Group Title: Research report (North Florida Research and Education Center (Quincy, Fla.)).
Title: Drying rate of two corn hybrids
Full Citation
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 Material Information
Title: Drying rate of two corn hybrids
Series Title: Research report (North Florida Research and Education Center (Quincy, Fla.)).
Physical Description: 6 leaves. : ill. ; 28 cm.
Language: English
Creator: Rhoads, Fred ( Frederick Milton )
North Florida Research and Education Center (Quincy, Fla.)
Publisher: North Florida Research and Education Center
Place of Publication: Quincy Fla
Publication Date: 1993
Subject: Corn -- Drying   ( lcsh )
Genre: bibliography   ( marcgt )
non-fiction   ( marcgt )
Bibliography: Includes bibliographical reference.
Statement of Responsibility: F.M. Rhoads.
General Note: Cover title.
 Record Information
Bibliographic ID: UF00066117
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 71174041

Full Text

/l '$ s NFREC Res. Rpt. 93-16


rc 7 1993'

University of Florida

F. M. Rhoads


Florida Agricultural Experiment Stations
Institute of Food and Agricultural Sciences
University of Florida, Gainesville



Institute of Food and Agricultural Sciences

Grain moisture % is a critical factor in silage quality. If
grain moisture is too low silage will spoil in a short time, on the
other hand if it is too high poor quality silage with a low feed
value will be the result. Good quality silage is produced if
harvest occurs when all kernels start to dent, at this stage about
90% of grain filling is complete (Aldrich and Leng, 1965). This
corresponds to a grain moisture content of 40 to 45%. Harvest
scheduling would be more precise if time of optimum grain moisture
could be predicted several days in advance. A linear increase of
dry-matter content in corn grain during most of the grain filling
period has been reported (Friedrich et al., 1979). This implies
a linear decrease in % moisture of grain. Two sample dates for %
moisture in grain would be adequate to determine the linear drying
rate of a corn hybrid grown for silage. Drying rate in % per day
can be calculated, if linear, as follows: % moisture of sample date
one minus % moisture of sample date two divided by number of days
between samples equals moisture loss in % per day. Harvest date
can be calculated by dividing required moisture loss by drying rate
and adding the resulting number of days to the last sample date.
Drying rate may differ among hybrids and the greatest
difference is expected to occur between those of different maturity
dates. The purpose of this report was to compare corn grain drying
rate between a full season and a short season hybrid.

Two corn hybrids (Sunbelt brand '5613' and '1882') were
planted 7 April, 1987 in four separate plots (10' X 20') for each
hybrid. Sunbelt brand '5613' is a short season hybrid and '1882'
is a full season hybrid. Recommended cultural practices, including
irrigation, were applied uniformly to all plots.
Silking date was determined as the date when 50% of plants of
each hybrid contained silks. Silking dates were 5 and 9 June,
respectively, for the short and full season hybrids.
Two ears of grain from each plot were randomly harvested at
weekly intervals starting 22 June and continuing to the last
sampling date on 3 August. Samples were immediately transported to
the laboratory, hand shelled, and the grain put in zip lock plastic
bags. A 100 g subsample of grain at field moisture content was
immediately weighed for drying to constant weight at 700C in a
heated cabinet. Both moist and dry weight were recorded and
moisture content was calculated as % moisture = {(field weight -
dry weight)/field weight} X 100.
Analysis of variance procedures were performed on the data for
each sampling date. Regression analyses for gravimetric % moisture
versus time were performed separately on data for individual
hybrids. All statistical procedures are described in Steel and
Torrie (1960).


