MANAJEMEN KESUBURAN TANAH Selengkapnya di marno.lecture.ub.ac.id

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1 MANAJEMEN KESUBURAN TANAH Selengkapnya di marno.lecture.ub.ac.id
BAHAN ORGANIK TANAH Prod Dr Ir Soemarno MS 2 OKTOBER 2013 Selengkapnya di marno.lecture.ub.ac.id

2 ORGANISME DALAM TANAH

3 Mikroba tanah memerlukan bahan organik dan humus untuk kehidupannya.
BAHAN ORGANIK & HUMUS Mikroba tanah memerlukan bahan organik dan humus untuk kehidupannya. The organic matter in your garden helps feed all the organisms and release nutrients. Humus acts like glue that holds all the particles together, and it helps prevent erosion and increases a garden's moisture holding ability. Humus Juga meningkatkan kesuburan tanah dengan jalan membuat unsur hara lebih tersedia bagi akar tanaman

4 Distribusi Humin, Asam Humat dan Asam Fulvat dalam tanah

5 Dinamika BO dalam tanah
DEKOMPOSISI OKSIDATIF HUMIFIKASI: Sintesis senyawa organik seperti asam humat dan asam fulvat KHELASI: Pembentukan senyawa kompleks organo-metal

6 FAKTOR IKLIM FAKTOR YG MEMPENGARUHI BOT
Kandungan BOT merupakan fungsi dari faktor-faktor pembentuk tanah. Jenny (1930) found that for loamy soils in the United States the effect of soil forming factor to OM were in the order:   Iklim         Vegetation         Topography Bahan Induk Tanah Waktu   FAKTOR IKLIM HUJAN & SUHU, influence the amount and type of vegetation as well as the rate of decomposition. The organic matter content of a soil increases with increasing decomposition up to the limit set by temperature.

7 FAKTOR LINGKUNGAN Laju dekomposisi bahan organik, termasuk substrat sederhana seperti glukosa, sangat beragam akibat perbedaan lengas tanah, temperatur , pH dan ketersediaan hara seperti P dan N untuk mendukung aktivitas mikroba tanah. The simpler monomers from carbohydrates, proteins, fats, and many polyphenolic materials are decomposed within weeks in soil environments. Polymers (complex compounds) such as hemi-cellulose or cellulose are decomposed more slowly and their resistance to decomposition increase with complexity. Sebagian senyawa organik yang ada dalam tanah merupakan hasil dari proses sintesis in-situ yang dimediasi oleh proses-proses mikrobiologis .  

8 KLASIFIKASI SERESAH (LITTER)
Akumulasi seresah dan dekomposisinya pada tanah permukaan (O horizons) sangat berbeda di antara ekosistem dan juga beragam di dlaam suatu ekosistem. Climatic factors exert a strong influence on the rate of biomass turnover, and the composition of plant debris and mode(s) of its incorporation into the soil influence activity of the fauna and flora involved in the various transformation processes. Klasifikasi lapisan seresah atau Horison O didasarkan pada rasio C/N seresah tumbuhan. Biasanya, limbah-limbah yang kaya N berhubungan dengan tingginya kandungan senyawa organik larut air (mis. Asam amino, gula) dan unsur hara S dan P yang menstimulir aktivitas mikroba dan proses awal degradation limbah organik tersebut.  

9 The same effect is observed in acid to very acid soils.
PENGARUH FAKTOR IKLIM Kondisi iklim dingin dan kering memperlambat proses mikrobiologis dalam tanah , terutama dekomposisi dan mineralisasi . Therefore, those soils contain large portions of organic matter as plant debris (macroorganic matter) than as humus. The same effect is observed in acid to very acid soils. The warmer the climate the higher the rates of microbial processes, i.e., the lower the organic matter content in those soils.

10 PENGARUH FAKTOR IKLIM Kandungan air tanah sangat berpengaruh terhadap dekomposisi dan akumulasi BOT. Waterlogged soils tend to accumulate organic matter because the microbial processes, in particular decomposition and mineralization, are slowed down. In aquic moisture regimes the drainage and soil aeration is poor (anaerobic conditions). Anaerobic oxidation of organic residues is less efficient than aerobic oxidation. If organic matter is accumulated the soil development is towards organic soils (Histosols). Histosols generally form in wet, poorly aerated sites, such as shallow lakes and ponds, depression areas, swamps, and bogs and are the end product of natural eutrophication.  

