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BASIC CONCEPTS OF ECONOMIC VALUE

BASIC CONCEPTS OF ECONOMIC VALUE. …. This section explains the basic economic theory and concepts of economic valuation.

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BASIC CONCEPTS OF ECONOMIC VALUE

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  1. BASIC CONCEPTS OF ECONOMIC VALUE

  2. … This section explains the basic economic theory and concepts of economic valuation. Economic value is one of many possible ways to define and measure value. Although other types of value are often important, economic values are useful to consider when making economic choices – choices that involve tradeoffs in allocating resources. Measures of economic value are based on what people want – their preferences.  Economists generally assume that individuals, not the government, are the best judges of what they want.  Thus, the theory of economic valuation is based on individual preferences and choices.  People express their preferences through the choices and tradeoffs that they make, given certain constraints, such as those on income or available time.  The economic value of a particular item, or good, for example a loaf of bread, is measured by the maximum amount of other things that a person is willing to give up to have that loaf of bread.  If we simplify our example “economy” so that the person only has two goods to choose from, bread and pasta, the value of a loaf of bread would be measured by the most pasta that the person is willing to give up to have one more loaf of bread.  Thus, economic value is measured by the most someone is willing to give up in other goods and services in order to obtain a good, service, or state of the world.  In a market economy, dollars (or some other currency) are a universally accepted measure of economic value, because the number of dollars that a person is willing to pay for something tells how much of all other goods and services they are willing to give up to get that item. This is often referred to as “willingness to pay.” In general, when the price of a good increases, people will purchase less of that good.  This is referred to as the law of demand—people demand less of something when it is more expensive (assuming prices of other goods and peoples’ incomes have not changed).  By relating the quantity demanded and the price of a good, we can estimate the demand function for that good.  From this, we can draw the demand curve, the graphical representation of the demand function. It is often incorrectly assumed that a good’s market price measures its economic value.  However, the market price only tells us the minimum amount that people who buy the good are willing to pay for it.  When people purchase a marketed good, they compare the amount they would be willing to pay for that good with its market price.  They will only purchase the good if their willingness to pay is equal to or greater than the price.  Many people are actually willing to pay more than the market price for a good, and thus their values exceed the market price. In order to make resource allocation decisions based on economic values, what we really want to measure is the net economic benefit from a good or service.  For individuals, this is measured by the amount that people are willing to pay, beyond what they actually pay.  Thus, two goods that sell for the same price may have different net benefits. For example, I may have a choice between wheat and multi-grain bread, which both sell for $2.00 per loaf.  Because I prefer multi-grain, I am willing to pay up to $3.00 for a loaf.  However, I would only pay $2.50 at the most for the wheat bread.  Therefore, the net economic benefit I receive for the multi-grain bread is $1.00, and for the wheat bread is only $.50.   The economic benefit to individuals is often measured by consumer surplus. This is graphically represented by the area under the  demand curve  for a good, above its price.  DiunduhdariSumber: http://www.ecosystemvaluation.org/1-01.htm.................... 31/10/2011 .

  3. … The economic benefit to individuals, or consumer surplus, received from a good will change if its price or quality changes.  For example, if the price of a good increases, but people’s willingness to pay remains the same, the benefit received (maximum willingness to pay minus price) will be less than before. If the quality of a good increases, but price remains the same, people’s willingness to pay may increase and thus the benefit received will also increase. DiunduhdariSumber: http://www.ecosystemvaluation.org/1-01.htm .................... 31/10/2011 .

