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Growth traits and mineralconcentrations of maizehybrids grown on unlimedand limed acid soilR.B. Clark a , S.K. Zeto a , V.C. Baligar a & K.D.Ritchey aa Appalachian Soil and Water ConservationResearch laboratory, U. S. Department ofAgriculture , Agricultural Research Service , P.O.Box 400, Beaver, WV, 25813Published online: 21 Nov 2008.

To cite this article: R.B. Clark , S.K. Zeto , V.C. Baligar & K.D. Ritchey(1997) Growth traits and mineral concentrations of maize hybrids grown onunlimed and limed acid soil, Journal of Plant Nutrition, 20:12, 1773-1796, DOI:10.1080/01904169709365374

To link to this article: http://dx.doi.org/10.1080/01904169709365374

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JOURNAL OF PLANT NUTRITION, 20(12), 1773-1795 (1997)

Growth Traits and Mineral Concentrationsof Maize Hybrids Grown on Unlimed andLimed Acid Soil

R. B. Clark, S. K. Zeto, V. C. Baligar, and K. D. Ritchey

Appalachian Soil and Water Conservation Research laboratory, U. S.Department of Agriculture, Agricultural Research Service, P.O. Box 400,Beaver, WV 25813

ABSTRACT

Growing crop plants tolerant to acid soils is an alternative for successfulproduction on acid soils with limited inputs, especially lime. Acid soil- oraluminum (Al)-tolerant plants offer considerable protection against soil acidityproblems. Thirteen maize (Zea mays L.) hybrids developed for productionunder various environmental conditions were grown (greenhouse) on twoacid soils (unlimed and limed) to determine differences among hybrids forgrowth traits, mineral acquisition, and relative tolerance to acid soil. Porterssoil induced greater acid soil stress on maize than did Lily soil, althoughshoot/root dry matter (DM) ratios were affected more in plants grown onLily than on Porters soil. Shoot and root DM and total root length (RL) overall hybrids followed sequences of Limed Lily Limed Porters > UnlimedLily > Unlimed Porters, and the trait with the greatest variation among hybridswas total RL. Specific RL (total RL/root DM) over all hybrids followed asequence of Limed Lily=Limed Porters=Unlimed Lily>Unlimed Porters, withrelatively small variations among hybrids. Shoot DM/RL among hybrids

1773

Copyright © 1997 by Marcel Dekker, Inc.

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1774 CLARK ET AL.

followed a sequence of Unlimed Porters Unlimed Lily > Limed Lily =Limed Porters, and had the least variation among hybrids. Two Brazilianhybrids (HD 91102 and HD 9176) had highest DM and total RL to indicaterelatively high tolerance to acid soil stresses, while other hybrids (ten fromthe United States and one from Brazil) had relatively small differences forgrowth traits to indicate moderate to low tolerance to acid soils. Althoughgenotypes differed widely for mineral element concentrations, no significantdifferences in mineral elements between more and less tolerant genotypeswere noted.

INTRODUCTION

Maize is the third most important cereal crop in the world, and is grown onvarious soils under diverse environments. Nearly half of the total potentiallyarable land of the world is acidic (Clark, 1982), and much of the maize grownworld-wide is on acid soils. For example, maize is grown on »8 million ha ofacid soil in central/south America and Asia (Pandey and Gardner, 1992), and acidsoils comprise approximately 850 million ha in tropical America, 450 million hain tropical Africa, 210 million ha in tropical Asia (Van Wambeke, 1976), andabout 223 million ha in the United States (below pH 5.5) (R. Arnold, 1995, NaturalResources Conservation Service, Washington, DC, personal communication).Plants grown on acid soils commonly have reduced growth and yield. Liming isa common practice to alleviate acidity problems on acid soils (Adams, 1984), butlime is often too expensive or impractical for many crop production systems.Liming subsoils is particularly impractical and uneconomical (Foy, 1992). Usinggermplasm tolerant to acidic conditions would be an alternative for overcomingsome constraints with which plants must cope on acid soils with low or no limeinput.

Use of acid soil-tolerant plants is common in many parts of the world (Maranvilleet al., 1993; Rao et al., 1993). Many maize lines/genotypes (Bahia Filho et al.,1978; Clark and Brown, 1974;Furlanietal., 1986;Kasimetal., 1990;Kovacevicetal., 1996;Magnavacaetal., 1987b, 1987c; Nyamangombe and Lefèbvre, 1985;Oliveiraetal., 1983; Pandey and Gardner, 1992; Rhue etal., 1978) and populations(Bahia Filho etal., 1978; Ceballos etal., 1995; Duque-Vargas etal., 1994;Furlaniet al., 1986; Granados et al., 1993; Lima et al., 1992; Lopes et al., 1987; Magnavacaet al., 1987a; Pandey and Gardner, 1992; Pandey et al., 1984) have been identified,screened, and/or improved for acid soil/Al-tolerance, including some understandingof genetic/heritable processes/traits involved. Breeding to overcome acid soilproblems is practical and feasible (Magnavaca and Bahia Filho, 1993,1996). Forexample, a high yielding maize hybrid released to Brazilian producers/cooperativesin 1987 became acceptable to the extent that the market share ofthat hybrid incentral/south Brazil increased from 0.8% in 1988/89 (Magnavaca and Bahia Filho,1993) to > 15% in 1995/96 (Magnavaca and Bahia Filho, 1996). Maize germplasm

