land management effects on the near-surface physical quality of a clay loam soil

Land management effects on the near-surface physical

quality of a clay loam soil

W.D. Reynolds *, C.F. Drury, X.M. Yang, C.A. Fox, C.S. Tan, T.Q. Zhang

Greenhouse and Processing Crops Research Centre, Agriculture and Agri-Food Canada, 2585 County Road 20,

Harrow, Ontario, Canada N0R 1G0

Received 2 January 2007; received in revised form 20 June 2007; accepted 18 July 2007

www.elsevier.com/locate/still

Soil & Tillage Research 96 (2007) 316–330

Abstract

Although agricultural land management is known to affect near-surface soil physical quality (SPQ), the characteristics of these

affects are poorly understood, and diagnostic SPQ indicators are not well-developed. The objective of this study was to measure a suite

of potential SPQ indicators using intact soil cores and grab samples collected from the 0–10 cm depth of a clay loam soil with the

treatments: (i) virgin soil (VS); (ii) long-term continuous bluegrass sod (BG); (iii) long-term maize (Zea mays L.)—soybean (Glycine

max (L.) Merr.) rotation under no-tillage (NT); (iv) long-term maize–soybean rotation under mouldboard plough tillage (MP); (v)

short-term (1–4 years) NTafter long-term MP; (vi) short-term MP after long-term BG; (vii) short-term MP after long-term NT. Organic

carbon content, dry bulk density, air capacity, relative water capacity and saturated hydraulic conductivity appeared to be useful SPQ

indicators because they were sensitive to land management, and proposed optimum or critical values are available in the literature. Soil

macroporosity was also sensitive to land management, but optimum or critical values for this parameter are not yet established. Soil

matrix porosity and plant-available water capacity did not respond substantially or consistently to changes in land management, and

were thus not useful as SPQ indicators in this study. Converting long-term BG to MP caused overall SPQ to decline to levels similar to

long-term MP within 3–4 years. Converting long-term NT to MP or vice versa caused only minor changes in overall SPQ. With respect

to the measured SPQ indicators and their optimum or critical values, both VS and BG produced ‘‘good’’ overall SPQ in the near-surface

soil, while long-term maize–soybean rotation under NT and MP produced equally ‘‘poor’’ SPQ.

Crown Copyright # 2007 Published by Elsevier B.V. All rights reserved.

Keywords: Soil quality indicators; Clay loam soil; No-tillage; Mouldboard plough tillage; Bluegrass sod; Virgin soil; Organic carbon; Bulk

density; Porosity; Air capacity; Plant-available water capacity; Hydraulic conductivity

1. Introduction

Soil quality may be defined as the ‘‘capacity of the

soil to function within ecosystem and land-use

boundaries to sustain biological productivity, maintain

environmental quality, and promote plant and animal

health’’ (Doran et al., 1996). An agricultural soil with

* Corresponding author. Tel.: +1 519 738 1265;

fax: +1 519 738 2929.

E-mail address: [email protected] (W.D. Reynolds).

0167-1987/$ – see front matter. Crown Copyright # 2007 Published by E

doi:10.1016/j.still.2007.07.003

good ‘‘quality’’ thus possesses all of the physical,

chemical and biological attributes necessary to promote

and sustain good agricultural productivity with negli-

gible environmental degradation. A soil with poor

quality, on the other hand, may not possess some or all

of the attributes required for good agricultural produc-

tion, or it may be prone to environmental degradation

through wind/water erosion and leaching of agrochem-

icals, nutrients and pathogens into surface and ground

water resources.

Due to the extreme complexity of the soil environ-

ment, agricultural soil quality is often segmented into

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http://dx.doi.org/10.1016/j.still.2007.07.003

W.D. Reynolds et al. / Soil & Tillage Research 96 (2007) 316–330 317

‘‘soil physical quality’’, ‘‘soil chemical quality’’ and

‘‘soil biological quality’’ (e.g. Dexter, 2004a), although

it is generally recognized that these components interact

and are thus not truly separable. Soil physical quality

refers primarily to the soil’s strength and fluid

transmission and storage characteristics in the crop

root zone; which in turn result from soil physical

properties (e.g. texture, structure, hydrology), climate,

management practices (e.g. tillage, trafficking), crop

types, and various soil-based chemical and biological

processes (e.g. oxidation–reduction, mineralization,

faunal activity). An agricultural soil with ‘‘good

physical quality’’ is one that is strong enough to

maintain good structure and hold field crops upright, but

also weak enough to allow optimal proliferation of crop

roots, soil flora, and soil fauna. Soil with good physical

quality also has the ability to store and transmit water,

air, nutrients and agrochemicals in ways which promote

both maximum crop performance and minimum

environmental degradation (Topp et al., 1997).

Soil physical quality is relevant and important for

the entire crop rooting zone, which is approximately

the top 1 m of the soil profile. However, the top 10 cm

of soil is particularly important because it controls

many critical agronomic and environmental processes,

such as seed germination and early growth, aggrega-

tion, tillage impacts, erosion, surface crusting, aera-

tion, infiltration, and runoff. In addition, many studies

have found that the majority of soil physical quality

responses to livestock treading, cropping and tillage

occur in the top 5–15 cm of the soil profile (e.g.

Drewry, 2006). For example, Singleton et al. (2000)

showed that the deleterious effects of dairy cattle

treading on the soil physical properties of pasture

occurred primarily in the top 10 cm, regardless of soil

type; and data in Drewry et al. (2001, 2004) and

Drewry and Paton (2005) largely confirm this for dairy

pasture on a humid silty clay loam soil. Carter (1988,

1990) also found changes in soil physical quality to

occur primarily in the top 10 cm for row-crop spring

cereals produced on a humid, fine sandy loam under

mouldboard plough tillage and no-tillage. Hence, this

study will focus on the physical quality of the top

10 cm of the soil profile.

A coherent and formalized set of soil physical

quality indicators have not yet been developed, despite

extensive efforts over the last couple of decades

(Arshad and Martin, 2002). In addition, optimum/

critical values or ranges for soil physical quality

indicators are still largely unknown (e.g. Arshad and

Martin, 2002), although various ‘‘guidelines’’ have

been proposed for agricultural and non-agricultural

soils (e.g. Hall et al., 1977; Greenland, 1981; Carter,

1990; Craul, 1999; Reynolds et al., 2002; Drewry and

Paton, 2005). Nevertheless, it is becoming increas-

ingly clear that organic carbon content, bulk density,

permeability, and various forms of porosity, aeration

and water retention will form key components of any

integrative parameter or suite of parameters indicating

soil physical quality. For example, Shukla et al. (2006)

recently identified organic carbon content as the single

most important parameter indicating the degree of soil

aeration; and Dexter (2004b) found the slope of the

soil water desorption curve at the inflection point to be

a plausible indicator of soil structural quality. In

addition, work by Hall et al. (1977), Greenland (1981),

Carter (1990), de Witt and McQueen (1992), Reynolds

et al. (2002), Drewry and Paton (2005) and others

suggests that density, hydraulic conductivity and

various air and water capacity relationships are

potentially useful indicators of soil strength, soil

water transmission, and soil air–water storage,

respectively.

Studies aimed at defining and measuring soil

physical quality should make use of soils under

consistent, long-term land management (e.g. annual

mouldboard plough cropping, continuous pasture, etc.)

in order to ensure that quasi-stable end points or ‘‘quasi-

steady states’’ in soil quality have been reached (Arshad

and Martin, 2002; McQueen and Shepherd, 2002;

Reynolds et al., 2002). It is also instructive, however, to

investigate how soil physical quality parameters

respond to sudden changes in land management, as

this may shed light on the rate and mechanism by which

the physical quality of a soil ‘‘migrates’’ from one

steady state to another (Arshad and Martin, 2002;

McQueen and Shepherd, 2002).

