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Copyright 2005, Board of Trustees, University
A3ro r.:.y research Report, Ay-88-04.
PARTITIONING OF DRY MATTER IN FALL-GROWN, NO-TILLAGE
TROPICAL CORN IN FLORIDA.
J. J. Bustillo and R. N. Gallaher
Graduate student and Profesor of Agronomy, University of Florida,
Inst. Food and Agr. Sci., Dept. of Agronomy, Gainesville, 32611.
The long frost-free period.in Florida could allow numerous
multiple cropping alternatives to farmers. This study was
conducted to 1) determine the best plant population for highest
yield of tropical open pollinated corn (Zea mays L.) when planted
as a second crop in the late summer in north :central Florida and
to 2) determine the partitioning of dry matter among the corn
parts. Six populations were studied in increments of 10,000
plants per ha and ranged from 30,000 to 80,000 plants per ha. The
study was conducted at two locations on the Green Acres Agronomy
Farm on a Arredondo loamy sand (Grossarenic Paleudult) in 1987.
Treatments were replicated six times in a randomized complete
block design. Corn was harvested at black layer formation. Plants
were separated into leaves, stalks, shucks, cobs, and grain and
dried at 70 C for estimation of dry matter production. Maximum
yield was obtained at the 80,000 plants per ha population.
Additional index words: population density,J tfropcal corn,
temperature and daylength vs. grain fillini1,r& ty matter, and grain
F 9 2S 1991
Most corn Zea mays L.) is produced between:latitudes 300
and 55 with relatively little corngrown ~ht latitudes higher
than 47 Brasil and Mexico are the only two major areas of corn
production outside this latitudinal range. The United States is
responsible for almost 50% of world corn production (Shaw, 1977).
Several corn belt States: Indiana, Iowa, Illinois, and Minnesota,
mainly, have record yields of more than 18 T ha- (300 bu a ).
The growth and yield of five highland varieties of tropical
maije studied, gave yields between 470-880 g m-2 (4.7 and 8.8 T
ha ). However, even under good management, the grain yields of
maize in tropical latitudes are usually smaller than the yields
obtained in the maize producing areas of the United States with
an average of 739 g m (121 bu a ). These results, suggested
that "the capacity of the grain sink to utilize assimilates,
limited yields in the tropical varieties" (Goldsworthy, 1974).
The nearly 250 latin american races of corn are mostly
photosensitive, and so are severely limited by late flowering and
excessive growth under field conditions encountered in latitudes
exceeding 30 (Stevenson, 1972). ..
The State of Florida is on the border line-of the 30
latitude, it is not a large corn producer and its corn yield
average is about 379 g m (62 bu a ) (USDA, 1987). On the other
hand, the dairy and beef cattle farmers of North Florida, have a
need of high quality forage in the fall and winter months. At
present their choices of a summer annual forage crop that will
grow in the fall, are limited to crop species, such as forage
sorghum (Sorghum bicolor L. Moench), grain sorghum (Sorghum
bicolor L. Moench), sudangrass (Sorghum sudanense) and corn.
Corn is the most commonly ensiled crop in the USA, preferred
for its better quality and yield of digestable nutrients over the
other choices. Corn grain is over 90% digestable and
corn silage is about 70%, while sudangrass silage is about 46%
(Wright et al., 1983). However, there has been limited success
with fall grown corn when using the Pioneer 304C brand (Gallaher,
During the past 5-yr, field research has been conducted to
develop an open pollinated variety selected for the hot humid
summer and cool fall climate;of North Florida. This material
originated in the hot humid tropics of Costa Rica has been
allowed to cross with selected tropical and temperate hybrids in
Florida. The experimental Cultivar FLOPUP is ready for testing.
FLOPUP has been developed for planting in August and harvest in
the late fall in North and Central Florida. However, the low fall
temperatures and short daylength, during the critical stage from
silking to maturity, may severely reduced dry matter
accumulation and final grain yield. Several authors (Canel, 1938;
Francis, 1969; Breuer et al. 1976; Hunter 1977; and Warrington,
1983), have established that many maize genotypes are
photoperiodically sensitive. Roberts and Struckmeyer (1938) were
among the first to report the effects of temperature on the
response of maize to photoperiod. Corn genotypes also differ in
their response to temperature (Hunter and Kahnenberg, 1974).
Numerous research studies have dealt with determining the
optimum plant population for a given hybrid under a certain
environment. The majority of results show that optimum plant
population vary from about 40,000 to over 100,000 plants per ha
(Larson and Hanway, 1977). In Georgia, optimum plant populations
for two hybrids over a 2-yr period varied from 45,000 to 103,000
plants per ha. under irrigated conditions (Brown et al., 1970).
