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Group Title: Agronomy research report - University of Florida Agronomy Department ; AY-95-03
Title: Double-cropped soybeanoat root growth and development affected by tillage
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Permanent Link: http://ufdc.ufl.edu/UF00056099/00001
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Title: Double-cropped soybeanoat root growth and development affected by tillage
Physical Description: 11, 9 leaves : ; 28 cm.
Language: English
Creator: Bruniard, Graciela Cordone de, 1951-
Gallaher, Raymond N
University of Florida -- Agronomy Dept
Publisher: Agronomy Department, Institute of Food and Agricultural Sciences, University of Florida
Place of Publication: Gainesville Fla
Publication Date: 1995?]
 Subjects
Subject: Roots (Botany) -- Florida   ( lcsh )
Soybean -- Roots   ( lcsh )
Oats -- Roots   ( lcsh )
Tillage -- Florida   ( lcsh )
Genre: bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: by G.E. Cordone and R.N. Gallaher.
Bibliography: Includes bibliographical references (leaves 9-11).
General Note: Agronomy research report - University of Florida Agronomy Department ; AY-95-03
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Bibliographic ID: UF00056099
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 62627655

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Agronomy Research Report AY-95-03




DOUBLE-CROPPED SOYBEAN/OAT ROOT

GROWTH AND DEVELOPMENT AFFECTED BY


TILLAGE




By


G. E. Cordone and R.N. Gallaher

Research Soil Scientist, INTA (Instituto Nacional de Tecnologia
Agropecuaria), Pergamino Experimental Station, Pergamino, Buenos
Aires, Argentina and Professor, Agronomy Department, University
of Florida, Gainesville, Florida, USA.








Agronomy Research Report AY-95-03


DOUBLE-CROPPED SOYBEAN/OAT ROOT GROWTH AND
DEVELOPMENT AFFECTED BY TILLAGE

By

G. E. Cordone and R.N. Gallaher

Research Soil Scientist, INTA (Instituto Nacional de Tecnologia Agropecuaria),
Pergamino Experimental Station, Pergamino, Buenos Aires, Argentina and Professor,
Agronomy Department, University of Florida, Gainesville, Florida, USA.

ABSTRACT

The long-term effect of reduced or no-tillage farming on root development
and morphology under different multicropping system combinations remains unknown.
The objective of this study was to evaluate root patterns of double-cropped
soybean [Glycine max (L.) Merr.] and oat (Avena sativa L.) crops in an 11 and
12-yr old experiment grown under four tillage systems. The experimental site was
dominated by Arenic and Grossarenic Paleudults near Gainesville, Florida. Root
systems were sampled during the 1986/87 and 1987/88 growing cycles from an area
of 1 m2 to 0.45 m depth. Roots were collected from different soil depth
increments. The tillage treatments were no-tillage (NT) and conventional tillage
(CT) plus and minus subsoiling for the soybean crop and no-tillage and
conventional tillage for the oat crop. A randomized complete block with
strip-strip plot design was used. Tillages were the whole plots, depths the
strip plots and year the strip-strip plots. Tillage treatments did not affect
total soybean and oat root densities, nor the density of each soybean root
diameter. However, tillage changed the root distribution in the soil profile.
Total soybean root density was higher in the 0.00 to 0.05 m soil depth under both
no-tillage treatments compared to both conventional treatments. Subsoiling
treatment increased the total root density in the 0.15 to 0.45 m soil layer. The
oat root density was equal for each tillage treatment in the 0.00 to 0.05 m, but
no-tillage had lower density in the 0.05 to 0.10 m soil depth. Neither root
density nor root distribution of the whole rooting system was influenced by
tillage. Root concentration near the soil surface under NT could be a problem
in sandy soils during water stress periods.

INTRODUCTION

Heredity determines the major type of root system of each plant species,
but the great variability in roots forms within species is often due to the soil
environment. Rooting patterns are different for different plant genotypes (Raper
and Barber, 1970), but the soil environment usually restricts rooting habits
(Pearson, 1974). Portas (1973) found root growth patterns of vegetable crops
reflected soil conditions more than genotype; Mayaki et al. (1976) reported
different root depth and distribution under irrigated and non-irrigated
conditions for the same cultivars of soybean [Glycine max (L.) Merr], corn (Zea
mays L.) and grain sorghum (Sorghum bicolor L. Moench). A different soil water
use for two soybean isolines during a midsummer drought was found by Garay and
Wihelm (1983). Soil texture, structure, compactation (Peterson and Barber,
1981), soil flora and fauna, salt concentration, soil reaction, root competition
among species and within the same genotype when planted at different row spacing