The objectives of this study were consequently to: (i)

measure selected soil physical quality parameters in the

near-surface (top 10 cm) of an annually cropped clay

loam soil under long-term bluegrass sod, long-term

mouldboard plough tillage, and long-term no-tillage;

(ii) track the annual changes in the physical quality of

this soil after converting long-term no-tillage to

mouldboard plough tillage, long-term mouldboard

plough tillage to no-tillage, and long-term bluegrass

sod to mouldboard plough tillage; (iii) compare the

measured parameter values to ‘‘ideal/optimal/critical’’

levels proposed in the literature, and to ‘‘benchmark’’

levels obtained for the soil under a ‘‘native’’ or

‘‘virgin’’ condition. Including virgin soil measure-

ments provides an indication of the level of physical

quality the soil attains through natural (non-anthro-

pogenic) processes.

W.D. Reynolds et al. / Soil & Tillage Research 96 (2007) 316–330318

2. Soil physical quality parameters

The soil properties measured included organic

carbon content, OC (wt.%), dry bulk density, BD

(Mg m�3), soil macroporosity, MacPOR (m3 m�3), soil

matrix porosity, MatPOR (m3 m�3), air capacity, AC

(m3 m�3), plant-available water capacity, PAWC

(m3 m�3), relative water capacity, RWC (dimension-

less), and saturated hydraulic conductivity, KS (cm s�1).

These parameters are often used as indicators (or

potential indicators) of soil physical quality in humid,

medium–fine-textured agricultural soils (e.g. Drewry,

2006; Topp et al., 1997; Reynolds et al., 2002). Brief

‘‘working definitions’’ of the parameters are included

below along with proposed ‘‘ideal/optimal/critical’’

values obtained from the literature. Aggregate size

distribution and stability were not considered in this

study because their ‘‘function’’ in terms of soil strength

and the storage and transmission of water and air is

already accounted for (albeit indirectly) by the various

parameters mentioned above. The soil physical quality

indicators ‘‘least limiting water range’’ (Letey, 1985; da

Silva et al., 1994) and ‘‘S-theory’’ (Dexter, 2004b,c,d)

were also not considered.

2.1. Organic carbon

Soil organic carbon content (OC) is a measure of the

total amount of organic material present in the soil (i.e.

living and dead plant, animal and microbial materials;

highly stable humic substances), and it is known to

influence virtually all aspects of soil quality including

soil physical quality (Gregorich et al., 1997). For

example, Shukla et al. (2006) used statistical factor

analysis to show that OC is the single most important

soil constituent contributing to aeration and aggrega-

tion. Despite this, optimal or preferred OC levels for

sustainable field-crop production and minimum off-

field environmental degradation have not yet been

identified. However, an OC range of 3–5 wt.% is

frequently cited as being ‘‘optimal’’ for establishment

and maintenance of plants in ‘‘constructed’’ land-

scaping soils (e.g. urban parks, sports fields, curb-side

plantings, etc.), as it correlates with the ranges of bulk

density, aeration, plant-available soil water, and

drainage necessary for good plant growth and good

resistance to soil compaction (Craul, 1999). Although

an OC criterion for landscaping soils is obviously not

directly related to field crops, it nonetheless falls

between the lower ‘‘critical limit’’ (2.3 wt.%) proposed

by Greenland (1981) below which tillage-induced loss

of structure may occur in fine-textured soils, and the

upper ‘‘critical limit’’ (6 wt.%) proposed by Sojka and

Upchurch (1999) beyond which the soil may be prone to

compaction and absorption of soil-incorporated pesti-

cides.

Pieri (1992) suggests that OC levels required to

maintain soil structure can be estimated using:

SI ¼ 1:72OC ðwt:%ÞðClayþ SiltÞ ðwt:%Þ � 100 (1)

where SI (%) is a soil structural ‘‘stability index’’, and

(Clay + Silt) is the soil’s combined clay and silt content.

SI � 5% indicates structurally degraded soil due to

extensive loss of organic carbon; 5% < SI � 7% indi-

cates high risk of structural degradation due to insuffi-

cient organic carbon; 7% < SI � 9% indicates low risk

of soil structural degradation; and SI > 9% indicates

sufficient soil organic carbon to maintain structural

stability. For the soil in this study (see Section 3), the

optimal OC range proposed by Craul (1999) (i.e.

3 wt.% � OC � 5 wt.%) corresponds to 7.2% � SI

� 11.9%, which spans the ‘‘low risk’’ and ‘‘stable’’

categories. The critical minimum OC proposed by

Greenland (1981) (i.e. OC = 2.3 wt.%) corresponds to

the boundary between the ‘‘high risk’’ and ‘‘degraded’’

categories.

2.2. Bulk density

Soil dry bulk density (BD) is often used in soil

quality studies as an index of the soil’s mechanical

resistance to root growth (e.g. Carter, 1988, 1990;

Reynolds et al., 2003; Drewry, 2006); and is defined

here by:

BD ¼ MS

Vb

(2)

where MS (Mg) is the mass of the oven-dry soil and Vb

(m3) is the bulk volume of the soil at pore water pressure

head, c = �1 m. For fine-textured soils, the optimum

BD range for field crop production appears to be on the

order of 0.9–1.2 Mg m�3 (Olness et al., 1998; Drewry

et al., 2001; Reynolds et al., 2003; Drewry and Paton,

2005). BD values <0.9 Mg m�3 may provide insuffi-

cient root–soil contact, water retention and plant

anchoring, while BD values >1.2 Mg m�3 may impede

root elongation or reduce soil aeration (Jones, 1983;

Olness et al., 1998; Reynolds et al., 2003; Drewry and

Paton, 2005; Drewry, 2006). The upper BD limit for

adequate aeration of fine-textured soils appears to be on

the order of 1.25–1.30 Mg m�3 (Jones, 1983; Carter,

1988; Carter et al., 1999; Shepherd, 1994; Drewry et al.,


2001; McQueen and Shepherd, 2002), while mechan-

ical resistance to root elongation in fine-textured soil

often becomes excessive for BD � 1.4–1.6 Mg m�3

(Veihmeyer and Hendrickson, 1948; O’Connell,

1975; Jones, 1983; Jones et al., 2003).

2.3. Macroporosity and matrix porosity

The macroporosity (MacPOR) and matrix porosity

(MatPOR) parameters define the volume of soil

macropores and matrix pores, respectively, and are

given by:

MacPOR ¼ uS �MatPOR (3)

MatPOR ¼ um (4)

where uS (m3 m�3) is the saturated volumetric water

content of the soil (see Section 3.4), and um (m3 m�3) is

the saturated volumetric water content of the soil matrix

exclusive of macropores (i.e. soil matrix porosity). The

c value at which um is measured is not yet fixed, and

values of c = �0.1, �0.5 and �1 m have been used

(e.g. Jarvis et al., 2002; de Witt and McQueen, 1992;

Hall et al., 1977) which correspond to maximum

equivalent pore diameters of 0.3, 0.06 and 0.03 mm,

respectively, according to the capillary rise equation

(Hillel, 1980). In this study, um was defined as the

equilibrium volumetric soil water content at

c = �0.1 m, and hence soil macropores had equivalent

diameters>0.3 mm, while soil matrix pores had equiva-

lent diameters �0.3 mm. Minimum or optimum Mac-

POR and MatPOR values as defined above have not yet

been identified. However, data in Carter (1988), Drewry

et al. (2001), and Drewry and Paton (2005) suggest

that the top 10 cm of medium- to fine-textured soils

may yield MacPOR �0.05–0.10 m3 m�3 when ‘‘un-

degraded’’, and MacPOR < 0.04 m3 m�3 when

‘‘degraded’’ by compaction or consolidation.

2.4. Air capacity

The soil air capacity (AC) is an indicator of soil

aeration, and may be defined as

AC ¼ uS � uFC (5)

where uFC (m3 m�3) is the so-called field capacity

which is defined here as the equilibrium volumetric

soil water content at c = �1 m. An AC � 0.10 m3 m�3

has traditionally been recommended to achieve mini-

mum susceptibility to crop-damaging aeration deficits

in the root zone (e.g. O’Connell, 1975; de Witt and

McQueen, 1992). Cockroft and Olsson (1997) suggest,

however, that AC � 0.15 m3 m�3 is required for fine-

textured soils to compensate for low gas diffusion rates

and the respirative demands of biological activity. This

higher value is consistent with Drewry (2006), Drewry

et al. (2001) and Drewry and Paton (2005) who

found that AC > 0.12–0.17 m3 m�3 was required for

maximum ryegrass production on silty clay loam soil,

while AC < 0.07–0.11 m3 m�3 caused substantially

reduced ryegrass yield. Carter (1988) reported that

AC > 0.14 m3 m�3 was required in a fine sandy loam

for adequate root-zone aeration.

