Leaching of Phosphorus

From the Organic Soils

of The Holland Marsh

A Report to the Ministry of the Environment

R.L. Thomas

and

G. Sevean

January 15, 1985

INTRODUCTION

Agricultural lands have recently been implicated as a significant non-point source

of nutrients enriching our surface waters. Phosphorus (P) additions resulting in higher

than desirable levels may result in the acceleration of natural rates of eutrophication.

Interactions of phosphorus with mineral soils are well understood. As a result of

the high P sorption capacity of mineral soils, P contributions to drainage systems are

generally the result of surface runoff and erosion (Miller and Spires, 1978). Organic

soils, however, are less likely to retain phosphorus. Miller (1979) and Cogger and

Duxbury (1984) have demonstrated leaching of phosphorus from organic soils.

Cultivation and phosphorus fertilization of the organic soils in the Holland Marsh

has been implied as a factor contributing to the phosphorus concentration in the

Holland River and the resulting nutrient enrichment of Lake Simcoe (Nichols and

MacCrimmon, 1974). Phosphorus losses from organic soils vary between 1-30 kg/ha/yr

and some studies have documented concentrations in drainage waters approaching 10

mg/L (Duxbury and Peverly, 1978; Miller, 1979; Nicols and MacCrimmon, 1974).

SOURCES OF PHOSPHORUS IN CULTIVATED

MUCK AND CONTROLLING FACTORS

Crop response to fertilizer application of phosphorus is favourable on organic

soils and the amount varies with the crop. Some is removed by crop uptake and

harvesting. According to Sharpley et al. (1982), fertilizer applications of phosphorus

are associated with increases in water soluble phosphorus. This amount apparently

decreases as the length of time to next rainfall increases.

The amount of P adsorbed by organic soils is influenced by the soils water

content. The association between drying of the soil and reductions in water soluble P

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is based on the fact that the capacity of a solid to adsorb a solute tends to increase

with an increase in the concentration of the solute in the fluid phase (Travis et al.,

1981). The concentration of P in the soil solution becomes greater as water is lost

through evaporation and plant uptake, which results in a greater adsorption of P.

The potential amount of leachable inorganic phosphorus (Pi) in a cultivated muck

may be increased by P mineralization in the volume of soil, above the water table

(Duxbury et al., 1978). The amount of Pi formed in this manner will be subject to

losses due to leaching, especially for P mineralized below the root zone. Duxbury et al.

(1978) calculated that as much as 50 kg P/ha was mineralized annually from a

cultivated muck. Annual returns of organic residues to any soil constitute an addition

of phosphorus to the soil, Sharpley (1982). According to Singh et al. (1976) the

content of phosphorus in typical organic materials returned to the soil ranges from

0.1-0.5%. The phosphorus is largely in the organic form (Po) and constitutes a

substantial source of nutrition to the crop throughout the season, as it is mineralized

by the microbial population. Microbial assimilation may result in temporary P retention

as P is immobilized in the form of lipids, nucleoproteins and other organic compounds.

However, microbial turnover rates are high and P soon becomes available upon death

of microbial cells.

For organic soils used in agricultural production the rate of P mineralization will

be markedly influenced by the cultivation techniques employed and the exposure of the

surface to alternate wetting and drying cycles. Soil tillage may influence aerobic

processes by enhancing soil aeration, therefore, mineralization may be more rapid in

the plough layer.

In addition, the amount of soil subjected to wetting and drying will increase,

resulting in a larger amount of P mineralization near the surface. According to Sharpley

et al. (1982) ploughing may have the added effect of altering the depth of interaction

between surface soil and runoff.

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As the above discussion would indicate, mineralization may provide a potential

source of Pi for plant uptake and leaching, when chemical and physical conditions in the

soil environment are conducive to microbially-mediated processes. However, the

importance of the contribution of Pi from this source to the total amount of Pi actually

leached must not be overestimated. A study, conducted by Cogger and Duxbury,

(1984) indicated that P released from organic soils was controlled by an equilibrium of

Pi between more and less labile forms of P but not directly by biological mineralization.

FACTORS CONTROLLING RETENTION OF PHOSPHORUS

According to Stevenson (1981) up to 80% of the phosphorus in a peat is the

organic form. Po is largely immobile until it is mineralized, although small and variable

amounts of soluble Po can occur in the liquid fraction of a soil.

