Bahan kajian Dasar-dasar PENGELOLAAN KESUBURAN TANAH Oleh: Prof.Dr.Ir.Soemarno,M.S. Jur. Tanah FP-UB, September 2011 Bahan kajian Dasar-dasar PENGELOLAAN KESUBURAN TANAH Oleh: Prof.Dr.Ir.Soemarno,M.S. Jur. Tanah FP-UB, September 2011

LIMA FAKTOR PENGELOLAAN TANAH Pengendalian GULMA. PERGILIRAN TANAMAN Penyediaan AIR YANG CUKUP PENGENDALIAN HAMA & PENYAKIT PENYEDIAAN UNSUR HARA

DINAMIKA HARA TANAH Mempertahankan jumlah optimum unsur hara hanya dapat terlaksana dengan menciptakan keseimbangan yang baik antara penambahan dan kehilangannya Benefits of Organic Matter Increases soil CEC Stabilizes nutrients Builds soil friability and tilth Reduces soil splash Carbon Sequestration C cycling in agroecosystems has a significant impact at the global scale because agriculture occupies approximately 11% of the land surface area of the earth. Benefits of Organic Matter Reduces compaction and bulk density Provides a food source for microorganisms Increases activities of earthworms and other soil critters

POKOK-POKOK PENGELOLAAN KESUBURAN TANAH. 1. Suplai nitrogen dari: Sisa TanamanTanaman biasa Pupuk kandangTanaman legume Hujan & irigasiPupuk hijau Pupuk nitrogenKompos 2. Penambahan bahan organik melalui: Sisa tanaman legume dan non legume Pupuk kandang Pupuk hijau 4. Penambahan fosfat: Pupuk superfosfat, atau Pupuk lainnya 3. Penambahan kapur bila diperlukan Batu kapur kalsit atau dolomit yg biasa dilakukan 7. Penambahan unsur mikro: Sebagai garam terpisah atau campuran 5. Penambahan kalium tersedia: Pupuk kandang Sisa tanaman Pupuk Kalium 6. Kekurangan belerang diatasi dg: Belerang, gipsum, superfosfat, Amonium sulfat, Senyawa belerangdalam air hujan

MENGATASI KEKURANGAN NITROGEN Ketersediaan nitrogen dalam tanah sangat dipengaruhi oleh keberadaan bahan organik dalam tanah Apa saja yang dapat dilakukan untuk itu? Penambahan & Kehilangan N-tersedia N-tersedia dlm tanah Atmosfer Pengikatan NitrogenPupuk Buatan SimbiotikNon-Simbiotik Sisa tanaman Pupuk Kandang Bahan Organik Panen Tanaman Hilang Pencucian Hilang Erosi

MEMPERTAHANKAN BAHAN ORGANIK TANAH Carbon Inputs to Soil Crop residues Cover crops Compost, and Manures Carbon Substrate The majority of C enters the soil in the form of complex organic matter containing highly reduced, polymeric substances. During decomposition, energy is obtained from oxidation of the C-H bonds in the organic material. Soil Carbon Equilibrium Input primarily as plant products Output mediated by activity of decomposers It is common that from 40 to 60% of the C taken up by microorganisms is immediately released as CO2.

PENTINGNYA Ca & Mg Ketersediaan Ca dan Mg dalam tanah biasanya ditentukan oleh bahan induk tanah. Kapur pertanian merupakan sumber Ca dan Mg yang lazim digunakan ke tanah-tanah masam yang defisien Ca dan Mg Penambahan dan kehilangan Ca dan Mg tersedia dalam tanah Sisa tanaman & Pupuk Kandang Pupuk Komersial Mineral Tanah KAPUR PANEN TANAMAN Hilang pencucian Hilang Erosi

MEMPERTAHANKAN KETERSEDIAAN FOSFAT. Ketersediaan fosfat dalam tanah ternyata berkaitan erat dengan fenomena fiksasi fosfat oleh partikel-partikel tanah dan pH tanah. …………. Bagaimaan optimasinya?.. Kehilangan & Penambahan P-tersedia P-tersedia dalam tanah Sisa tanaman Pukuk kandang Pupuk komersial Mineral P-tanah Bahan Organik Tanah Terangkut tanaman Hilang Pencucian Hilang Erosi Fiksasi

KETERSEDIAAN KALIUM Tanah mineral umumnya mengandung cukup banyak kalium, kisaran 40 ton setiap hektar lapisan olah tanah. Namun demikian hanya sebagian kecil yangtersedia bagi tanaman Kehilangan & Penambahan Kalium: K-tersedia tanah Pupuk komersial Sisa tanaman & Pupuk Kandang Mineral-K lambat tersedia Terangkut tanaman Kehilangan pencucian Kehilangan erosi Kehilangan Fiksasi

The Soil Food Web In 1 teaspoon of soil there are… 5 or more Earthworms Up to 100 ……………. Arthropods 10 to 20 bacterial feeders and a few fungal feeders ……. Nematodes Several thousand flagellates & amoeba One to several hundred ciliates ……. Protozoa 6-9 ft fungal strands put end to end ………. Fungi 100 million to 1 billion …………. Bacteria

11 Classical C Pools Nonhumic substances—carbohydrates, lipids, proteins Humic substances—humic acid, fulvic acid, humin BOT berpengaruh terhadap: -Plant nutrition -Soil and Plant health -Soil physical, chemical and biological properties

12 BOT FRAKSI RINGAN The light fraction (LF) with a density of ~1.6 gm cm-3 is relatively mineral free and consists of partially decomposed plant material, fine roots and microbial biomass with a rapid turnover time. The LF is a source of readily mineralizable C and N, accounts for ~50% of total soil C and declines rapidly under cultivation.