2.5. Plant-available water capacity

The plant-available water capacity (PAWC) is often

used as an indicator of the soil’s capacity to store and

provide water that is available to plant roots, and is

usually defined by:

PAWC ¼ uFC � uPWP (6)

where uPWP (m3 m�3) is the permanent wilting point,

which for most practical applications, corresponds to the

equilibrium volumetric soil water content at c =

�150 m. For the Ap horizon of medium- to fine-textured

soils, Hall et al. (1977) proposed four PAWC categories:

‘‘ideal’’ for PAWC > 0.20 m3 m�3; ‘‘good’’ for

0.15 m3 m�3 � PAWC � 0.20 m3 m�3; ‘‘limited’’ for

0.10 m3 m�3 � PAWC � 0.15 m3 m�3; and ‘‘poor’’ for

PAWC < 0.10 m3 m�3. These categories are consistent

with the recommendation of Verdonck et al. (1983) and

Cockroft and Olsson (1997) that PAWC � 0.20 m3 m�3

is required in fine-textured field soils for maximum

root growth/function and minimum susceptibility

to ‘‘drougthiness’’. Soils with PAWC < 0.10–

0.15 m3 m�3 are often considered ‘‘droughty’’ or

‘‘potentially droughty’’.

2.6. Relative water capacity

The relative water capacity (RWC) is defined by,

RWC ¼�

uFC

uS

�¼�

1��

AC

uS

��(7)

and it expresses the soil’s capacity to store water (and

air) relative to the soil’s total pore volume (as repre-

sented by uS). The optimal balance between root-zone

soil water capacity and soil air capacity appears to be

achieved in field soils when 0.6 � RWC � 0.7 (Olness

et al., 1998), as this range corresponds to the propor-

tions of soil water and soil air that produce maximum

soil microbial activity, regardless of soil texture and


bulk density (Linn and Doran, 1984; Skopp et al., 1990).

RWC < 0.6 causes reduced microbial activity due to

insufficient soil water (‘‘water limited’’ soil), while

RWC > 0.7 causes reduced microbial activity due to

insufficient soil air (‘‘aeration limited’’ soil) (Linn and

Doran, 1984; Skopp et al., 1990). The rationale for this

criterion is that rain-fed agricultural soils with

0.6 � RWC � 0.7 are more likely to have desirable

water and air contents (for maximum microbial activity)

more frequently and for longer time periods than soils

that have larger or smaller ratios (Reynolds et al., 2002).

2.7. Saturated hydraulic conductivity

The saturated hydraulic conductivity (KS) is an

indicator of the soil’s ability to imbibe and transmit

plant-available water to the root zone, as well as

drain excess water out of the root zone (Topp et al.,

1997). A KS value in the range, 5 � 10�3 cm s�1 to

5 � 10�4 cm s�1 may be considered ‘‘ideal’’ for

promoting rapid infiltration and redistribution of

needed crop-available water, reduced surface runoff

and soil erosion, and rapid drainage of excess soil water

(Reynolds et al., 2003). Values substantially above this

range may encourage nutrient/pesticide leaching and

soil droughtiness related to the fact that infiltration and

drainage are too rapid to allow adequate water sorption

into the soil matrix. Values substantially below the

range may cause excessive ponding, runoff and erosion,

reduced trafficability, and aeration deficits associated

with prolonged water-logging (saturation) of the root

zone. de Witt and McQueen (1992) and McQueen and

Shepherd (2002) proposed a lower ‘‘critical limit’’ of

KS = 1.0 � 10�4 cm s�1 for fine-textured agricultural

soils, below which crop production was frequently and

substantially impaired by inadequate root zone aera-

tion, reduced trafficability, and increased surface

runoff and erosion.

3. Materials and methods

3.1. Soil

The soil was a flat (<1% slopes), poorly drained

Brookston clay loam (U.S. classification: fine, loamy,

mixed, mesic, Typic Argiaquoll; Canadian classifica-

tion: Orthic Humic Gleysol) located in Essex County,

Ontario, Canada, at the Hon. Eugene F. Whelan

Experimental Farm, Agriculture and Agri-Food

Canada, Woodslee (428130N, 828440W; mean annual

air temperature = 8.9 8C; mean annual precipita-

tion = 831 mm). The average soil texture in the Ap

horizon (0–20 cm) was by weight 28% sand, 35%

silt, and 37% clay; and the pH and organic carbon

content under long-term cropping were 6.1–6.5 and

2.0–2.5 wt.%, respectively. The soil structure in the Ap

was fragile (Stone et al., 1985), and consisted of: well-

developed, fine–medium granular under virgin soil

conditions; fine–medium angular blocky under long-

term grass/legume cropping; and massive to poorly

developed medium-coarse subangular blocky or pris-

matic under long�term maize/soybean cropping

(McKeague et al., 1987; MacDonald et al., 1994).

Shrinkage cracking occurred under dry conditions due

to the presence of vermiculite clays (MacDonald et al.,

1994). Brookston clay and clay loam are major

agricultural soils, occupying approximately 76%

(121,000 ha) of the agricultural land base in Essex

County (Richards et al., 1949).

3.2. Treatments

The treatments were arranged in a randomized

complete block design (two replicate blocks, each plot

6 m wide � 35 m long), and consisted of both long-

term (14–17 years) and short-term (1–4 years) land

management. Long-term management included con-

ventional mouldboard plough tillage (MP), no-tillage

(NT), and a continuous bluegrass sod (BG) which was

harvested annually. The MP treatment consisted of fall

mouldboard ploughing to �15 cm depth, then spring

disking to 10 cm depth plus secondary harrowing and

packing as required. Soil disturbance in the NT

treatment was limited to that caused by the no-till

planter and side-dress nitrogen application. Short-term

management included 1–4 years of MP after 13 years

BG (MPBG1–4), 1–4 years MP after 13 years NT

(MPNT1–4), and 1–4 years NT after 13 years MP

(NTMP1–4). Both the long-term and short-term MP and

NT treatments were cropped to a maize (Zea mays L.)—

soybean (Glycine max (L.) Merr.) rotation, with both

crops present each year. The crop rows were neither

ridged nor furrowed, and they were consistently

oriented in a north-south direction. The east-west

positioning of no-tillage rows varied back and forth by

several centimetres from year-to-year to avoid planting

soybean on top of the stalks from the previous maize

crop. The above tillage and cropping practices are

commonly used by the region’s farmers. Also included

in the study was a nearby area (within 500 m) of never

cropped or cultivated ‘‘virgin soil’’ (VS) which

supported native deciduous trees and grasses. As

mentioned above, this area was included to provide a

soil quality ‘‘benchmark’’ against which the cropping


treatments could be compared, at least on a subjective

basis. All treatments except VS were under-drained

using clay tile (10 cm diameter, 60–70 cm depth) which

had been in place for greater than 25 years.

3.3. Sample collection

Ten intact soil cores (10 cm diameter � 10 cm long)

and accompanying soil grab samples were collected

each year from the 0–10 cm depth of each treatment

(five sub-samples per replicate � two replicates). The

cores were collected in sharpened, thin-walled (3 mm)

stainless steel sampling cylinders, and the accompany-

ing soil grab samples were collected by scraping the

wall of the hole left by the cylinder. A drop-hammer

system (Reynolds, 1993; Fig. 56.4) was used to insert

the sampling cylinders; and core collection proceeded

only when the soil water content (measured in situ using

a TDR instrument with a 12 cm probe length) was

within the range that prevented visual shattering or

compaction (�0.35–0.40 m3 m�3) so that the antece-

dent soil structure was retained. The cores and grab

samples were collected from untrafficked areas and in

the crop inter-rows to avoid possible artefacts asso-

ciated with wheel compaction and progressive root/

stem development. The cores and grab samples were

collected during June–September so that near-surface

soil conditions during active crop growth were

measured. After extraction, the cores and grab samples

were wrapped in plastic (to prevent water loss or gain),

and stored in the dark at 4 8C (to minimize biological

activity) until laboratory analysis.

