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Group Title: Research report - North Florida Research and Education Center ; 87-8
Title: Relative availability of three mg sources to corn and soybean
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Permanent Link: http://ufdc.ufl.edu/UF00066063/00001
 Material Information
Title: Relative availability of three mg sources to corn and soybean
Series Title: Research report (North Florida Research and Education Cener (Quincy, Fla.))
Physical Description: 8 leaves : ill. ; 28 cm.
Language: English
Creator: Rhoads, Fred ( Frederick Milton )
North Florida Research and Education Center (Quincy, Fla.)
Publisher: North Florida Experiment Station
Place of Publication: Quincy Fla
Publication Date: 1987
 Subjects
Subject: Soybean -- Fertilizers -- Florida   ( lcsh )
Corn -- Fertilizers -- Florida   ( lcsh )
Genre: bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Includes bibliographical references.
Statement of Responsibility: by F.M. Rhoads.
General Note: Caption title.
 Record Information
Bibliographic ID: UF00066063
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 71050896

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P06~f


Relative Availability of Three Mg Sources

to Corn and Soybean






F. M. Rhoads








University of Florida
North Florida Research and Education Center
Route 3 Box 4370
Quincy, Florida 32351


slB









Relative Availability of Three Mg Sources to Corn and Soybean!/
F. M. Rhoads"/

ABSTRACT

Dolomite and magnesium sulfate are widely used sources of

fertilizer Mg consequently there is little information available

on plant uptake of Mg from magnesia (MgO). The main objective of

this experiment was to determine relative Mg uptake from

Dolomite, MgSO4, and MgO by corn and soybean. Corn and soybean

were grown in greenhouse pots and supplied with 0, 50, and 100 mg

kg-I of Mg from the above sources. Dry-matter yield, Mg concen-

tration, and Mg content of shoots were determined after five and

seven weeks of growth of corn and soybeans respectively. Dry-

matter yield of soybean was not influenced by any of the Mg

sources. Corn dry-matter yield was increased by MgO only. All

Mg sources increased tissue concentration of Mg in both corn and

soybean. The 50 mg kg-1 Mg rate was as effective as the 100 mg

kg-1 rate in all cases for total Mg uptake. Magnesia was as

effective in supplying Mg to corn and soybean as dolomite and

MgSO4.

Additional Index Words: Dolomite, magnesium sulfate, magnesia,

MgO, MgSO4, Mg uptake, Dry-matter yield.

Cost and ability to obtain a particular material are

important factors when determining the source of fertilizer



!/North Florida Research and Education Center Research Report No.

87-8.

2/Professor of Soil Science, North ?lorida Resrch nd Zd:: in

Center, Quincy, University of Florida.








magnesium (Mg) to use in crop production. However, availability

of Mg to the crop after it is applied to the soil may alter the

cost:return ratio for a particular crop.

Dolomite is generally used as a source of liming material

which also supplies calcium (Ca) and Mg (11%). When lime is not

needed, dolomite may be considered as a source of Mg based on its

Mg content. Dolomite will have very little influence on soil pH

when applied in amounts required for Mg needs of most crops.

Magnesium sulfate can be purchased in several forms, among

them are epsom salts (10% Mg) and dehydrated MgSO4 (20% Mg)

(Berg. 1986). Both compounds are highly soluble in water. Cost

per lb of Mg is usually higher for MgSO4 than for other forms of

Mg fertilizers.

Magnesia (MgO) is about 56% Mg and not as soluble as MgSO4,

but it is usually less expensive per unit of Mg. Some specialty

fertilizers contain MgO but it is seldom used as a Mg source in

general crop production.

Objectives of this experiment were to determine relative Mg

uptake from Dolomite, MgSO4, and MgO by corn and soybean and

determine the effect of these Mg sources on dry matter

production.
METHODS

Corn and soybean were seeded in 0.2 m diameter greenhouse

pots containing 3.2 kg of soil on 1 May 1986. Dolomite, MgSO4,

and MgO were added in amounts to supply approximately 50 and 100

mg of Mg kg-1 of soil. Seven treatments consisting of two levels

of Mg from each source and a control with no Mg added were

replicated five times for both corn and soybean. In addition to









the Mg source, each pot of soil was mixed with 0.5 g of triple

super phosphate (46% P20 ), 1.0 g of K2SO and 3 g of calcitic

lime. Each pot of soil containing corn was supplied with 1.0 g

of ammonium nitrate after the plants emerged.

Corn shoots were harvested 5 June 1986 and soybean shoots

were harvested 17 June 1986. Plant tissue was dried to constant

weight at 700C and weighed to determine dry matter production.

The dry tissue was ground and ashed for Mg determination on an

atomic absorption spectrophotometer.

Soil samples were taken from each pot after harvest,

extracted with Mehlich I extractant (double acid), and analyzed

for Mg on an atomic absorption spectrophotometer.

The experimental design was a randomized complete block.

Analysis of variance procedures and single degree of freedom

comparisons were used to identify treatment differences.

RESULTS AND DISCUSSION

Magnesium source or rate did not influence dry-matter yield

of soybean (Table 1), but MgO increased corn dry-matter by

approximately 29%. Dolomite and MgSO4 did not increase

dry-matter yield of corn in comparison to the zero Mg treatment

(Table 1).

All Mg sources increased tissue concentration of Mg above the

zero Mg treatment in both corn and soybean (Table 2). There were

no significant differences between Mg sources regarding their

influence on Mg concentration in soybean tissue (Table 2).

Dolomite was not as effective as MgO and MgSO, for increasing Mg

annncradcn in -as e ec .-e as he i mg kg f aSO

and MgO was nct as effective as the 100 mg ka-i race for








Table 1. Effect of magnesium (Mg) source on dry-matter (DM)
yield of corn and soybean in greenhouse pots.