The objectives of this research were: 1) to determine the
best plant population for highest yield of FLOPUP, an
experimental tropical open pollinated corn cultivar when planted
as a second crop in the late summer in north central Florida,
and 2) to determine the the distribution of dry matter among the
MATERIALS AND METHODS
FLOPUP was planted in early august, 1987 at the Green Acres
Agronomy Farm, 13 miles from the main campus of the University of
Florida, west of Gainesville, FL. The randomized complete block
design had six replications with six plant populations as
treatments of four rows, 6 m. (20 ft) long and 0.75 m. (2.5ft.)
wide. The population treatments were 30,000, 40,000, 50,000,
6Q,000, 70,000 and 80,000 plants ha.
Planting was done with a Brown-Hardin in-row-subsoil no-
tillage planter, in which 300 kg N ha" was placed 30 cm under
the row as anhydrous ammonia. Additional fertilizer K, Mg, S, P,
and micro nutrients were broadcasted as required based on
extension soil test. About 100,000 seed ha were planted and
the populations were fixed by thinning when corn reached an
averaged of about 10 cm in height.
Prelmergence herbicides such as Atrazige (Atrazine) (2.2 kg
a.i. ha ), Sencor (Metribuzin) (0.5 kg ha ), Lasso (Alachlor)
(2.2 kg a.i. ha-1) and Paraquat (Paraquat)(0.5 kg a.i. ha-1)
plus recommended surfactant, were sprayed over the plots. It was
necessary to apply Paraquat as postedirected to control weed
problems in certain areas. Small areas of weeds were also
controlled mechanically by hand.
Irrigation was applied by overhead sprinkler and guns as
needed, depending on natural rainfall. The insects were
controlled as needed by use of Lannate (Metho yl) (2.2 kg ha )
and granulated Furadan (Carbofuran) (100 g m ). Lannate was
sprayed over the plants and furadan was applied directly to the
whorl, by hand application. ..
At black layer formation on the grain, it was assumed that-
the crop-had-reached physiological maturity. At this stage
-several measurements-were made: -1. Number of plants. 2. Number-of
I ears. 3. Ear height. 4. Plant-height. 5. Whole plant dry weight.
6. Ear dry weight. 7. Grain dry weight. 8. Cob dry weight. 9.
Shuck dry weight. 10. Leaf dry weight. 11. Stem dry weight. 12.
Number and diameter of nodes. 13. Ear size and number.
Data was calculated on whole plant yield, grain yield and
grain shelling percent, to determine the effects of plant
population on these factors and the best population required to
optimize yield under the prevailing conditions. Silage yield and
value was estimated from dry matter data. ..
Statistical analysis was done using a Tandy TRS-80, model
1000 SX microcomputer using the MSTAT program for the AOV of a
randomized complete block design and mean separation Fisher
protected (LSD) test. Regression anaylisis of the dependent
variables dry matter of grain, cob, shuck, stem, leaves and whole
plant yield, were tested against the independent variable plant
RESULTS AND DISCUSSION
In general all yield variables responded to increased pla2t
populations (Tabl 1). For the lowest treatment of 3 plants m
(1I,500 plants a ) to 8 plants per square meter (32,400 plants
a ), the maximum treatment, the grain yield obtained went from
129 g m to 211 g m respectively. This represented a
proportional increase of up to 60% over the lowest yield for the
lowest population treatments. These yield were low compared with
yields of tropical hybrids, sach as Pioneer brand 304C, with a
yield of 621 g m- (124 bu a ) (Gallaher, 1985), grown at the
same location during a previous years but planted in march rather
The same relationship reported'above can be said about the
rest of the plant parts. They all responded to increased plant
populations, but the total plant yield was lower than Pioneer
brand 304C1with a yield of 1441 g m for a population of 76,279
plants ha (Gallaher, 1985).
Dry matter yield of the rest of the plant parts w re as
follows: the stalk dry matter went from 436 to 776 g m an
increase of 49%; the leaf dry matter went from 136 to 279 g m-2
an increase of 56%; the shuck went from 64 to 100 g m an
.increase of 64%; and cob dry matter went from 41 to 69 g m- an
increase of 60%. The linear regression is positive for grain and
plant dry matter, with an equation y = 88.8 + 15.3x (Figure 1)
for grain yield, and y = 260.2 + 64.7x (Figurg 2) for plant dry
matter. The coeficient of determination was R = 0.85 for grain
and R = 0.94 for plant dry matter, which suggests a high
relationship between the independent variable, population, in
the response of the dependent variable, dry matter accumulation.