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GROWTH TRAITS OF MAIZE HYBRIDS 1775

from the Maize Improvement Program of CIMMYT is also becoming availablefor production on many acid soils of central/south America and Asia (Granadoset al., 1993; Narro et al., 1996). Other acid soil-tolerant maize hybrids have beenor will be released, which should enhance production of maize on acid soils.

Common features of plants grown with excess Al or on acid soils are reducedyields. Root growth is especially reduced by soil acidity (Taylor, 1989) so thatroots are unable to obtain sufficient nutrients (and water) to sustain optimumgrowth. The objectives of our study were to determine growth traits and mineralacquisition differences among hybrids of young maize grown on unlimed andlimed acid soils, and to assess relative tolerance of the hybrids to acid soil.

MATERIALS AND METHODS

Acid Porters (coarse-loamy mixed, mesic, Umbric Dystrochrept from easternTennessee) and Lily (fine loamy, siliceous, mesic, Typic Hapludult from southernWest Virginia) soils were used. Properties of these soils before addition of fertilizerand lime treatments are provided in Table 1. Soils were air dried, screened (2 mmscreen), fertilized with 143 mg NH4NO3 and 878 mg KH2PO4 kg1 soil, and limetreatments [chemical grade CaCO3 (2.0 g) + Mg(OH)2 (0.5 g) kg-1 soil] were added,and soils thoroughly mixed. Soils received moisture to near field capacity, put inplastic bags, and incubated seven d before being placed in pots (1.0 kgpot1) forplant growth.

Seeds of 13 maize hybrids (Table 2) were surface sterilized with 0.1-strengthNaOCl (household bleach) for 5 min, rinsed thoroughly with distilled water, andgerminated between wrapped germination papers. Three 3-d-old seedlings weretransplanted in each pot of soil and distilled water was added. Water was addedmanually every other day initially and daily after about one week to provideadequate water for plant growth, to prevent splashing on leaves/stalk, and to preventleaching from pots. Pots were arranged in completely randomized blocks withfour replications.

Plants were grown 28 d in a greenhouse (March) with added artificial light(high pressure sodium halide 1000-watt lamps) to provide 16 h day lengths. Theexperiment was terminated by severing shoots from roots, and shoots were driedat 60°C and weighed. Soil was shaken from roots [representative soil sampleswere saved for pH and electrical conductivity (EC) determinations] and rootswere thoroughly rinsed with water to remove adhering soil. Roots were blotteddry, cut into 1-2 cm segments, and ~2 g subsamples were collected for total RLdetermination using a Comair RL scanner (Commonwealth Aircraft Corp. Ltd.,Melbourne, Australia1 ). Remainder of roots were dried and weighed, as were

1Mention of company or commercial products does not imply recommendation orendorsement by the U. S. Department of Agriculture over others not mentioned.

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1776 CLARK ET AL.

TABLE 1. Properties of acid Porters and Lily soils before addition of lime and growth ofmaize.

Property/element

Sand

Silt

Clay

Organic matter

pHw (soil.HjO, 1:1)

pHc. (Soil:0.01 AfCaCI,, 1:1)

Electrical conductivity (EC)

Exch. acidity (1 M NH40Ac extr.)

Exch. AI (1 M KCI extr.)

Effective cation exchange capacity (CEO

Effective AI saturation

P (Bray-I extr.)

S (1 M NH4OAc extr.)

Cations (1 M NH40Ac extr.)

Ca

K

Mg

Na

Cations (0.005 M DTPA extr.)

Mn

Fe

Zn

Cu

Unit

%

%

%

%

dSm"1

cmol kg"'cmol kg"1

cmol kg"'

%

Mg"1

WO'*

cmol kg"'

^flg-'

Porters

81

14

5

3.91

4.50

4.210.09

5.71

4.89

6.45

76

2.33

83.4

0.270

0.144

0.117

0.205

4.0

86.0

1.20

0.09

Uly

63

31

7

5.02

4.82

4.570.08

3.022.55

3.97

65

4.00

66.9

0.280

0.146

0.081

0.391

60.2

33.5

2.81

0.11

roots used for total RL determination. Other parameters calculated from DM andRL data were shoot/root DM ratios, specific RL (total RL/root DM; m-g-1), andshoot DM/RL (mg-m1)-

Dried shoot samples were ground (0.5 mm screen), representative samplesweighed (50 to 100 mg) into teflon containers, and digestion solution (1.7 mL15.8 M HNO3+0.2 mL 11.4 M HC1+0.1 mL 28.9 M HF) was added. The tefloncontainers with plant tissue and digestion solution were placed in microwave

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GROWTH TRAITS OF MAIZE HYBRIDS 1777

TABLE 2. Maize hybrids grown on unlimed and limed acid Porters and Lily soils.