(Raper and Barber, 1970) and the interaction of root species with other soil
factors, such as soil nutrient status and water availability, are involved in the
environmental control of root growth. Tillage changes both the soil physical and
chemical properties in the root environment (Blevins et al., 1983; Ehlers et al.,
1983) and then the root growth patterns may be altered. Compact hard-soil layers
more or less restrict root growth and penetration, depending on the soil moisture
level. In some cases roots can penetrate the compact layer when it is wet
causing an abrupt decrease in their diameters. When soil is re-hydrated
impedances decreases, lateral roots form and the older roots expand their radii
(Taylor, 1981). Some tillage systems involving deeper cultivation may modify
the physical environment and allow roots to grow through compact soil layers.
It is important to say that mechanical impedance to root growth itself does not
reduce yield if the impeding layer does not increaseplant water and nutrient
stress, and if the root system can supply the anchorage the plant needs.
Hallmark and Barber (1981) reported that the detrimental effect of increasing
soil bulk density on shoot growth and nutrient status of soybean plants may have
been caused by decreased root growth, coarser roots, and lower root surface area
per g of shoot. However, Drew (1975) concluded that despite the contrasting form
of their root systems, no differences between control and impeded barley (Hordeum
vulgare L.) plants could be detected in root weight and shoot growth. The
ability of impeded roots to absorb nutrients was not impaired. The soil water
content is another aspect that can be influenced by the different tillage
systems. Rowse and Stone (1981) reported that the changes in leaf water
potential, stomatal conductance and patterns of water extraction associated with
deep cultivation are due to an increase in rooting depth rather than any change
in the water retention or drainage properties of the soil. Taylor and Klepper
(1974) reported that where the water potential is not uniform, roots develop most
where the matric potential is above -1500 kPa. In general, roots appear to
proliferate in those soil zones with lowest soil water tension; under a drough,
the soybean root profile has been characterized by a low root density in the dry
surface layer and a maximum root proliferation in the deeper, wetter soil layers
(Sivakumar et al., 1977; Boyer et al.; 1980; Garay and Wilhelm, 1983). Root
growth and development are influenced by the fertility status of the soil at
every stage from germination to maturity. The proliferation of roots in zones
surrounding fertilizer granules is well known. Duncan and Ohlrogge (1958)
demonstrated that when soluble P compounds and ammonium N are applied together
in a band, plant roots proliferate extensively in the treated soil area. Similar
results were found (Anghinoni and Barber, 1980) for corn roots which proliferated
in the portion of the soil where P was added. In general, it appears that root
patterns are influenced by the soil nutrient status. On the other hand, the size
and morphology of a root system can have a profound effect on the extraction of
nutrients from the soil. Long and thin roots have a larger surface area than
short thicker roots and explore the same soil volume more effectively by reducing
the mean diffusion pathway through the soil (Sumner, 1981). Tillage can affect
the concentration and distribution of nutrients which, in turn, can affect root
growth. No-tillage (NT) systems have resulted in increased organic matter and
P very near the soil surface and in a gradually diminished amount of nutrients
in the deeper portions of the soil (Thomas and Frye, 1986; Gallaher and Ferrer,
1987). Baeumer and Bakermans (1973) concluded that the available K and P near
the soil surface was higher in NT than conventional tillage (CT) soil, but that
the reverse was found in deeper layers; in contrast, Mg and Ca was found to be
lower near the soil surface and higher in lower layers of NT soil. It can be








concluded that root distribution in the soil profile is a function of the
interaction of genetic characteristics of the plant with the microclimate in the
plant canopy and the physical, chemical, and microbiological properties of the
soil profile. Therefore, different tillage systems are expected to produce
modifications in the rooting habits of the crops. Significant effort has been
made to characterize the root distributions of agronomic crops in diverse soil
conditions, to determine the soil conditions which contribute to optimum root
growth and to modify soils for greater distribution of roots in the soil profile
to reduce the risks of water and nutrient stress. However, information about
rooting patterns of double-cropped systems in long-term experiments is limited.
The objective of this study was to determine the root distribution of
double-cropped soybean/oat (Avena sativa L.) crops grown under four tillage
systems in an 11 and 12 yr old experiment.


MATERIALS AND METHODS

The experiment was conducted at the Green Acres Agronomy farm located 20 km
west of Gainesville, Florida, during the 1986/87 and 1987/88 growing cycles. The
experimental site was dominated by Arenic and Grossarenic Paleudults (Soil Survey
Staff, 1984). The original experiment was set up in 1976 as a randomized
complete block design (RCB) with four blocks and four tillage treatments for the
'Florida 501' oat and 'Centenial' soybean double cropping system. The tillage
treatments were NT and CT plus and minus subsoiling (NT, NT+, CT, CT+) for the
soybean crop and NT and CT for oat.

Conventional tillage seedbed preparation was accomplished by two passes of
a rototiller, 15 cm deep before planting. No seedbed preparation was involved
in NT plots. An in-row subsoil NT planter was used to plant all tillage
treatments for soybean. In the non-subsoiling treatments the subsoil implement
was removed. Oat was planted in mid-November, 1986 and 1987, using a "Tye" NT
drill at a seeding rate of 120 kg ha"'. Ammonium nitrate fertilizer was applied
at oat's planting time and top dressed in February at the rates of 35 and 65 kg
ha"', respectively. Winter weeds were controlled with broadcast application of
2,4-D (2,4-dichlorophenoxy aceticacid) at a rate of 1 kg ha-i active ingredient
(a.i.). Soybean was planted in mid-May at the rate of 35 seed m' of row. A
preemergence-broadcast mix of paraquat (1,1', dimethyl, 4,4'bipyridinium ion) at
0.4 kg ha-i a.i., metribuzin (6-t-butyl, 3-methyl, thio-4-amino, 5-(4H)
one-l,2,4-triazine) at 0.4 kg ha" a.i., alachlor [N-(2,6-diethylphenol
N-metoxymethyl- chloro ethanamide] at 2.2 kg ha'' a.i. rate and X77 surfactant,
was applied for soybean weed control. Row widths were 0.76 m and 0.25 m for
soybean and oat, respectively. Acephate (O,S-Dimethyl acetylphosphoramido
-thiodate) and methomyl (S-Methyl-N-(methylcarbamoyl)oxy) thioacetimidate] were
used for insect control at a rate of 0.60 and 0.45 kg ha"' a.i., respectively.
Benomyl [Methyl l-(butylcarbamoyl)-2-benzimidazole -carbamate] was used for
disease control at a rate of 0.60 kg ha-' a.i.

Root samples were taken from a 1 m2 area of approximately uniform plant
density to 0.45 m depth in each plot at the R7 (Fehrs and Caviness, 1977) and
milk growth stages for soybean and oat, respectively, during the 1986/87 and
1987/88 growing cycles. Above ground plant parts were sampled from the same
area. Samples were taken by shovel using a plastic frame to measure the area