11 VEGETASI / ORGANISME TANAH
Vegetasi mempengaruhi BOT melalui efeknya pada tipe, jumlah, dan penempatan residu organiknya. Komposisi BOT berkaitan dnegan sifat komunitas flora dan fauna tanah. Kalau biomasa ditambahkan ke tanah , ada tiga macam rekasi yang berlangsung:   Reaksi Dekomposisis dikatalisis oleh ensim-ensim. Pada umumnya, kalau rasio C/ N > 25, terjadi imobilisasi neto, sedangkan pada rasio C/N < 25 terjadi mineralisasi neto. Classically, organic matter has been characterized via various extraction/fractionation procedures into non-humic (lipids, carbohydrates and other 'simple' organic compounds) and the more complex humic susbstances (humic acids, fulvic acids and humin). These divisions do not align well with current understanding of the biological and biochemical processes operating during decomposition and stabilization of organic material in soil.  

12 VEGETASI / ORGANISME TANAH
Microorganisms use litter and other organic compounds for respiration, where organic material is mineralized and CO2 and inorganic elements are released. The prokaryotes include the bacteria and actinomycetes, the eukaryotes include the fungi, algae and protozoa. They can be classified in heterotrophs, which require C in the form of organic molecules for growth, and the autotrophs, which can synthesize their cell substance from the C of CO2, harnessing the energy of sunlight (in the case of photosynthetic bacteria and algae) or chemical energy from the oxidation of inorganic compounds (the chemoautotrophs). Pengelompokkan mikroba tanah berdasarkan kebutuhan O2: Aerob, those requiring O2 as the terminal acceptor of electrons in respiration Anaerob Fakultatif, those normally requiring O2 but able in anaerobic conditions to use NO3- and other inorganic compounds as electron acceptor in respiration Anaerob Obligat, mikroba yang hanya dapat tumbuh dalam kondisi tidak ada oksigen O2.

13 Cation Exchange Capacity = Kapasitas Tukar Kation (KTK)
SIFAT & CIRI BOT Cation Exchange Capacity = Kapasitas Tukar Kation (KTK) Organic matter makes a substantial contribution to the cation exchange capacity (CEC) of the whole soil, and hence to the retention of exchangeable cations. Proses humifikasi menghasilkan koloid organik yang mempunyai luas permukaan-jenis sangat tinggi. KTK bahan organik tanah sepenuhnya tergantung pada pH (pH-dependent) dan dibuffer (disangga) pada kisaran konsentrasi H+

14 SIFAT & CIRI BOT Gugus fungsional seperti -COOH (karboksilat) dan gugus >OH (fenolat), melepaskan H+ sehingga dapat mengikat kation K+, Na+, Ca++ , atau Mg++. These cations are generally considered to be part of a reservoir of exchangeable cations in the soil. Nilai KTK bahan organik beragam di antara cmol/kg. Sekitar % dari KTK tanah berasal dari bahan organik.  

15 Interaksi BOT dengan Material LIAT
SIFAT & CIRI BOT Interaksi BOT dengan Material LIAT Tipe liat dan kandungan liat tanah berpengaruh terhadap akumulasi BOT dan stabilisasi humus. This is because clay content is usually correlated with other factors that result in organic matter production. In particular, clay content is often correlated with greater plant growth for chemical (plant nutrients) and physical (water regime) reasons and results in greater annual input of C. There is also evidence that clay type and associated cations influence organic matter stabilization. Sebaliknya, adanya bahan organik sangat penting bagi pembentukan dan stabilisasi struktur (agregat) tanah.

16 SIFAT & CIRI BOT Asam Humat & Fulvat
Asam-asam fulvat dan humat, serta polimernya dijerap pada permukaan mineral oleh gugus-gugus fungsional, seperti karboksil (-COOH), carbonyl (-C=O), hydroxyl (-OH), amino (=NH), dan amine (-NH 2). Large uncharged polymers (e.g. polysaccharides) can be adsorbed by hydrogen-bonding and by van der Waals' forces, and also function as bonding agent between mineral particles.