13 BOT --- FRAKSI BERAT --- The Heavy Fraction The heavy fraction (HF) is organic matter adsorbed onto mineral surfaces and sequestered within organomineral aggregates. The HF is less sensitive to disturbance an chemically more resistant than the LF.

14 Bacteria vs. Fungi Bacteria are smaller than fungi and can occupy smaller pores and thus potentially have greater access to material contained within these pores. Bacteria are less disrupted than are fungi by tillage practices commonly used in agriculture. Major features of some representative soil bacteria (true bacteria). Sumber:

15 Bacteria vs. Fungi Fungi tend to be selected for by plant residues with high C/N ratios. Fungi have a greater influence on decomposition in no-till systems in which surface residues select for organisms that can withstand low water potentials and obtain nutrients from the underlying soil profile.

16 Bacteria vs. Fungi Fungi often produce more cell wall than cytoplasmic material when starved for N, and thus can extend into new regions of the soil without requiring balanced growth conditions. The filamentous growth structure of a fungus permits it to access C in one location and nutrients in another.

17 Soil Organic Matter Content How organic matter in soil influences the soil-plant relationship? Decomposed organic matter provides nutrients for plant growth (Mineralization) It determines the soil’s temperature, air ventilation, structure and water management It contains bioregulators which affects plant growth It contains bioregulators, which affects plant growth (enzymes, hormones, etc.) Its carbon and energy content is the soil’s energy battery for future use It determines the soil’s capacity to compensating, regenerating and protecting the environment

18 PENTINGNYA BOT ➢ Organic material in the soil is essentially derived from residual plant and animal material, synthesised by microbes and decomposed under influence of temperature, moisture and ambient soil conditions ➢ Soil organic matter is extremely important in all soil processes ➢ Cultivation can have a significant effect on the organic matter content of the soil ➢ In essentially warm and dry areas like Southern Europe, depletion of organic matter can be rapid because the processes of decomposition are accelerated at high temperatures ➢ Generally, plant roots are not sufficiently numerous to replace the organic matter that is lost

19 MANFAAT BOT ➢ Storehouse for nutrients ➢ Source of fertility ➢ Contributes to soil aeration thereby reducing soil compaction ➢ Important ‘building block’ for the soil structure ➢ Aids formation of stable aggregates ➢ Improves infiltration/permability ➢ Increase in storage capacity for water. ➢ Buffer against rapid changes in soil reaction (pH) ➢ Acts as an energy source for soil micro-organisms

20 Degradation: HILANGNYA BOT ➢ During field operations, fresh topsoil becomes exposed and dries rapidly on the surface ➢ Organic compounds are released to the atmosphere result from breakdown of soil aggregates bound together by humic materials ➢ Unless the organic matter is quickly replenished, the system is in a state of degradation leading eventually to un-sustainability ➢ The removal of crop residues in dry ecosystems, which are inherently marginal, can cause such systems to be quickly transformed from a stage of fragility to total exhaustion and depletion

21 FAKTOR YG PENGARUHI BOT Natural factors: ➢ Climate ➢ Soil parent material: acid or alkaline (or even saline) ➢ Land cover and or vegetation type ➢ Topography – slope and aspect Human-induced factors: ➢ Land use and farming systems ➢ Land management (cultivation) ➢ Land degradation

22 FAKTOR IKLIM PENGARUHI BOT: Temperature: OM decomposition rapid in warm climates OM Decomposition is slower for cool regions Result: Within zones of uniform moisture and comparable vegetation -- Av total OM increases 2x to 3x for each 10 deg C fall in mean temperature Moisture: OM decomposition rapid in warm climates OM Decomposition is slower for cool regions Result: Under comparable conditions Av total OM increases as the effective moisture increases

23 Sumber: pgsgrow.com/blog/tag/organic- gardening/ Dalam tanah terdapat beragam organisme tanah yang berperan sangat penting dalam menentukan kualitas kesuburan tanah Sebagian dari mikroba tanah ini berperan dalam dekomposisi bahan organik dalam tanah dan melepaskan hara mineral dalam bentuk tersedia bagi tanaman

24 Structure of soil, indicating presence of bacteria, inorganic, and organic matter Sumber:

INTEGRATED SOIL FERTILITY MANAGEMENT Integrated soil fertility management (ISFM) aims at the optimal and sustainable use of soil nutrient reserves, mineral fertilizers and organic amendments. We explain in this reference how to calculate mineral and organic fertilizer needs to obtain target yields as a function of the soil nutrient.supplying capacity (mainly nitrogen, N; phosphorus, P; potassium, K) and taking into account yield potential (determined by cultivar choice, sowing date and climate). Analysis of soil fertility using laboratory procedures is seldom possible in farmers' fields, and the relation between such analyses and rice growth is often poor, especially for nitrogen. This reference offers another method to determine the soil nutrient-supplying capacity. The rice yield from a mini-plot, with good soil.fertility management but without application of one nutrient (for instance, without N, P or K) is considered as an indicator of the capacity of the soil to supply that Imissing nutrient.

