5.KHROMA 2 atau lebih, dan tidak ada konsnetrasi redoks (mis. Aeric Endoaquerts). Soil color is used also to differentiate the 'chromic' subgroup of Vertisols. The chromic characteristic encompass soils that have, in one or more horizons within 30 cm of the mineral soil surface, 50 percent or more colors as follows: 1.VALUE, lembab, 4 atau lebih; atau 2.VALUE, kering, 6 atau lebih; atau 3.KHROMA 3 atau lebih (mis. Chromic Epiaquerts). Diunduh dari: ………….. 25/2/2013

29 TANAH VERTISOLS KLASIFIKASI VERTISOLS Vertisols yang tipis (dangkal) diklasifikasikan dengan sebutan 'leptic' (tanh yang mempunyai kontak densik, lithic, atau paralithic, di dalam 100 cm tanah mineral permukaan) atau 'lithic' (mis. Leptic Salaquerts atau Lithic Haploxererts). Vertisols which are low in clay content are differentiated as 'entic'. To meet the 'entic' designation the Vertisol must have a layer 25 cm or more thick that contains less than 27 percent clay in its fine-earth fraction and has its upper boundary within 100 cm of the mineral soil surface (e.g. Entic Salaquerts, Entic Haplotorrerts). Tanah-tanah disebut 'halic' kalau kandungan garamnya tinggi. Tanah-tanah ini memenuhi kriteria : seluruh lapisan 15 cm atau lebih tebal mempunyai konduktivitas elektrik minimal 15 dS/m atau lebih (tanah: air 1:1) selama 6 bulan atau lebih per tahun, dalam 6 tahun atau lebih selama periode 10 tahun (mis. Halic Durixererts). Vertisols with a high sodium content are classified as 'sodic' (e.g. Sodic Durixererts). They must have an exchangeable sodium percentage of 15 or more (or a sodium adsorption ratio of 13 or more) for 6 or more months per year in 6 or more out of 10 years. Diunduh dari: ………….. 25/2/2013

30 TANAH VERTISOLS Coefficient of linear extensibility (COLE) and bulk densities of selected Vertisols. Diunduh dari: 1/3/2013 ClassificationDepth (cm)COLE (cm cm -1 )Bulk density (g cm -3 ) 0.03 Mpaoven-dry Udic Chromustert Entic Chromoxerert Udic Pellustert Typic Torrert

31 TANAH VERTISOLS KARAKTERISTIK PENCIRI Soils at higher elevations and on steeper slopes formed in the same parent material as Vertisols are classified as Inceptisols and Alfisols and they may have vertic properties. In a catenary association Alfisols may occur on the top of the slopes - Entisols, Inceptisols, and Alfisols with vertic properties on the erosional hillslope positions - and Vertisols on the lower slopes and in the depressions. The main associated soils formed in calcareous parent material are Ustolls, Aqualfs in the less calcareous clays, and soils in vertic subgroups of Ustolls and Aquolls on nearly level slopes. With advancement of leaching and the formation of an argillic horizon, the soil would evolve into Alfisols (e.g. Vertic Hapludalfs). Leaching also promotes the destruction of smectites, i.e., the vertic properties of the soils are destroyed and Alfisols are formed. A number of Inceptisols, Entisols, Alfisols, Mollisols, Ultisols, and Aridisols intergrade to Vertisols at the subgroup level. These soils have vertic characteristics such as cracking, slickensides or wedge-shaped aggregates, but not enough to be Vertisols. Diunduh dari: ………….. 25/2/2013

32 TANAH VERTISOLS Pembentukan Horison VERTIK Pembentukan agregat struktural yang khas (`vertic structure') merupakan proses genetik utama dalam Vertisols. Struktur tipikal ini dapat ditemukan dalam solum, tetapi ekspresi yang paling kuat ada pada `vertic horizon'; derajat perkembangan dan ukuran agregat berubah secara bertahap dnegan kedalaman tanah. When the saturated surface soil starts to dry out, shrinkage of the clayey topsoil is initially one- dimensional and the soil surface subsides without cracking. Upon further drying, the soil loses its plasticity and tension builds up until the tensile strength of the soil material is locally exceeded and the soil cracks. Cracks are formed in a pattern that becomes finer as desiccation proceeds. In most Vertisols, the surface soil turns into a `surface mulch' with a granular or crumb structure. Vertisols, which develop surface mulch, are called `self-mulching‘. Granules or crumbs of the mulch fall into cracks. Upon re-wetting, part of the space that the soil requires for its increased volume is occupied by mulch material. Continued water uptake generates pressures that result in shearing: the sliding of soil masses against each other. Shearing occurs as soon as the `shear stress' that acts upon a given volume of soil exceeds its `shear strength'. The swelling pressure acts in all directions. Mass movement along oblique planes at an angle of 20 to 30 degrees with the horizontal plane resolves this pressure Diunduh dari: 1/3/2013