It is .concluded from the analysis of means, that the treatment
with the highest plant population had the highest dry matter
Yield is proportional to the number of grains m According
to Goldsworthy and Colegrowe (1974), grain size usually decreases
with a high plant density, but the effect on grain yield is
compensated by an increase in2the number of ears and so an
increased grain weight per m
In relation to plant population density and row spacing,
Benson (a pioneer in row spacing research) once said that "the
factor which has had the greatest influence in determining the
width of corn rows is the width of the oxyoke" (Dungan, 1945).
Dungan, concluded after 7-yr of research on:plant density, that
the greatest advantage of the single-plant hills was obtained at
relatively high plant populations rates. This supports our
findings, and it is also in agreement with Boff and Mederski
(1960) who once theorized that the superiority of equidistant
planting patterns is that it reduces competition between rows for
water and nutrients, and thereby increase grain yield.
The daylength required to produce a minimum'of one
footcandle of light at the Gainesville, Florida latitude (300
north), is estimated to be from 14.61 to 13.67 hours in august
(time this study was planted), and 10.85 to 10.91 hours in
december (time this study was harvested) (Francis, 1970). This
drop in daylemgth represents a difference of 23%.'The monthly
mean temperature went from 28.3 C (82.9 F) in august to 14 9 C
(58.9 F) in december. This represents a drop of 13.4 C (24 F)
in the five months period. Table 3 shows the temperatures and
daylengths registered during the year 1987, and in particular
during the growing period from august to december.
Low day and night temperature during the ear filling period
is one of the major critical limiting factor in the fall in order
to obtain high grain yield, in north Florida. The gradual drop in
temperature (Figure 3) during the grain filling stage along with
shortening of daylength (Figure 4), reduced the grain yield and
total dry matter (Table 1 and 2). This is consistent with
Breuer, Hunter and Kannenberg (1976) who reported that during the
grain filling period, temperature and photoperiod interact to
reduce the number of grain filling days. They reported that "the
filling period at 20 C was shorter under the 10-h photoperiod
than under the 20-hour photoperiod. On the other hand they found
that at 30 C, the 10-hour photoperiod treatment had the longer
Most of the dry matter yield of corn is produced during the
50 to 60 day period from tasseling to maturity (Hanway, 1963;
Wright et al., 1983). In our experiment, the last 50 to 60 days
of growth were characterized by decreasing daylength and
temperature (table 3.). The same authors have estimated that
between 40 and 75 days after corn seedlings emergence, "the
maximum amount of dry matter is produced as leaves, stalks and
The date of planting has an effect on the total number of
days required to reach 50% tassel. According to Wright (1983),
the later we plant in the season in.North Florida conditions
(february to may), the sooner 50% tasseling and 50% moisture is
reached. The flowering date of maize has been advanced by
increasing temperature or decreasing photoperiod (Allisson, 1979;
Tollenaar, 1979). The photoperiod and temperature affects the
number of days to tassel, and this is different for each corn
genotype (Hunter et al., 1973). According to Coligado and Brown
(1974), there is a constant decrease in time from planting to
tasseling as temperature is increased from 15 to 25 C, regardless
of photoperiod, however photoperiod increased the time to
initiation of leaf at all temperatures from 15 to 30 C,
particularly at low temperatures of 15 C. As photoperiod is
extended, the number of leaves increases at all temperatures,
this resulted from prolonging the time to tassel (Coligado,
1974). In contrast Gmelig (1973) concluded that light intensity
and'temperature affected relative growth rate (of the leaf)
considerably, but daylength had negligible effect. Warrington
and Kanemasu (1982), also concluded that the leaf number
increased as photoperiod increased (this means from january to
july, for Gainesville), with an average increase of 0.71 leaves
per additional hour of photoperiod. In contrast with others,
Warrington and Kanemasu (1982), concluded that photoperiod
sensitivity was not altered by temperature, and that the number
of unexpanded leaves present at tassel inititation was almost
constant under different temperature treatments. All this
suggests to us that dry matter yield of the whole corn plant,
planted in midsummer as a second crop, will'also be affected,
because the time from emergence to tasseling is shortened by
short daylenths and perhaps by the dropping temperatures from
august to december. It was also observed that during the late
part of the growth, after silking, certain desuniformity in the
number of green and drying leaves occurred, this could be
explained by the effect that low day and night temperatures have
on the leaves of different ages. According to Alberda (1969), day
temperature is the important factor in influencing the
chlorophyll concentration in growing leaf parts. Parts subjected
to low night temperatures remain fully green and their growth is
virtually unaffected. This is an important factor for silage
purposes. Nevertheless, FLOPUP shows promising results as a fall
crop (table 2). The amount and timing of fertilizer applied also
has a great deal of influence on the quality of the silage, in
terms of crude protein.