Hybrid No. Hybrid name/description/origin

1 B73 x Mo17: Open pedigree; developed from inbreds B73(Iowa) and Mo17 (Missouri)

2 BR2O1: Developed by EMBRAPA, Brazil (double cross hybrid)

3 Crow 445: UN t

4 Golden Harvest H2343: UN

5 HD 91102: Developed by EMBRAPA, Brazil (HD = double crosshybrid)

6 HD 9176: Developed by EMBRAPA, Brazil (HD = double crosshybrid)

7 Jacques 7770: UN

8 NC+ 5963: UN

9 PA329 x PA353P: Open pedigree; developed from inbredsPA329 and PA353P (both from Pennsylvania)

10 Pioneer 3362: UN

11 Pioneer 3394: UN

12 Pioneer 3592: UN

_13 Wilson 1660: UN

tUN = origin unknown.

digestion bombs (Parr Instrument Co., Moline, IL) and micro waved 2 min at fullpower (635-W delivered) then 4 min at 70% power, and allowed to cool in themicrowave 5 min before being removed to cool to ambient temperature (30 min).Digested solutions were transferred to 10.0 mL volumetric flasks and brought tovolume with distilled deionized water. Solutions were filtered and stored at -10°Cuntil analyzed by inductively coupled plasma (ICP) spectroscopy.

Data were statistically analyzed using analyses of variance procedures in aGeneral Linear Model of SAS (SAS Users Guide, 1989). Differences amongmeans for hybrids, soils, and liming treatments were evaluated using probabilitiesof significance and LSD values (P=0.05).

RESULTS AND DISCUSSION

Many treatment and interaction effects were significant for growth traits andmineral elements (Table 3). Porters soil generally had lower pH than Lily soil

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TABLE 3. Probabilities of significance and coefficient of variation (CV) for growth traits and mineral concentrations of maize hybrids ^grown on unlimed and limed acid Porters and Lily soils.

Soli Lime GenotypeGrowth trait/Element (S) (L) (G) S x L L x G S x G S x L x G CV (%)

.. .« •• .. . 1 4

. . . • 32• . . . . . . . 20

• . 34• • .. •• 28.. .. .. •• 29

•• • 57. . . . •• 18

19.. .. .• 32

.• .. •• .. .. 21

.. .. .. •• .. 8

.. .. .• 31

• • •• •• 20

24 g

Si- «t* and **= significance at P<0.05 and P<0.01, respectively. ^

Shoot DMRoot DMShoot/root DM ratioTotal RLSpecific RLShoot DM/RL

AlPSBSi

KCaMg

MnFeZnCu

. . t* tt

« t t

tt»

tt«

• •

• •

. .

• •

• "

• •

• •

• •

• •• •

• •

• •

* •

• •

• •

• •

• •

• •

• •

• «

• •

•

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GROWTH TRAITS OF MAIZE HYBRIDS 1779

TABLE 4. The pH and EC of unlimed and limed Porters and Lily soils after plants hadbeen grown.

Soil trait

p H w (soil:water, 1:1)

pHCa (soil:O.O1 M CaCI2, 1:1)

EC (soil:water, 1:1) dS m~1

PortersUnlimed

4.68

3.78

0.060

Limed

5.36

4.72

0.087

Unlimed

4.76

3.88

0.060

Lily

Limed

5.77

5.10

0.093

(Table 4). Mean soil pHw and pHCa after plant growth was 4.72 and 3.83,respectively, for unlimed and 5.57 and 4.91, respectively, for limed Lily and Porterssoils. Mean EC over both soils was 0.06 dS m 1 for unlimed and 0.09 dS m 1 forlimed soil, with similar values for Porters (0.074 dS m1) and Lily (0.076 dS m1)soils over lime treatments (Table 4).

Plants had higher shoot and root DM and total RL when grown on Lily comparedto Porters soil, whether unlimed or limed (Figures 1, 2, and 3). Both shoot androot DM over all hybrids increased similarly (~3.4-fold) when plants were grownon limed compared to unlimed Porters soil, while root DM had greater increasesthan shoot DM when plants were grown on limed (3.8-fold) compared to unlimed(2.4-fold) Lily soil (Figures 1 and 2). Differences in root DM were generallygreater than differences in shoot DM. Because of similarities in shoot and rootDM increases for plants grown on unlimed and limed Porters soil, shoot/root DMratio did not change, while shoot/root DM ratios of plants grown on unlimed Lilysoil were higher (1.70) than for plants grown on limed Lily soil (1.11) to indicaterelatively large changes in root DM of these plants (Table 5).

Results from these growth traits indicated that the Porters soil induced greateracidity stress on plants than did the Lily soil. The stress was most likely causedby Al toxicity since Porters soil had higher initial exchangeable Al and lower pHthan Lily soil (Table 1), and soil pH did not rise as high from added lime onPorters as on Lily soil (Table 4). However, shoot mineral concentrations indicatedthat the high Mn (Table 8) could also have been a toxicity factor for maize grownon these soils.