33 TANAH VERTISOLS Vertisols mempunyai kandungan mineral liat tipe mengembang yang sangat tinggi. Mereka mengalami perubahan volume yang sangat nyata dnegan adanya perubahan lengas tanah. Mereka mempunyai retakan-retakan di permukaan yang membuka dan menutup secara periodik, dan menunjukkan bukti- bukti pergerakan tanah dalam profilnya. Karena mereka mengembang ketika basah, vertisols merembeskan air sangat lambat dan hanya sedikit mengalami pencucian. Kesuburan alamiahnya cenderung tinggi. Vertisols meliputi sekitar 2% dari permukaan lahan dunia yg bebas es Diunduh dari: ………….. 25/2/2013

34 TANAH VERTISOLS Konsep sentral dari Vertisols adalah tanah-tanah yang mempunyai (kaya) kandungan mineral liat tipe mengembang dan mempunyai nretakan-retakan permukaan yang lebar dan dalam. Tanah-tanah ini mengkerut bila kering dan mengembang bila menjadi lebih basah. Diunduh dari: ………….. 28/2/2013

35 TANAH VERTISOLS Tanah-tanah vertisols berkembang pada bahan induk bertekstur halus dengan > 60% liat, minimal separuhnya berupa montmorillonit. Proses genesis tanah yang dominan : retakan, argilli- pedoturbation (pencampuran liat dalam pedon) dan pergerakan material karena mengembang- mengkerutnya liat selama siklus pembasahan/pengeringan. Tanah-tanah ini mempunyai dua horison yang khas (B atau C): slickensides (ss = horison bawah- permukaan berliat yg mempunyai “polished and grooved ped surfaces -'slickensides', atau agregat yang berbentuk wedge ) dan vertik (v = horizon dengan retakan yang lebar & dalam ketika kering, sehingga memungkinkan material permukaan turun ke bawah sepanjang retakan dan menyebabkan tanah menjadi “heave”). Siklus pembasahan dan pengeringan menyebabkan liat mengembang dan mengkerut. Diunduh dari: ………….. 28/2/2013

36 TANAH VERTISOLS Retakan-retakan di permukaan tanah Vertisol dari Utah Tingginya kapasitas Vertisols untuk mengembang dan mengkerut menciptakan retakan-retakan di permukaan tanah. Retakan-retakan ini cukup lebar untuk membuat “the terrain treacherous” bagi binatang. Material permukaan mengakumulasi dalam retakan ini selama musim kering dan "swallowed" oleh tanah pada musim basah, sehingga menghasilkan aksi mencampur- sendiri pada tanah Vertisols. Diunduh dari: ………….. 28/2/2013

37 TANAH VERTISOLS SUB-ORDO 1.Aquerts - Vertisols with a water table at or near the surface for much of the year 2.Cryerts - Vertisols di daerah iklim dingin 3.Xererts - temperate Vertisols with very dry summers and moist winters 4.Torrerts - Vertisols di daerah iklim kering 5.Usterts - Vertisols di daerah iklim semiarid dan subhumid 6.Uderts - Vertisols di daerah iklim basah Diunduh dari: ………….. 28/2/2013

38 TANAH VERTISOLS Horison pada Vertisols 1.The A horizon, called topsoil by most growers, is the surface mineral layer where organic matter accumulates. Over time, this layer loses clay, iron, and other materials to leaching. This loss is called eluviation. Materials resistant to weathering, such as sand, tend to remain in the A horizon as other materials leach out. The A horizon provides the best environment for the growth of plant roots, microorganisms, and other life. 2.The C horizon lacks the properties of the A and B horizons. It is the soil layer less touched by soil-forming processes and is usually the parent material of the soil. Diunduh dari: ………….. 28/2/2013

39 TANAH VERTISOLS 1.a vertic h. starting within 100 cm of the soil surface; dan 2.after the upper 20 cm have been mixed, 30 percent or more clay between the soil surface and the vertic h. throughout; dan 3.Retakan-retakan yang membuka dan menutup secara periodik. Diunduh dari: ………….. 28/2/2013

40 TANAH VERTISOLS Vertisols are dark clays and difficult to work. Good management can bring them to medium or high potential. Diunduh dari: ………….. 28/2/2013

41 TANAH VERTISOLS RETAKAN DI PERMUKAAN Cracks, surface mulch and soil structure in a Vertisol during the dry season Cracks are formed in a pattern that becomes finer as desiccation proceeds. In most Vertisols, the surface soil turns into a ' surface mulch ' with a granular or crumb structure. Vertisols, which develop surface mulch, are called ‘ self-mulching'. Diunduh dari: or_soils_of_the_world/set3/vr/vertisol.pdf? ………….. 28/2/2013 Cracks, surface mulch and soil structure in a Vertisol during the dry season Diunduh dari: ………….. 1/3/2013