The cores and grab samples were collected in 1997

from the VS treatment, in 1997 and 1999 from the BG,

MP and NT treatments, and in 1997–2000 inclusive

from the MPBG, MPNT and NTMP treatments. The cores

were always collected from the same plots, and hence

the crop present in the tillage treatments at sampling

alternated between soybean (1997, 1999) and maize

(1998, 2000). The BG, MP and NT results were

averaged over the 2 sampling years (n = 20), while the

MPBG, MPNT and NTMP results were specific to each

year-crop combination (n = 10).

3.4. Measuring sequence

The soil physical and hydraulic properties were

determined sequentially. First, the soil cores were

incrementally saturated from the bottom up over a 4-day

period using temperature-equilibrated tap water (Rey-

nolds, 2007). Next, KS was determined using the

conductivity tank method (Reynolds, 2007). The cores

were then moved to tension tables (Reynolds and Topp,

2007), u(c) obtained for drainage from saturation, and

MacPOR, MatPOR, AC and RWC calculated using

Eqs. (3)–(5) and (7), respectively. Next, the cores were

oven dried at 105 � 5 8C for 4 days (Reynolds and

Topp, 2007), and BD (Hao et al., 2007) calculated using

Eq. (2). The uPWP values required for PAWC

determination (Eq. (6)) were obtained via the pressure

plate extraction method (Reynolds and Topp, 2007)

using 4.7 cm diameter by 3.8 cm long rings filled to

1 cm depth with disturbed soil (from the grab samples)

that had been air-dried and ground to �2 mm. The

ground soil was also used to determine OC by dry

combustion (Skjemstad and Baldock, 2007) in a LECO

CN-2000 Carbon Analyzer (LECO Corp., St. Joseph,

MI). Given that the soil was slightly acid (pH 6.1–6.5)

and free of mineral carbonates, total carbon was

assumed equal to organic carbon.

The uS parameter in Eqs. (3), (5) and (7) was

determined using,

uS ¼MW �MS

MS

��

BD

WD

�(8)

where MW (Mg) is the saturated core weight, MS (Mg)

the oven-dry core weight, and WD = 1 Mg m�3 is the

water density. This approach was used, as opposed to

assuming uS = porosity, because it avoids the need to

measure (or assume) average soil particle density,

which changes with changing OC content. The con-

ductivity tank, tension table and pressure plate extrac-

tion measurements were conducted at 20 � 1 8C.

3.5. Statistical analyses

For all parameters except OC, analysis of variance

was conducted separately on the conversion of BG to

MP, the conversion of NT to MP, and the conversion of

MP to NT. For OC, the analysis of variance included

long-term BG, NT and MP, and the 4th year only of the

three management conversions (i.e. MPBG4, NTMP4,

MPNT4). This was done because the time scale for

significant OC change in the plough layer of cool,

humid soils is on the order of several years to decades

(e.g. Janzen et al., 1997).

When treatment main effects occurred, significant

differences among treatment means were determined

using Duncan’s multiple range test (P < 0.05). Standard

error was also calculated to indicate the variability about

the mean values. At this field site, KS is log-normally

distributed while all other parameters are normally

distributed. Hence, KS was natural log-transformed


Fig. 1. Mean soil organic carbon content (OC) in the 0–10 cm depth

for virgin soil (VS), long-term continuous bluegrass sod (BG), long-

term maize–soybean cropping under no-tillage (NT) or mouldboard

plough tillage (MP), 4th year of maize–soybean cropping under

mouldboard plough tillage after long-term bluegrass (MPBG4) or after

long-term no-tillage (MPNT4), and 4th year of maize–soybean crop-

ping under no-tillage after long-term mouldboard plough tillage

(NTMP4). The two horizontal lines demark a proposed optimal OC

range. Columns labelled with the same letter are not significantly

different at P < 0.05 according to the Duncan’s Multiple Range test.

The vertical T-bars indicate standard error about the means.

before statistical analyses were conducted, and the

reported KS values are ‘‘geometric’’ means.

4. Results and discussion

4.1. Organic carbon content

The virgin soil (VS) produced a very high average OC

(6.81 wt.%) (Fig. 1), which is likely the result of both

uninhibited activity of soil flora and fauna over a very

long time period, and lack of anthropogenic disturbance.

Long-term bluegrass (BG) produced a substantially

lower OC (3.61 wt.%) relative to VS, implying (perhaps

surprisingly) that monoculture bluegrass production and

changes in the soil environment associated with tile

drainage, annual fertilization and annual harvest pro-

duces much lower accumulations of OC than an

undisturbed virgin soil environment. Long-term no-

tillage (NT) produced a mean OC (2.54 wt.%) that was

significantly and substantially lower than those for VS

and BG, but significantly greater than the OC for long-

term MP (2.07 wt.%). The mean OC values for the three

tillage conversion treatments, on the other hand, fell

between NT and MP; and decreased in the order

MPBG4 > NTMP4 > MPNT4 with no significant differ-

ence among NT, MPBG4 and NTMP4, and no significant

difference among NTMP4, MPNT4 and MP (Fig. 1). It is

also interesting to note that the OC for long-term MP (i.e.

2.07 wt.%) was nearly the same as the OC obtained by

McQueen and Shepherd (2002) (2.2 wt.%) in the top

10 cm of a poorly drained silty clay loam soil in New

Zealand under a long-term barley–wheat–maize rotation.

The OC of the virgin soil (6.81 wt.%) exceeded the

optimum OC range for urban soils (i.e. 3–5 wt.%) by a

substantial margin, and also produced a stability index,

SI = 16.3% (Eq. (1)), which indicates more than enough

organic carbon to maintain stable soil structure. Hence,

the observed granular soil structure under VS should be

stable, but perhaps also susceptible to compaction and

pesticide sorption due to above-optimal OC. The BG

treatment produced an OC level that was both within the

optimum range and sufficient to produce low risk for

degradation of its well-developed fine–medium angular

blocky structure (SI = 8.6%). The BG treatment might

therefore be considered ‘‘ideal’’ from an OC perspec-

tive. The five tillage treatments, on the other hand, fell

below the optimal OC range, and their SI indexes were

in the ‘‘high risk’’ or ‘‘degraded’’ categories (i.e.

SI = 6.1% for NT; 5.9% for MPBG4; 5.5% for NTMP4;

5.1% for MPNT4; 4.9% for MP), which was consistent

with their visually massive or coarse soil structures.

Note also that the OC for MP, MPNT4, and NTMP4

(2.07 wt.%, 2.14 wt.%, and 2.29 wt.%, respectively)

fell below the lower ‘‘critical limit’’ proposed by

Greenland (1981) (2.3 wt.%) for maintaining soil

structure in tilled soil; and that the favourable OC

and SI levels of long-term BG were reduced to

unfavourable levels after only 4 years of maize–

soybean cropping under MP tillage (MPBG4).

4.2. Bulk density

The virgin soil (VS) produced an average BD

(0.88 Mg m�3) that fell just below the lower limit of the

optimum range for crop production proposed by Olness

et al. (1998) and Reynolds et al. (2003) (Fig. 2), and this

probably occurred because of the well-developed fine–

medium granular structure and high organic carbon

content in this treatment (Fig. 1). Surprisingly, the

continuous bluegrass treatment (BG) produced a much

greater mean BD value (1.15 Mg m�3) which fell just

below the upper limit of the optimal BD range (Fig. 2).

Presumably, this 31% increase for BG relative to VS is

due to BG’s lower organic carbon content (3.61 wt.%

vs. 6.81 wt.%; Fig. 1), generally poorer soil structure

(angular blocky vs. granular), and perhaps greater

traffic-induced compaction associated with annual

fertilization and harvesting.