Maize hybrids used in our study were chosen to represent variations ofadaptability to soil environments, especially from different regions of the UnitedStates. Hybrids represented those grown in eastern states of the United States(Nos. 9 and 12), Corn Belt states of the United States (Nos. 1, 7, and 11), GreatPlains states of the United States (Nos. 3,4, 8, 10, and 13), and central states ofBrazil (Nos. 2, 5, and 6). The Brazilian hybrids HD 91102 and HD 9176 hadhighest shoot and root DM and total RL values of all hybrids grown on unlimed

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1780 CLARK ET AL.

Porters soil

cJOa.O>

QSo

a.o

8rr2 3 4 5 6 7 8 9 10111213 1 2 3 4 5 6 7 8 9 10111213

Hybrid numberUnlimed Limed

FIGURE 1. Shoot and root dry matter (DM) of maize hybrids grown on unlimed andlimed acid Porters soil [I=LSD (P-0.05)]. See Table 2 for names of hybrids represented bynumbers.

acid soil, but this advantage did not appear when these hybrids were grown onlimed soil. The Brazilian hybrid BR 201 response was similar to that of manyUnited States hybrids. The Brazilian hybrid BR 201 has received extensiveacceptance for production on Brazilian acidic soils (Magnavaca and Bahia Filho,1993, 1996). Only limited separation could be made among the United Stateshybrids relative to DM when plants were grown on these acid soils.

Total RL increased 7.2-fold for plants grown on limed compared to unlimedPorters soil, while total RL increased only 4.0-fold for plants grown on limedcompared to unlimed Lily soil (Figure 3). Hybrids did not respond similarly forshoot and root DM and total RL when grown on unlimed compared to limed soil.For example, HD 91102 and HD 9176 had the highest shoot and root DM andtotal RL when grown on both unlimed soils, but not when grown on the limedsoils. Specific RL was higher for the genotypes grown on limed compared tounlimed Porters soil (2.2-fold increase), but were similar for plants grown onunlimed and limed Lily soil (Figure 4). Differences in specific RL among hybridswere larger for plants grown on unlimed compared to plants grown on limed soil.

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GROWTH TRAITS OF MAIZE HYBRIDS 1781

Lily soil

Q.O)

8

Q .

CD

E

1500

1200

900

600

300

0

300

600

900

1200

15001 2 3 4 5 6 7 8 9 10111213 1 2 3 4 5 6 7 8 9 10111213

.. ,. . Hybrid number , . .Unlimed Limed

FIGURE 2. Shoot and root dry matter (DM) of maize hybrids grown on unlimed andlimed acid Lily soil [I=LSD (P=0.05)]. See Table 2 for names of hybrids represented bynumbers.

Differences in total RL were greater among hybrids than were shoot and rootDM. Root growth is normally affected considerably when plants are grown withAl in solutions/sand or on many acid soils (Taylor, 1989), and this trait is widelyused to identify and evaluate plants for tolerance to acid soils (Foy, 1992),especially maize (Magnavaca and Bahia Filho, 1993; Urrea-Gómez et al., 1996).Good relationships were noted between relative seminal root length and grainyield for maize grown on Brazilian acidic soils (Magnavaca and Bahia Filho,1993), and relatively good relationships were also noted between various maizeroot length measurements and growth on Colombian acidic soils (Urrea-Gómezet al., 1996). Other studies with both maize and sorghum [Sorghum bicolor (L.)Moench] showed seminal and auxiliary root lengths to be good traits compared toDM for evaluating plant tolerance to Al(Furlani and Clark, 1981,1987; Magnavacaetal., 1987a, 1987b, 1987c).

Morphological traits like specific RL are sometimes preferred to developmentaltraits like total RL to evaluate plants for root growth constraints (Keltjens, 1987;Tan et al., 1992). High specific RL indicates small diameter, fine, and highly

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1782 CLARK ET AL.

140 Porters soil

1 2 3 4 5 6 7 8 9 10111213 1 2 3 4 5 6 7 8 9 10111213

Hybrid numberUnlimed soil Limed soil

FIGURE 3. Total root length of maize hybrids grown on unlimed and limed acid Portersand Lily soils [I=LSD (P=0.05)]. See Table 2 for names of hybrids represented by numbers.

TABLE 5. Shoot/root dry matter ratios of maize hybrids grown on unlimed and limedacid Porters and Lily soils.

Hybrid No t

1

2

3

4

5

6

7

8

9

10

11

12

13

Porters sou

Unlimed

1.04

1.23

1.23

1.23

0.6S

0.67

0.92

1.07

0.72

0.91

1.09

0.98

1.06

Umed

0.99

1.01

1.28

1.18

0.87

0.72

1.12

1.47

0.87

0.87

1.01

1.28

0.93

Uly soil

Unlimed

1.64

1.32

1.86

.82

1.25

1.41

1.69

1.73

1.66

1.53

2.01

1.78

2.36

Umed

1.45

0.87

1.29

1.07

0.96

0.97

1.31

0.89

1.19

1.10

1.20

1.05

1.03

fSee Table 2 for names of hybrids represented by numbers.