across three soybean rows for representing the tractor traffic and no
traffic middles. Soil was loosened around the outside area of the frame, then
shovels were placed under the loosened plants to lift the soil while holding the
plants by hand. The whole plant-soil samples were placed on a sheet of plywood
with nails arranged in square patterns of 0.05 m. Roots were washed by a stream
of water (69 10 Pa). The above ground plant parts were cut from the roots,
washed to eliminate the rest of soil and then separated into the different
components. The washed roots were collected in 0.00 to 0.05 m, 0.05 to 0.10 m,
0.10 to 0.15 m, 0.15 to 0.30 m and 0.30 to 0.45 m soil depth increments for
soybean and in the first four depths for oat because very few roots were present
deeper than 0.30 m. Root samples from each depth were washed again with water
by hand in containers using a screen to avoid root loss. All plant parts were
dried in a forced air oven at 65 C. Excess sand and crop residues impurities
were removed and total root dry weight for each depth and plant part dry weights
were measured. The soybean roots were sized by diameter within each depth by
superimposing the dried roots on a drawing of < 0.001 and > 0.001 m diameter and
weighed. The remaining sand contamination was determined after ashing the root
samples by filtration and substracting from the previous weight to obtain the
final root dry weight by diameter and depth for soybean and by depth for oat,
respectively.
Statistical analysis was conducted using a RCB strip-strip plot design for
each soybean root diameter and for the total root weight by depth for both crops.
Tillage treatments were the whole plots, depths the strip plots and year the
strip-strip plots (Steel and Torrie, 1980), considering that the experiment was
conducted without re-randomization during 12 yr. The analysis of variance was
performed by SAS (1987) General Lineal Model procedure for unbalance data.
Treatments means were tested by orthogonal and non-orthogonal contrasts. The
objective of this study was to evaluate root patterns of double-cropped soybean
and oat crops in an 11 and 12-yr-old experiment grown under four tillage systems.
Data are reported in root mass per unit of soil volume (g m3) for each depth and
diameter, and for each depth, for soybean and oat, respectively. Oat and total
soybean root density were added together by depth to calculate the root
production of the double-cropped system. Statistical analysis was performed
using a RCB strip-strip plot design for the total soybean and oat root density,
and for each soybean root diameter. The experiment has been conducted at the
same site during 12 yr without re-randomization to study the accumulated
long-term effects of the different tillage systems.

RESULTS AND DISCUSSION

Total soybean root density

Tillage did not influence the average total root density (g m-3) in the
0.0-0.45 m soil depth (Table 1). Root yields decreased with increased soil
depths, but because of the tillage x depth interaction, roots in each depth
changed depending on the tillage treatment. Even though tillage treatments were
equal for average root densities, the root distribution in the soil profile was
different. Root density was over 50% greater in 1986 compared to 1987. Mean
values for each year and contrasts are presented in Table 2. During 1986 NT
produced greater root density in the 0.00 to 0.05 and 0.05 to 0.10 m soil layers
as contrasted with the other treatments, the reverse situation occurred in the
0.15 to 0.30 m soil depth where NT had lower root density than the other tillage








treatments. Greater concentration of roots was only observed in the upper 0.05
m when NT and NT+ were combined, and the 0.15 to 0.30 layer had less root density
compared to the combination of CT and CT+. On the other hand, when both
treatments involving subsoiling were compared with both non-subsoiling
treatments, subsoiling had more root mass in the 0.15 to 0.45 m soil depth. The
0.10-0.15 m layer appeared to be transitional where no differences were
detected. During 1987 a trend of higher root density for both NT treatments was
observed only in the upper 0.05 m layer and subsoiling treatments tended to have
more root mass in the rest of the soil profile. No-tillage farming, with adequate
crop residues retained in the surface, has the capability of maintaining higher
levels of soil organic matter near the soil surface. Continuous NT results in
a relatively undisturbed soil profile. Soil nutrients are in greater
concentrations near the soil surface compared to CT where physical mixing of the
soil results in a relatively homogeneous soil to the depth of tillage (Juo and
Lal, 1979; Hargrove et al.,1982; Blevins et al., 1983, Ortiz Vega, 1985; Dyal,
1987). In addition, bulk density and mechanical impedance measurements have
shown that compactation occurs in the Ultisols under reduced tillage and NT
systems used in double-cropping (Ortiz Vega, 1985; NeSmith et al., 1987). All
these modifications result in a unique soil environment for the root growth under
NT. Conditions are more favorable in the surface layer of soil (water,
nutrients, continuity of microscopic natural porosity) and less favorable
conditions can occur deeper in the soil profile for root penetration (compacted
layers). No-tillage was shown to have greater root density in the soil surface
but a lower root density below a depth of 0.15 m in the soil profile (Na Nagara
et al., 1976). The possible mechanical impedance existing in the 0.15 to 0.45
m soil depth appears to have been removed under the tillage systems involving
in-row subsoiling allowing more roots to grow in that soil layer. Trouse (1983)
has reported that in the southeastern United States, plowpans often prevent crops
from developing to their maximum capabilities by denying roots rapid access to
the large reservoir of moisture stored in the subsoil. The benefitial effects
of random subsoiling are usually destroyed by recompactation during subsequent
tillage operations, therefore in-row subsoil should locate channels directly
beneath the row to be planted and prevent recompactation from subsequent interrow
traffic. The benefitial effect of deep tillage have also been reported by
several authors (Campbell et al., 1974; Kamprath et al., 1979 and Ide et al.,
1984). The year to year variation in root yield can be attributed to the
differential top growth and to a smaller amount of photoassimilates available
for the root growth.

Soybean Root Density by Diameter

As soil strength increases rate of root elongation decreases and root
diameter increases (Peterson and Barber, 1981). Rate of root growth and size of
root radius are among the most sensitive parameters in determining nutrient
uptake (Barber, 1984).

Roots < 0.001 m of diameter.