INTEGRATED SOIL FERTILITY MANAGEMENT To increase yield by 1 t / ha, nutrient uptake at maturity needs to increase by 15 kg N / ha, 6 kg P2O5/ha and 18 kg K2O / ha. A well.balanced fertilization thus requires an application of 50 kg N / ha, 30 kg P2O5/ha and 60 kg K2O / ha to increase yield by 1 t / ha, based on a recovery rate of applied fertilizer of 30% for N and K and of 20% for P. The recovery rate is the percentage of fertilizer effectively absorbed by the plant as compared to the quantity applied. These relations are approximate and only valid for yields not exceeding 70 to 80% of the potential yield. For higher yield targets, more nutrients have to be applied to get the same return, and this is not usually cost.effective. Nitrogen losses are irreversible, thus it is very important to increase the recovery rate of this nutrient. The recovery rate of nitrogen is strongly related to crop management.

INTEGRATED SOIL FERTILITY MANAGEMENT This reference provides instructions to help increase this recovery rate. For P and K, losses are much less (P and K are absorbed by the soil), and the residual effect of the fertilizer applied is often visible several years after application. Organic fertilizer can, to a certain extent, replace mineral fertilizers, but large quantities need to be applied as organic fertilizers have a low nutrient content. However, using both mineral fertilizers and organic amendments often has synergistic effects, increasing the soil's nutrient.supplying capacity in the long term and in some cases increasing the recovery rate of mineral fertilizer nutrients.

SITE SPECIFIC INTEGRATED SOIL FERTILITY MANAGEMENT Integrated soil-fertility management aims at the optimal and sustainable use of nutrient stocks from the soil, mineral fertilizers and organic amendments. A procedure is given below for calculating fertilizer needs to reach target yields as a function of the soil nutrientYsupplying capacity and potential yield. Three steps are necessary: Fix a target yield. Estimate the capacity of the soil to supply N, P and K. Calculate fertilizer requirements.

A number of good crop management practices help limit losses of N applied with mineral fertilizers: 1.Using good-quality seed. 2.Transplanting seedlings at the right age. 3.Using a plant spacing that is adequate for the variety used, usually 0.2 × 0.2 m. 4.Removing weeds before fertilizer application. 5.Using pest and disease control. 6.Harvesting on time, at maturity. 7.Applying N when the crop most needs it: at tillering, panicle initiation and, if required, at heading; for small N doses, apply at tillering and panicle initiation. 8.Using N in two splits of 50% each, at the start of tillering and at panicle initiation, or in three splits of 40%, 40% and 20%, respectively, at the start of tillering, at panicle initiation and at heading.

MODEL NEPALESE: Integrated plant nutrient components in the farming system FAO. Paper Number 3. Plant nutrient management for improving crop productivity in Nepal. D.P. Sherchan and K.B. Karki.

MODEL NEPALESE: Nutrient flow components in the Nepalese farming system FAO. Paper Number 3. Plant nutrient management for improving crop productivity in Nepal. D.P. Sherchan and K.B. Karki.

Model of soil-plant transfer of mineral nutrients Modelling nutrient uptake by crops implies considering and integrating the processes controlling the soil nutrient supply, the uptake by the root system and relationships between the crop growth response and the amount of nutrient absorbed. We have developed a model that integrates both dynamics of maize growth and phosphorus (P) uptake. The crop part of the model was derived from Monteith's model. A complete regulation of P-uptake by the roots according to crop P-demand and soil P-supply was assumed. The soil P-supply to the roots was calculated using a diffusion equation and assuming that roots behave as zero sinks. The actual P-uptake and crop growth were calculated at each time step by comparing phosphate and carbohydrate supply-demand ratios. Model calculations for P-uptake and crop growth were compared to field measurements on a long term P-fertilization trial. aquitaine.inra.fr/tcem_eng/recherche/nutrition_minerale_et_gestio n_de_la_fertilite

Biogeochemical cycle of mineral nutrients in agricultural ecosystems The objective is to develop new approaches to the measurement and understanding of the behaviour of P cycling in agricultural ecosystems. This includes both to analyze and quantify inputs and outputs of P at the field scale for different cropping systems and also to assess associated P transformations in soils. We mainly focuse our research on the soil P availability to plants in agricultural soils because available soil P often control the greatest annual P flux that affect P cycling. We develop a process- based assessment of plant-available soil P which accounted for orthophosphate ions in solution and the amount of P ions associated to soil constituents that can diffuse with time towards solution.

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