basic concepts of economic value

BASIC CONCEPTS OF

ECONOMIC VALUE

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Diunduh dari Sumber: http://www.ecosystemvaluation.org/1-01.htm.................... 31/10/2011 .

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.

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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.

http://www.ecosystemvaluation.org/demand_curve1.gif

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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.

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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.

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Diunduh dari Sumber: http://people.hofstra.edu/geotrans/eng/ch6en/conc6en/landeconomics.html.................... 31/10/2011 .

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.

SOIL EVALUATION THE ROLE OF SOIL SCIENCE IN LAND EVALUATION…

Diunduh dari Sumber: http://edafologia.ugr.es/comun/congres/cartart.htm.................... 31/10/2011 .

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.”

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.

Very favourable Favourable Unfavourable Very unfavourable

Intrinsic properties

Effective depth, cm >120 120-70 70-30 <30

Texture balanced moderate heavy heavy light

Course fragments, % <10 10-30 30-60 >60

Structure f, md, 3, 2 c, 1 sg, 0 ms, 0

Compact, cemen, gr, cm Absent md, >60 md, >20 or st, >60 st, < 30

Available water, mm >100 100-60 60-20 <20

Internal drainage Without hydro Hydro > 80 cm Hydro > 40 cm Hydro a 0 cm

Permeability, cm/hour >2 2-0.5 0.5-0.1 <0.1

Organic matter, % >5 5-2 2-1 <1

CEC, cmol(+)kg-1 >40 40-20 20-10 <10

Saturation degree, % >75 75-50 50-25 <25

pH 7.3-6.7 6.7-5.5 or 7.3-8.0 5.5-4.5 or 8.0-9.0 <4.5 or >9.0

Carbonates, % <7 7-15 15-25 >25

Salinity, dSm-1 <2 2-6 6-12 >12

Extrinsic properties

Slope, % <4 4-10 10-25 >25

Surface stoniness,% <2 2-20 2-20 >50

Surface rockiness, % <2 2-20 2-20 >50

Flooding, months 0 <1 1-3 >3

Erosion, Tm/ha/year <10 10-20 20-60 >60

Ploughing no problems limited severe very severe

Precipitation, mm >1000 1000-600 600-300 <300

Frost, Tª<0º, months <1 1-3 3-6 >6

Comparisons between the classes defined by the soil-evaluation systems.

LCC, Land Capability Classification; Si, Storie Index; RPI, Riquier Productivity Index; FK, FAO Framework.


LCC SI RPI FK

Intensive soil cultivation I 1 P1 S1

Moderate soil cultivation II 2 P2 S2

Limited soil cultivation III 3 P3

Occasional soil cultivation IV 4 S3

Grazing V, VI 5 P4 N

Forestry VII 6 P5

Natural reserves VIII

… Storie Index (1933).

Diunduh dari Sumber: .................... 31/10/2011 .

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).

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.

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.

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 Orthic Solonchak, 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).

…


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:

1. The land is qualified, not only the soil. 2. Land suitability must be defined for a specific soil use (crop and management). 3. Land evaluation was to take into account both the physical conditions as well as economic ones; 4. The concept of land evaluation is essentially economic, social and political. 5. The evaluation requires a comparison between two or more alternative kinds of use. 6. The evaluation must propose a use that is sustainable. 7. 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.

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.