All tillage systems produced equal total density of roots < 0.001 m
diameter, but the distribution in the soil profile was found to be different
among tillage treatments for both years (Table 3). No-tillage concentrated 175%
and 10% more fine roots in the upper 0.10 m soil layer as compared to the other









treatments in the first and second year, respectively (Table 4). In 1986, the
0.15 to 0.30 m layer of NT had lower root density than the other treatments, and
it was also lower when NT and NT+ were compared to CT and CT+. Even though
during 1986 the treatments involving subsoiling had a trend (P < 0.10) to produce
lower root density in the 0.05 to 0.10 m soil depth, during 1987 they produced
a higher density; and they tended to produce more (P < 0.10) in the 0.30 to 0.45
layer in both years. The root distribution patterns of these fine roots resemble
those of the total root density distribution patterns. A positive correlation
(r=0.71 and P=0.001) was found between the total and the < 0.001 m root
densities. Therefore, the differences found in the total root yield could be due
to the differential distribution of the fine roots in the soil. Because NT
concentrated a higher mass of fine roots in the top part of the soil, a greater
root surface area would be available to absorb water and nutrients from that soil
layer. It is known that water and nutrients also accumulate in the soil surface
under NT, therefore, that pattern of root distribution does not appear to be
detrimental to crop growth. If the upper soil layer fails to supply adequate
nutrients and moisture, growth will be reduced, and eventually photosynthesis
will decrease. Borkert and Barber (1983) studying the efficiency of fertilizer
uses concluded that there was an advantage for localizing P which was due to
reduction in P adsorption by the soil and stimulation of root growth in the P
fertilized zone. Drew (1975) found branching stimulation in sectors where barley
(Hordeum vulgare L.) roots had been supplied with higher concentrations of P.
Phosphorus is one of the nutrients most authors have reported as accumulating in
the top layer of soil under NT, therefore it could be in part responsible for
that greater root density.

Roots > 0.001 m diameter

Tillage did not affect the density of roots > 0.001 m (Table 3). Decreasing
root density was found with increasing soil depth. Root production was almost
60% greater in 1986 than in 1987 (Table 5). Decreasing root density rate by
depth was different depending on the tillage system and year. In 1986, NT+ and
NT treatments had 20% greater root density in the upper 0.05 m soil layer when
compared with the CT+ and CT treatments. No-tillage had 24% more in the same
layer when contrasted with the other tillage systems (Table 6). Tillage systems
involving subsoiling resulted in higher root density in the 0.15 to 0.45 m soil
depth in 1986, but that difference was not observed in 1987. Subsoil effect may
be negligible when the soil moisture content by itself allows roots to growth
through layers that are very hard to penetrate under drier conditions.
Increasing soil bulk density was found to increase the diameter of cotton
(Gossipium hirsutum L.) roots (Taylor and Ratliff, 1969) and to produce coarser
corn roots and to decrease P and K uptake (Philips and Kirham, 1962). Peterson
and Barber (1981) observed that soybean roots grown in solution and in sand had
0.17 and 0.22 mm root radii, respectively. The higher bulk density reported for
several authors under different soil types for the NT systems in the top soil
layer, could be the cause for the greater root density of roots > 0.001 m
diameter found in the present study in the upper 0.05 m soil depth.

Although it is generally thought that only the young root tips are capable
of absorption of water and nutrients, laboratory experiments in solution culture
show that the relatively older portions of seminal roots of cereals situated up
to 0.50 m behind the root tips, can continue to absorb and translocate P, K and








water. The pattern of root growth is one important parameter to determine the
pattern of ion and water absorption and translocation to the shoot. Taylor and
Klepper (1974) reported that the spatial pattern of water uptake from various
regions of the soil depends upon root distribution as well as the distribution
of soil moisture in the soil profile. Sensitivity analyses of models predicting
nutrient uptake revealed the importance of the root radius in that function
(Claassen and Barber, 1976). Decreasing root radius increased root surface area
for absorption and increased predicted P uptake as roots became longer and finer
(Silberbush and Barber, 1983). Calculations of the effect of changing root
radius and density on P, K and N03" uptake showed that practically all the N03"
was predicted to be absorbed by relatively thick and short root systems. A very
thin and dense root system with a radius of the size of root hairs would be
required to take up a high proportion of the P in the soil. For K absorption,
because of its higher diffussion rate, the existence of very fine roots is not
as important (Barber and Silberbush, 1984). No-tillage concentrated more fine
roots in the upper layers of the soil. Nutrient accumulation and higher moisture
content in this soil zone could have caused branching stimulation. Ehlers et al.
(1983) concluded that smaller pores created by the roots of preceding crops can
serve as passageways for the new roots when the soil is left mechanically
undisturbed. They also reported that the percentage area of round-shaped holes
< 0.002 m in diameter was larger in NT than in CT soil. Some of those pores were
re-entered by roots of the next crop smaller in diameter than the small biopores
which they were growing through. This small variation in soil strength of CT soil
will hardly be noticeable with a field penetrometer with a base area larger than
the biopores, and therefore measurements will result in higher soil strength for
NT soils. On the other hand, density of roots of 0.002 to 0.003 m diameter was
also higher in the soil surface, some authors (Hallmark and Barber, 1981) have
reported that the higher soil bulk density that is characteristic of the top soil
layer under NT treatments could cause coarser roots. Therefore, soil nutrient
status would be causing the fine roots to proliferate and the soil bulk density
could cause higher coarse root production. Subsoiling allowed greater root
densities in the > 0.15 m soil layers. Even though the distribution patterns of
the roots of less than 0.001 to 0.002 m diameter were affected by the tillage
treatments, the distribution of the coarsest roots remained unaffected.

Oat Root Density

Tillage did not influence the average total oat root density in the 0.00 to
0.30 m soil profile (Table 6). Root yield decreased with increased soil depth.
Root distribution in the profile changed depending on the tillage treatments
(Table 7). During the 1986/87 growing cycle the root production was 60% higher
than that of the 1987/88. Even though both growing cycles studied concentrated
most of the roots in the upper 0.05 m layer, that accumulation was 72% and 85%
of the total for the first and second cycle, respectively. Therefore, crop
production in the 1987/88 cycle depended on the nutrients and water accumulated
in the top soil layer more than it did in the 1986/87 cycle. No-tillage produced
equal root density to the other treatments in the 0.00 to 0.05 m and lower
density in the 0.05 to 0.10 m soil layer. Ehlers et al. (1983) found that the
limiting penetration resistance for oat root growth was 3.6 MPa in the Ap-horizon
of the CT soil but 4.6 MPa in Ap-horizon of the NT soil. That difference was
explained by the build up of a continuous pore system in NT soil created by
earthworms and the roots from preceding crops. It is possible that the tillage