  4. … Economic values are also affected by the changes in price or quality of substitute goods  or complementary goods .  If the price of a substitute good changes, the economic value for the good in question will change in the same direction.  For example, wheat bread is a close substitute for multi-grain bread.  So, if the price of multi-grain bread goes up, while the price of wheat bread remains the same, some people will switch, or substitute, from multi-grain to wheat bread.  Therefore, more wheat bread is demanded and its demand function shifts upward, making the area under it, the consumer surplus, greater. Similarly, if the price of a complementary good, one that is purchased in conjunction with the good in question, changes, the economic benefit from the good will change in the opposite direction.  For example, if the price of butter increases, people may buy less of both bread and butter.  If less bread is demanded, then the demand function shifts downward, and the area under it, the consumer surplus, decreases. Producers of goods also receive economic benefits, based on the profits they make when selling the good.  Economic benefits to producers are measured by  producer surplus, the area above the supply curve and below the market price.  The supply function tells how many units of a good producers are willing to produce and sell at a given price.  The supply curve is the graphical representation of the supply function.  Because producers would like to sell more at higher prices, the supply curve slopes upward.   If producers receive a higher price than the minimum price they would sell their output for, they receive a benefit from the sale—the producer surplus.  Thus, benefits to producers are similar to benefits to consumers, because they measure the gains to the producer from receiving a price higher than the price they would have been willing to sell the good for. DiunduhdariSumber: http://www.ecosystemvaluation.org/1-01.htm .................... 31/10/2011 .

  5. … When measuring economic benefits of a policy or initiative that affects an ecosystem, economists measure the total net economic benefit.  This is the sum of consumer surplus plus producer surplus, less any costs associated with the policy or initiative. DiunduhdariSumber: http://www.ecosystemvaluation.org/1-01.htm .................... 31/10/2011 .

  6. … Land Economics In a market economy, most of the urban land can be freely sold or purchased. Thus land economics are concerned about how the price of urban land is established and how this price will influence the nature, pattern and distribution of land uses. The above figure provides some basic relationships between the quantity of land and its price and assumes that there is a free land market. This market mechanism follows the standard relationship between supply and demand, where an equilibrium price is reached. A quantity of land Q1 would be available at a price of P1. However, what is particular to cities is that the supply is fixed since there is a limited amount of available land. When land is reasonably available (Q1), the price (P1) will be moderate. Moving towards the downtown the demand rises, land becomes scarcer (Q2) and its price goes up (P2). Moving towards the periphery, more land is available, demand drops (Q3), and so does the price (P3). Not every type of activities is willing to pay a price P1. Some may even need a price lower than P3. High land values impose a more intensive usage of space so a higher number of activities can benefit from a central location. The logic behind the construction of skyscrapers is therefore obvious and takes place at optimal locations of competition for land. Different type of activities, each having their own land use, are willing to pay different rents. DiunduhdariSumber: http://people.hofstra.edu/geotrans/eng/ch6en/conc6en/landeconomics.html.................... 31/10/2011 .

  7. SOIL EVALUATION THE ROLE OF SOIL SCIENCE IN LAND EVALUATION… A review has been made on the concepts and the methodology of land evaluation. The results of several evaluation methods have been compared, applying them to a selection of diverse soils. Although the studies on land evaluation have been conducted on a broad diversity of characteristics—not only physical but also social, economic and political—in practice, it is frequent to limit such studies to the physical medium, given the heterogeneity of these projects. Land evaluation requires a team of multidisciplinary evaluators. The difficulty of forming these teams makes it common for such studies on land evaluation to be reduced to the analysis of the physical medium of the soil, creating a certain confusion. Therefore, we propose using the term “soil evaluation” for the assessment of the soil properties as a phase prior to land evaluation, considering soil properties in their broader sense, both the intrinsic ones (those of the soil itself: depth, texture, etc.) as well as the extrinsic ones (the soil surface: topography, climate, hydrology, vegetation, use, etc.). Soil evaluation would be similar to what today is understood as land evaluation, but excluding all the social, economic and political characteristics which would be covered under the concept of “land evaluation.” DiunduhdariSumber: http://edafologia.ugr.es/comun/congres/cartart.htm.................... 31/10/2011 .