Downward movement of phosphorus is largely associated with the inorganic

fraction. Nicholls and McCrimmon (1974) found that 90% of total P in surface runoff

from a cultivated muck was in an inorganic soluble reactive form. Phosphorus is readily

leached from organic soils but the extent of leaching is variable and dependant upon

several soil characteristics. Duxbury et al. (1978) determined that 30% of the inorganic

phosphorus added to an organic soil from fertilizer (40 kg P/ha) and mineralization (50

kg P/ha) on an annual basis was subject to leaching. However another 30% was

assumed to be fixed when crop uptake was considered.

Duxbury et al. (1978) assumed that, although the P fixation ability of an organic

soil is limited, substantial pools of labile P could accumulate with long time fertilizer

applications. Researchers agree that fixation probably involves the amount of and

interactions with the mineral components contained in organic soils (Duxbury et al.,

1979; Larson et al., 1959; Miller, 1979; Okruszko et al., 1962). The quantities and

composition of the mineral components are highly variable between organic soils.

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Larson et al. (1959) determined that iron and aluminum were primarily

responsible for P fixation in muck. Since iron and aluminum content increase with aging

(time in cultivation) due to subsidence and mineralization, the ability of the soil to fix

P will increase also.

The reactions in organic soil are comparable to mineral soils, in which the

calcium, iron and aluminum in the soil system control the P concentration in the soil

solution. Okruszko et al. (1962) recognized the fact that most iron and aluminum enter

an organic soil in the soluble reactive form and are either precipitated as insoluble

phosphates or are chelated by humic acid. Larson et al. (1959) realized this, but

assumed that iron and aluminum would increase continuously with age and eventually

reach amounts that would overshadow the effect of humic acid, which would reach an

equilibrium content.

Okruszko et al. (1962) agreed that the wide variation in water soluble

phosphorus in organic soils was due to the state of decomposition and amount of

sesquioxides in the soil. However, they determined that calcium was the dominant ion

controlling the P concentration in the liquid phase. Any change in the concentration of

calcium ions in soil solution would inversely change the H2PO4 concentration. The

solubility product principle appears to explain the change in P content that occurs.

Additions of calcium to an organic soil in the form of lime applications will reduce the

amount of potentially leachable P in the soil, as well as reducing P availability to a crop

(Okruszko et al., 1962).

Recent studies by Miller (1979) agree with Larson (1959) and confirm that the

extent of P leaching in an organic soil, subjected to cultivation is dependant on the

sesquioxide content (particularly Al 3+) and the pH of the system.

Miller (1979) was able to develop a prediction equation to serve as a criteria for

evaluating the acceptability of an organic soil area for development. Based on the total

iron and total aluminum contents of an organic soil, the regression equation can predict

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the phosphorus concentration of the soil solution expected from a given fertilizer

application and determinations of significant cation concentrations.

THE STUDY AREA

The Holland Marsh is comprised of 13 organic soil series and a small area of

mineral soil (Figure 1). Table 1 presents a list of the series, the great group and

subgroup classification and the percentage area occupied by each. For the purposes

of this study, the series documented by Hoffman (1971) are assumed to be consistant

with existing soils even through soil depths may have decreased due to subsidence

since the time of their classification.

The great group classification (humisol, mesisol) is largely based on the degree

of decomposition of the middle tier (depth 40-80 cm). Thus the middle tier of a mesisol

is moderately decomposed and the middle tier of a humisol is highly decomposed. The

subgroup classification (humic mesisol) refers to the stage of decomposition of the

bottom tier (depth 80-100 cm).

The stage of decomposition of the middle tier and hence the great group

classification of these soils will reflect, the length of time in cultivation, cultivation

practices, soil management and water table levels. All of these factors contribute to the

enhancement of microbial activity, decomposition and subsidence.

The amount and size of fibre in the middle and surface tiers is an indication of

the degree of decomposition and is in fact a standard method in its determination. The

mesisol will contain 10-40% rubbed fibre and the humisol will contain less than 10%

rubbed fibre. The variation in fibre content implies differences in other properties

considered important to this study. These properties include bulk density, porosity,

water holding capacity, hydraulic conductivity, mineral content and P sorption capacity.

For these reasons, it was thought that sampling sites for an experiment designed to

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characterize the entire marsh area, would have to include a few of the important soil

series which reflected the extremes in properties important to phosphorus reactions

and movement.