17 SIFAT & CIRI BOT Percobaan lapangan dan laboratorium dnegan menggunakan senyawa organik mengandung karbon berlabel 14C dilakukan untuk mengevaluasi perilaku bahan organik yang ditambahkan ke tanah. The finer textured soils typically show a larger initial flush of microbial activity that is followed by greater incorporation and stabilization of organic matter in the soil than found in coarser textured soils.   Porositas tanah sangat berpengaruh terhadap perilaku residu organik yang ditambahkan ke tanah, karena porositas ini menentukan jenis mikroba yang dominan dan juga dapat menentukan pergerakan molekul organik dalam tanah sehingga terhindar dari serangan mikroba.

18 SIFAT & CIRI BOT Menurut Kilbertus (1980), bakteria hanya dapat berfungsi dalam pori tanah yang ukurannya tiga kali lebih besra dari ukuran bakteri. Bakteri tidak dapaty berfungsi dalam pori tanah yang besar-besar, efek bakteri lebih besar dnegan semakin meningkatnya kandungan liat tanah (tanah semakin halus teksturnya). Thus, in clay-rich soils the physical separation between microorganisms and organic molecules can be extensive and account in part for their tendency to have larger accumulations than coarser-textured soils formed under otherwise comparable conditions.

19 SIFAT & CIRI BOT It has been suggested that stabilization of organic molecules may occur between quasi-crystals (a packet of several layers) and within interlayers of 2:1 swelling clays such as montmorillonite. This mechanism has been inferred from examination of high resolution transmission electron micrographs that show presence of organic molecules within ~1.0 µm diameter pores between clay crystals. It is assumed that these domains provide considerable protection against microbial attack. Humic substances coat, partially or totally, mineral particles such as clay, often protecting the coated particles from weathering.  

20 JEMBATAN KATION & RETENSI BAHAN ORGANIK
SIFAT & CIRI BOT JEMBATAN KATION & RETENSI BAHAN ORGANIK Polyvalent cations (e.g., Ca2+, Mg 2+, Fe3+, Al 3+) play a major role in the stabilization of organic and inorganic colloids - when in abundance limiting their ability to shrink and swell - favoring a flocculated (stable) condition. Polyvalent cations serve as bridges between negatively charged clays (inorganic colloids) and negatively charged organic colloids, which enhances structural stability.   In neutral and alkaline soils, Ca2+ and Mg2+ are the major cations responsible for bridging and the hydroxypolyvalent cations, Fe3+ and Al3+, serve a similar role in acid soils and those with a large amount of hydrous oxides. There are empirical observations that calcareous soils tend to have larger accumulations of organic matter than their non-calcareous neighbors.

21 SIFAT & CIRI BOT Percobaan pengapuran memberikan informasi mengenai peranan Ca2+ dalam konversi residu tanaman menjadi bahan organik yang stabil . Addition of CaSO 4 or CaCO3 to soil containing 14C-labelled wheat straw produces an initial 'priming effect' on microbial biomass activity resulting in accelerated release of CO 2 that is followed by a greater retention and stabilization of organic matter than found in control treatments (i.e., no Ca 2+ addition). ‘Priming effect' dari penambahan Ca++ ke tanah adalah stabilisasi bahan organik.

22 SIFAT & CIRI BOT JEMBATAN KATION
Mekanisme stabilisasi yang terjadi adalah melalui pembentukan jembatan kation Ca++.   The mechanisms that control Fe3+ and Al3+ linkages with organic molecules are poorly understood. Fe3+ is only sparingly soluble in most soils and occurs mainly in hydrous oxide forms, some of which may be positively charged at low pH because of protonation or addition of hydrogen ions to surface exposed hydroxyl groups. Such positive charged surfaces may attract negatively charged organic molecules. Mekanisme serupa yang mungkin terjadi adalah dengan oksida-oksida hidrat Al Akan tetapi pada tanah yang sangat masam dengan pH rendah, dapat terjadi toksisitas Al3+ pada tumbuhan, yang selanjutnya akan membatasi masukan karbon ke tanah.  

23 The complexes can hardly be dissolved.
SIFAT & CIRI BOT Pembentukan Khelat The chelation process results in the formation of chelates, which are stable complexes containing organic compounds and metallic cations, which are trapped within the ring structures. The complexes can hardly be dissolved. Chelates formed with certain di- and polyvalent cations are the most stable, the stability falling in the order Cu > Fe = Al > Mn = Co > Zn.   Soil Moisture Humic and fulvic acids are considered to be hydrophilic colloids. As such, they have a high affinity for water and are solvated in aquaeous solution.  