42 PENGELOLAAN VERTISOLS Large areas of Vertisols in the semi-arid tropics are still unused or are used only for extensive grazing, wood chopping, charcoal burning and the like. These soils form a considerable agricultural potential but adapted management is a precondition for sustained production. The comparatively good chemical fertility and their occurrence in extensive level plains where reclamation and mechanical cultivation can be envisaged are assets of Vertisols. Kendala serius yang dihadapi adalah karakteristik fisika tanah dan sulitnya pengelolaan air.. SISTEM PERTANIAN PADA Vertisols The agricultural use of Vertisols ranges from very extensive (grazing, collection of fire wood, charcoal burning) through smallholder post-rainy season crop production (millet, sorghum, cotton, chick peas) to small-scale (rice) and large-scale irrigated agriculture (cotton, wheat, barley, sorghum, chickpeas, flax, noug (Guzotia Abessynica) and sugar cane). Cotton is known to perform well on Vertisols allegedly because cotton has a vertical root system that is not severely damaged by cracking of the soil. Tree crops are generally less successful because tree roots find it difficult to establish themselves in the sub- soil and are damaged as the soil shrinks and swells. Praktek pengelolaan untuk produksi tanaman harus diarahkan pada pengelolaan air yang dikombinasikan dengan konservasi atau perbaikan kesuburan tanah. Diunduh dari: ………….. 28/2/2013

43 PENGELOLAAN VERTISOLS Manajemen lahan secara fisik pada Vertisols Sifat-sifat fisika dan rezim lengas-tanah pada Vertisols menjadi kendala serius bagi pengelolaannya. The heavy soil texture and domination of expanding clay minerals result in a narrow soil moisture range between moisture stress and water excess. Tillage is hindered by stickiness when the soil is wet and hardness when it is dry. The susceptibility of Vertisols to waterlogging is the single most important factor that reduces the actual growing period (below estimates based on climatic data). Kelebihan air selama musim hujan harus dapat disimpan untuk digunakan pasca musim hujan (‘panen air hujan') pada Vertisols yang mempunyai sifat laju infiltrasi sangat lambat. Diunduh dari: ………….. 28/2/2013

44 Pengelolaan Vertisols untuk memperbaiki rezim lengas tanah: Evacuation of excess surface water – SISTEM SURJAN Drainage permukaan dnegan sistem surjan (bedengan lebar dengan parit dalam), dapat melindungi tanaman dari efek buruk akibat jenuhnya zone perakaran. Air drainage dapat disimpan dalam kolam-kolam kecil dan digunakan untuk keperluan ternak dan tanaman sayuran yang dibudidayakan. This practice proved very successful in the Ethiopian Highlands where the yields of local wheat varieties increased by 150 % and horse bean yields went up by 300 %. The only disadvantage of broad bed and furrow systems recognised so far is that they promote soil erosion by concentrating water flow in the furrows. The broad bed and furrow technology solves problems on individual farmers’ fields but solutions have still to be found to bring the runoff water safely down to the lowest part of the landscape (e.g. along grassed waterways) without enhancing erosion of neighbouring farmland. A participatory approach involving all stakeholders is needed to solve this problem at watershed scale. Diunduh dari: ………….. 28/2/2013

45 Pengelolaan Vertisols untuk memperbaiki rezim lengas tanah: Storage of excess water within the watershed – EMBUNG Kalau kelebihan air hujan dapat dipanen dan disimpan dalam embung (micro-dams), air ini dapat digunakan untuk irigasi Vertisols di daerah bawahannya.. Seepage losses from the dams benefit the ecosystem as a whole, since the water will surface as recharge in lower landscape positions. Livestock benefit from these micro-dams in many ways, e.g. by increased fodder availability from crop residues, presence of drinking water and increased fodder production in recharge zones. Even though micro-dam projects are generally appreciated as successful, salinisation and sodification of the irrigation perimeters and high percolation losses are serious hazards. At some of the dam sites, up to 50 % of the harvested water is lost each year. This is a direct consequence of the swell-shrink behaviour of smectite clay. The use of a membrane or of other construction materials, e.g. more weathered clay which may occur in the same landscape, has been suggested as a remedy. Akumulasi salinitas tanah menjadi masalah serius. Dalam waktu satu dekade saja, salinitas tanah dapat menjadi sangat tinggi dan seluruh embung harus “to be demolished “ dan lahan di sekitarnya harus dibiarkan memulihkan dirinya selama beberapa tahun, sebelum dibudidayakan kembali. Diunduh dari: ………….. 28/2/2013