As a result of this, three series were chosen to represent the marsh area. The

three series cover the range of stages of decomposition of the organic soils in the

marsh as well as the extremes in agricultural capability of soils in the marsh based on

the ARDA classification. Agricultural capability is reflected in the depth of the organic

soil to mineral layer, permeability and the presence and size of hardwood and softwood

in the control section. Table 2 outlines the series chosen, their classification and

properties. Figure 2 illustrates the relative position and areas of each of these series

in the Holland Marsh as well as the sites sampled.

MATERIALS AND METHODS

FIELD SAMPLING

For each of the series, three mapping units were selected. Sampling was carried

out on three sites within each mapping unit. It should be noted that one extra mapping

unit with one site is included in the Goderich series to represent the uncultivated state.

Sample cores (6-7 from each site) were collected before spring planting in 1983.

A hydraulic coring device was used to collect all samples to minimize compaction. The

core was contained by a split sleeve, 5 cm in diameter, within the coring tube which

facilitated transfer to the split ABS drainpipe of the same diameter and 100 cm long

used for storage as well as leaching studies.

When depth to the mineral substratum was not prohibitive, sample cores were

removed to a maximum depth of 80 cm, (the approximate depth of the tile drain

system). Much variation in soil depth was encountered between soil series, mapping

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units of the same series and in some cases even between sites within mapping units.

It should also be noted that in some cases the depth of organic soil encountered did

not conform to the classification system used. Table 3 indicates the variation in soil

depth between series. Soil depth could be a factor influencing the fate of phosphorus

in these soils.

All cores were stored at 2°C until leaching and analysis began.

CORE PREPARATION

In the laboratory, all of the mineral layer was removed and sample cores were

measued. The ABS drainpipe was sealed with silicone sealant. A hose clamp tightened

in place near the bottom of the core provided extra strength to the seal. Glass wool

was added to the bottom of the core before a rubber stopper fitted with a glass tuber

was sealed in place. Five cm of silica sand was placed on top of the core to facilitate

distribution of water.

LEACHING

A constant head bottle, adjusted to drip aproximately 180 ml of phosphorus-free

water every three days was provided for each column of soil. Leachate collection

bottles placed under the column outlet tube and were removed for analysis every three

days. The amount of leachate at each sampling was measured and a subsample of

approximately 100 ml was stored at 2°C until analysis.

ANALYSIS OF LEACHATE

Inorganic phosphorus was determined in leachate samples using the ammonium

molybdate reaction adapted for autoanalysis (Thomas, 1972).

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FERTILIZER ADDITION

After leaching had reduced the phosphorus output of the columns to a relatively

stable level, a simulated addition of phosphorus fertilizer was added to designated

columns at a low rate of 50 kg P/ha and a high rate of 100 kg P/ha. Other columns had

no fertilizer addition. A small amount of KCl was also added since the Cl- should act as

a tracer to indicate the leaching pattern of a non-reactive ion.

The Cl- was detected by a change in the electrical conductivity of the column

effluent and the fertilizer P was detected by the P analysis as given above.

COLUMN SECTIONING AND ANALYSIS

Four cores (one unleached and three leached) from each site were sectioned into

5 cm segments. Total wet weight of each segment was determined immediately and

then all samples were stored at 2°C until further analysis.

Moisture content and bulk density were determined by standard gravimetric

procedures. Ash content was taken as the residue after ignition. The ash was dissolved

in 1:1 HCl, diluted, filtered and analyzed for P by colorimetric analysis and for Fe, Al,

Ca, and Mg by atomic absorption spectrophotometry.

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RESULTS AND DISCUSSION

1. Leaching studies

Soil cores were leached continuously as described for over six months. The

amount of leaching represents an exaggerated rate of leaching compared to the normal

rate of leaching in the field. Examples of leaching data are presented in figures 3-6.

The data from replicate columns at most sites were in good agreement.

1.1 Sources of Leachable Phosphorus

It is evident from the leaching patterns that substantial amounts of P have been

released from the soil cores. The P can originate from two sources: mineralization of

P from the organic material as it decomposes, or desorption of P from fertilizer P

previously added to and retained by the organic soils of the Holland Marsh. The latter

explanation would seem to be the most reasonable. A comparison of an uncultivated

Goderich soil with cultivated soils of the same series illustrates that only a very small

amount of P is leached from the uncultivated soil while substantial amounts are leached

from the cores from cultivated sites. The consistent concentration of about 0.1 µg P/ml

from the uncultivated site would be indicative of a natural rate of P release from the

organic materials.