The first year of MP tillage after 13 years of BG

(MPBG1) caused mean BD to increase to a value


Fig. 2. Mean soil dry bulk density (BD) in the 0–10 cm depth for

virgin soil (VS), long-term continuous bluegrass sod (BG), long-term

maize–soybean cropping under mouldboard plough tillage (MP) or

no-tillage (NT), and 1–4 years of maize–soybean cropping under: (a)

mouldboard plough tillage after long-term bluegrass (MPBG1–4); (b)

mouldboard plough tillage after long-term no-tillage (MPNT1–4); (c)

no-tillage after long-term mouldboard plough tillage (NTMP1–4). The

two horizontal lines demark a proposed optimum BD range. Means

labelled with the same letter are not significantly different at P < 0.05

according to the Duncan’s Multiple Range test. The vertical T-bars

indicate standard error about the means.

(1.35 Mg m�3) that was significantly greater than

long-term BG (1.15 Mg m�3) (Fig. 2a). Note also that

BD for the succeeding years of MP after BG (i.e.

MPBG2, MPBG3, MPBG4) were variable, but together

with MPBG1, produced a general non-linear pattern of

increase that produced a mean BD equivalent to that

of long-term MP (1.42 Mg m�3) within 3–4 years

(Fig. 2a). On the other hand, converting long-term NT

to MP (Fig. 2b) and long-term MP to NT (Fig. 2c) had

no consistent effect on near-surface BD, i.e. the two

long-term tillages (NT, MP) and the two sets of 1–4

year conversions from one tillage to the other

(MPNT1–4, NTMP1–4) were for the most part not

significantly different and did not show any distinct

patterns.

It is clear in Fig. 2 that maize–soybean cropping

under both MP and NT tillage produced near-surface

BD values that were not only above the optimum range

for field-crop production (0.9–1.2 Mg m�3), but above

the upper limit for adequate aeration in fine-textured

soil (1.25–1.30 Mg m�3) and entering the range where

root elongation becomes severely restricted in fine-

textured soil (1.4–1.6 Mg m�3). Hence, crop growth in

all six tillage treatments was likely impaired by

excessive soil bulk density.

4.3. Macroporosity and matrix porosity

The virgin soil (VS) and long-term bluegrass (BG)

produced some surprising differences in their Mac-

POR and MatPOR values (Figs. 3 and 4). While BG

yielded an expectedly large MacPOR (0.116 m3 m�3),

the VS value was �50% smaller (0.063 m3 m�3) and

in the same general range as the MacPOR values for

the short-term and long-term NT treatments (Fig. 3).

Conversely, VS gave an expectedly large MatPOR

value (0.574 m3 m�3), while BG yielded a much

smaller value (0.428 m3 m�3) that was similar to those

of the tillage treatments (Fig. 4). The relatively small

MacPOR under VS (only about 10% of total porosity)

and the similar MatPOR between BG and the tillage

treatments (i.e. BG = 0.428; MP = 0.445; NT = 0.427)

seem counter-intuitive; i.e. one might expect that the

lack of soil disturbance, coarse roots and the abundant

soil fauna in VS would favour the creation of

macropores, while the dense, fibrous root systems

under BG would promote the creation of matrix pores.

The reasons for this reversal are currently unex-

plained.

Conversion of long-term BG and long-term NT to

MP caused overall declines in MacPOR over the 4-

year period (Fig. 3a and b), as well as minor increases

in MatPOR (Fig. 4a and b). This response is perhaps

not surprising, as it is consistent with the well-

documented loss of near-surface organic carbon,

destruction of soil macrostructure/biopores, and

‘‘loosening’’ of the soil matrix that usually occurs

when conventional mouldboard plough tillage is

instituted on fine-textured soil (e.g. Grandy et al.,

2006). The first 2 years of NT after long-term MP (i.e.

NTMP1, NTMP2) caused a rapid and significant


Fig. 3. Mean soil macroporosity (MacPOR) in the 0–10 cm depth for






no-tillage after long-term mouldboard plough tillage (NTMP1–4).

Means labelled with the same letter are not significantly different

at P < 0.05 according to the Duncan’s Multiple Range test. The

vertical T-bars indicate standard error about the means.

Fig. 4. Mean soil matrix porosity (MatPOR) in the 0–10 cm depth for






no-tillage after long-term mouldboard plough tillage (NTMP1–4).

Means labelled with the same letter are not significantly different

at P < 0.05 according to the Duncan’s Multiple Range test. The

vertical T-bars indicate standard error about the means.

increase in MacPOR (Fig. 3c) and a concomitant

significant decrease in MatPOR (Fig. 4c), then a more

gradual reversal in the succeeding 2 years (i.e. NTMP3,

NTMP4). The initial increase in MacPOR was likely

due to the initial development of persistent macro-

pores (e.g. cracks) as NT became established, while

the initial decline in MatPOR may reflect consolida-

tion of the soil matrix due to the cessation of tillage.

The mild reversal during years 3 and 4 may reflect

‘‘bioturbation’’ as earthworms and roots gradually

recolonized the upper 10 cm of the soil. It was also

noted for the cropped treatments (i.e. MP, NT,

MPBG1–4, MPNT1–4, NTMP1–4) that MacPOR versus

BD produced a negative and highly significant

(P < 0.0001) linear correlation, while MatPOR versus

BD was uncorrelated (i.e. slope not significantly

different from zero) (data not shown). Hence, the

observed BD changes under the cropped treatments

(Fig. 2) were due primarily to changes in the volume of

soil pores > 0.3 mm equivalent diameter.


Fig. 5. Mean soil air capacity (AC) in the 0–10 cm depth for virgin

soil (VS), long-term continuous bluegrass sod (BG), long-term maize–

soybean cropping under mouldboard plough tillage (MP) or no-tillage

(NT), and 1–4 years of maize–soybean cropping under: (a) mould-

board plough tillage after long-term bluegrass (MPBG1–4); (b) mould-

board plough tillage after long-term no-tillage (MPNT1–4); (c) no-

tillage after long-term mouldboard plough tillage (NTMP1–4). The

horizontal line demarks a proposed minimum AC value for adequate

root-zone aeration. Means labelled with the same letter are not

significantly different at P < 0.05 according to the Duncan’s Multiple

Range test. The vertical T-bars indicate standard error about the

means.

4.4. Air capacity

The mean AC values for virgin soil (VS) and long-

term bluegrass (BG) were effectively equivalent

(0.194 m3 m�3 and 0.197 m3 m�3, respectively), and

well above the proposed minimum of 0.15 m3 m�3 for

adequate aeration of clay loam soil (Fig. 5). The VS and

BG were consequently well aerated, which is consistent

with the lack of grey-brown mottling in the top 10 cm of

these treatments.

Conversion of long-term BG to MP (Fig. 5a) caused

an immediate and rapid decline in AC to sub-optimal

values; and after only 3 years of MP tillage (i.e.

MPBG3), the AC value was not significantly different

from the very low value under long-term MP. The

remaining four tillage treatments (i.e. MP, NT,

MPNT1–4, NTMP1–4) were also consistently below

the AC minimum (Fig. 5b and c). Hence, all five tillage

treatments were susceptible to frequent and potentially

severe aeration deficits; confirming field evidence for

this appears in the form of grey-brown mottling in the

top 10 cm of the tillage treatments, which is diagnostic

of intermittent anoxia (e.g. Brady, 1974). Note also

that NT has a slightly greater AC value than MP (by

29%), and consequently conversion of long-term

NT to MP (Fig. 5b) probably caused a slight decline

in soil aeration, while conversion of long-term MP to

NT (Fig. 5c) probably caused a slight increase in

aeration.

4.5. Relative water capacity

The virgin soil (VS) and long-term bluegrass (BG)

produced RWC values (0.663 and 0.645, respectively)

which fell within the optimum range (0.6–0.7) for

maximum soil microbial activity (Fig. 6). One to four

years of MP after long-term BG (Fig. 6a) caused

substantial increases in RWC (from 0.645 to 0.840),

while 1–4 years of MP after long-term NT (Fig. 6b)

caused more modest increases (from 0.791 to 0.857).

Converting long-term MP to NT, on the other hand,

caused RWC to drop within the first year to a value not

significantly different from long-term NT, and then

remain roughly constant for the succeeding 3 years

(Fig. 6c). For all five tillage treatments (MP, NT,

MPBG1–4, MPNT1–4, NTMP1–4), RWC was substan-

tially above the optimum range, suggesting that soil

microbial activity would often be impeded by insuffi-

cient soil air.