  8. Environmental indicators of the degree of suitability of soils for agricultural use.… Texture: balanced = loam, silt loam, sandy clay loam; heavy = sandy clay, clay loam, silty clay loam, silt; heavy = clay, silty clay; light = sand, loamy sand. Structure. f = fine; md = medium; c = coarse; sg = single grain; ms = massive; 3 = strong; 2 = moderate; 1 = weak; 0 = structureless. Compact = compaction, cemen = cementation, gr = degree, cm = depth at which it appears; md = moderate; st = strong. Internal drainage: hydro = hydromorphy. CEC = cation-exchange capacity. Ploughing: no problems = ploughing is possible at any time of the year; limited = not possible during wet periods, clayey soils; severe = only in dry periods, soils very clayey. Very severe = not possible due to steep slopes or high groundwater table; Precipitation = Annual precipitation. DiunduhdariSumber: http://edafologia.ugr.es/comun/congres/cartart.htm.................... 31/10/2011 .

  9. Comparisons between the classes defined by the soil-evaluation systems. LCC, Land Capability Classification; Si, Storie Index; RPI, Riquier Productivity Index; FK, FAO Framework. DiunduhdariSumber: http://edafologia.ugr.es/comun/congres/cartart.htm.................... 31/10/2011 .

  10. …Storie Index (1933). This represents the first parametric approach that was developed. It is an index that uses the multiplicative scheme. In addition, it uses intrinsic properties of the soils (genetic profile, parent material, profile depth, texture, drainage, nutrients, acidity an alkalinity), characteristics of the soil surface (slope and microrelief) and aspects of soil conservation (degree of erosion). The evaluation properties are grouped into four factors that are quantified in the corresponding tables. The factors are weighed a priori, the more important being related on a scale from 5 to 100 and the less important factors from 80 to 100.             With this index, general agricultural soil uses can be evaluated (hence it is a soil-capability evaluation method). To formulate the index, the four factors are multiplied together and the index is expressed as a percentage. Six classes are defined at the degree level, with decreasing values from 1 to 6. The degrees 1 to 3 are for agricultural use, degree 4 for very limited agricultural use, 5 for pasture and 6 without use. Subdegrees are established according to limiting factors: “s” for depth, “p” for permeability, “x” for texture, “t “ slope, “d” for drainage and “a” for salts. It is important to emphasize that this system does not consider climatic characteristics. Thus the evaluation is of the soil itself, valid for comparing the soils of a certain region with the same type of climate. This evaluation index was developed for California, and thus application to other regions of the world has involved numerous modifications (in Canada by Bowser, 1940; in India by Shome and Raychaudhuri, 1960; in tropical countries by Sys and Frankart, 1972; in arid regions by Sys and Verheye, 1974). DiunduhdariSumber: .................... 31/10/2011 .

  11. Land Capability Classification. … This method was established by the Soil Conservation Service de USA according to the system proposed by Klingebiel and Montgomery (1961) and has been widely used throughout the world with numerous adaptations. It is a categorical system that uses qualitative criteria. The inclusion of a soil within a class is made in the inverse manner—that is, without directly analysing its capacity, but rather its degree of limitation with respect to a parameter according to a concrete use. Some factors that restrict soil use can be used to define the productive capacity (intrinsic: soil depth, texture, structure, permeability, rockiness, salinity, soil management; extrinsic: temperature and rainfall) and yield loss (slope of the terrain and degree of erosion). Five systems of permanent agricultural exploitation are considered: permanent soil cultivation, occasional soil cultivation, pasture, woods and natural reserves. This system seeks maximum production with minimum losses in potential. Depending on the type of limitation, various subclasses of capacity are established: e, for erosion risks; w, for wetness and drainage; s, for rooting and tillage limitations resulting from shallowness, drought risk, stoniness, or salinity; c, for climatic limitations. The capability units represent similar proposals of use and management.  DiunduhdariSumber: http://edafologia.ugr.es/comun/congres/cartart.htm.................... 31/10/2011 .