It is known that only 2-20% of P in virgin peat is in the inorganic form compared

to 30-60% for cultivated organic soils (Wier and Black, 1968). The higher

concentrations from cultivated sites must be considered to be the result of previous

management practices and past fertilizer P additions. The contribution of Pi from

natural P mineralization appears to be of minor significance. Cogger and Duxbury

(1984) also concluded that P release from organic soils was controlled by an

equilibrium of Pi between more and less labile forms (or adsorbed and soluble Pi). They

also found that the influence of biological mineralization on Pi in solution was indirect

and insignificant.

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Only one site had been fertilized in the 1983 season prior to sampling, yet, the

leaching pattern was not different from the other sites of the same soil series. Thus,

it can be concluded that the P leached from the soils results from many previous years

of activity and not just the most recent year.

While differences do exist, the similarities of the leaching patterns are apparent.

It would appear that the characteristics of each soil series is not a major factor in

controlling the rate of P leaching from the soils.

1.2 Total Amounts of P Removed

The volume of leachate collected and the total amount of P removed from each

soil series to the time of fertilizer addition (average of all cores of the series) is given

in Table 4. Some differences in total volume of leachate exist, but the differences are

not significant because of the variability of individual cores. A summation of the total

amount of P removed from each soil series is also given and ranges from 1.7 mg P/core

in the uncultivated Goderich soil to 80.1 mg P/core in the Ustis. If these data are

calculated to an area basis, they represent 8.66 kg P/ha, 343.8 kg P/ha, 408.0 kg P/ha

and 342.8 kg P/ha for the uncultivated Goderich, and cultivated Fennel, Ustis and

Goderich respectively. Because the leaching was at an accelerated rate compared to

the natural system, and since a hydrologic balance was not known for the organic soils,

the rate of release of stored P over time cannot be readily predicted. The leaching data

clearly show, however, that there is a potential pool of phosphorus that could be

leached downward or used by future crops.

The consistency of the leaching patterns and the remarkable similarity of the

amount of P leached from the three cultivated soils again indicates that soil type is not

a major factor in determining the behavior of phosphorus in organic soils. The

difference between the cultivated soils and the uncultivated Goderich soil clearly shows

that past agronomic practices have left a major reserve of phosphorus in the cultivated

soils that is potentially susceptible to leaching in the future. Duxbury et al. (1978)

reported similar results concerning accumulations of adsorbed fertilizer P.

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1.3 Interaction of P With Soil

The leaching pattern for the Cl- and P from fertilizer addition are of considerable

interest. The volume of leachate required to remove the Cl- reflects the liquid volume

of the soil core which is displaced as the Cl- is leached through the core. The

differences in leachate volume for Cl- between soils are the result of small differences

in bulk density and length of the soil column, and are not of great consequence.

However, the difference of several hundred milliliters of leachate between the removal

of Cl- and P (Table 4) reflects the interaction of P with the soil and thus, the delay in

its downward movement. The delay in the fertilizer P observed illustrates the point

discussed above, that phosphorus that appears in leachate during a given season has

originated from fertilizer additions in previous years and not in the year of leaching.

2. Core Analysis

The soil cores were sectioned, digested and analyzed for total P, Fe, Al, Ca and

Mg. The results are presented graphically in figures 7-11. We will consider the data for

the Goderich soil, but the data for the other soil is similar.

2.1 Total P in Soil

The most interesting result is the much larger accumulation of accumulation of

phosphorus near the surface of the cultivated soils and the reduction in the total P in

cores that were leached. The core analyses clearly support the removal of P illustrated

by the leaching data. In fact, for the Goderich soil, an average of 67.3 mg P was

removed from the soil cores in the leaching experiment. The difference between the

leached and non-leached Goderich cores indicated a loss of 68.5 mg P per core. Such

agreement is remarkable. If these data are an indication of the amount of P that can

be removed by simple leaching, extrapolation would suggest that in the order of 340

kg P/ha could be leached from the organic soils. The rate at which such P would be

leached out naturally cannot be predicted, since, as discussed earlier we do not have

the necessary hydrologic data to calculate the net leaching in the Holland Marsh soils.

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2.2 Critical Elements in the Soil

The data for Fe, Al, Ca and Mg do not seem to provide any remarkable insights.

The total of the inorganic constituents is indicated by the ash content (Figure 12).

There is obviously sufficient inorganic material in the soils to provide the adsorption

sites with which the fertilizer P can interact to slow its leaching through the soil. There

is a suggestion that some Fe and Mg and perhaps Ca are removed with P during the

leaching process.

