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 Title Page
 Abstract
 Introduction
 Materials and methods
 Results and discussion
 Summary
 Acknowledgements
 Reference






Group Title: Research report - North Florida Experiment Station, University of Florida - NF 87-3
Title: Phenological events of corn in relation to time of planting
CITATION PAGE IMAGE ZOOMABLE PAGE TEXT
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00073732/00001
 Material Information
Title: Phenological events of corn in relation to time of planting
Series Title: Research report
Physical Description: 12 p. : ill. ; 28 cm.
Language: English
Creator: Wright, D. L ( David L )
Teare, I. D ( Iwan Dale ), 1931-
Kidd, B. T ( Brian T )
North Florida Research and Education Center (Quincy, Fla.)
Publisher: North Florida Research and Education Center
Place of Publication: Quincy FL
Publication Date: 1987
 Subjects
Subject: Corn -- Planting time -- Florida   ( lcsh )
Corn -- Growth -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Includes bibliographical references (p. 12).
Statement of Responsibility: D.L. Wright, I.D. Teare and B.T. Kidd.
Funding: Research report (North Florida Research and Education Center (Quincy, Fla.)) ;
 Record Information
Bibliographic ID: UF00073732
Volume ID: VID00001
Source Institution: Marston Science Library, George A. Smathers Libraries, University of Florida
Holding Location: Florida Agricultural Experiment Station, Florida Cooperative Extension Service, Florida Department of Agriculture and Consumer Services, and the Engineering and Industrial Experiment Station; Institute for Food and Agricultural Services (IFAS), University of Florida
Rights Management: All rights reserved, Board of Trustees of the University of Florida
Resource Identifier: oclc - 83793202

Table of Contents
    Title Page
        Page 1
    Abstract
        Page 2
    Introduction
        Page 3
    Materials and methods
        Page 4
        Page 5
    Results and discussion
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
    Summary
        Page 11
    Acknowledgements
        Page 11
    Reference
        Page 12
Full Text


" In


Phenological Events of Corn in Relation to Time of
Planting/







D. L. Wright, I. D. Teare and B. T. Kidd!/














Additional Index Words: Physiological Stage of Growth,
Phenology, Modified Growing Degree Unit, Planting date, Zea
mays L.










1/Research Report No. NF 87-3 from North Florida Research
and Education Center, Quincy, FL, University of Florida.
Agricultural Experiment Station, Institute of Food and
Agricultural Sciences.

I/Associate Professor, Professor of Agronomy, and Biological
Scientist II, University of Florida, North Florida
Research and Education Center, Quincy, FL 32351.








ABSTRACT

An accurate method of predicting corn (Zea mays L.)
maturity early in the development of the corn plant would
help farmers in the subtropics evaluate the feasibility of
planting a second crop in a multiple cropping system. Corn
(Dekalb XL71) was planted at fifteen planting dates in 1981
and 1982. Three corn phenological events (emergence, 50%
tasseling and harvest maturity [30% moisture]) were recorded
in terms of "days to event" and "modified growing degree
unit (MGDU) to event" and regressed on planting date. When
"days to event" are regressed in relation to days Julian for
emergence, tasseling or maturity, the three slopes are
significantly different (P>.0001). However, orthogonal
comparisons show that the slopes for tasseling and harvest
are not significantly different. This means that XL71 corn
harvest maturity can be predicted and used in the decision
making process for the multiple cropping of soybean of
sorghum by the addition of 58 days to time of 50% tasseling
in Northern Florida. A modified growing degree unit base
has been established for Dekalb XL71 in the Southeast. When
MGDU's to event (emergence, tasseling or maturity) are
regressed on planting date (days Julian), the three slopes
are not statistically different. Thus MGDU's from planting
date, emergence, and 50% tassel can be used to predict corn
harvest maturity.