According to Alexander et al. (1963) if the population is
increased so the amount of fertilizer must be increased. Our plant
dry matter for silage estimated at 35%, went from 12.6 to
22 Mt ha which is considered acceptable, for conditions of this
Yield variables of Fall planted corn affected by plant population
(average of two locations in 1987 at Gainesville, Florida).
Treatment2 Grain Cob Shuck _ar Leaf Stalk Shelling
plants m -----------------g m ---%(1)--
if z i% 3 129 c 41 c 64 c 234 c 66 c 136 c 75.9 n.s.
,j 4 144 c 47 c 80 b 271 c 67 c 167 c 75.4 n.s.
5 189ab 61ab 93ab 343ab 84 bc 213 b 75.6 n.s.
S6 173ab 57ab 90ab 320 b 103ab 228 b 75.2 n.s.
g 7 191ab 62ab 96ab 349ab ll0a 231 b 75.5 n.s.
3 8 211a 69a. ,100a 380a 118a 279a 75.4 n.s.
c.v.(%) .8.95 7.8 5.6 8.4 12.9 10.1
(1) Estimated by dividing grain DM by grain + cob DM
LSD protected (0.05) Where n.s. means not significant.
Estimated fall planted corn silage yield and value(l), affected by
plant population (average of two locations in 1987, at Gainesville,
Treatment Plant Plant Silage Value
plant m g m ---(Mt ha )--- ($ ha )
3 436 c 4.6 12.6 485
4 505 c 5.1 14.6 562
5 640 b 6.4 18.3 705
6 651 b 6.5 18.6 716
7 690ab 6.9 19.7 759
8 776a 7.7 22.0 847
(1) Silage at 35% DM and $38.5 Mt-1. LSD (0.05)
Temperatures for 1987 fog Gainesville Florida and
daylenth for Florida (30 latitude).
Month, Temperature (F) Daylength (Hrs) Rain
Max. Min. 7th day 22nd day (in)
Jan 66.9 42.6 10.9 11.2 4.17
Feb 70.5 47 11.5 11.9 5.4
March 74 52.5 12.3 12.7 10.3
April 79.8 50 13.3 13.7 0.45
May 86.2 64.3 14.1 14.5 4.3
.June 91.4 .70 14.7 14.74 2.9
July 92.8 72.1 14.7 14.4 3.9
August 93 72.7 14.1 13.7 5.4
Sept 89.7 69.4 13.1 12.7 3.7
Oct 79.7 55.5 12.3 11.8 0.27
Nov 75.8 54.3 11.5 11.1 4.3
Dec 72.2 45.7 10.9 10.8 1.2
(1) Agronomy Dept. IFAS and NOAA, 1987.
y~~~4 t- --. F3xR i~
Ui = %.%
P 1ts' E~
5 7 E 8 10
Figure 1. Corn grain dry matter yield.
E .2 5.
100 = -9,.2 64.7 x R, -.9
n! i I
6 7 I0
Figure 2. Corn plant dry-matter accumulation.
A Max. Temp.
o Min. Temp.
Hrves ti n
S2 3 4
6 7 8 10 I
of the aar
Figure 3. Maximum and minimum temperature 1987 for Gainesville,
D Dayl engh t
1 2 3 4 b
IL) I IL1II fI I .
/ 0I a ~ n r
Months of the ymar-
Figure 4. Daylenght in 1987 for Gainesville, Florida.
; 1 U
II I I.
0 / 0
All yield variables responded to increased plant population.
The maximum grain and plant yield of 211 g m and 771 g m
respectively, were obtained at the highest population of 80,000
plants per ha. So both grain and total plant dry matter responded
to the highest population. The ear size and shelling percent were
not affected by plant population density. The effect was only in
the number of ears. FLOPUP showed promising results as a fall
silage crop if well managed.
Temperature during the grain filling period is one of the
major critical limiting factor in the fall to obtain high grain
yield. The short daylength correlated with low temperature, and
high insect damage perhaps, will affect the final grain yield.
Insect control needs further research, to determine the most
effective and economical control program. Plant dry matter yield
increased from increasing plant population, and it was highest at
the highest plant population. Shelling percent did not responded
to increasing plant population but remained almost constant.
Alexander, R. A., J. F. Hentges, Jr., W. K. Robertson, G. A.
Barden and J. T. McCall. 1963. Composition and digestability of
corn silage as affected by fertilizer rate and plant population.
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