Discussion

The data presented here suggest a number of important implications for the

drainage system of the Holland Marsh. It is clear that P has accumulated in the soils

of the Marsh and that such P can be leached out if sufficient water is passed through

the soil. This result indicates a potential problem, but the actual problem cannot be

readily evaluated. To estimate the annual leaching of P from the Marsh, a measure of

the hydrologic balance of the Marsh would be required. Such hydrologic studies were

not part of the present study. An estimate of the annual leaching of P could be

obtained if assumptions of the natural leaching rate were made.

The data obtained also suggest a serious concern for the future. It is well known

that the soils of the Holland Marsh are subsiding. It cannot be estimated how much of

the accumulation of P near the surface of the soils is a result of past subsidence. But,

if we project into the future, subsidence will essentially compress the content of P that

now exists. It is to be expected then that the concentration of P/unit of soil will

increase, creating a potential for higher P loss at some time in the future. The severity

of the problem cannot be easily evaluated, but clearly the situation is one that should

be followed over the remaining productive life of the Holland Marsh.

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SUMMARY

The extensive leaching experiment on organic soils of the Holland Marsh has

revealed that substantial amounts of P have been retained in the soils as a result of

previous cultural practices. The phosphorus so retained is identified by the higher P

content near the surface of the soil.

The leaching of the organic soils at an accelerated rate in the laboratoryremoved

some of the accumulated P. It was estimated that approximately 340 kg/ha was

removed during leaching. Such a result has important implications for the future. The

results suggest that P will continually leach from the soils of the Holland Marsh for

many years. Changes in current agronomic practices would not likely change the

problem. The rate of such P loss will be contingent on the hydrologic characteristics of

the Marsh and the net leaching that will occur. A major unknown factor is the fate of

P in the soils as the organic soils continue to subside. It should be anticipated that as

the soils become shallower, the concentration of P will become closer to the depth of

drainage tile and the future rate of leaching of P may accelerate.

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LITERATURE CITED

Cogger, Craig and John M. Duxbury. 1984. Factors Affecting Phosphorus Losses fromCultivated Organic Soils. J. Environ. Qual. 13: 111-114.

Duxbury, J.M. and J.H. Peverly. 1978. Nitrogen and Phosphorus Losses from OrganicSoils. J. Env. Qual. 7: 566-570.

Hoffman, D.W. and G. Pohoral. 1971. The Organic Soils of Southern Ontario. CanadaLand Inventory Program, ARDA. (unpublished report).

Larson, J.E., J.F. Warren and R. Langston. 1959. Effect of Iron, Aluminum and HumicAcid on Phosphorus Fixation by Organic Soils. Soil Sci. Soc. Am. Proc. 438-440.

Miller, M.H. 1979. Contribution of Nitrogen and Phosphorus to Subsurface DrainageWater from Intensively Cropped Mineral and Organic Soils in Ontario. J. Env.Qual. 8: 42-48.

Miller, M.H. and Spires, A.C. 1978. Contribution of Phosphorus to the Great Lakes FromAgricultural Land in the Canadian Great Lakes Basin. International ReferenceGroup on Great Lakes Pollution from Land Use Activities International JointCommission Report.

Nicholls, K.H. and H.R. McCrimmon. 1974. Nutrients in Subsurface and Runoff Watersof the Holland Marsh, Ontario. J. Env. Qual. 3: 31-35.

Okruszko, H., G.F. Warren and G.E. Wilcox. 1962. Influence of Calcium on PhosphorusAvailability in a Muck Soil. Soil Sci. Soc. Am. Proc. 68-71.

Sharpley, A.N. 1982. Prediction of Water-extractable Phosphorus Content of SoilFollowing Phosphorus Addition. J. Env. Qual. 11: 166-170.

Singh and Jones. 1976. Phosphorus Sorption and Desorption Characteristics of Soilsas Affected by Organic Residues. Soil Sci. Soc. Am. J. 389-393.

Stevenson, F.J. 1982. Humus Chemistry. Wiley-Interscience, New York.

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Thomas, R.L. 1972. A System for the Rapid Analysis of Organic Phosphorus in WaterSamples or Fractions from Chromatographic Columns. Comm. Soil Sci. P1. Anal.3(5): 351-354.

Travis, C.C. and E.L. Etnier. 1981. A survey of sorption relationships for reactivesolutes in soils. J. Environ. Qual. 10: 8-17.

Wier, D.R. and C.A. Black. 1968. Mineralization of organic phosphorus in soils asaffected by addition of inorganic phosphorus. Soil Sci. Soc. Am. Proc. 32: 51-55.