46 Pengelolaan Vertisols untuk memperbaiki rezim lengas tanah: Water harvesting in areas with Vertisols – PANEN AIR HUJAN The deep and wide cracking of Vertisols retards wetting of the surface soil after a dry spell. Management should therefore be directed at storing water in the subsurface soil; the greater soil moisture reserves extend the possible length of a crop’s growing period. Beberapa teknik panen air hujan pada vertisols adalah: 1.Construction of small ponds for harvesting (drainage) water and keeping it in the higher parts of a watershed. This water can be used later, e.g. for strategic irrigation of vegetable gardens and/or for watering livestock. 2.Contour ploughing and bunding to enhance infiltration of water in the soil. A beneficial side effect of contour bunding is that it diminishes soil erosion, which is a severe problem of many Vertisols on slopes. In the highlands of Northern Ethiopia, continued contour ploughing resulted in stepped landscapes (‘dagets’) with step heights from 0.3 m to 3 metres. Grasses are planted on the riser and a more or less large strip of grass is maintained on the shoulder. 3.Mulsa vertikal untuk memperbaiki infiltrasi air ke dalam subsoil. Resitu tanaman ditempatkan secara vertikal dalam parit-parit kontur dengan bagian yang muncul di permukaan tanah sekitar 10 cm. Parit-parit dengan barisan mulsa vertikal ini berjarak pisak m. Diunduh dari: ………….. 28/2/2013

47 Pengelolaan Vertisols untuk memperbaiki rezim lengas tanah: Perbaikan Kondisi Perakartan Beberapa teknik untuk memulihkan kembali struktur tanah : 1.Soil heating/burning is practised in the Ethiopian highlands (the technique is locally known as ‘guie’). Burning causes the clay fraction to fuse to sand-sized particles. 2.Flood fallowing’ (flooding the land for 6 to 9 months) has been tried on low-lying Vertisols. Gases produced by fermentation and redistribution of oxides improve rooting conditions in heavy clay surface soils. 3.Pengolahan-datam tanah-tanah Vertisols yang mempunyai horison “indurated “ (mis. Beberapa Verisols Calcic dan Gypsic Vertisols dan Duric Vertisols) untuk menghancurkan subsoil yang keras dan kompak. Diunduh dari: ………….. 28/2/2013

48 Pengelolaan Status Hara pada Vertisols Vertisols merupakan tanah-tanah yang subur di daerah tropika bermusim kering. Tanah-tanah ini kaya kation basa, kalsium dan magnesium mendominasi kompleks pertukaran. Banyak sistem pertanian tradisional melibatkan periode bera (kosong) 1 – 4 tahun, dimana Vertisols dapat memulihkan kembali BOT nya pada tanah lapisan atas. Increased population pressure has now reduced the proportion of fallow land (read: the fallow period) and many areas are left in fallow only when completely degraded. Trials have shown that continuous cropping can be sustainable provided that soil and water conservation and fertiliser management are adequate. Diunduh dari: ………….. 28/2/2013

49 Pengelolaan Status Hara pada Vertisols Banyak Vertisols defisien nitrogen, sesuai dnegan rendahnya kandungan BOT. Pupuk Nitrogen harus diaplikasikan sedemikian rupa sehingga dapat dihindarkan penguapan amoniak yang berlebihan dan pencucian nitrat yang intensif. Placement of nitrate fertiliser in the root zone is best in dry regions whereas split banded application is preferred in wet conditions (Van Wambeke, 1991). If nitrogen is supplied in the ammonium form, is may be retained by the exchange complex of Vertisols, which curbs (leaching) losses. Diunduh dari: ………….. 28/2/2013

50 Pengelolaan Status Hara pada Vertisols Many Vertisols have a low content of available phosphorus. In the East-African highlands, Vertisols on weathered basalt showed little response to application of phosphate under low-intensity farming but phosphorus became strongly limiting if farming was intensified (and yields went up). Aridic, Alic and Chromic Vertisols contain much exchangeable aluminium and are notorious for inactivating fertiliser phosphate. In places Vertisols are low on sulphur and/or zinc. It is generally believed that application of animal manure would improve soil organic matter and soil physical properties, but trials remained largely inconclusive. Crop residues should be returned to the land but are rather used as animal feed, fuel and building materials. Penelitian dnegan pupuk hijau (legumes) menunjukkan peningkatgan hasil yang signifikan tanaman serealia dan peningkatan efisiensi serapan pupuk. Kombinasi bedengan lebar dan parit-dalam dengan aplikasi pupuk fosfat dan tumpangsari sereal- legume dapat memanfaatkan manfaat intekasi tanaman-ternak. The legumes overgrow the cereal stover after harvest (Jutzi et al., 1987; Gryseels, 1988). Diunduh dari: ………….. 28/2/2013

51 DESKRIPSI PROFIL-TANAH VERTISOLS INFORMASI TENTANG LOKASI : Soil Classification: USDA (1990): Very fine, montmorillontic, thermic Family of Entic Chromoxererts(EAAB) FAO/UNESCO: VR : Vertisol Location: 1.5 km EN Aidun Coordinates: Geographical : E/ N JTM: E/ N Elevation: 610 m asl Landform: Position: Lower slope Land System : 8/8 ( Undulating piedmont alluvial and colluvial plains) [GIS] Land Facet: 7 (Concave to flat lower slopes of alluvial plain ) Microrelief: Class: Even (<25 cm) Type: other Slope: Gently sloping (2%), rectilinear to NE Land Use : 1.5 Mixed tree /annuals Plant /Crop: olives, Toot Climate:Mean annual precipitation: Mean annual temperature: Air : 17.1° C / Soil (50cm): 20.0° C Soil moisture regime: Xeric Precipitation zone: mm p.a. Diunduh dari: ag.arizona.edu/oals/IALC/jordansoils/_pdf/jordan_vertisols.pdf ………….. 28/2/2013

