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Group Title: Agronomy research report - University of Florida Institute of Food and Agricultural Sciences ; AY-87-05
Title: Soybean root development under four tillage systems
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Permanent Link: http://ufdc.ufl.edu/UF00056067/00001
 Material Information
Title: Soybean root development under four tillage systems
Physical Description: 10 leaves : ill. ; 28 cm.
Language: English
Creator: Bruniard, Graciela Cordone de, 1951-
Gallaher, Raymond N.
University of Florida -- Agronomy Dept
Publisher: Agronomy Department, IFAS, University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 1987
 Subjects
Subject: Soybean -- Florida   ( lcsh )
Soybean -- Roots   ( lcsh )
Tillage -- Florida   ( lcsh )
Genre: bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: G. C. Bruniard and R.N. Gallaher.
Bibliography: Includes bibliographical references (leaves 4-5).
General Note: Agronomy research report - University of Florida Institute of Food and Agricultural Sciences ; AY-87-05
 Record Information
Bibliographic ID: UF00056067
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 62523853

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HISTORIC NOTE


The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source
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Copyright 2005, Board of Trustees, University
of Florida











Agronomy Research Report AY-87-05


Soybean Root Development Under Four Tillage Systems.


G.C. Bruniard and R.N. Gallaher

Graduate Student (Former Agronomy Research Scientist, INTA, Argentina)
and
Professor of Agronomy, Agronomy Department
Institute of Food and Agricultural Sciences, University of Florida
Gainesville, Florida, 32611 ;.'..l idrISC
Library'

ABSTRACT FE 2 8 199

Tillage practices affect the growth and development-of rsoybear (Glycine
max. L. Merr.). The Objective of this research was to:-eVaiuate' oybean roots in
a 10-yr-old oat (Avena sativa L. )/soybean double-cropping-Fillage'experiment
growing in an Arredondo loamy sand (Grossarenic Paleudult). Tillage treatments
were 1) no-tillage plus subsoiling (NT+), 2) no-tillage (NT), 3) conventional
tillage plus subsoiling (CT+), and 4) conventional tillage (CT). Roots were
collected at the R7 growth stage in 0.05 m soil increments to a depth of 0.45 m.
Total root weight to the 0.45 m soil depth was equal, but NT concentrated 79% of
the roots in the upper 0.10 m of soil as compared to 61, 60 and 58% for CT, NT+,
and CT+, respectively. There was 139% more fibrous roots less than 1 mm diameter
in this top 0.10 m for NT as compared to the other treatments. Weight of roots
greater than 1 mm diameter at greater than 0.20 m soil depth for NT+ and CT+ was
100% more than for NT and CT. Pod yield was less for CT. The concentration of
roots near the soil surface in NT has implications for fertilizer and water
management of NT soybean.


INTRODUCTION

Many factors such as soil type, nutrient status, climatic conditions, crop
variety and cropping practices can influence the activity and distribution of
plant roots in the soil. Extensive reports are available describing the
anatomical features, primary growth and nodule development of soybean (Glycine
max L. Merr.). There is also information concerning soybean root development and
distribution under field conditions.
Borst and Thatcher (1931) reported that most root dry weight of soybean was
concentrated in the upper 0.60 m of the soil profile. Raper and Barber (1970)
found morphological differences among root systems of 26 soybean varieties, and
different patterns of root growth in a plant growing alone when compared with
plants growing in adjacent rows. Root dry weight was concentrated in the upper
portion of the soil profile, 90% or more in the upper 0.75 m early in the season
and in the upper 0.15 m during the remainder of the season (Mitchell and
Russell, 1971). Maximum rate of downward soybean root growth was determined to
occur during early spring in R1 to R3 stages (Kaspar et al., 1978). Portas
(1973) found that root growth patterns of vegetable crops reflected soil
conditions more than crop genetics. Other research dealt with soil root depth