4.6. Plant-available water capacity

Of the seven treatments, only virgin soil (VS)

provided a PAWC value (0.225 m3 m�3) that fell within

the ‘‘ideal’’ category (�0.20 m3 m�3) proposed by Hall

et al. (1977) and Cockroft and Olsson (1997) for

maximum root growth/function and minimum droughti-

ness in fine-textured soils (Fig. 7). This was probably

due largely to the very high OC under VS (Fig. 1). With

the exception of MPBG4 (Fig. 7a) and MPNT4 (Fig. 7b),

all other treatments fell into the ‘‘limited’’ and ‘‘poor’’

categories, and were therefore substantially sub-optimal


Fig. 6. Mean relative water capacity (RWC) in the 0–10 cm depth for






no-tillage after long-term mouldboard plough tillage (NTMP1–4). The

two horizontal lines demark a proposed optimum RWC range. Means




Fig. 7. Mean plant-available water capacity (PAWC) in the 0–10 cm

depth for virgin soil (VS), long-term continuous bluegrass sod (BG),

long-term maize–soybean cropping under mouldboard plough tillage

(MP) or no-tillage (NT), and 1–4 years of maize–soybean cropping

under: (a) mouldboard plough tillage after long-term bluegrass

(MPBG1–4); (b) mouldboard plough tillage after long-term no-tillage

(MPNT1–4); (c) no-tillage after long-term mouldboard plough tillage

(NTMP1–4). The horizontal lines demark the ‘‘ideal’’, ‘‘good’’, ‘‘lim-

ited’’ and ‘‘poor’’ PAWC categories as defined in the text. Means




with respect to root growth/function and resistance to

drought. For the tillage treatments, the low PAWC

values are due to a combination of inconsistent

increases in uPWP and decreases in uFC relative to VS

(data not shown). For long-term BG, on the other hand,

the surprisingly low PAWC was due primarily to a

substantial decrease in uFC relative to VS, while uPWP

increased only slightly (data not shown). Hence, the low

PAWC for long-term BG relative to VS appears to be

due primarily to a decrease in the number of pores in the

0.0002–0.03 mm equivalent diameter range, which is

consistent with the low MatPOR of BG relative to VS

(Fig. 4). The relatively large PAWC values for MPBG4

and MPNT4 were due primarily to decreases in uPWP in

that particular year, which is currently unexplained but

considered aberrant.


Fig. 8. Geometric mean saturated hydraulic conductivity (KS) in the 0–

10 cm depth for virgin soil (VS), long-term continuous bluegrass sod

(BG), long-term maize–soybean cropping under mouldboard plough

tillage (MP) or no-tillage (NT), and 1–4 years of maize–soybean

cropping under: (a) mouldboard plough tillage after long-term bluegrass

(MPBG1–4); (b) mouldboard plough tillage after long-term no-tillage

(MPNT1–4); (c) no-tillage after long-term mouldboard plough tillage

(NTMP1–4). The two horizontal lines demark a proposed optimum KS

range. Means labelled with the same letter are not significantly different

at P < 0.05 according to the Duncan’s Multiple Range test. The vertical

T-bars indicate standard error about the means.

4.7. Saturated hydraulic conductivity

The mean KS values for virgin soil (VS), long-term

bluegrass (BG) and long-term no-till (NT) were similar

(2.9 � 10�2 cm s�1, 5.3 � 10�2 cm s�1, and 2.4 �10�2 cm s�1, respectively), and also a factor of 4.8–

10.6 above the optimum range (5.0 � 10�3 cm s�1 to

5.0 � 10�4 cm s�1) proposed by Reynolds et al. (2003)

for agricultural soils (Fig. 8). The near equivalence of

KS among these treatments was surprising, given their

large differences in organic carbon content (Fig. 1), bulk

density (Fig. 2), macroporosity (Fig. 3) and matrix

porosity (Fig. 4). Evidently, the substantial differences

among the three treatments in number, size, morphol-

ogy and connectedness of the water-conducting pores

were largely compensating from a water conduction

perspective. In addition, the small MacPOR and

MatPOR values under long-term NT relative to VS

and BG (Figs. 3 and 4) suggests that the KS value for NT

must be due primarily to a small number of highly

water-conductive macropores (e.g. large, continuous

cracks, worm holes, abandoned root channels).

The first year of MP after long-term BG (MPBG1,

Fig. 8a) and long-term NT (MPNT1, Fig. 8b) caused KS

to decrease by about an order of magnitude to values

within the proposed optimum KS range. Note also that

the KS values for MPBG1 and MPNT1 were not

significantly different from either the KS value under

long-term MP or most of the KS values under the 2d, 3rd

and 4th years of MP (i.e. MPBG2–4, Fig. 8a; MPNT2–4,

Fig. 8b). Similarly, the first year of NT after long-term

MP (NTMP1, Fig. 8c) increased KS by about an order of

magnitude to a value that was above the optimum KS

range, but not significantly different from either the KS

value for long-term NT or most of the KS values for the

2nd, 3rd and 4th years of NT (i.e. NTMP2–4, Fig. 8c).

Hence the first year of MP or NT cropping caused

‘‘order of magnitude’’ changes in the soil’s near-surface

KS, and also produced KS values that were similar to

those of long-term MP or long-term NT, respectively.

The mean KS values for VS, BG, NT and NTMP1–4

were consistently at or above the upper limit of the

proposed optimum KS range (Fig. 8c). These treatments

may therefore be susceptible to solute leaching losses

and droughtiness due to rapid infiltration and drainage,

and this has indeed been confirmed for nearby plots

under long-term no-till cropping (Tan et al., 2002). All

seven treatments exceeded the proposed critical

minimum KS of 1 � 10�4 cm s�1 (de Witt and

McQueen, 1992; McQueen and Shepherd, 2002;

Drewry and Paton, 2005), and thus severe impairment

of crop production by frequent surface ponding is

unlikely. Note also that only MP cropping produced KS

values that were generally within the proposed ‘‘ideal’’

range which optimizes infiltration, redistribution,

drainage, runoff, erosion and leaching (Fig. 8).

4.8. Transient effects of tillage on soil physical

properties

Converting long-term BG to MP and long-term NT

to MP caused effectively continuous changes in BD,

MacPOR, AC, and RWC over a 3–4 year period.


Specifically, BD (Fig. 2a and b), and RWC (Fig. 6a and

b) increased, while MacPOR (Fig. 3a and b) and AC

(Fig. 5a and b) decreased; with all four parameters

approaching the corresponding values for long-term MP

after 3–4 years. Note, however, that converting long-

term BG to MP caused changes that were mostly non-

linear and substantial, whereas converting long-term

NT to MP caused changes that were near-linear and

much smaller. Note also that these two conversions

caused the change in KS (Fig. 8a and b) to occur almost

entirely within the first year, but left PAWC (Fig. 7a and

b) effectively unchanged except for apparently sporadic

and patternless annual variations.

The multi-year and substantial changes produced by

the conversion of long-term BG to MP most likely

reflects a progressive mechanical break-up of the dense,

fibrous bluegrass root system and the associated angular

blocky soil structure. This would explain the rapid

decline of MacPOR (Fig. 3a), AC (Fig. 5a), and KS

(Fig. 8a), which are highly sensitive to soil structure and

macropores, and it is consistent with the decrease in soil

organic carbon content (Fig. 1). On the other hand, the

generally much smaller changes produced by converting

long-term NT to MP probably reflects the disruption of a

relatively small number of large macropores (e.g. cracks,

worm holes, etc.), which is also consistent with the small

change in organic carbon content (Fig. 1), and the

substantial (order of magnitude) decrease in KS (Fig. 8b).

The lack of substantial or consistent change in near-

surface PAWC is due to erratic and partially compensat-

ing changes in uFC and uPWP (data not shown).