INTRODUCTION

Multiple cropping is an accepted practice in tropical
and subtropical belts where an accurate method of predicting
the maturity of the first crop (corn) early in its develop-
ment would help farmers evaluate the feasibility of planting
the second crop. During the past 50 years, various measures
have been utilized by researchers and the hybrid corn in-
dustry for predicting the ontogeny of corn, but "no single
system can show the exact number of days from planting to
maturity or harvest that will be constant in an area over a
period of years" (Carney, 1980). Daughter et al. (1984)
give a thorough literature review of the use of days and
heat units to predict silking, tasseling, and pollen shed so
this will not be re-reviewed in this article. We will only
review that portion of the literature related to predicting
harvest maturity of corn so that the economic potential of a
second crop can be predicted. Shaw & Thom (1951a) concluded
that the interval from silking to maturity was relatively
constant (50 to 52 days for early and late cultivars in
Iowa), but they did not expose the corn to varying tempera-
ture environments which could be obtained by planting in
relation to time from early (cold) to late (warm) planting
dates or by planting at one time, but at different eleva-
tions to get temperature differences. They also did not
relate statistics to their observations. Mederski et al.
(1973) analysed 2 years data from 6 locations and 4 planting
dates in Ohio in relation to maturity with three cultivars
of corn and found that silking to maximum dry weight ranged
from 76 to 82 days and silking to black layer maturity
ranged from 55 to 71 days. They showed that genetics af-
fects time from tasseling to maturity and compared six
methods of calculating AHU with chronological time. He
stated in his summary, "Research is needed to clarify....
whether the accumulated heat units (AHU) in the interval
silking to maturity is constant or if some functional rela-
tionship or correlation exists between AHU from planting to
silking and silking to maturity." Daughtery et al. (1984)
had enough planting dates in Indiana to obtain the answer to
Mederskis question but had defined a different objective.
Gilmore and Rogers (1958) with one years data had five
planting dates in Texas, but maturity in the title referred
to silking.

The ontogeny of corn in relation to accumulated thermal
units has received much attention and there are many methods
of calculating thermal units (Gilmore and Rogers, 1958;
Cross and Zuber, 1972; Mederski et al., 1973; Daughtry et
al., 1984). The thermal unit accumulation concept assumes
that the photoperiod does not influence the rate of crop
development (Wang, 1960). Corn development, particularly
tassel and ear initiation is influenced by photoperiod
(Coligado and Brown, 1975) however, thermal models are
generally accepted as adequate to predict growth and devel-
opment of corn.








The objectives of this research were to:

1. Measure chronological time periods between easily
identifiable physiological growth stages of one
cultivar of corn relative to planting date in order
to predict the maturity of corn as a function of
temperature and/or time at a subtropical location
so that planting date and yield potential for the
second crop (soybean or sorghum) in a multiple
cropping system could be predicted and evaluated
prior to planting.

2. Add subtropical information to the international
accumulated thermal units data base for predicting
the ontogeny of one cultivar of corn.

MATERIALS AND METHODS

'Dekalb XL71' Corn (Zea mays L.) was selected because it
has been used as a standard in many subtropical experiments.
It was planted at eight different dates in 1981 and 7 dif-
ferent dates in 1982. Planting dates range from 9 Feb. to 1
May and are illustrated in fig. 1. Two planting date ex-
periments were conducted each year. Both studies were grown
on a Norfolk sandy loam (fine-loamy, siliceous, thermal
Typic Paledult). The studies were fertilized (exception:
the corn following crimson clover received no fertilizer
nitrogen) and irrigated with a lateral move, low pressure
irrigation system when tensiometers placed at 0.15m depth
registered 0.020 MPa according to the plow layer management
concept (Wright, Rhoads, and Stanley, 1980) for 19.5 Mg ha-1
of corn (Wright and Rhoads, 1980). Fertilizers were applied
as follows: Eleven kg ha1 of zinc and magnesium were
applied one day after planting. Potassium was applied in
two 270 kg ha- applications (one at planting and one six
weeks after emergence) and four boron applications (0.6 kg
ha-1 each time) were made 4, 6, 7, and 8 weeks after emer-
gence through the irrigation system. The corn-nitrogen
study conducted during 1981 and 1982 was grown by no-till
planting corn into wheat stubble each year. It was ferti-
lized four times with liquid nitrogen (101 kg ha- each
time) through the irrigation system at 4, 6, 7, and 8 weeks
after emergence (Wright and Rhoads, 1980), and the corn of
the corn-clover study was no-till planted into a crimson
clover mulch crop each year (approximately 3.48 Mg ha- of
mulch furnishing approximately 112 kg ha- of nitrogen) with
no other source of nitrogen.

Weeds were controlled in corn by atrazine [2-Chloro-4-
ethylamino-6-isopropylamino-1, 3, 5-triazine] (1.7 kg ha 1
ai) and Lasso [2-Chloro-2'-6'-diethyl-N-(methoxymethyl)-
acetanilide] (2.2 kg ha-1 ai) at planting. Carbofuran [2,
3,-Dihydro-2, 2-dimethyl-7-benzofuranyl methylcarbamate] was
applied at planting (0.6 kg ha-1 ai) and four weeks after





5


emergence (0.2 kg ha-i ai) to control soil insects (root
worm and cutworm) and nematodes.