  12. Productivity index of Riquier et al. (FAO, 1970). The basic concept of this method is that agricultural-soil productivity, under optimal management conditions, depends on the intrinsic characteristics. This is a multiplicative parametric method to evaluate soil productivity, from a scheme similar to the Storie index. The concept of productivity is defined as the capacity to produce a certain quantity of harvest per hectare per year, expressed as a percentage of optimal productivity, which would provide a suitable soil in its first year of cultivation. The introduction of improvement practices leads to a potential productivity or potentiality. The quotient between the productivity and the potentiality is called the improvement coefficient.             The evaluation is made for three general types of use: agricultural crops, cultivation of shallow-rooted plants (pastures), and deep-rooted plants (fruit trees and forestation).                The determining factors of soil depth are: wetness, drainage, effective depth, texture/structure, base saturation of the adsorbent complex, soluble-salt concentration, organic matter, cation-exchange capacity/nature of the clay and mineral reserves. The parameters of the soil surface (e.g., slope, erosion, flood tendency, or climate) are not considered                   The different parameters are evaluated in tables and, as also occurs in the Storie index, the evaluation factors present different weights.             Productivity is expressed as the product of all these factors expressed in percentages. Five productivity classes are defined: class P1 = excellent; class P2 = good, valid for all types of agricultural crops; class P3 = medium, for marginal agricultural use, suitable for non-fruiting trees; class P4 = poor, for pasture or forestation or recreation; class P5 = very poor or null, soils not adequate for any type of exploitation. DiunduhdariSumber: .................... 31/10/2011 .

  13. Soil Fertility Capability Classification (FCC). … This was proposed by Buol et al., (1975) and modified by Sanchez et al. (1982) to evaluate soil fertility. In this system, three levels or categories were established. The first, the type, was determined by the texture of the arable layer, or of the first 20 cm, if this is thinner. Its denomination and range are: S, sandy (sandy and sandy loam); L, loams <35% clay (excluding sandy and sandy loam); C, clayey > 35% clay; O, organic > 30% organic matter to 50 cm or more. The type of substrate is the second level and is used when there is a significant textural change in the first 50 cm of the soil. It is expressed with the same letters, adding “R” when a rock or a hard layer is found within this depth. The third level is comprised of the modifiers, which are the chemical and physical parameters that negatively influence soil fertility. These are numerous and are represented by lower-case letters.             In the denomination of the soil class, the principle limitations for use are directly represented. For example, for an OrthicSolonchak, the FCC class that represents it is LCds, which signifies that it is a soil susceptible to severe erosion (L), limited drainage (C), dry soil moisture regime (d) and with salinity (s). DiunduhdariSumber: .................... 31/10/2011 .

  14. … The FAO Framework for Land Evaluation (1976). The FAO Framework for Land Evaluation (FAO 1976 and subsequent guidelines: for rainfed agriculture, 1983; forestry, 1984; irrigated agriculture, 1985; extensive grazing, 1991) is considered to be a standard reference system in land evaluation throughout the world (Dent and Young, 1981; van Diepen el al., 1991), and has been applied both in developed as well as developing countries.             This framework is an approach, not a method. It is designed primarily to provide tools for the formulation of each concrete evaluation. The system is based on the following concepts: The land is qualified, not only the soil. Land suitability must be defined for a specific soil use (crop and management). Land evaluation was to take into account both the physical conditions as well as economic ones; The concept of land evaluation is essentially economic, social and political. The evaluation requires a comparison between two or more alternative kinds of use. The evaluation must propose a use that is sustainable. A multidisciplinary approach is required (Purnell, 1979; van Diepen et al., 1991). These limiting factors are used to define the third category of the system, which is the subclass. In the symbol of each subclass, the number of limitations involved should be kept to the minimum one letter, or, rarely, two. The limitations proposed include: t, slope; e, erosion risk; p, depth; s, salinity; d, drainage; c, bioclimatic deficiency; r, rockiness; i, flood risk. DiunduhdariSumber: .................... 31/10/2011 .

  15. Evaluation of 30 soils by four methods of soil-capability evaluation. … LCC, Land Capability Classification; SI, Storie Index; RPI, Riquier Productivity Index; FK, FAO Framework. Limiting characteristics: e, erosion; d, depth; g, gravels; f, frozen; m, moisture; p, permeability or drainage or flooding; r, rocks or pebbles or stones; s, slope; t, texture or structure. In bold, the results that do not coincide with the evaluations of the other methods; in parenthesis the results that would correspond with the other methods. In bold and cursive, results that strongly differ from those of the other methods. DiunduhdariSumber: http://edafologia.ugr.es/comun/congres/cartart.htm.................... 31/10/2011 .