52 DESKRIPSI PROFIL-TANAH VERTISOLS INFORMASI TANAH SECARA UMUM: Geology: Chalk / Limestone [q5 Fluv.deposits, sand, loess (Bender 1968)] Parent Material: Alluvium Drainage: Surface Runoff: None Soil Drainage Class: Well Surface Cover: Stones (15 %) Surface Feature: Cracks (10 %) Soil Surface Conditions: Dry / Extremely hard Erosion: Nil Soil Depth: 210 cm + Diagnostic Horizon or Property: Vertic at 0 cm and Calcic at 83 cm\ Diunduh dari: ag.arizona.edu/oals/IALC/jordansoils/_pdf/jordan_vertisols.pdf ………….. 28/2/2013

53 DESKRIPSI PROFIL-TANAH VERTISOLS Diunduh dari: ag.arizona.edu/oals/IALC/jordansoils/_pdf/jordan_vertisols.pdf ………….. 28/2/2013 Ap 0-20 cm Brown (10 YR 4/3) dry and dark yellowish brown (10 YR 3/4) moist; clay; very strong coarse angular blocky breaking to strong medium angular blocky; dry extremely hard; moist very friable; moderately sticky; moderately plastic; many medium (5-10 mm) vertical cracks; common fine (1-2 mm) fibrous and woody roots; 10 % angular chert fine gravel (2-5 mm); 1 % small (<5 mm) soft calcareous concretions; weak thin clay coating; slight reaction to HCl; gradual wavy boundary to cmBrown (10 YR 4/3) dry and dark yellowish brown (10 YR 3/4) moist; clay; moderate coarse angular blocky breaking to strong coarse platy; dry very hard; moderately sticky; moderately plastic; common medium (5-10 mm) vertical cracks; many fine (1-2 mm) fibrous and woody roots; 5 % angular chert fine gravel (2-5 mm); 2 % small (<5 mm) moderately hard calcareous concretions; moderately thin clay coating; slight reaction to HCl; clear wavy boundary to: cmBrown (10 YR 4/3) moist; clay; strong coarse prismatic breaking to strong medium prismatic; dry extremely hard; moist very friable; moderately sticky; very plastic; many fine (1-5 mm) irregular cracks; few very fine (<1 mm)fibrous roots; 5 % irregular chert fine gravel (2-5 mm); 3 % small (<5 mm) moderately hard calcareous concretions; moderate thick clay coating; slight reaction to HCl; gradual smooth boundary to: 83 – 210+ cm Dark yellowish brown (10 YR 4/4) moist; clay; very strong coarse prismatic breaking to strong medium subangular blocky; dry extremely hard; moist friable; moderately sticky; modeerately plastic; common fine (1-5mm) irregular cracks; few very fine (<1 mm) fibrous roots; 5 % irregular chert fine gravel (2-5 mm); 5 % medium (5-15 mm) hard calcareous concretions; strong thick clay coating; moderate reaction to HCl.

54 DESKRIPSI PROFIL-TANAH VERTISOLS INFORMASI TENTANG LOKASI : Soil Classification: USDA (1990): Very fine, montmorillontic, calcareous, thermic Family of typic Chromoxererts(EAAD) FAO/UNESCO: VR : Vertisol Location: Middle sample area 1/6 Coordinates: Geographical : E/ N JTM: E/ N Elevation: 815 m asl Landform: Position: Upper slope Land System : 8/10( Dissected limestone plateau with deep colluvial mantles) [GIS] Land Facet: 3 (Deep colluvial mantles on mid/lower slopes ) Microrelief: Class: Even (<25 cm) Type: Slope: Sloping (7%), rectilinear to NE Land Use : 1.4 Tree crops,orchards Plant /Crop: olives Climate:Mean annual precipitation: Mean annual temperature: Air : 15.8° C / Soil (50cm): 18.8° C Soil moisture regime: Xeric Precipitation zone: mm p.a. Diunduh dari: ag.arizona.edu/oals/IALC/jordansoils/_pdf/jordan_vertisols.pdf ………….. 28/2/2013

55 DESKRIPSI PROFIL-TANAH VERTISOLS INFORMASI TANAH SECARA UMUM: Geology: Limestone/chert [c2 Chalky/sandy LSt (Sir, Fuh (Bender 1968)] Parent Material: Colluvium Drainage: Surface Runoff: None Soil Drainage Class: Well Surface Cover: Stones (5 %) Surface Feature: Cracks (10 %) Soil Surface Conditions: Dry / Very hard Erosion: Nil Soil Depth: 200 cm + Diagnostic Horizon or Property: Calcic at 86 cm Diunduh dari: ag.arizona.edu/oals/IALC/jordansoils/_pdf/jordan_vertisols.pdf ………….. 28/2/2013