Mg
Source rate Corn Soybean

mg kg1 ----------g pot-1

Check 0 11.8 a' 9.2 a
MgSO4 50 11.3 a 8.7 a
MgSO4 100 12.1 a 7.7 a
Dolomite 50 12.2 a 9.2 a
Dolomite 100 11.3 a 9.9 a
MgO 50 15.1 b 10.7 a
MgO 100 15.2 b 8.6 a


Means within columns followed by the
icantly different (P>0.05).


same letter are not signif-


Table 2. Effect of magnesium (Mg) source on Mg concentration of
corn and soybean tissue grown in greenhouse pots.


Mg
Source rate Corn Soybean


mg kg ---------g kg1----------

Check 0 2.3 a' 2.5 a
MgSO4 50 2.9 c 3.2 bI
MgSO4 100 3.4 3.5
Dolomite 50 2.5 bi 3.2 bI
Dolomite 100 2.8 3.2
MgO 50 2.8 c 3.2 bl
MgO 100 3.1 3.5


Means within columns followed by the same letter are not signif-
icantly different (P>0.05). Letters indicate differences be-
tween sources and vertical lines indicate no difference between
rates within sources.









increasing tissue Mg concentration in corn. However, 50 mg kg-"

of Mg from all sources was as effective for increasing Mg con-

centration in soybean as 100 mg kg-.

Total Mg uptake from all three sources was higher in both

corn and soybean than from the zero Mg treatment (Table 3).

However, the 50 mg kg-1 Mg rate was as effective as the 100 mg

kg-1 rate in all cases for total Mg uptake. Uptake of Mg by

soybean was about equal among sources (Table 3). Dolomite was

least effective for increasing Mg uptake by corn and MgO was most

effective. The higher Mg uptake by corn from MgO was due mainly

to increased plant size (Tables 1,2, and 3).

Soil-test Mg was increased by each source in proportion to

the amount applied (Table 4). All sources were equally effective

in increasing soil-test Mg. Regression analyses showed a highly

significant linear relationship between soil-test Mg and rates of

fertilizer Mg (Fig. 1 and 2). The quadratic component was not

significant (P > 0.10) A smaller proportion of the variation in

soil-test Mg was accounted for by fertilizer Mg in corn soil

samples than in soybean soil samples (Fig. 1 and 2). An increase

of 0.265 mg kg"1 soil-test Mg per unit of fertilizer Mg was pre-

dicted in corn soil samples (Fig. 1), while an increase of 0.309

mg kg-1 soil-test Mg per unit of fertilizer Mg was predicted in

soybean soil samples (Fig. 2). However, the slope of the regres-

sion line (soil-test Mg vs fertilizer Mg) for corn was not sig-

nificantly different from that of soybean (Steel and Torrie,

1960).










Table 3. Effect of magnesium (Mg) source on Mg content of corn
and soybean tissue grown in greenhouse pots.


Mg
Source rate Corn Soybean


mg kg- --------mg pot--------
Check 0 26.6 a' 23.1 a
MgSO4 50 32.6 cj 28.0 b
MgSO4 100 41.5 26.7
Dolomite 50 30.6 bI 29.0 b
Dolomite 100 31.6 31.0
MgO 50 41.8 dl 34.1 b
MgO 100 48.5 30.6


Means within columns followed by the same letter are not signif-
icantly different (P>0.05). Letters indicate differences be-
tween sources and vertical lines indicate no difference between
rates within sources.




Table 4. Effect of magnesium (Mg) source on soil test Mg after
harvest of corn and soybean in greenhouse pots.


Mg
Source rate Corn Soybean


--------------------mg kg------------------

Check 0 32 a' 38 a
MgSO4 50 41 b 52 b
MgSO4 100 55 69
Dolomite 50 48 b 49 b
Dolomite 100 56 67
MgO 50 48 b 49 b
MgO 100 65 67


Means within columns followed by the same letter are not signif-
icantly different (P>0.05). Letters indicate differences be-
tveen sources and vertical lines indicate no difference between
rates within sources.












S60-
-




50-





E-40

-,-4
o 30-
Cn


? 60-




4J 48-
tn
a)

,-I

o 36-
cn


R2= 0.511**


Y = 32.2 + 0.265X


I I I I I
0 20 40 60 80 100
Fertilizer Mg (mg kg- )

Fig. 1. Soil-test Mg as a function of
fertilizer Mg in soil samples taken
from pots where corn was grown.


R2= 0.782**


Y = 36.1 + 0.309X


Si 1 I I I
0 20 40 60 80 100

Fertilizer Mg (mg kg-1)

Fig. 2. Soil-test Mg as a function of
fertilizer Mg in soil samples taken
from pots where soybean was grown.




4 *


CONCLUSIONS

Dolomite is the best source of Mg for corn and soybean if the

soil pH is low (Usherwood and Miller, 1967). Magnesia (MgO) was

as effective in supplying Mg to corn and soybean as dolomite and

MgSO Therefore, MgO would be the best source of Mg for corn

and soybean when cost is favorable and lime is not needed. The

growth response of corn to MgO should be investigated further.



REFERENCES

1 Berg, G. L. 1986. Farm Chemicals Handbook. Meister

Publishing Co., Willoughby, OH.

2 Steel, R. G. D. and J. H. Torrie. 1960. Principles and

Procedures of Statistics. McGraw-Hill, New York. p.

173-174.

3 Usherwood, N. R. and J. R. Miller. 1967. Effect of soil pH

on the availability of magnesium to corn (Zea mays L.) from

magnesium sulfate and high magnesium liming materials. Soil

Sci. Soc. Amer. Proc. 31:390-393.




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