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GROWTH TRAITS OF MAIZE HYBRIDS 1783

.. Porters soil

cMoS

1a.

2 3 4 5 6 7 8 9 10111213 1 2 3 4 5 6 7 8 9 1011 1213

Hybrid numberUnlimed soil Limed soil

FIGURE 4. Specific root length of maize hybrids grown on unlimed and limed acidPorters and Lily soils {I=LSD (P-0.05)]. See Table 2 for names of hybrids represented bynumbers.

branched roots while low specific RL indicates large diameter, stubby, and poorlybranched roots. Lime added to acid soils may help alleviate acid soil toxicity andimprove root growth, and should enhance fine and highly branched roots. Higherspecific RL for plants grown on limed compared to unlimed Porters soil indicatedthat root morphology was improved when lime was added to this soil. However,specific RL was similar for plants grown on limed or unlimed Lily soil, whichindicated that Lily soil did not induce as much acid soil stress on these maizehybrids as did Porters soil. The specific RL trait may not have been important tothe acid soil-tolerant Brazilian hybrid DH 91102, since this hybrid had the lowestspecific RL of all hybrids grown on unlimed Lily soil and had a moderate valuewhen grown on unlimed Porters soil. In addition, acid soil-tolerant HD 91102had the lowest specific RL of all hybrids when grown on both limed acid soils.

Shoot DM/RL was higher for plants grown on unlimed than on limed soil, anddifferences among hybrids were greater for plants grown on unlimed than onlimed soil (Figure 5). The Pioneer 3394 hybrid stood out as having the highestshoot DM/RL when grown on both limed and unlimed Lily soil. The amount ofshoot (above ground) tissue that roots must support (shoot DM/RL) may beimportant in assessing plant tolerance to acid soil problems. Roots of acid soil-tolerant Brazilian hybrids HD 91102 and HD 9176 grown on unlimed Porters soil

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1784 CLARK ET AL.

E

E

oo

Porters soil

1 2 3 4 5 6 7 8 9 10 1112 13 1 2 3 4 5 6 7 8 9 1011 1213

Hybrid numberUnlimed soil Limed soil

FIGURE 5. Shoot dry matter (DM)/root length of maize hybrids grown on unlimed andlimed acid Porters and Lily soils [I=LSD (P-0.05)]. See Table 2 for names of hybridsrepresented by numbers.

had the least amount of shoot tissue per unit RL to support, while some otherhybrids had considerably more shoot tissue to support. For example, Pioneer3394 had the highest shoot DM/RL when grown on both limed acid soils andunlimed Lily soil, and among the highest value for plants grown on unlimed Porterssoil. This hybrid also had the lowest or among the lowest total RL values for thehybrids tested.

Plants grown on Porters soil had overall higher shoot concentrations of Al,sulfur (S), boron (B), calcium (Ca), magnesium (Mg), manganese (Mn), iron (Fe),zinc (Zn), and copper (Cu), lower concentrations of potassium (K), and similarconcentrations of phosphorus (P), and silicon (Si) compared to plants grown onLily soil (Tables 6, 7, and 8). When soils received lime treatments, shootconcentrations of Al, S, B, Si, K, Mn, Zn, and Cu were lower and Ca and Mg werehigher for plants grown on limed compared to unlimed soil. Shoot P and Feconcentrations were both lower for plants grown on unlimed compared to limedPorters soil, and higher for plants grown on unlimed compared to limed Lily soil.The elements to change the most between limed and unlimed soil were Mg (4.3-fold), Mn (4.1-fold), Si (2.2-fold), Zn (2.1-fold), and Ca (1.8-fold). Most mineralelements had relatively normal coefficients of variation (CVs) (<35%) in thisexperiment, but considerably high CVs were noted for Al, Fe, and Cu (Table 3).

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TABLE 6. Concentrations of Al, P, S, and B in shoots of maize hybrids grown on unlimed (U) and limed (L) acidic Porters (Port) andLily soils.