56 DESKRIPSI PROFIL-TANAH VERTISOLS Diunduh dari: ag.arizona.edu/oals/IALC/jordansoils/_pdf/jordan_vertisols.pdf ………….. 28/2/2013 Ap 0-20 cm Reddish brown (5 YR 5/4) dry and dark reddish brown (5 YR 4/4) moist; silty clayloam; moderate coarse subangular blocky breaking to moderate medium subangular blocky; dry hard; moist very friable; very sticky; slightly plastic; common fine (0.5-2 mm) tubular pores; common medium (5-10 mm) vertical cracks; few very fine (<1 mm) fibrous roots; 5 % angular chert coarse gravel ( mm); strong reaction to HCl; clear smooth boundary to: cm. Reddish brown (5 YR 5/4) dry and reddish brown (5 YR 4/4) moist; clay; strong very coarse angular blocky; moist very friable; slightly sticky; very plastic; few fine (0.5-2 mm) tubular pores; common fine (1-5 mm) vertical cracks; common fine (1-2 mm) fibrous roots; 5 % angular chert fine gravel (2-5 mm); weak thin clay coating; strong reaction to HCl; diffuse smooth boundary to: cm. Reddish brown (5 YR 4/4) dry and dark reddish brown (5 YR 3/4) moist; clay; strong coarse prismatic breaking to medium subangular blocky; dry very hard; moist friable; slightly sticky; very plastic; few very fine (0.5 mm) tubular pores; common very fine (<1 mm) vertical cracks; few very fine (<1 mm) fibrous roots; 5 % irregular hard limestone fine gravel (2-5 mm); moderate thick clay coating; strong reaction to HCl; diffuse smooth boundary to : cm. Dark raddish brown (5YR 3/4) moist; strong coarse prismatic breaking to strong medium prismatic; dry very hard; moist friable; slightly sticky; very plastic; few very fine (0.5 mm) tubular pores; common fine ( 15 mm) moderately hard calcareous concretions; strong thick clay coating; strong reaction to HCl; diffuse smooth boundary to : cm Yellowish red (5 YR 4/6 ) moist; clay; strong coarse prismatic breaking to strong medium prismatic; dry very hard; few very fine (0.5 mm) tubular pores; common fine ( 15 mm) moderately hard calcareous concretions; strong thick clay coating; violent reaction to HCl.

57 DESKRIPSI PROFIL-TANAH VERTISOLS INFORMASI TANAH SECARA UMUM: Field description of Pelloxerert (SSS, 1988). Classif.: Typic Pelloxerert, fine, montmorillonitic, thermic. (SSS, 1988). Typic Haploxerert, fine, montmorillonitic, thermic. (SSS, 1997). Location: Pietranera farm, Sicily, Italy (33S UB ). Physiographic position: gently sloping side of a hill; 371 m elevation. Topography: south-facing, 3 percent slope Vegetation: durum wheat (Triticum durum) Parent material: marly clays Diunduh dari: 28/2/2013

58 DESKRIPSI PROFIL-TANAH VERTISOLS Diunduh dari: ………….. 28/2/2013 Ap 0-25 cm. Black (5Y2/1) clayey, black (5Y2/1) moist; strong, fine and medium angular and subangular blocky structure with self-mulching on the surface; hard (dry), firm (moist); sticky and plastic (wet); fine and very fine roots; common fine and many very fine pores; strongly effervescent; 4 percent gravel by volume; clear smooth boundary. A cm. Black (5Y2/1) clayey, black (5Y2/1) moist; strong, medium and coarse angular blocky structure; common nonintersecting slickensides; cracks; hard (dry), firm (moist); sticky and plastic (wet); fine and very fine roots; few very fine pores; strongly effervescent; 4 percent gravel by volume; clear, wavy boundary A cm. Black (5Y2/1) clayey, black (5Y2/1) moist; strong, coarse and very coarse angular blocky structure; many nonintersecting slickensides; cracks; hard (dry), firm (moist); sticky and plastic (wet); few fine and very fine roots; few fine pores; strongly effervescent; 5 percent gravel by volume; gradual, wavy boundary. A cm. Black (5Y2/1) clayey, black (5Y2/1) moist; strong, coarse prisms breaking to strong, coarse angular blocky structure; many wide nonintersecting slickensides; cracks; hard (dry), very firm (moist); sticky and plastic (wet); few very fine roots; very few fine pores; strongly effervescent; gradual, wavy boundary. A4k cm. Black (5Y2/1) clayey, black (5Y2/1) moist; strong, coarse prisms breaking to strong, coarse angular blocky structure; many wide nonintersecting slickensides; little cracks; common fine soft masses of carbonate; hard (dry), firm (moist); sticky and plastic (wet); very few fine pores; strongly effervescent; gradual, wavy boundary. C 160+ cm. Marly clays