'Dekalb XL71' was planted in 6.1 X 9.1 m plots with 8
rows and 0.76 m between rows with a population density of
79000 plants ha-1 at variable dates from Feb 9 to June 1
during 1981 and 1982. The reduction of 1982 corn planting
dates from 8 to 7 was because we missed one planting date
due to a cold wet period. Phenological events of corn were
classified as follows:

1. emergence the occurence of 50% of the plants
emerging.

2. tasseling the occurence of 50% of the tassels
emerged.

3. maturity when the percent moisture of the grain
averaged 30% [Most of the corn in the Southeast is
harvested at approximately 30% kernel moisture and
either stored in airtight silos or dried in grain
bins]. The two center rows (4.9 m length) were
harvested for yield.

Modified growing degree units (MGDU) are defined as the
summation of daily maximum temperatures with an imposed
threshold of 300C and daily minimum temperatures with an
imposed threshold of 100C from the beginning to the end of
each stage of development specified. For daily maximum
temperatures >300C, MGDU=20, and for daily minimum tempera-
tures <100C, MGDU=0 (Daughtry et al., 1984).

A randomized complete block design with four replica-
tions was used for analysis of variance to determine statis-
tical significance for the corn yield data. Planting dates
were the treatments. To predict one phenological event
curve from another phenological event curve it is necessary
that the two curves are parallel or have the same slope.
This is what we've done when comparing "days to event" and
"MGDU's to event" for emergence, tasseling, and maturity of
corn versus planting date. Planting date was coded as days
Julian so that regression analysis and the test for equality
of slopes could be used to determine statistical signifi-
cance (Snedecor, 1957, pp. 394-399). Three events were
observed: 50% emergence, 50% tassel, and harvest maturity.
Elapsed time to each event and MGDU to each event were
recorded. For each event, days to event and MGDU's were
regressed on planting date giving rise to three independent,
simple, linear regressions for which homogeneity of slopes
was tested. Slope estimates and orthogonal comparisons that
test if slopes for tassel and harvest are the same, and if
tassel and harvest slopes are different from emergence
slopes were determined.








RESULTS AND DISCUSSION

Corn yields in relation to planting dates in our mul-
tiple cropping system were similar within experiments for
1981 and 1982 and were pooled for illustration. Analysis of
variance tables for corn-nitrogen experiments and corn-
clover experiments are shown in Tables 1 and 2, respective-
ly.


Table 1. Analysis of variance for grain yield of
fertilized experiments for 1981 and 1982.


corn in


1981


Source df SS F value PR>F

P1 Date 4 184.88 18.36 0.0001
Block 7 31.53 1.79 0.1290
Error 28 70.47

1982

Source df SS F value PR>F

P1 Date 3 188.65 63.39 0.0001
Block 7 10.54 1.52 0.2153
Error 21 20.83 0.99


Table 2. Analysis of variance for grain yield of corn in
crimson clover plowdown experiments for 1981 and
1982.

1981

Source df SS F value PR>F

P1 Date 2 98.11 302.66 0.0001
Block 3 2.01 4.13 0.0426
Error 6 1.46

1982

Source df SS F value PR>F

P1 Date 2 84.63 55.82 0.0001
Block 3 8.61 3.79 0.0524
Error 6 6.82








Minimum significant differences for the Waller-Duncan K
ratio t test for yield were: 1981 corn-nitrogen = 1.4913,
1982 corn-nitrogen = 0.9363, 1981 corn-clover = 0.5447, and
1982 corn-clover = 1.1925. Corn following crimson clover
always yielded less than the corn in nitrogen plots. In
general corn yields remained high until the planting date of
18 Mar. and then yields decreased in relation to planting
date (Fig. 1). This supports the findings of Duclos and
Arnold (1979) and Ashbacker (1981) for the southeast and the
coined expression "dare the frost".


, 15


0
-C




LU

z5


U


A Fertilized


2-9 2-25 3-18


4-17 5-1


PLANTING DATE


Figure 1.


Corn yield in relation to planting date for North
Florida for 1981 (open) and 1982 (solid) (curves
fitted by eye).