Element

AI

M í '

P

mg g"1

Smg g '

B

Soil

Port

Uly

Limetreat

ULUL

LSD (0.05)

Port

Uly

ULUL

LSD (0.05)

Port

Uly

ULUL

LSD (0,05)

Port

Uly

ULUL

LSD (0.05)

1

282155198115

2.584.684.173.82

5.725.355.024.15

60.652.066.034.0

2

28917114190

3.623.724.253.48

4.453.623.803.11

79.942.629.934.3

3

249316271

62

2.484.853.752.37

5.454.874.442.69

74.443.855.822.3

4

247332257124

2.554.724.632.59

4.634.294.782.76

53.243.159.532.4

5

275226176130

2.344.314.842.96

3.413.834.453.17

53.862.847.431.1

Hybrid number t

6

366228215101

2.274.374.202.87

3.574.224.263.15

70.070.859.735.8

7

26417018590

162

2.665.145.473.570.98

7.026.477.524.971.23

57.051.640.632.723.9

8

23217111668

2.695.294.043.23

6.045.205.103.84

66.145.723.030.8

9

31112218294

3.105.374.972.77

5.624.635.042.92

106.722.770.730.9

10

42031719491

4.174.044.432.94

6.444.594.973.50

130.880.358.039.7

11

262273208

95

3.005.034.852.70

3.695.494.972.88

68.964.961.235.2

12

265239216109

2.655.045.552.81

6.025.626.803.27

88.964.077.132.0

13

22618611191

2.524.545.263.03

4.504.485.073.39

69.543.551.629.1

Mean

28426119097

2.824.704.653.01

5.124.825.103.37

75.456.753.932.3

tSee Table 2 for names of hybrids represented by numbers.

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TABLE 7. Concentrations of Si, K, Ca, and Mg in shoots of maize hybrids grown on unlimed (U) and limed (L) acidic Porters (Port) andLily soils.

j

<3\

Element

Simgg"1

K

mgg"1

Camgg 1

Mg

mgg 1

Soil

Port

Uly

Urnetreat

U

LU

LLSD (0.05)

Port

Uly

LSD

Port

Uly

LSD

Port

Uly

ULU

L(0.05)

U

LUL

(0.05)

U

L

U

LLSD (0.05)

1

14.5

5.2

19.04.2

57.457.2

65.159.4

2.0814.10

2.689.58

1.516.180.94

4.85

2

13.45.0

20.34.5

57.647.0

58.755.8

1.8511.44

3.229.41

2.16

6.28

0.97

5.40

3

12.916.2

18.72.3

60.756.1

56.047.9

2.0811.03

2.376.00

1.46

5.15

0.763.02

4

10.9

13.2

18.5

3.3

55.055.758.2

47.5

1.6410.67

2.546.71

1.36

5.42

0.97

4.09

5

13.3

5.320.1

4.2

54.151.961.957.6

1.6011.52

3.438.26

1.47

6.05

1.05

5.28

Hybrid number

6

13.6

7.219.94.4

58.554.763.2

59.3

1.8713.SS

3.198.62

1.29

7.920.99

5.65

7

11.35.1

20.312.22.3

56.754.1

56.5

51.26.6

2.0313.10

3.229.19

2.63

1.66

6.99

1.14

5.61

0.90

t

8

11.85.4

18.64.1

55.9

57.8

64.749.6

1.8511.87

2.437.83

1.48

5.570.80

4.00

9

10.7

16.818.5

3.2

53.355.4

62.149.6

7.6012.17

2.516.96

1.57

5.63

0.87

3.66

10

13.5

11.1

19.03.7

45.1

55.259.259.3

2.4210.95

2.857.42

2.10

7.481.06

5.07

11

8.617.8

18.43.4

51.2

57.263.949.7

2.00

7.862.064.83

1.85

5.830.94

3.88

12

14.217.6

19.3

4.0

58.5

57.964.561.1

1.7911.79

2.345.95

1.31

7.070.92

4.43

13

12.2

4.318.4

4.3

56.155.468.448.4

1.6012.04

2.398.51

0.98

5.710.82

4.46

Mean

12.410.0

19.2

4.4

55.2

55.161.753.6

2.3411.70

2.717.64

1.56

6.25

0.94

4.57

fSee Table 2 for names of hybrids represented by numbers.

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TABLE 8. Concentrations of Mn, Fe, Zn, and Cu in shoots of maize hybrids grown on unlimed (U) and limed (L) acidic Porters (Port) andLily soils.

Element

Mn

rao'1

Fe

va a*

Zn

^gg'1

Cu

Soil

Port

Lily

LSD

Port

Lily

Limetreat

U

LU

L(0.05)

ULU

LLSD 10.05)

Port

Lily

LSD

Port

Lily

ULU

L

(0.05)

U

L

U

L

LSD (0.05)