59 DESKRIPSI PROFIL-TANAH VERTISOLS TOC, TEC, C(HA+FA), referred to DM at 105°C, humification rate (HR) and degree of humification (DH Diunduh dari: ………….. 28/2/2013 Pelloxerert TOCTECC(HA+FA)HR(%)DH(%) Ap A A A A4k C

60 DESKRIPSI PROFIL-TANAH VERTISOLS DSC and TGA parameters: peak temperatures (°C), weight losses (%) related to the overall exothermic reactions (exotot), content of residue of combustion at 800°C (%), relative percentage of the fraction giving the first weight loss respect to the total (exo1%) Diunduh dari: ………….. 28/2/2013 Peak temp.(°C) Peak temp.(°C) Peak temp.(°C) Peak temp.(°C) Esotot (%) Residue 1°endotherm 1°exotherrm 2°exotherm 3°exotherm at 800°C (%) eso1% Pelloxerert Ap n.d A175.3n.d.426.5n.d A A376.9n.d A4k77.5n.d C

61 PENGELOLAAN VERTISOLS BERDASARKAN KENDALANYA Struktur dan Konsistensi Tanah Permukaan Vertisols are extremely hard when they are dry, but when wet they become extremely plastic, to almost a liquid state, with a very low bearing capacity. Their structure and consistency are generally a direct function of the ratio of clay to sand and the mineral composition of the clay. Vertisols with more than 50% clay and a dominance of montmorillonite have poor theological characteristics, since montmorillonite has a high surface charge and a low Zero Point of Net Charge (ZPNC). At the normal pH of Vertisols ( ), the soil is at least three units above the ZPNC, and if water is available, the mineral will be in a dispersed state. In this situation, interparticle binding forces are minimal and aggregates rupture fast. On drying, the tissue-paper-like sheets of montmorillonite pack against each other to form a very compact, low porosity aggregate. The bulk density (Table 1) changes from about 1.33 g cm -3 at 0.03 MPa tension to more than 1.8 g cm -3 at oven-dry conditions. Few roots can penetrate a medium with a bulk density of more than 1.6 g cm -3, and the shrinking force also tends to crush any roots. Tillage, unless high energy machinery is used, is extremely difficult in the dry state. In the moist state, the low bearing capacity and the plastic nature of the material are deterrents. Thus, tillage can only be conducted at a moisture tension close to, but not at, field capacity. Diunduh dari: ………….. 1/3/2013

62 PENGELOLAAN VERTISOLS BERDASARKAN KENDALANYA RETAKAN-RETAKAN DI PERMUKAAN Pengkerutan masa tanah yang sedang mengering mendorong terbentuknya retakan-retakan dengan pola poligonal. Retakan-retakan pada Vertisols dikelompokkan mnejadi tiga, yaitu (Grossman et al., 1985): 1.Retakan-retakan vertikal yang melingkupi struktur gumpal atau prismatik berukuran besar, pada bagian atas tanah. Retakan ini lebarnya 5-10 mm, dan menjadi semakin dalam kalau tanah mengering terus. 2.Cracks which form angular or blocky elements at the soil surface. These form at high water tensions, perhaps close to the wilting point. 3.Cracks which form deeper in the soil and are related to the internal pedoturbation associated with the slickensides. Diunduh dari: ………….. 1/3/2013

63 PENGELOLAAN VERTISOLS BERDASARKAN KENDALANYA RETAKAN-RETAKAN DI PERMUKAAN Vertisols with a granular surface soil mulch (the first set) tend to have lower bulk densities, perhaps due to a slightly higher organic matter content and to the space between the granules. Soils with angular surface structure (the second set) are easier to till and roots can permeate the spaces and move deeper. In addition, the filled crack spaces are probably the most likely areas for roots to establish during the next season because water flows easily through these areas (Grossman et al, 1985). Cracks have several indirect effects on crop performance. Because the rhizosphere is dehydrated last, the cracks normally form away from the stubble of the previous crop which sits at the centre of the polygon. In this case, dislodging of the plant is not a problem, but when the rhizosphere also dries out, soil shrinkage could strangle or shred crop roots. Cracks also retard surface wetting from any off-season rains. At the beginning of the rainy season, much of the water is not available to the plants since the water is rapidly evacuated by the void system. During the initial rain showers, the subsoil below the zone of the cracks is moistened. Hujan yang berturu-turut membasahi lapisan tanah-atas beberapa sentimeter, menyebabkan lapisan tipis ini mengembang dan “seal “ permukaan. Hujan selanjutnya menyebabkan genangan air di permukaan, pengolahan tanah menjadi sulir dan memacu terjadinya erosi.. Diunduh dari: ………….. 1/3/2013