Soil type Parent material LCC SI RPI FK

1 Typic Cryosaprist micaschist IVsp 4ps P5fp-->(P3) S3sp

2 Typic Xerofluvent alluvial II 2 P2 S2

3 Typic Xerofluvent alluvial I 1 P1 S1

4 Typic Xeropsamment dolomite VIIr 3g-->(6) P5g S3r-->(N)

5 Lithic Xerorthent micaschist VIIs 6dg P5dg Ns

6 Lithic Xerorthent dolomite VIgr 5dgr P5dg-->(P4) S3d-->(N)

7 Typic Chromoxeret marl II 3p-->(2) P2p S3-->(S2)

8 Calcixerollic Xerochrept marl IVd 4d P3d S3d

9 Calcixerollic Xerochrept sandstone VIg 4gd-->(5) P5g-->(P4) S2-->(N)

10 Calcixerollic Xerochrept conglomerate III 3d P2-->(P3) S2





11 Lithic Xerochrept slate IIId-->(4) 5dr-->(4) P3d S3d

12 Lithic Xerochrept granite IId 3d-->(2) P2dt S2

13 Typic Humaquept micaschist Vp 5p P5p-->(P4) S3pf-->(N)

14 Typic Cryumbrept micaschist IIIs-->(IV) 4s 5fg-->(P3) S3sf

15 Typic Haplumbert micaschist VIIs 5sg-->(6) P5gf Ns

16 Vertic Haplargid andesite Vm 2-->(5) P5m-->(P4) Nm

17 Petrogypsic Gypsiorthid silts, gypsum IVdg 5dg-->(4) P4dg-->(P3) S3d

18 Lhitic Haploxeroll conglomerate VIIrd 6d P5dg Nd

19 Calcic Haploxeroll micaschist VIIs 4dg-->(6) P2-->(P5) Ns

20 Typic Haploxeroll sandstone VIIs 5sg-->(6) P2-->(P5) Ns





21 Typic Haploxeroll micaschists VIIs 6s P5gf Ns

22 Udic Haplustoll serpentine IIId 3dt P3d S2

23 Mollic Haploxeralf limestone IVd 4d P3d S3d

24 Typic Haploxeralf slate IIIe 3e P2-->(P3) S3e

25 Xerochreptic Haploxeralf slate IIIs 3se P1-->(P3) S3se

26 Typic Rhodoxeralf conglomerate I 1 P1 S1

27 Calcic Rhodoxeralf conglomerate IIg 1-->(2) P1-->(P2) S2m

28 Mollic Palexeralf limestone IIIr 3t P2t-->(P3) S2

29 Typic Palexerult slate IIIs 3r P2-->(P3) S2

30 Typic Palexerult clays IIes-->(III) 3t P3t S2

NILAI SEWA-EKONOMI

LAHAN

LAND ECONOMIC RENT = Sewa-ekonomi Lahan

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” adalah bagian pembayaran atas “lahan” yang melebihi dari pendapatan yang diterima dari pilihan terbaik penggunaan lahan yang mungkin dilakukan; dalam hal ini “lahan” dipandang mempunyai beberapa

macam kegunaan.


. 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:

1. The natural fertility of the soil; and the productivity of the existing technology in utilizing currently available labour and capital;

2. The relative distance from the same market:

3. We are discussing this in terms of regional economics with one market.4. 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).

5. 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.


SEWA LAHAN ..… VON THUNEN

Von Thünen mengembangkan teori dasar konsep marginal produktivitas secara matematis, dan menyusun rumus sewa lahan:

R = Y(p − c) − YFm,

dimana R=sewa LAHAN; Y=hasil per unit tanah; c=pengeluaran produksi per unit komoditas; p=harga pasar per unit komoditas; F=harga pengangkutan; m=jarak ke pasar.

Model Von Thünen untuk lahan pertanian diciptakan dengan asumsi:1. Kota terletak terpusat di dalam keadaan terisolir2. Keadaan terisolir dikelilingi oleh alam liar.3. Lahan benar-benar datar dan tidak memiliki sungai atau pegunungan.4. Kualitas tanah (kesuburan tanah) dan iklim yang konsisten.5. Petani di keadaan terisolir mengangkut barang mereka sendiri ke pasar

melalui gerobak melewati tanah langsung ke pusat kota, tidak ada jalan.6. Petani bersikap rasional untuk memaksimalkan keuntungan.

Diunduh dari Sumber: http://id.wikipedia.org/wiki/Johann_Heinrich_von_Th%C3%BCnen.................... 5/11/2011 .

KESUBURAN TANAH - PRODUKTIVITAS…

Ksuburan tanah merupakan “kualitas tanah” dalam hal kemampuannya untuk menyediakan unsur hara yang sesuai, dalam

jumlah yang cukup , dalam keseimbangan yang tepat dan lingkungan yang sesuai untuk pertumbuhan dan produksi spesies tanaman.