1

1376

4841021

156

293

364291214

89.4

47.578.0

32.1

27.1

19.3

23.2

12.3

2

1311

3731127

144

243

285176

166

94.639.4

74.929.7

43.9

20.7

17.6

18.4

3

1444

400

802100

259

311263

112

100.3

44.9

71.9

19.6

40.8

45.4

26.18.4

4

1137

349933114

234318291

141

71.9

47.7

74.6

33.4

22.4

17.6

16.6

12.7

5

1080

3921176

172

230

363266330

57.839.1

72.2

34.7

26.7

24.2

16.9

13.9

Hybrid number t

6

1139

4691182

153

263445204

183

81.0

49.672.7

28.4

29.028.0

17.1

14.7

7

1430

3561052

132268

273

271336164

247

87.348.590.4

31.9

32.7

33.630.1

16.0

13.834.2

8

1394

404

928134

296352275194

91.443.0

73.1

32.5

37.5

24.0

21.6

13.3

9

1502

425890122

346234

205130

98.635.0

71.126.8

52.622.3

16.9

11.3

10

1543

385T089

130

417403261

190

92.8

63.088.7

30.6

46.1

52.0

37.8

11.3

11

639

627

75088

250

440279

141

69.3

87.062.0

30.5

50.5

33.1

22.1

11.2

12

1389

458

916118

257

347279167

85.557.3

93.8

35.1

21.2

31.5

31.0

14.9

13

1233

414

936126

260290301

152

112.9

36.470.6

29.3

47.828.7

24.3

15.6

Mean

1278

426985130

279

394264

176

87.149.1

76.5

30.4

39.2

32.3

22.1

13.2

fSee Table 2 for names of hybrids represented by numbers. vj00<1

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1788 CLARK ET AL.

The Al concentrations in shoots of the genotypes grown on unlimed soils,especially Porters, indicated that Al might have been near toxic levels in maize(-400 ug-g'1, Reuter, 1986). The mean shoot Al concentration over all genotypesgrown on unlimed Porters soil was 284 ug-g"1, and one genotype had >400 ug-g'1

in shoots (Table 6). Shoot Al concentrations for plants grown on limed Porterssoil were higher (mean of 261 ug-g'1) than for plants grown on unlimed Lily soil(mean of 190 ug-g'1), and were even lower for plants grown on limed Lily soil (97ug-g"1). Shoot Al concentrations did not appear to be sufficiently high to indicateAl toxicity in the plants grown on the Lily soil, but may have been a toxicityfactor to maize grown on Porters soil. The effects of Al on acquisition of othermineral nutrients and interactions of other minerals with Al are important.Aluminum normally reduces concentrations of P (Cambraia and Calbo, 1980;Kesser et al., 1975), K (Alam, 1983; Gerzabek and Edelbauer, 1986), Ca (Clark,1977), Mg (Alam, 1983; Clark, 1977; Gerzabek and Edelbauer, 1986), and Zn(Cambraia et al., 1983), and Al also appears to be inactivated by P (Clarkson,1986), Ca (Furlani and Clark, 1981; Kinraide et al., 1987), Mg (Pavan andBingham, 1982; Taylor and Foy, 1985; Baligar et al., 1987), and Si (Galvez andClark, 1991; Peaslee and Frink, 1969; Clements et al., 1967).

The shoot P concentrations in some maize genotypes were approaching a criticallevel of 2.2-2.6 mg-g'1 for deficiency (Reuter, 1986) grown on unlimed Porterssoil (Table 6). Shoot P concentrations in plants grown on soils with the othertreatments were not as low as those noted for the unlimed Porters soil. Phosphorusdeficiency on maize was noted in other studies using unlimed Porters soil withoutadded P (Clark et al , 1995). Liming had no effect on S in shoots over unlimedsoil for plants grown on Porters soil, but shoot S concentrations were lower inplants grown on limed compared to unlimed Lily soil (Table 6). Increased levelsof Al had no significant effect on shoot S concentrations in sorghum (Bernai andClark, 1997). The lower shoot B concentrations for plants grown on limedcompared to unlimed soil (Table 6) were as might be expected with the conceptthat B acquisition is reduced as soil pH increases (Clark, 1982; Marschner, 1995).

Shoot Si concentrations were higher in plants grown on unlimed than on limedPorters and Lily soils (Table 7). The high shoot Si concentrations were normalfor plants (Werner and Roth, 1983; Clark et al., 1990; Flores et al., 1991). Overallshoot K concentrations in plants grown on Porters and Lily soils were comparable,but K was lower in shoots of plants grown on limed compared to unlimed Lilysoil (Table 7). Soil K levels were sufficient to provide adequate K to plants abovea critical concentration of 20-25 mg-g1 for deficiency (Reuter, 1986). Bothdecreased and increased concentrations of K in shoots of plants grown with toxicAl in solution or on acidic soils have been reported (Alam, 1983; Andrew et al.,1973; Baligar et al., 1993a, 1993b; Gerzabek and Edelbauer, 1986; Lee, 1971).

Shoot concentrations of both Ca and Mg were considerably lower for plantsgrown on unlimed compared to limed soils (Table 7). Increased Ca and Mg inshoots of plants grown on limed soil would be expected since both CaCO3 and

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GROWTH TRAITS OF MAIZE HYBRIDS 1789