24 Generally, organic matter can hold up to 20 times its weight in water.
SIFAT & CIRI BOT Organic compounds (organic colloids < 2 micrometer) have the characteristic to increase field capacity because they tend to hydrolize. Generally, organic matter can hold up to 20 times its weight in water. This is important particularly for sandy soils to improve soil moisture conditions during summer seasons, when precipitation is limited and evapotranspiration rates are high. If organic matter becomes dry it is prone to wind erosion and can be transported over wide distances.  

25 This buffering helps to maintain an uniform reaction in the soil.
SIFAT & CIRI BOT Soil Temperature Because of the dark black color of organic compounds the adsorption of solar radiation is high and reflection low, therefore soils high in SOM tend to warm up faster than soils low in SOM.   Buffering Organic matter exhibits buffering in slightly acid, neutral, and alkaline range. This buffering helps to maintain an uniform reaction in the soil.    

26 PERUBAHAN IKLIM GLOBAL
BOT merupakan cadangan utama karbon di dalam biosfer, diperkirakan sekitar x 1015 g secara global, hampir duakali lipat dari jumlah CO2 di dalam atmosfer . BOT dapat berfungsi sebagai SUMBER dan SINK karbon selama perubahan iklim global. Perubahan iklim mempengaruhi laju akumulasi dan dekomposisi karbon dlaam BOT, baik secara langsung melalui perubahan suhu dan lengas tanah, dan secara tidak langsung melalui perubahan pertumbuhan tanaman dan rhizo-deposition. Faktor penggunaan lahan dan pengelolaannya juga sangat berpengaruh terhadap dinamika BOT.

27 Topografi mempengaruhi banyaknya runoff, erosi dan deposisi.
Kalau erosi mengangkut material tanah dari lahan-lahan yang miring, maka lapisan tanah yang tertinggal akan semakin tipis dan warnanya lebih terang dengan kandungan BOT yang rendah. Soils found on footslope or toeslope areas generally show a higher organic matter content and thicker A horizon. Because soil moisture often differs across a hillslope microbial activity is affected as well. Classification Litter Classification Litter accumulation and its extent of decomposition on the soil surface (O horizons) differs widely among ecosystems and locally within ecosystems. Climatic factors exert a strong influence on the rate of biomass turnover, and the composition of plant debris and mode(s) of its incorporation into the soil influence activity of the fauna and flora involved in the various transformation processes. The following classification of litter layers or O horizons is based on C:N ratios of the plant debris. In general, debris with a large amount of N is associated with large amount of water soluble organic compounds (e.g., amino acids, sugars) and elements such as S and P that stimulate microbial activity and thus initial degradation of the debris.  

28 Parent Material = BAHAN INDUK TANAH
On sandy soils less organic matter is found than on silty or clayey soils. This can be explained by the characteristics of different sized particles. Sandy soils are well aerated and tend to have a low soil moisture content, which are environmental conditions favor for low organic matter content. Vice versa, clayey soils are less aerated with a high amount of fine micropores and tend to have a higher soil moisture content than medium and fine textured soils, hence, they tend to have a high organic matter content. Furthermore, calcareous or Al/Fe rich soils tend to have higher organic matter contents.  

29 Time = WAKTU "Turnover times" UNTUK C-ORGANIK DALAM TANAH dapat diperoleh dengan jalan membagi kandungan bahan organik tanah dengan input biomasa tahunan dan hasilnya dinyatakan dalam tahun. The turnover time for global C is 30 to 40 years, but varies by orders of magnitude for different ecosystems (the estimates are gross averages and subject to error). Organic soils (Histosols) whose formation is favored by water logging may have turnover times exceeding 2000 y and soils of tundra regions where low temperatures retard oxidation may have turnover times exceeding 100 y. “Turnover time” yang paling pendek, sekitar 4 tahun terjadi untuk hutan-hutan di daerah ekuator. Walaupun produksi primer neto di ekosistem hutan ekuator ini snagat tinggi, namun proses dekomposisi bahan organik yang cepat tidak memungkinkan akumulasi BOT dalam jumlah yang besar.