64 PENGELOLAAN VERTISOLS BERDASARKAN KENDALANYA Pengelolaan Lengas Tanah Konservasi air selama musim kering dan pembuangan kelebihan air selama musim basah menjadi praktek pengelolaan yang sangat penting bagi Vertisols, yang membedakannya dengan tanah-tanah lainnya. Vertisols adalan tanah liat, dan karena mineral montmorillonitik, mempunyai kapasitas menahan air yang besar, hal ini mengakibatkan rendahnya konduktivitas hidraulik dan rendahnya laju infiltrasi. The high amount of available water illustrated in Figure 4 is deceptive, since not all the water is available to the plant. The water retention difference calculated from water retained at 0.03 MPa and 1.5 MPa tensions indicates the potential of the soil. Due to shrinkage and cracking, the water is not readily available to the roots even though there is moisture in the peas. Conserving the soil moisture while inducing more uniform soil wetting and maintaining a suitable surface filth requires deep tillage prior to the onset of the rains. Mulsa organik dan penambahan material tanah non-Vertisol dapat membantu berlangsungnya proses-proses ini dnegan baik. Bedengan lebar dan parit-dalam dapat membantu dan menguntungkan. Kalau curah hujan dicirikan oloeh tintensitas yang tinggi, durasi hujan yang pendek, maka saluran air yang mengikuti kontur sangat membantu menyalurkan kelebihan air hujan, dan meminimumkan erosi tanah permukaan. Diunduh dari: ………….. 1/3/2013

65 PENGELOLAAN VERTISOLS BERDASARKAN KENDALANYA Pengelolaan Lengas Tanah At the end of the rainy season, the challenge is to reduce evapotranspiration losses and conserve soil moisture, so that a succeeding crop can be grown from the stored moisture. Surface soil temperatures of the top few centimeters may reach 60°C in the dry season. Mulching, in combination with deep filth, reduces evaporative losses and surface soil temperatures. Matching crops to these soil conditions is also a partial solution, but socio-economic considerations do not always make this feasible. Pengelolaan air-tanah pada sebidang (petakan) lahan sangat sulit dan dalam beberapa kasus tidak mungkin dilakukan. Sistem drainage dan irigasi teknis untuk keseluruhan daerah aliran ternyata lebih menguntungkan dan dapat meningkatkan efektivitas pengelolaan air. Diunduh dari: ………….. 1/3/2013

66 PENGELOLAAN VERTISOLS BERDASARKAN KENDALANYA Depth functions of available moisture. (Russell M B Profile moisture dynamics of soil in Vertisols and Alfisols. Proceeding of the International Workshop on the Agroclimatological Research Needs of the Semi- Arid Tropics. ICRISAT (International Crops Research Institute for the Semi-Arid Tropics). Hyderabad, India, pp ) Diunduh dari: ………….. 1/3/2013

67 Soil Use and Management (2003) 19, Improved management of Vertisols in the semiarid tropics for increased productivity and soil carbon sequestration S.P. Wani, P. Pathak, L.S. Jangawad, H. Eswaran & P. Singh Hipotesis: Sistem pengelolaan daerah aliran yang diperbaiki dikombinaiskan dnegan praktek pertanmana yang tepat dapat meningkatkan produksi tanamn dan memperbaiki kualitas tanah Vertisols, dibandingkan dnegan praktek pertanian tradisional yang ada. Sistem yang diperbaiki mulai 1976, terdiri atas pengelolaan lahan terpadu untuk konservasi tanah dan air dengan kelebihan air hujan didsalurkan secara terkendali. Teknologi ini dikombinasikan dengan rotasi tanaman (berbasis legume) dan manajemen hara terpadu. The average grain yield of the improved system over 24 years was 4.7 t ha±1 yr±1, nearly a five-fold increase over the traditional system (about 1 t ha±1 yr±1). There was also evidence of increased organic C, total N and P, available N, P and K, microbial biomass C and N in the soil of the improved system. Hubungan positif antara P-tanah yg tersedia dan BOT menunjukkan bahwa aplikasi pupuk P pada Vertisols meningkatkan penangkapan karbon sebesar 7.4 t C ha ± 1 dan selanjutnya meningkatkan produktivitas pola tanam berbasis legum, dan akhirnya memperbaiki kualitas tanah. Diunduh dari: ddr.nal.usda.gov/bitstream/10113/48109/1/IND pdf………….. 28/2/2013

68 PENGELOLAAN VERTISOLS BERDASARKAN KENDALANYA Diunduh dari: ………….. 1/3/2013

69 TANAH VERTISOLS Diunduh dari: FOTO:SMNO.HTJATI.SARADAN.NOP2012. Further Reading Ahmad N., and A. Mermut Vertisols and Technologies for their Management. Development in Soil Science 24. Elsevier, New York. Developments in Soil Science 24 VERTISOLS AND TECHNGLOGIES FOR THEIR MANAGEMENT Edited by N. AHMAD The University ofthe West Indies, Faculty 0f Agriculture, Depart. 0f Soil Science, St. Augustine, Trinidad, West Indies A.MERMUT University of Saskatchewan, Saskatoon, sasks. S7N OWO, Canada


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