Kesuburan tanah merupakan manifestasi dari sifat dan kemampuan tanah.

Produktivitas Tanah merupakan “kemampuan tanah” untuk memproduksi sesuatu spesies tanaman dengan sistem pengelolaan

tertentu. Aspek pengelolaan yang dimaksud misalnya pengaturan jarak tanaman, pemupukan, pengairan, pemberantasan hama dan

penyakit, dll.

Diunduh dari Sumber: http://ielmasblog.blogspot.com/2012/02/kesuburan-tanah-dan-produktivitasnya.html .................... 5/11/2011 .

PRODUKTIVITAS TANAHProduktivitas tanah pada dasarnya adalah konsep ekonomi dan bukan sifat tanah,

ada tiga hal yang terlibat:

1. Masukan (sistem pengeloalaan khusus), 2. Keluaran (hasil tanaman tertentu), 3. Tipe tanah.

Dengan menetukan biaya dan haraga, keuntungan bersih dapat dihitung dan digunakan sebagai dasar untuk menentukan nilai lahan, yang penting dalam

penaksiran NILAI SEWA-EKONOMI LAHAN.

Ada dua segi penting produktivitas tanah, yaitu:

4. Tanah yang berbeda mempunyai kapasitas yang berbeda untuk menyerap masukan (INPUT) PRODUKSI untuk menghasilkan keuntungan tertinggi.

5. Tanaman yang berbeda mempunyai kapasitas yang berbeda untuk meyerap masukan (input) produksi untuk menghasilkan keuntungan tertinggi pada tipe tanah tertentu.

Diunduh dari Sumber: http://ielmasblog.blogspot.com/2012/02/kesuburan-tanah-dan-produktivitasnya.html .................... 5/11/2011 .

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.

Diunduh dari Sumber: http://www.agrosciencejournal.com/public/agro7o3-1.pdf.................... 5/11/2011 .

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.Diunduh dari Sumber: .................... 5/11/2011 .

. Sufficiency for Organic Carbon Contents …

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 (Enwexor et

al., 1981).

Diunduh dari Sumber: http://www.agrosciencejournal.com/public/agro7o3-1.pdf .................... 5/11/2011 .

The rating of organic carbon (Source: Enwezor et al.( 1981 )

Organic carbon content (%) Sufficiency0.50 0.00.65 0.10.80 0.20.95 0.31.10 0.41.25 0.51.40 0.61.55 0.71.70 0.81.85 0.92.0 and above 1.0

Source: Enwezor et 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.

. Sufficiency for Available Phosphorus Content…

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).


Sufficiency rating of available phosphorus

Available phosphorus

Sufficiency

5 0.110 0.215 0.320 0.1425 0.530 0.635 0.740 0.845 0.950 1.0

1. 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.

. 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

1. Mclean, F.T. and Gilbert, B.E. (1927). The relative aluminium tolerance of crop plants. Soil Sci. 24: 163-175.

2. Pratt, F.P. (1966) Aluminium. Department of Soil and Plant nutrition, University of California Div. Agric, Sci. 12pp..

Exchangeable aluminiumconcentration (cmol kg-1)

Sufficiency

2.8 1.05.6 0.88.4 0.6

11.2 0.414.0 and above 0.2

…


…1. 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):139-149.2. Bergstrom, J. C., J. R. Stoll, J. P. Titre, and V. L. Wright. 1990. “Economic Value of Wetlands-Based Recreation.” Ecological

Economics 2(2):129-147.3. Crocker, T. D. 1985. “On the Value of the Condition of a Forest Stock.” Land Economics 61(3):244-254.4. Diamond, D. B., Jr., 1980. “The Relationship Between Amenities and Urban Land Prices.” Land Economics 56(1):21-32.5. Loomis, J., and Anderson, P. 1992. “Idaho v. Southern Refrigerator.” In Natural Resource Damages: Law and Economics,

Ward, K. M. and6. Duffield, W. J. (ed.), Wiley Law Publications, New York, pp. 389-414.7. 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.

Diunduh dari Sumber: http://www.hss.energy.gov/sesa/environment/guidance/cercla/valuation.pdf.................... 31/10/2011 .

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