Converting long-term MP to NT produced near-

surface changes that occurred primarily in the first year,

with little or no change occurring in the succeeding 3

years. Specifically, BD (Fig. 2c), MatPOR (Fig. 4c) and

RWC (Fig. 6c) decreased in the first year to values

similar to those of long-term NT, while MacPOR

(Fig. 3c), AC (Fig. 5c), and KS (Fig. 8c) increased. Note,

however, that the changes were often erratic and not

significantly different; and they were of the same

magnitude as those for the conversion of long-term NT

to MP. Note also that PAWC (Fig. 7c) remained

essentially unchanged except for erratic year-to-year

variations, similar to what was observed for the

conversion of long-term BG to MP (Fig. 7a) and

conversion of long-term NT to MP (Fig. 7b).

4.9. Land management effects on overall soil

physical quality

None of the four land managements (i.e. VS, BG,

NT, MP) met all of the proposed criteria for good

physical quality in the near-surface of Brookston clay

loam soil. The virgin condition (VS) produced

potentially ‘‘excessive’’ OC (Fig. 1) and KS (Fig. 8),

and may therefore be susceptible to compaction,

reduced pesticide efficacy and increased solute leaching

losses (Craul, 1999; Sojka and Upchurch, 1999;

Reynolds et al., 2003). Long-term continuous BG

had ‘‘limited’’ PAWC (Fig. 7) and ‘‘excessive’’ KS

(Fig. 8), making it potentially susceptible to both

droughtiness and enhanced solute leaching losses.

Long-term NT and long-term MP were non-optimal

for all parameters except KS under MP, and were

therefore susceptible to loss (or continuing degradation)

of soil structure (‘‘insufficient’’ OC), appreciable

mechanical resistance to root growth (‘‘excessive’’

BD), frequent and potentially severe root-zone aeration

deficits (‘‘insufficient’’ AC), impeded microbial activity

(‘‘excessive’’ RWC), droughtiness (‘‘insufficient’’

PAWC), and enhanced solute leaching losses (‘‘exces-

sive’’ KS–NT only).

Assuming equal importance of all measured indica-

tors (which may or may not be justified), VS ranked first

among the four managements with generally good

overall soil physical quality (two non-optimal indica-

tors), and long-term BG ranked a close second with only

slightly poorer soil physical quality (three non-optimal

indicators). Long-term MP and NT, on the other hand,

ranked an equally distant third with by far the poorest

overall soil physical quality, as evidenced by substantial

departures from the optimum values or ranges for nearly

all of the measured indicators. Furthermore, converting

long-term MP to NT or vice versa produced only minor

changes in overall soil physical quality. It therefore

appears that the maize–soybean rotation under NT and

MP tillage substantially degraded the near-surface

physical quality of Brookston clay loam soil; and as a

consequence, crop yield and environmental impact

were far from optimized by these two crop production

systems.

5. Conclusions

The parameters, OC, BD, AC, RWC and KS, appear

to be useful indicators of soil physical quality in fine-

textured soils because they are responsive to changes in

land management, and because optimal values or ranges

appear to exist for good crop production with minimum

environmental impact. The MacPOR parameter was

also responsive to changes in land management, and

may consequently be a useful indicator, once optimal

values or ranges are established. The MatPOR and

PAWC parameters may be less useful indicators of


physical quality in fine-textured soils, as they did not

respond substantially or consistently to changes in

cropping and/or tillage practice.

Converting long-term BG and long-term NT to MP

caused continuous and generally significant changes in

near-surface BD, MacPOR, AC and RWC, with all four

parameters approaching the corresponding values for

long-term MP over a 3–4 year period. Converting long-

term MP to NT, on the other hand, caused the above

parameters to become generally similar to the long-term

NT values within the first year after the conversion.

Changes in KS were usually substantial, and they

occurred primarily within the first year for all three

conversions in land management.

With respect to the measured soil parameters and

their proposed optimum values or ranges, VS and BG

produced good overall physical quality in the near-

surface of a Brookston clay loam soil. On the other

hand, long-term maize–soybean cropping under NT and

MP produced equally poor overall physical quality, and

this implies as a consequence, that crop yield and

environmental impact may not have been optimized for

these two crop production systems. Future studies will

consider the entire crop rooting zone (�top 1 m), crop

yields, off-field environmental impacts (e.g. water and

air quality), and changes in soil pore size distribution, to

further refine optimal soil physical quality for field-crop

production on fine-textured soils.

Acknowledgements

The competent technical assistance of J. Gignac, K.

Rinas, V. Bernyk and D. Pohlman is gratefully

acknowledged. We also wish to thank two anonymous

reviewers, whose comments and recommendations

greatly improved the manuscript. Funding for this

work was provided by the Research Branch of

Agriculture and Agri-Food Canada.

References

Arshad, M.A., Martin, S., 2002. Identifying critical limits for soil

quality indicators in agro-ecosystems. Agric. Ecosyst. Environ.

88, 153–160.

Brady, N.C., 1974. The Nature and Properties of Soils, eighth ed.

MacMillan Publishing Co. Inc., New York, NY.

Carter, M.R., 1988. Temporal variability of soil macroporosity in a

fine sandy loam under mouldboard ploughing and direct drilling.

Soil Tillage Res. 12, 37–51.

Carter, M.R., 1990. Relative measures of soil bulk density to char-

acterize compaction in tillage studies on fine sandy loams. Can. J.

Soil Sci. 70, 425–433.

Carter, M.R., Angers, D.A., Topp, G.C., 1999. Characterizing equili-

brium physical condition near the surface of a fine sandy loam

under conservation tillage in a humid climate. Soil Sci. 164, 101–

110.

Cockroft, B., Olsson, K.A., 1997. Case study of soil quality in south-

eastern Australia: management of structure for roots in duplex

soils. In: Gregorich, E.G., Carter, M.R. (Eds.), Soil Quality for

Crop Production and Ecosystem Health. Developments in Soil

Science, vol. 25. Elsevier, New York, NY, pp. 339–350.

Craul, P.J., 1999. Urban Soils: Applications and Practices. Wiley,

Toronto.

da Silva, A.P., Kay, B.D., Perfect, E., 1994. Characterization of the

least limiting water range of soils. Soil Sci. Soc. Am. J. 58, 1775–

1781.

de Witt, N.M.M., McQueen, D.J., 1992. Compactibility of Materials

for Land Rehabilitation. DSIR Land Resources Scientific Report

7.

Dexter, A.R., 2004a. Soil physical quality. Soil Tillage Res. 79, 129–

130.

Dexter, A.R., 2004b. Soil physical quality: Part I. Theory, effects of

soil texture, density, and organic matter, and effects on root

growth. Geoderma 120, 201–214.

Dexter, A.R., 2004c. Soil physical quality: Part II. Friability, tillage,

tilth and hard-setting. Geoderma 120, 215–225.

Dexter, A.R., 2004d. Soil physical quality: Part III. Unsaturated

hydraulic conductivity and general conclusions about S-theory.

Geoderma 120, 227–239.

Doran, J.W., Sarrantonio, M., Lieberg, M.A., 1996. Soil health and

sustainability. Adv. Agron. 56, 1–54.

Drewry, J.J., 2006. Natural recovery of soil physical properties from

treading damage of pastoral soils in New Zealand and Australia: a

review. Agric. Ecosyst. Environ. 114, 159–169.

Drewry, J.J., Paton, R.J., 2005. Soil physical quality under cattle

grazing of a winter-fed brassica crop. Aust. J. Soil Res. 43, 525–

531.

Drewry, J.J., Cameron, K.C., Buchan, G.D., 2001. Effect of simulated

dairy cow treading on soil physical properties and ryegrass pasture

yield. N. Z. J. Agric. Res. 44, 181–190.

Drewry, J.J., Littlejohn, R.P., Paton, R.J., Singleton, P.L., Monaghan,

R.M., Smith, L.C., 2004. Dairy pasture responses to soil physical

properties. Aust. J. Soil Res. 42, 99–105.

Grandy, A.S., Robertson, G.P., Thelen, K.D., 2006. Do productivity

and environmental trade-offs justify periodically cultivating no-till

cropping systems? Agron. J. 98, 1377–1383.

Greenland, D.J., 1981. Soil management and soil degradation. J. Soil

Sci. 32, 301–322.