and distribution under irrigated conditions for soybean, corn (Zea mays L.) and
grain sorghum (Sorghum bicolor L. Moench) (Mayaki et al. 1976).
Bohm et al. (1977) discussed different methods for characterizing soybean
root density and development and Sanders and Brown (1978) studied techniques for
measuring root growth under field conditions without destroying the plot. Nelson
and Allmaras (1969), using the monolith technique, worked on corn and revealed
different patterns of root proliferation horizontally and vertically under three
straw mulch treatments.
In spite of all these references covering different aspects affecting root
growth, information about soybean root development and distribution under
different tillage systems is very limited. Barber (1971) found that corn grown
under conventional tillage (CT) had more roots deeper in the soil than with
other tillage practices. Onderdonk and Ketchenson (1973) reported that surface
applied fertilizer for no-tillage (NT) corn was more efficiently used than
fertilizer disked into CT soil for conventionally planted corn. The increase in
uptake was credited to the relatively greater root growth near the surface,
which in turn was believed to be due to temperature depression and a tendency
for a more horizontal direction or root growth. Growth and distribution
potential of soybean roots under different tillage systems is very important in
order to improve fertilization and irrigation management practices, especially
for NT management.
The objective of this study was to evaluate soybean root patterns in a
10-yr-old oat/soybean double cropping experiment grown under four tillage
systems.


MATERIALS AND METHODS

Soybean root and plant samples were taken in a 10-yr-old oat/soybean double
cropping-tillage experiment in an Arredondo loamy sand soil (sandy, siliceous,
thermic, Grossarenic Paleudult), at the University of Florida Green Acres
Agronomy Farm near Gainesville. A randomized complete block design with four
replications was used. Tillage treatments were: 1) NT plus subsoiling (NT+), 2)
NT, 3) CT plus subsoiling (CT+) and 4) CT. The 'Centenial' soybean variety was
sampled at the R7 growth stage (R7 based on classification by Fehr and Caviness,
1977). One site per plot of approximately uniform plant density was selected for
taking the sample.
Samples were taken across three rows (2.29 m) for representing the tractor
traffic and no traffic middles, 0.30 m along each row and to a depth of 0.45 m.
Soil was loosened around the outside area to the 0.45 m depth by shovel. Shovels
were placed under the loosened plants to lift the soil while holding the plants
by hand. The plant-root-soil samples were placed on a sheet of plywood
previously measured in 0.05 m increments. Roots were washed by a stream of water
(69 10 Pa). The washed roots were collected in 0.05 m soil depth increments.
The above ground part was cut, separated into leaves, petiols, stems and pods.
All plant parts were dried in a forced air oven at 70 C. Excess sand and crop
residue impurities were removed and total root weight was measured for each
depth. Roots of a diameter greater than 1 mm were separated and weighed. The
percentages of roots of 1 to 2 mm, 2 to 3 nm, 3 to 5 mm and 5 to 10 mm diameter
were estimated within each depth by superimposing the roots on a drawing of the
different diameters.
Statistical analysis was performed using standard ANOVA on a TRS 80 Model
III microcomputer. Means were tested using Duncan's Multiple Range test.











RESULTS AND DISCUSSION


Sampling Method

The 'framed monolith method' proposed by Nelson and Allmaras (1969) did not
work with the loamy sand soil in this study. It was necessary to take the
samples using the shovel method described in the Materials and Methods. The
merits of the different methods will depend upon the specific conditions that
are encountered (Bohm et al., 1977).

Above Ground Plant parts

Leaf and petiol dry weights were equal for all treatments (Table 1). Stem
and pod dry weights were less under CT than under the other tillage treatments.
Nitrogen concentration of all plant parts2was equal among the different tillage
treatments but the2total amount of N (g/m ) was less under CT (Table 1). The
number of plants/m was equal for all treatments. It is important to hold plant
density constant because the root patterns may be affected as has been found by
Raper and Barber (1970).