  16. Evaluation of 30 soils by four methods of soil-capability evaluation. … LCC, Land Capability Classification; SI, Storie Index; RPI, Riquier Productivity Index; FK, FAO Framework. Limiting characteristics: e, erosion; d, depth; g, gravels; f, frozen; m, moisture; p, permeability or drainage or flooding; r, rocks or pebbles or stones; s, slope; t, texture or structure. In bold, the results that do not coincide with the evaluations of the other methods; in parenthesis the results that would correspond with the other methods. In bold and cursive, results that strongly differ from those of the other methods. DiunduhdariSumber: http://edafologia.ugr.es/comun/congres/cartart.htm.................... 31/10/2011 .

  17. Evaluation of 30 soils by four methods of soil-capability evaluation. … LCC, Land Capability Classification; SI, Storie Index; RPI, Riquier Productivity Index; FK, FAO Framework. Limiting characteristics: e, erosion; d, depth; g, gravels; f, frozen; m, moisture; p, permeability or drainage or flooding; r, rocks or pebbles or stones; s, slope; t, texture or structure. In bold, the results that do not coincide with the evaluations of the other methods; in parenthesis the results that would correspond with the other methods. In bold and cursive, results that strongly differ from those of the other methods. DiunduhdariSumber: http://edafologia.ugr.es/comun/congres/cartart.htm.................... 31/10/2011 .

  18. NILAI SEWA-EKONOMI LAHAN

  19. LAND ECONOMIC RENT = Sewa-ekonomiLahan Definition of 'Economic Rent' The amount of money an owner of a factor of production must receive in order for that owner to rent out that factor of production. Factors of production include labor, capital and land. Sewa-ekonomi “lahan” adalahbagianpembayaranatas “lahan” yang melebihidaripendapatan yang diterimadaripilihanterbaikpenggunaanlahan yang mungkindilakukan; dalamhalini “lahan” dipandangmempunyaibeberapamacamkegunaan. DiunduhdariSumber: .................... 5/11/2011 .

  20. . David Ricardo's Concept of Economic Rent… Economic rent on land is the value of the difference in productivity between a given piece of land and the poorest [and/or most distant], most costly piece of land producing the same goods (e.g. bushels of wheat) under the same conditions (of labour, capital, technology, etc.). Productivity is defined here in terms of both: The natural fertility of the soil; and the productivity of the existing technology in utilizing currently available labour and capital; The relative distance from the same market: We are discussing this in terms of regional economics with one market. This part of theorem, on the ‘distance from the market’, did not originate with Ricardo, but rather with a German economist: Johann Heinrich von Thünen (1783- 1850), who noted , some years after the publication of Ricardo’s Principles, that the closer a piece of land was to the urban core the higher was its market rent (reflecting economic rent). You can readily appreciate the significance of this by noting that Toronto rents in the heart of the financial district on Bay or University are higher than those in, say, Orangeville or Bolton to the north of Toronto. 3. Thus productivity differences reflect the cost differences in supplying grain to that one market from that piece of land. DiunduhdariSumber: .................... 5/11/2011 .

  21. SEWA LAHAN ..… VON THUNEN Von Thünenmengembangkanteoridasarkonsep marginal produktivitassecaramatematis, danmenyusunrumussewalahan: R = Y(p − c) − YFm, dimana R=sewa LAHAN; Y=hasil per unit tanah; c=pengeluaranproduksi per unit komoditas; p=hargapasar per unit komoditas; F=hargapengangkutan; m=jarakkepasar. Model Von Thünenuntuklahanpertaniandiciptakandenganasumsi: Kota terletakterpusatdidalamkeadaanterisolir Keadaanterisolirdikelilingiolehalam liar. Lahanbenar-benardatardantidakmemilikisungaiataupegunungan. Kualitastanah (kesuburantanah) daniklim yang konsisten. Petanidikeadaanterisolirmengangkutbarangmerekasendirikepasarmelaluigerobakmelewatitanahlangsungkepusatkota, tidakadajalan. Petanibersikaprasionaluntukmemaksimalkankeuntungan. DiunduhdariSumber: http://id.wikipedia.org/wiki/Johann_Heinrich_von_Th%C3%BCnen.................... 5/11/2011 .