Gregorich, E.G., Carter, M.R., Doran, J.W., Pankhurst, C.E., Dwyer,

L.M., 1997. Biological attributes of soil quality. In: Gregorich,

E.G., Carter, M.R. (Eds.), Soil Quality for Crop Production and

Ecosystem Health. Developments in Soil Science, vol. 25. Else-

vier, New York, NY, pp. 81–114.

Hall, D.G.M., Reeve, M.J., Thomasson, A.J., Wright, V.F., 1977.

Water retention, porosity and density of field soils. Soil Survey

Tech. Monogr. No. 9, Rothamsted, Harpenden, U.K.

Hao, X., Ball, B.C., Culley, J.L.B., Cater, M.R., Parkin, G.W., 2007.

Soil density and porosity. In: Carter, M.R., Gregorich, E.G.

(Eds.), Soil Sampling and Methods of Analysis. second ed.

Canadian Society of Soil Science/Taylor and Francis, LLC,

Boca Raton, FL, pp. 743–759.

Hillel, D., 1980. Fundamentals of Soil Physics. Academic Press,

Toronto.

Janzen, H.H., Campbell, C.A., Ellert, B.H., Bremer, E., 1997. Soil

organic matter dynamics and their relationship to soil quality. In:

Gregorich, E.G., Carter, M.R. (Eds.), Soil Quality for Crop


Production and Ecosystem Health. Developments in Soil Science,

vol. 25. Elsevier, New York, NY, pp. 277–291.

Jarvis, N.J., Zavattaro, L., Rajkai, K., Reynolds, W.D., Olsen, P.-A.,

McGechan, M., Mecke, M., Mohanty, B., Leeds-Harrison, P.B.,

Jacques, D., 2002. Indirect estimation of near-saturated hydraulic

conductivity from readily available soil information. Geoderma

108, 1–17.

Jones, C.A., 1983. Effect of soil texture on critical bulk densities for

root growth. Soil Sci. Soc. Am. J. 47, 1208–1211.

Jones, R.J.A., Spoor, G., Thomasson, A.J., 2003. Vulnerability of

subsoils in Europe to compaction: a preliminary analysis. Soil

Tillage Res. 73, 131–143.

Letey, J., 1985. Relationship between soil physical properties and crop

production. Adv. Soil Sci. 1, 227–294.

Linn, D.M., Doran, J.W., 1984. Effect of water-filled pore space on

carbon dioxide and nitrous oxide production in tilled and nontilled

soils. Soil Sci. Soc. Am. J. 48, 1267–1272.

MacDonald, K.B., Jarvis, I., Hohner, B.H., 1994. 1994 vertisol tour,

Ontario, September 19–24. Agriculture and Agri-Food Canada,

Ontario Land Resource Unit, Centre for Land and Biological

Resources Research, Research Branch, Guelph, Ont. CLBRR

Pub. No. 94–100, 32 pp.

McKeague, J.A., Fox, C.A., Stone, J.A., Protz, R., 1987. Effects of

cropping system on structure of Brookston clay loam in long-term

experimental plots at Woodslee, Ontario. Can. J. Soil Sci. 67, 571–

584.

McQueen, D.J., Shepherd, T.G., 2002. Physical changes and compac-

tion sensitivity of a fine-textured, poorly drained soil (Typic

Endoaquept) under varying durations of cropping, Manawatu

Region. N. Z. Soil Tillage Res. 63, 93–107.

O’Connell, D.J., 1975. The measurement of apparent specific gravity

of soils and its relationship to mechanical composition and plant

root growth. Soil Physical Conditions and Crop Production. Tech.

Bull. 29 MAFF, HMSO, London, pp. 298–313.

Olness, A., Clapp, C.E., Liu, R., Palazzo, A.J., 1998. Biosolids and

their effects on soil properties. In: Wallace, A., Terry, R.E. (Eds.),

Handbook of Soil Conditioners. Marcel Dekker, New York, NY,

pp. 141–165.

Pieri, C.J.M.G., 1992. Fertility of Soils: A Future for Farming in the

West African Savannah. Springer-Verlag, Berlin.

Reynolds, W.D., 1993. Saturated hydraulic conductivity: field mea-

surement. In: Carter, M.R. (Ed.), Soil Sampling and Methods of

Analysis. Canadian Society of Soil Science/Lewis Publishers,

Boca Raton, FL, pp. 599–613.

Reynolds, W.D., 2007. Saturated hydraulic properties: laboratory

methods. In: Carter, M.R., Gregorich, E.G. (Eds.), Soil Sampling

and Methods of Analysis. second ed. Canadian Society of Soil

Science/Taylor and Francis, LLC, Boca Raton, FL, pp. 1013–1024.

Reynolds, W.D., Topp, G.C., 2007. Soil water desorption and imbibi-

tion: tension and pressure techniques. In: Carter, M.R., Gregorich,

E.G. (Eds.), Soil Sampling and Methods of Analysis. second ed.

Canadian Society of Soil Science/Taylor and Francis, LLC, Boca

Raton, FL, pp. 981–997.

Reynolds, W.D., Bowman, B.T., Drury, C.F., Tan, C.S., Lu, X., 2002.

Indicators of good soil physical quality: density and storage

parameters. Geoderma 110, 131–146.

Reynolds, W.D., Yang, X.M., Drury, C.F., Zhang, T.Q., Tan, C.S.,

2003. Effects of selected conditioners and tillage on the

physical quality of a clay loam soil. Can. J. Soil Sci. 83,

318–393.

Richards, N.R., Caldwell, A.G., Morwick, F.F., 1949. Soil survey of

Essex County. Report No. 11, Ontario Soil Survey. Experimental

Farms Service, Dominion Department of Agriculture and Ontario

Agricultural College, 85 pp.+ map.

Shepherd, T.G., 1994. Biophysical indicators for monitoring soil

quality under cropping, grazing and forestry. In: Burgham , S.,

Arand, J. (Eds.), Proceedings of Workshops into Research into

Monitoring Resources, Landcare Research. pp. 18–31.

Shukla, M.K., Lal, R., Ebinger, M., 2006. Determining soil

quality indicators by factor analysis. Soil Tillage Res. 87,

194–204.

Singleton, P.L., Boyes, M., Addison, B., 2000. Effect of treading by

dairy cattle on topsoil physical conditions for six contrasting soil

types in Waikato and Northland, New Zealand, with implications

for monitoring. N. Z. J. Agric. Res. 43, 559–567.

Skjemstad, J.O., Baldock, J.A., 2007. Total and organic carbon. In:

Carter, M.R., Gregorich, E.G. (Eds.), Soil Sampling and Methods

of Analysis. second ed. Canadian Society of Soil Science/Taylor

and Francis, LLC, Boca Raton, FL, pp. 225–237.

Skopp, J., Jawson, M.D., Doran, J.W., 1990. Steady-state aerobic

microbial activity as a function of soil water content. Soil Sci. Soc.

Am. J. 54, 1619–1625.

Sojka, R.E., Upchurch, D.R., 1999. Reservations regarding the soil

quality concept. Soil Sci. Soc. Am. J. 63, 1039–1054.

Stone, J.A., Allen, N.H.E., Grant, C.D., 1985. Corn fertility treatments

and the surface structure of a poorly drained soil. Soil Sci. Soc.

Am. J. 49, 1001–1004.

Tan, C.S., Drury, C.F., Reynolds, W.D., Gaynor, J.D., Zhang, T.Q., Ng,

H.Y., 2002. Effect of long-term conventional tillage and no-tillage

systems on soil and water quality at the field scale. Water Sci.

Technol. 46, 183–190.

Topp, G.C., Reynolds, W.D., Cook, F.J., Kirby, J.M., Carter, M.R.,

1997. Physical attributes of soil quality. In: Gregorich, E.G.,

Carter, M.R. (Eds.), Soil Quality for Crop Production and

Ecosystem Health. Developments in Soil Science, vol. 25. Else-

vier, New York, NY, pp. 21–58.

Veihmeyer, F.J., Hendrickson, A.H., 1948. Soil density and root

penetration. Soil Sci. 65, 487–493.

Verdonck, O., Penninck, R., De Boodt, M., 1983. Physical properties

of different horticultural substrates. Acta Hort. 150, 155–160.

land management effects on the near-surface physical quality of a clay loam soil

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