30 BOT & RESIDU PESTISIDA Kandungan BOT merupakan salah satu ciri tanah yang sangat penting, tetapi seringkali dilupakan. Residu pestisida secara khas melekat (terikat) pada bahan organik tanah, sehingga mengurangi peluang pencuciannya. Oleh karena itu semakin sedikti kandungan BOT, residu pestisida dlaam tanah akan mudah tercuci dan mencemari air tanah. When the organic-matter level is low, there is also an increased risk of applying excessive amounts of pesticides and possibly damaging the crop. Therefore, some pesticide labels will list lower application rates for soils with a lower organic-matter content. Kalau kita mengetahui kandungan BOT suatu tanah, maka kita dapat mengatur aplikasi dosis yang tepat, sehingga menghemat biaya.

31 BOT - TEKSTUR - PERMEABILITAS
BOT mempengaruhi tingkat pencucian residu pestisida dalam tanah. Pengaruh ini juga berkaitan dengan tekstur tanah dan permeabilitas tanah. Texture refers to the relative proportion of sand, silt, and clay in the soil. Leaching is more likely in sandy, coarse, or light-textured soils. Pesticides are less likely to leach in fine- or heavy-textured soils, such as those with a high percentage of clay. Permeabilitas menyatakan kemampuan air untuk bergerak di dalam tubuhn tanah. Kalau suatu tanah mempunyai permeabilitas yang rendah, air hujan dapat menggenang di permukaan tanah. Kalau suatu tanah permeabilitasnya tinggi, air dapat mengalir /bergerak dalam tanah secara lebih leluasa dan dapat menyebabkan pencucian unsur hara.

32 BOT & SIKLUS KARBON Siklus karbon mendeskripsikan bagaimana C disirkulasikan melalui atmosphere, biosphere, pedosphere, dan hydrosphere. The dead organic matter of the soil is colonized by (micro)organisms, which derive energy for growth from the oxidative decomposition of complex organic molecules. Decomposition is the biochemical breakdown of mineral and organic materials. During decomposition, anorganic elements are converted from organic compounds, a process called mineralization. For example, organic-N and -P is mineralized to NH 4+ and H 2PO4 -, and C is converted to CO2. The remainder of the substrate C used by the microorganisms is incorporated into their cell substance (biomass), which is called immobilization. Hara mineral-mineral dapat diimobilisasi dan dilepaskan kembali setelah organisme mati atau melapuk. Humifikasi merupakan proses pembentukan humus (polimer organik yang kompleks) dari bahan organik segar, seperti asam-asam fulvat, asam-asam humat dan humin.  

33 Bahan organik tanah merupakan kompleks kum,pulan organisme hidup, bangkai yang sedang terdekomposisi, dari tumbuhan dan hewan. As crop residues accumulate on the soil surface, they are added to the soil organic matter complex by the action of bacteria, fungi and larger organisms. In no till fields, soil organic matter is greatest in the top inch of soil Jumlah BOT dalam tanah lapisan atas tergantung pada sistem pengolahan tanah.

34 APA BAHAN ORGANIK ITU? Bahan organik terdiri atas berbagai macam senyawa karbon yang ada dalam tanah . Originally created by plants, microbes, and other organisms, these compounds play a variety of roles in nutrient, water, and biological cycles. For simplicity, organic matter can be divided into two major categories: stabilized organic matter which is highly decomposed and stable, and the active fraction which is being actively used and transformed by living plants, animals, and microbes. Dua kategori lain dari bahan organik adalah organisme hidup dan residu organik yang masih segar.

35 BAHAN ORGANIK STABIL Banyak organisme tanah men-dekomposisi sisa-sisa tanaman dan hewan, dan mengubah bahan organik menjadi senyawa-senyawa baru. Setelah proses transformasi ini berlangsung lama, material yang tertinggal berupa senyawa kompleks yang sulit terdekomposisi. Other compounds become bound inside soil aggregates where microbes cannot reach. These hard-to-decompose, or stabilized, substances make up a third to a half of soil organic matter. Scientists often divide stabilized organic matter into three chemical groups: humic acids, fulvic acids, and humins. Fungi and actinomycetes create many of the humic acids that combine in soil to become stable compounds. Much of the stabilized matter in your soil originated from plants that grew one or more centuries ago. Some of these old compounds are bound to clay, and are important in gluing together tiny aggregates of soil particles. Stabilized organic matter acts like a sponge and can absorb six times its weight in water. In sandy soils, water held by organic matter will make the difference between crop failure or success during a dry year.