Root Pattern

Total root dry weight (TRW) from the 0 to 0.45 m soil depth was equal for
all treatments, but the root patterns showed morphological and qualitative
differences. Both root distribution in the soil profile and root diameter were
affected by tillage system (Table 2 and Fig. 1). No-tillage was found to
concentrate 79% of the TRW in the upper 0.10 m of soil compared to 61, 60, and
58% for CT, NT+ and CT+, respectively. This greater percentage for NT was due to
a greater weight of roots less than 1 mm diameter, while the weight of those
greater than 1 mm was equal (Table 3). From these results it can be assumed that
not only was the root weight in the upper 0.10 m greater, but the soil area
explored by the roots was also greater. Because of the larger amount of roots
less than 1 mm diameter, it is possible to consider a greater number of roots, a
greater length of roots, and a greater potential area of absorption of nutrients
and water near the soil surface by NT soybean. Because some nutrients diffuse
slowly in the soil, ions more than a few mm away have little chance of reaching
roots. These considerations indicate that the volume of soil in close proximity
to absorbing root surfaces is very important by determining the level at which
such nutrients are available to the plant. During drought periods the pattern
of absorption can change from roots near the soil surface to roots deeper in the
soil profile. Therefore, during water stress periods treatments with a more
uniform root distribution in the soil profile could be beneficial. On the other
hand, if irrigation is applied it seems that NT would need more frequent and
less heavy irrigation to maintain moisture in the area of greater root density
near the soil surface. In the other treatments it would be more appropriate to
saturate the profile at greater depths. These considerations may also apply for
the placement of fertilizers. The optimum morphology of a root system has not
yet been defined, but when frequent irrigation and intensive fertilization is
used, the value of a deep root system is questionable. On the other hand crops
growing under field conditions which depend on irregularly occurring
precipitation and having restricted root systems could be more susceptible to
water and nutrient stresses than those with deep root systems.
Soybean under NT+ and CT+ had a greater weight of roots greater than 1 mm









diameter at depths greater than 0.20 m (Table 3). Raper and Barber (1970)
observed that 'depth of profuse branching of the tap-root could be affected by
changes in the soil compaction and aeration related to the depth of
cultivation'. Their observation would indicate that soybean under these two
subsoiling treatments could absorb water deeper in the soil profile during
drought stress compared to nonsubsoiling treatments.
Different trends were observed in the distribution of roots greater than 1
mn diameter as follows: 1) The percentage roots of 1 to 2 mm in diameter
increased with soil depth in all treatments, 2) the percentage roots of 2 to 3
mm in diameter increased to a depth of 0.10 m for NT, NT+, and CT, while those
in CT+ increased to 0.15 m, 3) the 3 to 5 mm diameter roots approached 0%
between the 0.20 and 0.30 m depths and 4) the percentage roots or 5 to 10 mm in
diameter decreased with soil depth in all treatments and was 0% at the 0.10 to
0.15 m for NT and CT (Table 4).

Shoot to Root Weight Ratio

The shoot weight to TRW ratio was equal for all treatments, but shoot
weight to root weight in the 0 to 0.10 m depth was different (Table 5). The
greater proportion of top growth supported by the roots near the soil surface in
NT means that if nutrients and water leach or evaporate from the upper 0.10 m of
soil, soybean plants under these treatments would suffer more stress than plants
under tillage systems with subsoiling which have more roots deeper in the soil
profile.


CONCLUSIONS

Soybean root distribution and diameter differed among tillage treatments,
although the TRW was equal. No-tillage was found to concentrate 79% of the TRW
in the upper 0.10 m of soil having a greater weight of roots less than 1 mm
diameter. Subsoiling treatments developed a greater weight of roots greater than
1 mm diameter at greater than 0.20 m soil depth. The different pattern of NT
root distribution did not cause different pod yield among NT, NT+ and CT+. Somne
climatic factors, not considered in this research, appeared to have been yield
determinant.