Mg(OH)2 were added. Calcium in shoots of several genotypes grown on bothunlimed soils was approaching a critical concentration of 1.0-2.0 mgg 1 fordeficiency (Reuter, 1986). Many studies concerned with Ca acquisition in plantsgrown with Al in solution or on unlimed acidic soils report low Ca (Foy, 1992;Taylor, 1989). Magnesium deficiency has been noted frequently when maize isgrown on both unlimed Porters and Lily soils (R.B. Clark and S.K. Zeto, 1995,personal observations). To remedy Mg deficiency symptoms on plants grown onthese soils, Mg needs to be added or the soil pH must be increased considerably.Magnesium concentrations in shoots of the plants grown on these unlimed soilswere approaching a deficiency critical concentration of ~ 1.0 mg-g1 (Reuter, 1986),and the mean shoot Mg concentration for the genotypes grown on unlimed Lilysoil was 0.94 mg-g1 (below the deficiency critical concentration). Other studiesusing unlimed Porters soil noted Mg deficiency symptoms to appear when maizeshoot Mg concentrations were -0.75 mg-g"1 (Clark et al., 1997). The change inMg between unlimed and limed soils was the greatest of the elements determined.In addition, Mg was the most affected element in maize grown with Al in solution(Clark, 1977), and other studies have reported reduced Mg acquisition in plantsgrown with Al or on acidic soil (Alam, 1983; Gerzabek and Edelbauer, 1986;Lee, 1971; Pavan and Bingham, 1982).

Manganese, Fe, and Zn are normally considerably higher and Cu usuallysomewhat higher in shoots of plants grown on unlimed compared to limed soils(higher pH) (Clark, 1982). Similar results were noted in our study, although Fedecreases were not large for plants grown on limed Porters compared to limedLily soil, and pH increased relatively little from added lime to Porters soil. Plantsgrown on unlimed Porters soil had higher Mn and Cu and relatively comparableZn compared to plants grown on unlimed Lily soil. Shoot concentrations of Mn,Fe, Zn, and Cu were on the high side for sufficiency (Reuter, 1986). Manganeseconcentrations were sufficiently high in the shoots of these maize plants to beconcerned with potential Mn toxicity. Even with the high shoot Mn in plantsgrown on unlimed soil, Si was also high in shoots of these plants; Si has beenreported to alleviate or decrease Mn toxicity symptoms in plants (Horst andMarschner, 1978; Galvezetal., 1989).

The genotypes differed considerably in shoot concentrations of the mineralelements, and no pattern emerged for any particular genotype or classification ofgenotypes (originating from different regions of the United States) having relativelyhigh or low concentrations of a given element (Tables 6, 7, and 8). Mineralelement concentrations did not appear to be good traits to assess maize genotypesfor differential tolerance to soil acidity.

CONCLUSIONS

The hybrids used in our study had wide differences in shoot and root DM, totalRL, specific RL, and shoot DM/RL when grown on unlimed and limed acid soils.

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1790 CLARK ET AL.

The hybrids had wider differences in root DM than in shoot DM, while hybriddifferences for total RL were wider than any of the growth traits measured. Porterssoil induced greater acid soil stress than Lily soil. Differences in tolerance to acidsoils among these hybrids relative to growth traits were relatively small, exceptfor two Brazilian hybrids (HD 91102 and HD 9176), which generally had highestshoot and root DM, total RL, and lowest shoot DM/RL. Brazilian hybrids had thebest growth trait evaluations considered important to acid soil tolerance. TheUnited States hybrids had relatively similar but lower tolerance to acid soils eventhough they are commonly grown on or adapted to wide ranges of environmentalconditions (e.g., relatively arid high pH Great Plains states soils versus near neutralpH Corn Belt states soils and relatively low pH eastern states soils). Deficiencyof Ca and Mg and toxicity of Al and Mn were of concern for maize grown onthese unlimed soils, and shoot mineral element concentrations were not goodtraits to evaluate maize hybrids for tolerance to acid soils.

ACKNOWLEDGMENTS

Preparation of figures by Ms. S.S. Boyer is greatly appreciated.

REFERENCES

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Alam, S.M. 1983. Effect of aluminum on the dry matter and mineral content of rice. J.Sci. Tech. 7:1-3.

Andrew, C.S., A.D. Johnson, and R.L. Sandland. 1973. Effect of aluminum on the growthand chemical composition of some tropical and temperate pasture legumes. Aust. J.Agric. Res. 24:325-339.

Bahia Filho, A.F.C., G.E. de Franca, G.V.E. Pitta, R. Magnavaca, J.F. Mendes, F.T.F.G.C.Bahia, and P. Pereira. 1978. Avaliacao de linhagens e populacoes de milho em condicoesde elevada acidez (Evaluation of lines and populations of maize in highly acidconditions), pp. 51-58. In: E. Paterniani (ed.), Proceedings of the XI Annual BrazilianMaize and Sorghum Conf., Dept. of Genetics, 'Louis de Queiroz' AgriculturalUniversity, Piracicaba, S.P., Brazil (in Portuguese).

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Clark, R.B., C.I. Flores, L.M. Gourley, and R.R. Duncan. 1990. Mineral elementconcentrations and grain yield of sorghum (Sorghum bicolor) and pearl millet(Pennisetum glaucum) grown on acid soil, pp. 391-396. In: M.L. van Beusichem(ed.), Plant Nutrition—Physiology and Applications. Kluwer Academic Publishers,Dordrecht, The Netherlands.

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GROWTH TRAITS OF MAIZE HYBRIDS 1793

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