Grain moisture % of the full season hybrid ranged from 86.5 at

13 days after silking to 31.7 at 55 days after silking (Table 1.).
The range in % grain moisture for the short season hybrid was 78.8
to 24.8 between 17 and 59 days after silking. The average drying
rate was near 1.3% per day for each hybrid during the 7 week
sampling period. However, there appeared to be a break in the
drying rate for both hybrids between 35 and 40 days after silking.
Sampling was stopped on 3 August because grain reaches maximum dry
weight when grain moisture drops below 35% and this is too dry for
high quality silage (Aldrich and Leng, 1965).
Drying rates were calculated for each hybrid from regression
analyses of gravimetric % moisture versus days after silking (Table
2.) The drying rate between 13 and 59 days after silking for each
* hybrid was best described with a quadratic equation having a
significant (P 5 0.01) quadratic component (Fig. 1.). Grain
moisture was predicted from the quadratic equations to be 31.9% 55
days after silking for the full season hybrid and 25.5% 59 days
after silking for the short season hybrid. The quadratic equations
for the two hybrids were nearly parallel until about 40 days after
silking when they began to diverge. Drying rate between 40 and 60
days after silking appeared greater for the short season hybrid
than for the full season hybrid.
Regression analyses between 13 and 40 days after silking
revealed a significant (P s 0.01) linear regression without a
significant quadratic component (Table 2.) The relationship
between 40 and 60 days was also linear with no quadratic component.
Therefore, the quadratic equations can be effectively divided into
8 two linear segments, one from silking to 40 days and the other from
40 to 60 days after silking. Student's t revealed that both
hybrids had the same drying rate (1.9% per day) between 13 and 40
days after silking but the drying rate for the short season hybrid
between 40 and 60 days after silking was about 1.5 times (P 0.01)
that of the full season hybrid.
Since the optimum grain moisture content for high quality
silage occurred for both hybrids during the first 40 days after
silking when drying rates were linear, two sampling dates should be
sufficient for determination of drying rate to be used to schedule
a harvest date for best silage quality. The calculated drying rate
for the full season hybrid between 13 and 27 days after silking was
1.9% per day. To reach 40% from 59.9% at 27 days would require
{(59.9 40)/1.9} 10 days which would be 37 days after silking. At
37 days after silking the actual grain moisture % of the full
season hybrid was between 45.9 and 40.5 which is in the range for
high quality silage. The calculated drying rate of the short
season hybrid 'was 1.7% per day between 17 and 31 days after
silking. To reach 40% from 54.8% at 31 days after silking would
require {(54.8 40)/1.7} 9 days which would be 40 days after
silking. This hybrid actually contained between 39.2 and 38.3%
grain moisture at 40 days after silking which is slightly below the
range for high quality silage. The error in estimating the optimum
date for silage harvest of the short season hybrid was due to under
estimating the drying rate from the two sampling dates (two weeks
apart). Estimating drying rate from the first two sampling dates
S (one week apart) resulted in an even greater error. Increasing the
time period between sampling increased the accuracy of the

estimated drying rate in comparison to the actual drying rate for
both hybrids. A graphical presentation of the estimated drying
rates are shown in figure 2.
If data similar to that in this report were available on all
corn hybrids, silage harvest could be scheduled with only one
sampling date per season using the drying rate calculated from
regression analysis. For example, 17 days after silking the %
moisture in grain was 78.8 for the short season hybrid and days to
harvest would have been {(78.8-40)/1.9} 20 which was 37 days after
silking when the grain contained 41.1% moisture.

Aldrich, S. R. and E. R. Leng. 1965. Modern corn production. F.
and W. Publishing Corp. Cincinnati, Ohio.

Friedrick, J. W., L. E. Schrader, and E. V. Nordheim. 1979. N
deprivation in maize during grain-filling. I. Accumulation
of dry matter, nitrate-N, and sulfate-S. Agron. J. 71:461-

Steel, R. G. D., and J. H. Torrie. 1960. Principles and
procedures of statistics. McGraw-Hill. New York.

Table 1. Grain moisture in two corn hybrids 13 to 59 days after
silking as measured by gravimetric (weighing and drying)
Full Season Hybrid Short Season Hybrid
(Sunbelt '1882') (Sunbelt '5613')
Days after Moisture Days after Moisture
silkinc in % silking in %
13 86.5 17 78.8
20 72.4 24 68.8
27 59.9 31 54.8
34 45.9 38 39.2
41 40.5 45 38.3
48 34.7 52 30.1
55 31.7 59 24.8

Table 2.

Regression analysis for per cent moisture in corn grain
versus days after silking (d) for a full season hybrid
(FSH) and a short season hybrid (SSH), showing student's
t for comparing linear regression coefficients (b)
between hybrids, F tests for significance of regression,
and coefficients of determination (r2).

Days after Regression t F
silking Hybrid equations value value r2

Total Seed Growth Period

13 to 55
17 to 59
13 to 55
17 to 59



n.d. 365.29**
n.d. 390.81**
n.d. 94.89**t
n.d. 26.33**t

Early Seed Growth

13 to 34
17 to 38



1.23 723.34** 0.981
1.23 322.98** 0.959

Late Seed Growth
41 to 55 FSH %GM=65.7-0.63d 16.44** 32.22** 0.763
45 to 59 SSH %GM=81.2-0.96d 16.44** 111.81** 0.918

n.d. = not determined. ** (under F) = regression significant at
P 0.01. ** (under t) = slope (b) of FSH < b of SSH.
t = F test for quadratic component only.


Fig. 1. Moisture content of corn grain
versus time.

% Moisture in Grain


60 ---


20 ---

0 "

----. Y-123-3.08X+0.0259X2

SY122-2.81X+0.0199X 2
x Full Season Means

o Short Season Means

0 10 20 30 40 50 60 70
Days After Silking

Fig. 2. Moisture content of corn grain
versus time in two hybrids, estimated
from two sample dates two weeks apart.

% Moisture in Grain
80 -




10 20


Means of Four Reps
x Full Season

o Short Season

40 50

4 I *

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