36 PERUBAHAN BENTUK BAHAN ORGANIK TANAH
PENAMBAHAN. When roots and leaves die, they become part of the soil organic matter. TRANSFORMASI. Soil organisms continually change organic compounds from one form to another. They consume plant residue and other organic matter, and then create by-products, wastes, and cell tissue. MIKROBA MEMBERI MAKAN TANAMAN. Some of the wastes released by soil organisms are nutrients that can be used by plants. Organisms release other compounds that affect plant growth. STABILISASI BAHAN ORGANIK. Akhirnya senyawa-senyawa organik menjadi stabil dan tahan terhadap perubahan lanjut.

37 BAHAN ORGANIK LEBIH DARI PUPUK
Bahan organik tidak hanya terdiri atas N, P, K, dan karbon. Two sources of organic matter with the same nutrient content or total organic matter content might not have equal effects on your crops and soils. In one research trial, fields treated with animal manure had different microorganisms and enzymes than fields where green manure or mineral fertilizers were used. The importance of these differences are not well studied, but they probably affect nutrient cycling and pests. In your system, manure may mean positive effects such as reducing some diseases, or negative effects such as increasing weed growth. Residu tumbuhan juga beragam sifatnya sebagai sumber bahan organik tanah. Biomasa bagian tajuk tanaman fungsinya dalam tanah berbeda dengan akar, meskipun ia dibenamkan ke dalam tanah. Demikian juga beragam akar tumbuhan tidak sama perilakunya. Misalnya, akar tunggang utama menciptakan liang-liang vertikal dalam tanah, sedangkan akar-akar serabut yang ukurannya lebih halus slebih banyak berfungsi dalam proses aggregasi tanah.

38 APA YANG DAPAT DILAKUKAN OLEH BOT? SIKLUS UNSUR HARA
Meningkatkan kemampuan tanah menahan hara (KTK). BOT menjadi cadangan hara tanaman . Chelates (binds) nutrients, preventing them from becoming permanently unavailable to plants. Is food for soil organisms from bacteria to worms. These organisms hold on to nutrients and release them in forms available to plants. Dinamika Air Tanah Memperbaiki infiltrasi air tanah. Mengurangi Evaporasi. Meningkatkan daya simpan air , terutama pd tanah berpasir.

39 APA YG DAPAT DILAKUKAN oleh BOT? Struktur Tanah Efek lain dari BOT
Reduces crusting, especially in fine-textured soils. Encourages root development. Memperbaiki aggregasi, mencegah erosi. Mencegah pemadatan tanah. Efek lain dari BOT Pesticides break down more quickly and can be "tied-up" by organic matter (and clays). Dark, bare soil may warm more quickly than light-colored soils, but heavy residue may slow warming and drying in spring. Efek-efek BOT berhubungan dengan aktivitas mikroba tanah yang menggunakan BOT sebagai sumber makanan dan energinya.

40 APA yg MENENTUKAN KANDUNGAN BOT?
Jumlah BOT dalam suatu tanah merupakan hasil dari dua proses: Penambahan bahan organik segar ke tanah (akar, seresah si permukaan tanah, pupuk kandang dll.), dan Kehilangan BO melalui proses dekomposisi. Faktor Pengelolaan Practices that increase plant growth on a field (cover crops, irrigation, etc.) will increase the amount of roots and residue added to the soil each year. On the other hand, intensive tillage increases the loss of organic matter by speeding decomposition. While tillage primarily burns younger organic matter, older, protected organic compounds can be exposed to decomposition if small aggregates are broken apart. Perubahan jumlah BOT dan praktek pengolahan tanah dapat berpengaruh terhadap kedalaman BOT.

41 APA yg MENENTUKAN KANDUNGAN BOT?
Tekstur Tanah Fine-textured soils can hold much more organic matter than sandy soils for two reasons. First, clay particles form electrochemical bonds that hold organic compounds. Second, decomposition occurs faster in well-aerated sandy soils. A sandy loam rarely holds more than 2% organic matter. Iklim High temperatures speed up the degradation of organic matter. In areas of high precipitation (or irrigation) there is more plant growth and therefore more roots and residues entering the soil.