  22. KESUBURAN TANAH - PRODUKTIVITAS… Ksuburantanahmerupakan “kualitastanah” dalamhalkemampuannyauntukmenyediakanunsurhara yang sesuai, dalamjumlah yang cukup , dalamkeseimbangan yang tepatdanlingkungan yang sesuaiuntukpertumbuhandanproduksispesiestanaman. Kesuburantanahmerupakanmanifestasidarisifatdankemampuantanah. Produktivitas Tanah merupakan “kemampuantanah” untukmemproduksisesuatuspesiestanamandengansistempengelolaantertentu. Aspekpengelolaan yang dimaksudmisalnyapengaturanjaraktanaman, pemupukan, pengairan, pemberantasanhamadanpenyakit, dll. DiunduhdariSumber: http://ielmasblog.blogspot.com/2012/02/kesuburan-tanah-dan-produktivitasnya.html .................... 5/11/2011 .

  23. PRODUKTIVITAS TANAH Produktivitastanahpadadasarnyaadalahkonsepekonomidanbukansifattanah, adatigahal yang terlibat: Masukan (sistempengeloalaankhusus), Keluaran (hasiltanamantertentu), Tipetanah. Denganmenetukanbiayadanharaga, keuntunganbersihdapatdihitungdandigunakansebagaidasaruntukmenentukannilailahan, yang pentingdalampenaksiran NILAI SEWA-EKONOMI LAHAN. Adaduasegipentingproduktivitastanah, yaitu: Tanah yang berbedamempunyaikapasitas yang berbedauntukmenyerapmasukan (INPUT) PRODUKSI untukmenghasilkankeuntungantertinggi. Tanaman yang berbedamempunyaikapasitas yang berbedauntukmeyerapmasukan (input) produksiuntukmenghasilkankeuntungantertinggipadatipetanahtertentu. DiunduhdariSumber: http://ielmasblog.blogspot.com/2012/02/kesuburan-tanah-dan-produktivitasnya.html .................... 5/11/2011 .

  24. The Soil Productivity Index Model … Neill’s (1979) productivity index was modified by Pierce et al. (1983). The productivity index was based on the use of simple easily measurable soil properties to predict the effect of soil environment on root growth. This is expressed as follows: r PI ∑ = S (Ai x Bi x Ci x Di x Ei x Wfi) i=1 where: PI = productivity index; Ai = Sufficiency for available water capacity for the ith soil layer; Bi = Sufficiency for aeration for the ith soil layer; Ci = Sufficiency for pH for the ith soil layer; Di = Sufficiency for bulk density for the ith soil layer; Ei = Sufficiency for electrical conductivity for the ith soil layer; Wfi = Root weighting factor; r = Number of horizons in the rooting zone. Other parameters like nutrients, management, climate and genetic factors are presumed to be constant. DiunduhdariSumber: http://www.agrosciencejournal.com/public/agro7o3-1.pdf.................... 5/11/2011 .

  25. The Soil Productivity Index Model … . Neill’s model (1979) did not take care of some soil parameters such as organic carbon, available phosphorus and exchangeable aluminium that exert key influence on the productivity of tropical soils. Consequently, a modifixation was carried out to include these three sufficiencies. The modified expressions are as follows: r P1Mi = ∑ (Ai x Ci x Di x Wfi). Where: P1Mi = Modified productivity index that involves the exclusion of sufficiencies for aeration and electrical conductivity. P1M2 = ∑ (Ai x Ci x Di x Ji x Ki x Li x Wfi). Where: P1M2 = Modified productivity index that involves the inclusion of sufficiencies for organic carbon, available phosphorus and exchangeable aluminium with simultaneous exclusion of sufficiencies for aeration and electrical conductivity; Ji = Sufficiency for organic carbon for the ith soil layer; Ki = Sufficiency for available phosphorus for the ith soil layer; Li = Sufficiency for exchangeable aluminium for the ith soil layer. The sufficiencies for available water capacity, bulk density, pH and root weighting factor for this modification were as established by Pierce et al. (1983), while other sufficiencies were established in this research. DiunduhdariSumber: .................... 5/11/2011 .