treatments do not affect root production of a fibrous root crop such as oat in
the top layer, although the soil bulk density measurements are affected by the
tillage systems. Residual effect of the in-row subsoil planter used in the
previous soybean crop was found to increase root density only in the 0.15-0.30
and in the 0.00-0.05 m layers in 1986/87 and 1987/88, respectively. Authors do
not agree about the mode of water influence on root growth. Soil water may
affect root growth per se as an essential medium for plant and root growth or it
may influence root growth by decreasing soil strength. Oat root growth in a field
experiment mainly depended on soil water per se and to a lesser degree, on soil
strength (Ehlers et al., 1983). Therefore, if available soil water is adequate,
soil strength is of minor importance in affecting root growth. That could be the
explanation why residual in-row subsoil effect for oat root growth was not very
important in this experiment in which, the rain during the 1986/87 oat growing
cycle was 50% higher than that of the 70-yr Gainesville average.

Double-Cropped Soybean/Oat Root Density

When root yield of both crops was combined in the 0.00 to 0.30 m soil depth,
it was found that tillage did not influence the root production of the whole
system (Table 8). Root density decreased with increased soil depth (Table 9),
the pattern of decrease resembles that of the oat because it is the crop
producing the higher root density. Although both crops had higher root densities
in the first cycle they decreased proportionally, therefore oat contributed 68%
of the double-cropping root production in both years. The 1987/88 growing cycle
produced over 36% smaller root density than the 1986/87 cycle. Because of the
year x depth interaction the degree at which root density decreased with the soil
depth was different between years. Percent root density by depth over the total
root density by year is observed in Table 10, more roots were growing deeper in
the soil profile during 1986/87. The oat crop contributed an average of 76% of
the total root production in the 0.00-0.05 m soil layer, but that percent
decreased to an average of 23% in the 0.15-0.30 m layer. Although the total root
production was different from one year to the next, the percent each crop
contributed to the total root yield and in the root yield by depth remained
nearly constant. Oat produced more superficial roots while soybean roots grew
deeper in the soil profile. That alternated archicteture also results in an
alternated pattern of nutrient absorption. While soybean is able to take up more
nutrients deeper in the soil profile, bringing them up and returning part to the
soil through the decomposition of the top residues and roots, oat accumulating
most of its roots in the upper layer of soil is able to take advantage of that
nutrient concentration. Mobile nutrients that leach easily in sandy soils are
absorbed by deeper rooted plants, cycled to the soil surface and made available
to the shallow root systems. Usually the higher accumulation of organic matter
and nutrients in the top soil under NT has been attributed to the decomposition
of the top residues and surface applied fertilizers that are not mixed when the
soil is left undisturbed. But it is important to point out that the
decomposition of roots that had a greater concentration in the upper 0.10 m soil
depth under NT as compared to the other treatments, is also contributing to that
accumulation.

CONCLUSIONS


Soybean Root Density








Tillage treatments did not affect the total root density nor the density of
each root diameter, but did change the root distribution in the soil profile.
When the density of the different soybean root diameters is considered as a unit,
it was found that both NT treatments had higher root density in the 0.00-0.05 m
soil depth compared to the CT treatments. Root density in the 0.15-0.45 m soil
layer was increased by subsoiling compared to the non-subsoiling treatments.
No-tillage concentrated higher density of the < 0.001 m diameter roots in the
upper 0.10 m soil depth compared to the other treatments. Greater density of
roots of < 0.001 m diameter was found under the subsoiling treatments in the
0.30-0.45 m soil layer. Distribution of the fibrous roots was positively
correlated with the distribution of the total root density. The distribution in
the soil profile of the roots >0.001 m diameter depended more on the year than
on the tillage treatments. In spite of that, density of roots of 0.001 m
diameter tended to be higher in the upper 0.05 m soil layer for the NT treatments
compared to the CT treatments. Subsoiling tended to allow greater density of the
coarsest roots in the 0.05-0.15 m soil depth.

Oat root density

Tillage did not influence the average total oat root density. Root
production was equal for all treatments in the upper 0.05 m soil depth.
No-tillage had lower root density in the 0.05-010 m soil layer. Root yield for
both NT treatments combined was lower in the 0.15-0.30 m as compared to the CT
treatments.

Double-Cropped Soybean/Oat Root Density

Tillage did not influence the root production, nor the root distribution in
the soil profile of the whole system. The oat crop contributed an average of 76%
of the total root yield in the 0.00-0.05 m, but that percent decreased to an
average of 23% in the 0.15-0.30 m soil layer. That proportion remained almost
constant in spite of the different root production among years.


ACKNOWLEDGEMENTS

The authors appreciate the technical assistance of Ruben Ortiz, Jose
Corella, Jose Espaillat, Howard Palmer, Jim Chichester and Walter Davis.

LITERATURE CITED

Anghinoni, I., and S.A. Barber. 1980. Phosphorus applications rate and
distribution in the soil and phosphorus uptake by corn. Soil Sci. Soc. Am. J.
44:1041-1044.
Baeumer, K., and W.A.P. Bakermans. 1973. Zero-tillage. Adv. Agron.
25:77-123.
Barber, S.A. 1984. Soil Nutrient Bioavailability: a Mechanistic Approach.
John Wiley & Sons, New York.
Barber, S.A., and M. Silberbush. 1984. Plant root morphology and nutrient
uptake. p.65-87. In S.A. Barber and D.R. Bouldin (ed.) Roots, Nutrients and
Water Influx, and Plant Growth. ASA Spec. Publ. 49. SSSA, CSSA and ASA,
Madison, WI.
Blevins, R.L., G.W. Thomas, M.S. Smith, W.W. Frye, and P.L. Cornelius.








1983. Changes in soil properties after 10 years continuous non-tilled and
conventionally tilled corn. Soil Tillage Res. 3:135-146.