LITERATURE CITED

1. Bohm, W., H. Maduakor, and H.M. Taylor. 1977. Comparison of five methods for
characterizing soybean rooting density and development. Agron. J.
69:415-419.
2. Barber, S.A. 1971. Effect of tillage practice on corn (Zea mays L.) root
distribution and morphology. Agron. J. 63:724-726.
3. Borst, H.L. and L.E. Thatcher. 1931. Life history and composition of soybean
plant. Ohio Agr. Exp. Sta. Res. Bull. 494, 96 p.
4. Fehr, W. R. and C. E. Caviness. 1977. Stages of soybean
development. Agricultural and Home Economics Experiment Station, Iowa State
and Technology University, Ames, Iowa. Special Report 80.
5. Kaspar, T.C., C.D. Stanley and H.M. Taylor. 1978. Soybean root growth during
reproductive stages of development. Agron. J. 70:1105-1106.
6. 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.












7. Mitchell, R.L. and W.J. Rusell. 1971. Root development and rooting patterns
of soybean (Glycine max L. Merr.) evaluation under field conditions. Agron.
J. 63:313-316.
8. Nelson, N.W. and R.R. Allmaras. 1969. An improved monolith method for
excavating and describing roots. Agron. J. 61:751-754.
9. Onderdonk J.J. and J.W. Ketchenson. 1973. Effect of stover mulch on soil
temperature, corn root weight, and phosphorus fertilizer uptake. Soil Sci.
Soc. Amer. Proc. 37:904-"06.
10. Portas, C.A.M. 1973. Development of root systems during the growth of some
vegetable crops. Plant Soil. 39:507-518.
11. Raper, C.D. and S.A. Barber. 1970. Differences in root morphology among
varieties. Agron. J. 62:581-589.
12. Sanders, J.L. and D.A. Brown. 1978. A new fiber optic technique for
measuring root growth of soybean under field conditions. Agron. J.
70:1073-1076.


Table 1. Soybena dry weight and nitrogen content of above ground soybean parts as
affected by tillage.
Plant Parts
Leaves Petioles Stems Pods Total
D Nl N DM N 1N4 N D4 N DN N

-----------------g/m2---------------

NT+ 68a 1.77a 38a 0.35a 152a 1.27a 311a 14.74a 569a 18.13a
NT 71a 1.80a 36a 0.33a 150a 1.24a 296a 13.78ab 553a 17.14a
CT+ 59a 1.42ab 35a 0.30ab 146a 1.10a 296a 15.10a 537a 17.92a
CT 49a 1.11 b 22a 0.20 b 111 b 0.83a 220 b 10.85 b 401 b 13.00 b


Treatment means within columns followed by
different at the 0.05 level of probability
test. NT+ = No-tillage plus subsoiling, NT
plus subsoiling, CT = Conventional tillage


the same letter are not significantly
according to Duncans new multiple range
= No-tillage, CT+ = Conventional tillage
and DM = Dry matter.












Table 2. Soybean root weight distribution by soil depth
and root diameter as affected by tillage.
Tillage
Soil Depth NT+ NT CT+ CT


14.9
17.9
8.3
2.5
1.5
0.5
0.3

45.9


------ g/m2 of roots


26.3 a
13.2 a
3.4 a
1.8 a
0.8 1
0.5
0.2 a


46.2


< 1 mm diameter ------


2.2
6.7
7.6
7.7
4.6
2.1
1.0

31.9


1.9
7.3
8.4
6.5
3.9
1.7
0.4

30.1


> 1 mm diameter ------


21.4
14.9
5.1
3.3
1.6
1.0
0.5

45.8


19.3
11.7
3.3
1.5
0.8
0.4
0.2

37.2


----------- g/m2 of


26.5
20.4
14.1
9.2
4.2
2.1
1.1

77.6


b 41.2
31.1
11.7
4.3
2.3
S 1.0
0.5


92.1


total roots ---------


23.6
21.6
12.7
11.0
6.2
3.1
1.5

77.7


21.2
19.0
11.7
8.0
4.8
2.1
0.6


66.4


Treatment means within rows followed by the same letter
are not significantly different at the 0.05 level of
probability according to Duncans new multiple range test.
NT+ = No-tillage plus subsoiling, NT = No-tillage, CT+ =
Conventional tillage plus subsoiling and CT =
Conventional tillage.