Early prediction of the corn harvest date would provide a
tool for predicting the yield potential of the second crop,
because, like corn, the earlier the planting date (within
the limits of multiple cropping) of soybeans or sorghum the
higher their potential yields.
When the ontogeny of corn is illustrated as days to
event (events were emergence, tasseling, and harvest ma-
turity) in relation to planting date, the curves indirectly
show the effect of temperature by the clockwise rotation of
each specific response curve (Fig. 2). The earliest
planting date required a longer time for emergence (14 days)
than the latest planting date (5 days), so the plotted curve
for emergence is rotated in a clockwise direction away from


I I I I









the X axis. Tasseling and harvest maturity curves are
further rotated clockwise from the X axis, so days from
planting or emergence are not good predictors of tasseling
or harvest maturity.


Planting Date
2-15 3-01 3-15 4-01 4-15 5-01 5-15


46 60 74 91 105 121 135
Days Julian


Figure 2.


Effect of date of planting on days to event
(emergence, tassel, and maturity) and regressed
curves showing the slopes and indicating the
value of planting date, emergence and tassel for
predicting harvest maturity.


Although Shaw and Thom (1951a&b) were not trying to predict
harvest maturity as a multiple cropping tool, they reported
that the time period from emergence to silking was the most
variable period and the period from silking to maturity was
the most constant in the growth of the corn plant. Similar-
ly, rotation of our response curve from the X axis appeared
to cease after tassel emergence, probably because the re-
lation between days and heat units became constant. The









curve for tasseling was Y=102.85-0.4421X, the curve for
harvest maturity was Y=165.16-0.4848X, and the curve for
emergence was Y=16.52-0.1010X. Statistically we can show
what Shaw and Thom noted in relation to days to event (Table
3), slopes are significantly different.



Table 3. Test of homogeneity for slopes when days to event
(emergence, tassel, and maturity) were regressed
on planting date (recorded in days Julian) giving
rise to three independent simple linear regres-
sions.


Source df SS F value PR>F

Event 2 104902.93 8485.11 0.0001
Pl Date 1 2946.53 476.66 0.0001
Slopes 2 740.25 59.88 0.0001
Tassel&harvest=emergence 1 732.64 118.52 0.0001
Tassel=harvest 1 7.61 1.23 0.2739
Error 39 241.08


When we break out orthogonal comparisons, the emergence
curve is significantly different from tasseling and harvest,
but the slopes for tasseling and harvest maturity are not
significantly different. This means that corn harvest
maturity can be predicted by the addition of 58 days to the
time of 50% tasseling. Fifty eight days is the mean dif-
ference in days between the two curves. This becomes a
powerful tool for timing seed purchases, scheduling and
maintaining machinery, and estimating the yield potential
for the second crop.

The heat unit approach based on accumulated daily maxi-
mum and minimum mean temperatures above or below certain
threshold values has been useful in predicting tasseling and
silking of corn, but only Mederski et al. (1973) and
Daughtry et al. (1984) have related heat units to corn
maturity for Ohio and Indiana. We have established a modi-
fied growing degree unit base for DeKalb XL 71 in a sub-
tropical location in the Southeastern United States (data in
table form may be obtained by contacting the authors). Fig-
ure 3 shows that the three curves for emergence, tasseling
and harvest maturity are parallel with the X axis which
indicates the value of heat units for driving the ontogeny
of corn from one phenological event to another.









Planting Date
2-15 3-01 3-15 4-01 4-15


I I


Harvest Maturity 00

00 C O oo OO 0







50% Tasseling

0 O O o U


400

200


(I '; vJ


Emergence
S--n L,.- nnn


^ I)


46 60 74 91
Days Julian


5-01 5-15


I I


( ) I


105 121 135


Figure 3.


Effect of date of planting on heat units (MGDU)
to event (emergence, tassel, and maturity) and
regressed curves showing homogeneity of slopes and
the value of planting date, emergence, and tassel
for predicting harvest maturity.


Equations for the three curves are Y=82.46-0.1531X for
emergence, Y=694.21 + 0.00088X for tassel, and Y=1573.52 +
0.2632X for harvest maturity. When heat units to event are
regressed on planting date (days Julian) (Table 4), the
three slopes are not significantly different.


Table 4. Test of homogeneity for slopes when heat units
(MGDU) to event (emergence, tassel, and maturity)
were regressed on planting date (recorded in days
Julian) giving rise to three independent simple
linear regressions.