Borkert, C.M. and S.A. Barber. 1983. Effect of supplying P to a portion of
the soybean root system on root growth and P uptake kinetics. J. Plant Nutr.
6:895-910.
Boyer, J.S., R.R. Johnson, and S.G. Saupe. 1980. Afternoon water deficits
and grain yields in old and new soybean cultivars. Agron. J. 72:981-985.
Campbell, R.B., D.C. Reicosky, and C.W. Doty. 1974. Physical properties and
tillage of Paleudults in the southeastern Costal Plains. J. Soil Water Conserv.
29:220-224.
Claassen, N., and S.A. Barber. 1976. Simulation model for nutrient uptake
from soil by growing plant root system. Agron. J. 68:961-964.
Drew, M.C. 1975. Comparison of the effects of localized supply of
phosphate, nitrate, ammonium and potassium on the growth of seminal root systems,
and the shoot, in barley. New Phytol. 75:479-490.
Duncan, W.G., and A.J. Ohlrogge. 1958. Principles of nutrient uptake from
fertilizer bands II. Root development in the band. Agron J. 50:605-608.
Dyal, S. 1987. Extractable Nutrients, Organic Nitrogen and Organic Matter
in Multicropping Systems as Affected by Tillage and Time of Sampling. M.S.
Thesis. University of Florida. Gainesville, Florida.
Ehlers, W., U. Kopke, F. Hesse, and W. Bohm. 1983. Penetration resistance
and root growth of oats in tilled and untilled loess soil. Soil Tillage Res.
3:261-275.
Fehr, W.R., and C.E. Caviness. 1977. Stages of soybean development. Iowa
Coop. Ext. Serv. Spec. Rep. 80.
Gallaher, R.N., and M.B. Ferrer. 1987. Effect of no-tillage vs.
conventional tillage on soil organic matter and nitrogen contents. Commun. in
Soil Sci. Plant Anal., 18(9):061-1076.
Garay, A.F., and W.W. Wilheim. 1983. Root systems characteristics of two
isolines undergoing water stress conditions. Agron. J. 75:973-977.
Hallmark, W.B., and S.A. Barber. 1981. Root growth and morphology,
nutrient uptake, and nutrient status of soybeans as affected by soil K and bulk
density. Agron. J. 73;779-782.
Hargrove, W.L., J.T. Reid, J.T. Touchton, and R.N. Gallaher. 1982.
Influence of the tillage practices on the fertility status of an acid soil
double-cropped to wheat and soybeans. Agron. J. 74:64-687.
Ide, G., G. Hofman, C. Ossermerct and M. Van Ruymbeke. 1984. Root growth
response of winter barley to subsoiling. Soil Tillage Res. 4:419-431.
Juo, A.S.R., and R. Lal. 1979. Nutrient profile in a tropical Alfisol under
conventional and no-till systems. Soil Sci. 127:168-173.
Kamprath, E.J., D.K. Cassel, H.D. Gross, and D.W. Dibb. 1979. Tillage
effects on biomass production and moisture utilization by soybeans on Coastal
Plain soils. Agrom. J. 71:1001-1005.
Mayaki, W.C., L.R. Stone, and I.D. Teare. 1976. Irrigated and nonirrigated
soybean, corn and grain sorghum root systems. Agron. J. 68:532-534.
Na Nagara, T., R.E. Phillips, and J.E. Leggett. 1976. Diffussion and mass
flow of nitrate-nitrogen into corn roots grown under field conditions. Agron.
J. 68:67-72.
NeSmith, D.S., D.E. Radcliffe, W.L. Hargrove, R.L. Clark, and E.W. Tollner.
1987. Soil compactation in double-cropped wheat and soybeans on a Ultisol. Soil
Sci. Soc. Am. J. 51:183-186.








Ortiz Vega, R.A. 1985. Soil Chemical and Physical Properties Affected by
Long-Term Oat/Soybean Versus Oat/Grain Sorghum Double-Cropping and Tillage
Systems. M.S. Thesis. University of Florida, Gainesville, Florida.

Peterson, W.R., and S.A. Barber. 1981. Soybean root morphology and K
uptake. Agron. J. 73:316-319.
Phillips, R.E., and D. Kirkham. 1962. Soil compactation in the field and
corn growth. Agron. J. 54:29-34.
Portas, C.A.M. 1973. Development of root systems during the growth of some
vegetable crops. Plant and Soil 39:507-518.
Raper, C.D., and S.A. Barber. 1970. Differences in root morphology among
varieties. Agron. J. 62:581-589.
Rowse, H.R., and D.A. Stone. 1981. Deep cultivation of a sandy clay loam
II. Effects on soil hydraulic properties and on root growth, water extraction and
water stress in 1977, especially of broad beans. Soil Tillage Res. 1:173-185.
SAS Institute. 1987. SAS/STAT Guide for Personal Computers. 6th ed. SAS
Institute Inc., Cary, NC, USA.
Silberbush, M., and S.A. Barber. 1983. Sensitivity analysis of parameters
used in simulating potassium uptake with a mechanistic mathematical model.
Agron. J. 75:851-854.
Sivakumar, M.V.K., H.M. Taylor, and R.H. Shaw. 1977. Top and root
relations of field grown soybeans. Agron. J. 69:470-473.
Soil Survey Staff. 1984. Official Series Description of the Arredondo
Series. United States Goverment Printing Office, Washington D.C.
Steel, R.G.D., and J.H. Torrie. 1980. Principles and Procedures of
Statistics: a Biometrical Approach. 2nd ed. McGraw-Hill Book Company, New York.
Sumner, M.E. 1981. Alleviating nutrient stress. p. 99-137. In G.F. Arkin
and H.M. Taylor (ed.) Modifying the Root Environment to Reduce Crop Stress. Am.
Soc. Agr. Eng., Michigan, WI.
Taylor, H.M. 1981. Root zone modification: fundamentals and alternatives.
p. 3-17. In G.F. Arkin and H.M. Taylor (ed.) Modifying the Root Environment to
Reduce Crop Stress. Am. Soc. Agr. Eng. Michigan, WI.
Taylor, H.M., and B. Klepper. 1974. Water relations of cotton. I. Root
growth and water use as related to top growth and soil water content. Agron. J.
66:584-588.
Taylor, H.M., and L.F. Ratliff. 1969. Root elongation rates of cotton and
peanuts as a function of soil strength and soil water content. Soil Sci.
108:113-119.
Thomas, G.W., and W.W. Frye. 1986. Fertilization and liming. p. 87-126.
In R.E. Phillips and S.H. Phillips (ed.) No-Tillage Agriculture. Van Nostrand
Reinhold Co., New York.
Trouse, A.C., Jr. 1983. Observations on under-the-row subsoiling after
conventional tillage. Soil Tillage Res. 3:67-81.