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Table 1: Organic soil series of the Holland Marsh described by Hoffman (1971).

SeriesTaxonomic

ClassificationArea(ha)

% of Total Area

CapabilityClassification

Area% of Total

Fennel Humic Mesisol 206 7.5 1 321 11.7

Hope Typic Mesisol 115 4.2

Vespra Typic Humisol 191 6.9 2 191 6.9

Capelton Terric Mesisol 123 4.5 3 542 20.4

Goderich Terric Humic Mesisol 228 8.3

Ivy Mesic Humisol 190 6.9

Sheldrake Typic Humisol 21 0.8

Mariposal Terric Mesic Humisol 46 1.7 4 458 16.6

Willow Terric Humisol 287 10.4

Picton Terric Humic Mesisol 125 4.5

Colbar Terric Humisol 213 7.7 5 213 7.7

Deerhurst Terric Humisol 32 1.2 6 529 19.2

Ustis Terric Humisol 497 18.0

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Table 2: Organic soil series chosen for study and associated properties.

Series Areas(ha)

% Taxonomic Associated Properties AgriculturalCapability

Associated Properties

Goderich 228 8.3 Terric HumicMesisol

< mineral layer >30 cmdeep below surfacetier

3 H < Shallow (H=depth to mineral layer)< depth restrictive to agriculture

presenting moderate limitations

Fennel 206 7.5 Humic Mesisol < humic (welldecomposed) layer inmiddle and bottomtier >25 cm in depth

1 < no limitations to agriculture

Ustis 497 18.0 Terric Humisol < mineral layer >30 cmdeep below surface

6 HKLtier

< limitations so severe as to excludeagricultural development

< restrictive due to: (H) depthshallow (L) presence of wood (K)poor permeability

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Table 3: Depths obtained from field collection of cores.

SeriesActual Core Length

Range Between MappingUnits of Same Series

AverageLength of

Cores Per Series

Length as in SeriesDescription

(Hoffman, 1971)

Goderich 65-83 cm 77.2 cm <52" (132 cm)

Fennel 62-83 cm 73.3 cm <52" (132 cm)

Ustis 41-81 cm 60.7 cm <36" (91.5 cm)

Table 4: Leaching volumes prior to fertilizer addition, P- removed during leaching andleaching volumes to remove added P and Cl-.

Leachate* Volume

Total Reactive* P Removed

Leachate VolumeTo Remove

Cl-

Leachate VolumeTo RemoveFertilizer P

SOLUTION (ml) (mg/core) (ml) (ml)

Fennel 7967 67.5 1333 2525

Ustis 7450 80.1 1100 1825

Goderich(cultivated)

7883 67.3 1033 1400

Goderich(uncultivated)

7867 1.7 1217 1550

* Average for 6 columns before addition of fertilizer.

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FIGURE 1

LEGEND

Soil Series Symbol

Fennel * Fe

Hope Ho

Vespra Vr

Capelton Cp

Goderich* Go

Ivy Iv

Sheldrake Sd

Mariposal Mp

Willow Wi

Picton Pn

Colbar Cb

Deerhurst Dh

Ustis* Ut

* Soil series sampled

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Figure 1: The Holland Marsh - Soil Series (See legend, previous page)

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FIGURE 2

*Sampling Sites

eg Go 1 a

Series Mapping SiteUnit

* These series were sampled in each of three mapping units and within eachmapping unit, three sites were sampled.

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Figure 2: The Holland Marsh - Sampling Sites.

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Figure 3: FENNEL SERIES.

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Figure 4: GODERICH SERIES.

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Figure 5: USTIS SERIES.

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Figure 6: GODERICH UNCULTIVATED.

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Figure 7: The Vertical Distribution of Phosphorus in a Goderich Soil. (Terric Mesisol).

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Figure 8: The Vertical Distribution of Calcium in a Goderich Soil. (Terris Mesisol)

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Figure 9: The Vertical Distribution of Magnesium in a Goderich Soil. (Terric Mesisol).

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Figure 10: The Vertical Distribution of Iron in a Goderich Soil. (Terric Mesisol)

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Figure 11: The Vertical Distribution of Aluminum in a Goderich Soil. (Terric Mesisol)

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Figure 12: The Vertical Distribution of Ash in a Goderich Soil. (Terric Mesisol)

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Figure 13: The Variation in Bulk Density with Depth in a Goderich Soil. (Terric Mesisol)

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