  26. . Sufficiency for Organic Carbon Contents … The rating of organic carbon (Source: Enwezoret al.( 1981 ) A sufficiency of 1.0 was assigned for organic carbon content of 2.0 percent in the study area. It is presumed that soil productivity approaches zero at organic carbon content of 0.5 or less (Enwexoret al., 1981). Organic carbon content (%) Sufficiency 0.50 0.0 0.65 0.1 0.80 0.2 0.95 0.3 1.10 0.4 1.25 0.5 1.40 0.6 1.55 0.7 1.70 0.8 1.85 0.9 2.0 and above 1.0 Source: Enwezoret al.( 1981 ) Enwezor, W.O. Udo, E.J. and Sobulo, R.A. (1981). Fertility Status and Productivity of acid sands. In: Acid of Southeastern Nigeria. Monograph No. 1 Soil Sci. Soc. of Nigeria 56-73pp. DiunduhdariSumber: http://www.agrosciencejournal.com/public/agro7o3-1.pdf .................... 5/11/2011 .

  27. . Sufficiency for Available Phosphorus Content… Sufficiency rating of available phosphorus In this study, a sufficiency of 1.0 was assigned for the highest available phosphorus content of 50 Cmol kg-1 and it is assumed that soil productivity declines at available phosphorus of 15 cmol kg-1 or less (Landon, 1991). Landon, J.R. (eds). (1991). Booker tropical Soil Manuel: A Handbook for Soil Survey and Agricultural land Evaluation in the Tropics and Sub-tropics. John Wiley and Sons Inc. Third Avenue, New York, U.S.A. 474pp. DiunduhdariSumber: http://www.agrosciencejournal.com/public/agro7o3-1.pdf .................... 5/11/2011 .

  28. . Sufficiency for exchangeable Aluminium… The highest sufficiency of 1.0 was assigned for exchangeable aluminium concentration of 2.8 cmol kg-1. Soil productivity approaches zero at exchangeable aluminium concentration of 14.0 cmol kg-1 and above (Pratt, 1966; Mclean and Gilbert, 1927). Sufficiency rating of exchangeable aluminium Mclean, F.T. and Gilbert, B.E. (1927). The relative aluminium tolerance of crop plants. SoilSci. 24: 163-175. Pratt, F.P. (1966) Aluminium. Department of Soil and Plant nutrition, University of California Div. Agric, Sci. 12pp.. DiunduhdariSumber: http://www.agrosciencejournal.com/public/agro7o3-1.pdf .................... 5/11/2011 .

  29. … DiunduhdariSumber: .................... 5/11/2011 .

  30. … Bergstrom, J. C., B. L. Dillman, and J. R. Stoll. 1985. “Public Environmental Amenity Benefits of Private Land: The Case of Prime Agricultural Land.” Southern Journal of Agricultural Economics 17(1):139-149. Bergstrom, J. C., J. R. Stoll, J. P. Titre, and V. L. Wright. 1990. “Economic Value of Wetlands-Based Recreation.” Ecological Economics 2(2):129-147. Crocker, T. D. 1985. “On the Value of the Condition of a Forest Stock.” Land Economics 61(3):244-254. Diamond, D. B., Jr., 1980. “The Relationship Between Amenities and Urban Land Prices.” Land Economics 56(1):21-32. Loomis, J., and Anderson, P. 1992. “Idaho v. Southern Refrigerator.” In Natural Resource Damages: Law and Economics, Ward, K. M. and Duffield, W. J. (ed.), Wiley Law Publications, New York, pp. 389-414. Palmquist, R. B., and L. E. Danielson. 1989. “A Hedonic Study of the Effects of Erosion Control and Drainage on Farmland Values.” American Journal of Agricultural Economics 71:55-62. DiunduhdariSumber: http://www.hss.energy.gov/sesa/environment/guidance/cercla/valuation.pdf.................... 31/10/2011 .

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