Table 1. ANOVA for soybean root density affected by
tillage, soil depth and year.

Source Overall Year 1986 Year 1987


Replication (R)
Tillage (T)
R*T (error a)
Depth (D)
R*D (error b)
T*D
R*T*D (error c)
Year (Y)
R*Y (error d)
T*Y
R*T*Y (error e)
D*Y
R*D*Y (error f)
T*D*Y
Residual error

Corrected Total
C.V.


d.f. F value

3 .47
3 1.48
9
4 236.86**
12
12 3.26**
36
1 54.51**
3
3 5.16*
9
4 14.73**
12
12 2.76**
36

159
25.81


d.f. F value d.f. F value

3 .54 3 1.60
3 2.77 3 .78
9 9
4 105.04** 4 252.75**
12 12
12 3.61** 12 1.76
36 36


79 79
26.18 26.94


*,**= Significant at the 0.05 and 0.01 probability levels,
respectively. NT+=No-tillage subsoling, NT=No-tillage,
CT+=Conventional tillage subsoiling and CT+=Conventional
tillage.







TABLE 2. Soybean root density in the 0.00 to 0.45 m affected by tillage,
soil depth and year.
Soil Depth (m)
Tillage 0.00-0.05 0.05-0.10 0.10-0.15 0.15-0.30 0.30-0.45 Mean
----------------------------------------~-3--------------------------
---- ---- ---------------- .m-3 --------------- ---

Year 1986


NT+
NT
CT+
CT

Mean


517.15 374.59 233.57 88.21 6.90
686.49 562.29 189.67 45.66 3.37
470.80 405.77 226.38 108.51 9.29
422.83 353.87 201.96 86.73 2.99

524.32 415.13 212.90 82.28 5.64


244.08
290.29
244.15
213.68

248.05


T*D Cotrasts ................... P > F .....................


0.017
NS
0.006


NS
NS
0.025


0.039
0.032
0.009


NS
0.056
NS


Year 1987


NT+ 537.05 213.85 118.10 28.47 1.72
NT 532.52 174.38 79.58 22.17 1.10
CT+ 441.23 248.61 82.74 19.62 1.28
CT 516.85 160.00 68.67 17.67 1.27

Mean 506.91 199.21 87.27 21.98 1.34

T*D Contrasts ................... P > F .....................


0.080
NS
NS


179.84
161.95
158.69
152.89

163.34


NT+=No-tillage subsoiling, NT=No-tillage, CT+=Conventional tillage subsoiling
and CT=Conventional tillage. C1=NT+ and NT vs. CT+ and CT, C2=Subsoiling vs.
non-subsoiling and C3=NT vs. others. T=Tillage, D=Depth.













Table 3. ANOVA for the < 0.001 m and > 0.001 m diameter soybean
root density affected by tillage, soil depth and year.
Root diameter (m)

Source < 0.001 > 0.001


Replication (R)
Tillage (T)
R*T (error a)
Depth (D)
R*D (error b)
T*D
R*T*D (error c)
Year (Y)
R*Y (error d)
T*Y
R*T*Y (error e)
D*Y
R*D*Y (error f)
T*D*Y
Residual error

Corrected Total
C.V.


d.f. F value

3 .82
3 2.49


30.04 **

2.58 **

48.23 **


1.97


14.30 **


2.47 *


159
50.61


d.f. F value

3 0.65
3 0.47


4 249.05 **


0.77


1 37.39 **


2.47


3 12.17 **


2.48 *


142
143.76


*,**= Significant at the 0.05 and 0.01 probability levels,
respectively. NT+=No-tillage subsoling, NT=No-tillage,
CT+=Conventional tillage subsoiling and CT+=Conventional tillage.







TABLE 4. Soybean root density for roots < 0.001 m diameter in the
0.00 to 0.45 m affected by tillage, soil depth and year.
Soil Depth (m)


Tillage 0.00-0.05 0.05-0.10 0.10-0.15 0.15-0.30 0.30-0.45
-------- ---------------------------- g.m-3------------------

Year 1986

NT+ 53.49 107.51 133.68 57.99 3.18
NT 154.94 261.03 121.88 25.37 1.84
CT+ 37.64 107.55 123.90 73.69 5.70
CT 30.14 116.06 134.01 67.42 2.21

Mean 69.05 148.04 128.37 56.11 3.23
C.V.= 66.43

T*D Contrasts ................... P > F .....................


NS
NS
0.035


NS
0.078
0.010


0.036
NS
0.014


Mean


71.17
113.01
69.69
69.97

80.96


NS
0.056
NS


Year 1987


NT+ 172.19 126.73 93.19 21.27 1.72
NT 193.32 100.21 58.72 14.16 0.83
CT+ 130.94 129.61 61.95 15.53 1.29
CT 155.99 85.50 49.51 12.99 0.82

Mean 163.11 110.51 65.84 15.99 1.16
C.V.= 28.69

T*D Contrasts ................... P > F .....................


0.042
NS
0.065


NS
0.006
NS


83.02
73.45
67.86
60.96

71.32


0.071
NS


NT+=No-tillage subsoiling, NT=No-tillage, CT+=Conventional tillage
subsoiling and CT=Conventional tillage. C1=NT+ and NT vs. CT+ and CT,
C2=Subsoiling vs. non-subsoiling and C3=NT vs. others. T=Tillage and
D=Depth.








TABLE 5 Soybean root density for roots > 0.001 m diameter in the
0.00 to 0.45 m affected by tillage, soil depth and year.