------ g/m2 of roots


.00-.05
.05-.10
.10-.15
.15-.20
.20-.25
.25-.30
.30-.45


Total


.00-.05
.05-.10
.10-.15
.15-.20
.20-.25
.25-.30
.30-.45


3.5
7.1
9.1
6.8
2.8
1.2
0.5


31.0


23.0
13.3
5.0
2.4
1.4
0.9
0.6

46.6


Total


.00-.05
.05-.10
.10-.15
.15-.20
.20-.25
.25-.30
.30-.45


Total











Table 3. Soybean root weight distribution by size and soil depth as
affected by tillage.
Soil depth
0.0-0.10 0.0-0.45 0.0-0.10 0.20-0.45 m
Root size Percent** Root size
Treatment > 1 mm < 1 mm Total TRW* of TRW > 1 mm

---------- g/2 m2 -- g/m2

NT 39.5 a 32.8 a 72.3 a 92.1 a* 79 a** 1.51 b
NT+ 36.3 a 10.6 b 46.9 b 77.6 b 60 b 3.13 a
CT+ 36.3 a 8.9 b 45.2 b 77.7 b 58 b 2.87 a
CT 31.0 a 9.2 b 40.2 b 66.4 b 61 b 1.41 b
Treatment means within columns followed by the same letter are not
significantly different at the 0.05 level of probability according
to Duncans new multiple range test. NT = No-tillage, NT+ =
No-tillage plus subsoiling, CT+ = Conventional tillage plus
subsoiling, and CT = conventional tillage. These data are total
root weight (TRW) including all sizes and depths (See data at
bottom of Table 2). ** These data are the TRW in the 0.0-0.10 m
depth as a percentage of the TRW in the 0.0-U.45 m depth.












Table 4. Estimated percentage by volume of soybean roots
greater than 1 mm diameter from the 0 to 0.45 m soil depth
as affected by tillage.
Soil Root diameter (mm)
Treatment Depth 1-2 2-3 3-5 >5

-- m -- -------------% ----------------

NT .00-.05 2 8 6 84
.05-.10 18 40 30 12
.10-.15 55 36 9 0
.15-.20 69 30 1 0
.20-.25 80 20 0 0
.25-.30 92 8 0 0
.30-.45 97 3 0 0

NT+ .00-.05 1 5 14 80
.05-.10 25 33 21 21
.10-.15 44 33 21 2
.15-.20 69 26 5 0
.20-.25 78 21 1 0
.25-.30 80 20 0 0
.30-.45 89 11 0 0

CT .00-.05 3 5 11 81
.05-.10 31 43 15 11
.10-.15 75 23 1 1
.15-.20 88 12 0 0
.20-.25 95 5 0 0
.25-.30 100 0 0 0
.30-.45 100 0 0 0

CT+ .00-.05 3 4 9 84
.05-.10 16 22 39 23
.10-.15 48 30 15 7
.15-.20 66 27 7 0
.20-.25 74 25 1 0
.25-.30 83 17 0 0
.30-.45 97 3 0 0










Table 5. Soybean shoot to root weight ratios for roots measured in
the 0 to 0.45 m and 0 to 0.10 m soil depths as affected by tillage.
Soil depth
Treatment 0 0.45 m 0 0.10 m

----------- Shoot to root weight ratios ----------

NT+ 7.5 a 12.5 a
CT+ 6.8 a 12.0 ab
CT 6.1 a 10.0 bc
NT 6.1 a 7.8 c
Treatment means within columns followed by the same letter are not
significantly different at the 0.05 level of probability according
to Duncans new multiple range test. NT+ = No-tillage plus
subsoiling, CT+ = Conventional tillage plus subsoiling, CT =
Conventional tillage, and NT = No-tillage.

















TOTAL ROOT WEIGHT DISTRIBUTION BY DIAMETER


60% >m






60% > 1 mn~i



60%


~-40% <1 rnm
CCl + --~~~-;


Fig. 1. Total root weight distribution by diameter
in the 0.0-0.45 m soil depth. NT+ = No-tillage plus
subsoiling, NT = No-tillage, CT+ = Conventional
tillage plus subsoiling and CT = Conventional
tillage.


50% > 1 rri




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