Source df SS F value PR>F

Event 2 17608199.21 12243.43 0.0001
Pl Date 1 39.43 0.05 0.8161
Slopes 2 736.55 0.51 0.6032
Tassel&harvest=emergence 1 466.00 0.65 0.4257
Tassel=harvest 1 270.56 0.38 0.5432
Error 39 28044.41


1600-


0 1400
CD

...1200
C
So1000
0
o
6 800

- 600
-I


I-


rrr\lhl II Il


v I I v I


- wV


v


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SUMMARY

1. A statistical technique is used that describes the
probabilities and values of other phenological events in
the ontogeny of corn for predicting harvest date in a
multiple cropping system.

2. Corn harvest can be predicted at 50% tasseling by adding
58 days for XL71 in subtropical areas.

3. Modified growing degree units are precise for predicting
harvest date from the three phenological events measured
(planting date, emergence and tasseling) but it is not a
simple predictive tool for farm management.

4. Research to elucidate the variation in harvest date
associated with the cultivars grown in the subtropics is
needed.


ACKNOWLEDGEMENTS


The data were statistically analyzed by James Clair,
Statistical Consultant at North Florida Research and Educa-
tion Center, University of Florida and PhD. graduate student
in statistics at Florida State University. His efforts and
time spent analyzing and clarifying the statistical perspec-
tive is appreciated.








SUMMARY

1. A statistical technique is used that describes the
probabilities and values of other phenological events in
the ontogeny of corn for predicting harvest date in a
multiple cropping system.

2. Corn harvest can be predicted at 50% tasseling by adding
58 days for XL71 in subtropical areas.

3. Modified growing degree units are precise for predicting
harvest date from the three phenological events measured
(planting date, emergence and tasseling) but it is not a
simple predictive tool for farm management.

4. Research to elucidate the variation in harvest date
associated with the cultivars grown in the subtropics is
needed.


ACKNOWLEDGEMENTS


The data were statistically analyzed by James Clair,
Statistical Consultant at North Florida Research and Educa-
tion Center, University of Florida and PhD. graduate student
in statistics at Florida State University. His efforts and
time spent analyzing and clarifying the statistical perspec-
tive is appreciated.









REFERENCES

Ashbacker, G. (1981) Early-planted corn responds to higher
N rates. PAG Crops Quarterly, Spring: 13.

Carney, S. (1980) Rating the corn maturity rating system.
PAG Crops Quarterly, Spring: 6-7.

Coligado, M. C., and D. M. Brown. (1975) Response of corn
in the pretassel initiation period to temperature and
photoperiod. Agric Meteoral. 14:357-367.

Cross, H. Z., and M. S. Zuber. (1972) Prediction of flower-
ing dates in maize based upon different methods of
estimating thermal units. Agronomy Journal 64:351-355.

Daughtry, C. S. T., J. C. Cochran, and S. E. Hollinger.
(1984) Estimating silking and maturity dates of corn
for large areas. Agron. J. 76: 415-420.

Duclos, J., and J. Arnold. (1979) Managing corn for top
yields in the South (Plant Early). Dekalb Research
Notes 15: 4-5.

Gilmore, E., and J. S. Rogers. (1958) Heat units as a
method of measuring maturity in corn. Agron. J. 50:
611-615.

Mederski, H. J., M. E. Miller, and C. R. Weaver. (1973)
Accumulated heat units for classifying corn hybrid
maturity. Agron. J. 65: 743-747.

Shaw, R.H., and H.C.S. Thom. (1951a) On the Phenology of
field corn, silking to maturity. Agron. J. 43:541-546.

Shaw, R.H., and H.C.S. Thom. (1951b). On the phenology of
field corn, the vegetative period. Agron. J. 43:9-15.

Snedecor, G.W. (1957) Statistical Methods Applied to Ex-
periments in Agriculture and Biology. The Iowa State
College Press, Ames, Iowa. pp. 394-399.

Wang, J. (1960) A critique of the heat unit approach to
plant response studies. Ecology 41: 785-790.

Wright, D. L., and F. M. Rhoads. (1980) Management prac-
tices for 300 bushel corn. Fla. Coop. Ext. Ser., Agro-
nomy Facts 108: 1-7.

Wright, D. L., F. M. Rhoads, and R. L. Stanley. (1980)
Irrigated corn production. Fla. Coop. Ext. Circular
486: 1-20.




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