Soil Depth (m)

Tillage .00-.05 .05-.10 .10-.15 .15-.30 .30-.45 Mean
------ -------------------- g.m-3-----------------------

Year 1986

NT+ 463.66 267.09 99.89 30.22 3.71 172.92
NT 531.54 265.27 67.79 20.30 2.04(3) 186.62
CT+ 433.17 298.22 102.48 34.83 3.58 174.45
CT 392.69 237.81 67.95 19.34 1.57(2) 159.68


Mean 455.26 267.10 84.53 26.17 2.96 173.60
C.V.=103.49

T*D Contrasts ............... P > F

Cl 0.023 NS NS NS NS
C2 NS NS 0.008 0.003 NS
C3 0.019 NS NS NS NS


Year 1987

NT+ 364.84 87.11 24.92 7.20 121.02
NT 296.71 74.17 20.86 8.01 1.05(1) 94.12
CT+ 310.29 119.00 20.79 4.10 113.54
CT 360.61 74.50 19.16 4.67 1.83(1) 108.09

Mean 333.11 88.70 21.43 5.99 1.44 108.95
C.V.=129.42

T*D Contrasts ............... P > F ................

C1 NS NS NS 0.084
C2 NS NS NS NS
C3 NS NS NS NS

NT+=No-tillage subsoiling, NT=No-tillage, CT+=Conventional tillage
subsoiling and CT=Conventional tillage. C1=NT+ and NT vs. CT+ and
CT, C2=Subsoiling vs. non-subsoiling and C3=NT vs. others. Tillage
and D=Depth. Number of samples is indicated within brackets when
different to four.








Table 6. ANOVA for oat root density affected by tillage, soil depth


Overall


Year 1986


Year 1987


Replication (R)
Tillage (T)
R*T (error a)
Depth (D)
R*D (error b)
T*D
R*T*D (error c)
Year (Y)
R*Y (error d)
T*Y
R*T*Y (error e)
D*Y
R*D*Y (error f)
T*D*Y
Residual error

Corrected Total
C.V.


d.f. F value

3 0.78
3 2.83
9
3 388.25 **
9
9 3.05 *
27
1 248.29 **
3
3 0.57 *
9
3 18.95 **
9
9 1.44
27

127
29.63


d.f. F value

3 0.41
3 1.06
9
3 220.97 **
9
9 2.20 *
27


d.f. F value

3 0.87
3 3.52
9
3 494.64 **
9
9 2.10
27


63
28.79


27.12


*,**= Significant at
respectively.


0.05 and 0.01 probability


'ear.


and y
Sourc


levels,


;e







TABLE 7. Oat root density in the 0.00 to 0.30 m affected by
tillage, soil depth and year.
Soil Depth (m)


0.00-0.05 0.05-0.10 0.10-0.15 0.15-0.30 Mean
------------------ g.m-3 ------------------ ----------


Growina cycle 86/87


2175.83 489.87 156.70 22.93
1888.15 379.62 71.94 11.48
1927.22 547.10 258.56 37.33
1690.72 684.43 289.36 30.80

1920.48 525.25 194.14 25.63


711.33
587.80
692.55
673.83

666.38


T*D Contrasts ................... P > F .....................


0.013
NS
0.018


0.000
NS
0.000


0.000
0.004
0.000


Growing cycle 87/88


NT+ 1440.79 155.05 31.18 3.64 407.81
NT 1217.64 141.00 45.06 5.78 352.37
CT+ 1642.79 245.72 93.58 5.99 497.02
CT 1316.67 226.79 64.91 7.49 403.96

Mean 1404.47 192.14 58.83 5.73 415.29

T*D Contrasts ................... P > F .....................

C1 NS 0.002 0.004 NS
C2 0.047 NS NS NS
C3 NS 0.018 NS NS

NT+=No-tillage subsoiling, NT=No-tillage, CT+=Conventional tillage
subsoiling and CT=Conventional tillage. C1=NT+ and NT vs. CT+ and
CT, C2=Subsoiling vs. non-subsoiling and C3=NT vs. others.
T=Tillage and D=Depth.


Tillage


NT+
NT
CT+
CT

Mean







Table 8. ANOVA for the double-cropped soybean/oat root density in
the 0.00-0.30 m affected by tillage, soil depth and year.

Source Overall Year 1986 Year 1987


Replication (R)
Tillage (T)
R*T (error a)
Depth (D)
R*D (error b)
T*D
R*T*D (error c)
Year (Y)
R*Y (error d)
T*Y
R*T*Y (error e)
D*Y
R*D*Y (error f)
T*D*Y
Residual error

Corrected Total
C.V.


d.f. F value

3 0.26
3 1.31
9
3 427.35 **
9
9 1.80
27
1 236.42 **
3
3 0.46
9
3 13.30 **
9
9 1.92
27


d.f. F value

3 0.21
3 0.39
9
3 192.18 **
9
9 2.13
27


63 63
63 63


127
21.93


22.49


d.f. F value

3 0.69
3 2.14
9
3 1343.18 **
9
9 1.08
27


21.24


*,**= Significant at 0.05 and 0.01 probability levels,
respectively.







TABLE 9. Double-cropped soybean/oat root density in the 0.00 to
0.30 m affected by soil depth and year.
Soil Depth (m)
Growing
cycle 0.00-0.05 0.05-0.10 0.10-0.15 0.15-0.30 Mean
--------- ------------------- g.m-3 --------------------------

1986/87 2444.80 940.38 407.04 107.91 975.03

1987/88 1911.38 391.35 146.10 27.70 619.13


Mean 2178.09 665.86 276.57 67.81 797.08


TABLE 10. Percent of the total double-cropped soybean/oat root
density in the 0.00 to 0.30 m affected by soil depth and year.
Soil Depth (m)
Growing
cycle 0.00-0.05 0.05-0.10 0.10-0.15 0.15-0.30 Total

--------- ----------------------- % ---------------------------

1986/87 62.8 24.0 10.4 2.8 100

1987/88 77.1 15.8 5.9 1.1 100




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