42 APA yg MENENTUKAN KANDUNGAN BOT?
Posisi Bentang Lahan Low, poorly-drained areas have higher organic matter levels, because less oxygen is available in the soil for decomposition. Low spots also accumulate organic matter that erodes off hill tops and steep slopes. Vegetasi In prairies, much of the organic matter that dies and is added to the soil each year comes from grass roots that extend deep into the soil. In forests, the organic matter comes from leaves that are dropped on the surface of the soil. Thus, farmland that was once prairie will have higher amounts of organic matter deep in the soil than lands that were previously forest.

43 Bgm Kandungan BOT Berubah?
Untuk membangun kandungan BOT dalam tanah-lapisan-atas, lebih banyak BO harus ditambahkan ke tanah untuk menggantikan BO yang terdekomposisi dan yang hilang akibat erosi. Like a person trying to lose or gain weight, increasing organic matter is about changing the balance between how much energy goes in and how much is burned off. Another way to think of soil is like a giant wood stove. You continually add organic matter (wood), and it burns to release energy and nutrients that will be used by plants and microorganisms. Kita menginginkan proses perombakan yg lambat & mantap, sehingga melepaskan unsur hara yang diperlukan tanaman pada saat yang tepat.

44 Pengaruh pengolahan tanah thd kehilangan dan penambahan BOT
Pengaruh pengolahan tanah thd kehilangan dan penambahan BOT . Most organic matter losses in soil occurred in the first decade or two after land was cultivated. Native levels of organic matter may not be possible under agriculture, but many farmers can increase the amount of active organic matter by reducing tillage and increasing organic inputs.

45 Ciri-ciri kimiawi dari substansi HUMIK

46

47 MENGAPA BAHGAN ORGANIK SANGAT PENTING?
Pengelolaan dan perbaikan BOT diperlukan untuk mempertahankan: Struktur tanah yg baik Aktivitas mikroba tanah Kemampuan tanah menyangga perubahan pH Cadangan unsur hara Penyimpanan air tanah. Soils with low organic matter have low microbial activity. The soil microbes break down harmful chemicals such as pesticides. When soils have low microbial activity and low water holding ability they are more likely to leach pesticides. This means that cropping soils leak pesticides more readily than other soils. Soils that have lost a lot of their organic matter need more and more fertiliser and water to maintain productivity.

48 MENGAPA BAHGAN ORGANIK SANGAT PENTING? Peningkatan BOT
Meminimumkan kultivasi dan gangguan atas tanah berarti meminimumkan kehilangan BOT. By implementing reduced tillage or no-tillage, where possible, soil structure and soil organic matter will be preserved. Erosion risks will be reduced as well. To increase the organic matter in the soil you can: grow annual cover crops between productive crops – these cover crops can then be mulched into the ground apply compost, organic manure or effluent to the soil. With more organic matter, soil is better able to store nutrients and water, and has improved soil structure. This makes soil more resistant to erosion by wind and water.

49 KONTRIBUSI BIOTA TANAH TERHADAP DEKOMPOSISI BOT DAN SUPLAI N ANORGANIK

50 KESEHATAN TANAH KESEHATAN TANAH didefinisikan sbg “kemampuan tanah untuk berfungsi di dalam batas-batas ekosistem guna melestarikan produktivitas biologis , menjaga kesehatan lingkungan, dan mendukung kesehatan tanaman dan ternak.” In some cases, the term “soil quality” may be used; the two terms have the same meaning. Soil properties that determine soil health include soil texture, depth of soil, infiltration, bulk density, water-holding capcity, soil organic matter, pH, electrical conductivity, microbial biomass, carbon and nitrogen, potentially mineralizable nitrogen, and soil respiration.

51 KESEHATAN TANAH vs BOT BOT terdiri atas bahan organik hidup, bahan organik yg terdekomposisi sebagian, dan bahan organik yg telah terdekomposisi Soil organic matter is typically 1 to 5 percent of the total dry weight of topsoil, with lower amounts in the subsoil. Different types of organic matter play unique roles in soil. Highly decomposed organic matter (also called humified organic matter) typically makes up 95% of the total soil organic matter, and contributes to the cation exchange capacity, the water holding capacity, and stability of small aggregates. Other, less highly decomposed types of organic matter such as polysaccharides are produced by bacteria and determine the stability of larger aggregates. Bahan organik hidup seperti fungi dan akar tanaman sangat penting untuk stabilitas agregat tanah yg berukuran besar.

52 TEORI PEMBENTUKAN HUMUS: TEORI POLI - FENOL