Apunch planter may offer better seeding
performance than conventional planters for no-
till conditions because it moves a minimum
amount of soil and residue and offers precision
in seed spacing. Minimal research has been completed to
overcome some limitations that this machine concept
offers, specifically mechanisms to change population rate.
Plant population stands have been widely studied. Local
recommendations for corn populations are available.
Schueller (1992) reported that seed companies have tried to
match their hybrids to localized conditions. Research in
this area tends to continue because of the increased
importance given to site specific management. The
adoption of a specific plant population for each
environmental condition has been studied and proposed as
a management solution for yield improvement (West et al.,
1989). Corn population rates have increased by more than
20% since 1980 in many areas of the USA (Reichenberger,
1995). Due to these rate changes, it is important that new
developments for planters have options for variable plant
population. Punch planters still have to overcome the basic
limitation of changing seed spacings and maintaining seed
distribution precision. Data from the Prairie Agricultural
Machinery Institute-PAMI (1984a), collected on a greased
belt, show a quality of feed index of 97% to 88% for
2.22 m/s travel speed and 96% to 87% for 3.06 m/s travel
speed, for a planter using a finger pickup metering unit. For
a machine using an airflow seed meter, PAMI (1984b)
reports a quality of feed index of 97% to 91% for 2.22 m/s
travel speed and 97% to 88% for 3.61 m/s travel speed.
Despite its importance as an evaluation criterion, the
volume of soil disturbed by a no-till planter has not been
frequently investigated. No-till is related to the concept of
leaving the soil and coverage with the minimum of
disturbance. In addition, the amount of soil disturbed is an
indication of energy required for the operation.
Tessier et al. (1991) measured soil disturbance caused by
furrow openers using a roughness meter made of a section
of steel pins positioned across seed rows. A roughness
coefficient was calculated as the standard deviation
between the elevation of steel pins on the surface and a
mean regression of the same data. The hoe type openers
resulted in the highest soil disturbance, followed by the
double disc openers. The same trend was observed by
Bahri (1992) and Schaaf et al. (1979), using photographic
images of the cross-sections.
Many different row cleaner devices are available today,
consisting of combinations of brushes, disks, and steel
finger trash wheels in front of the planters. They came to
the market in the 1990s as an option for managing residue
(Fee, 1993). Erbach and Kaspar (1994) tested row cleaners
and rolling coulters for planting corn in no-till. Row
cleaner devices resulted in less residue in the seed zone and
corn emerged quicker than where rolling coulters were
POPULATION RATE CHANGES AND OTHER EVALUATION PARAMETERS
FOR A PUNCH PLANTER PROTOTYPE
J. P. Molin, L. L. Bashford, R. D. Grisso, A. J. Jones
ABSTRACT.A prototype punch planter for no-till corn was developed to provide different seed spacings. Plant population
was adjusted by changing planter punch wheels. Seed spacings of 136, 165, and 210 mm were obtained by constructing
three punch wheels with different punch lengths, represented by external diameters of 650, 825, and 1,000 mm,
respectively. Laboratory and field tests were conducted at speeds of 1.5, 2.0, and 2.5 m/s to evaluate the effect of the
punch lengths and speeds. Field tests were conducted in three different residue covers (corn, grain sorghum, and
soybean). Overall, high values for quality of feed index (spaces between seeds or plants within 0.5 and 1.5 the theoretical
seed spacing) were observed. Despite problems with synchronization between the seed meter and punch wheels, the length
of the punches offered no performance limitations at the speeds tested. A soil cleaning device was designed to reduce soil
sticking to the punches and reduce soil disturbance. The volume of soil displaced by the smallest punch wheel (650 mm)
was less than half of that displaced by a commercial no-till planter. Differences in planting depth due to residue cover and
punch wheel diameter were minimal. Emergence was delayed under the corn residue cover and may have influenced the
lower performance of the planter prototype as compared to the other two residue types.
Keywords. Planters, Punch planter, Seed spacing, No-till, Corn.
Article has been reviewed and approved for publication by the Power
& Machinery Div. of ASAE. Presented as ASAE Paper No. 97-1094.
Published as Paper No. 11797, Journal Series, Agricultural Research
Division, University of Nebraska, Lincoln. Mention of trade and company
names are for the reader and do not infer endorsement or preferential
treatment of the products by the University of Nebraska.
The authors are José P. Molin, ASAE Member Engineer, (former
Graduate Student, Dept. of Biological Systems Engineering, University of
Nebraska-Lincoln) Assistant Professor, University of São Paulo, Brazil
(Sponsored by CNPq-Brazil) e-mail: firstname.lastname@example.org;
Leonard L. Bashford, ASAE Member Engineer,Professor, Department
of Biological Systems Engineering, University of Nebraska-Lincoln;
Robert D. Grisso, ASAE Member Engineer,Professor, Department of
Biological Systems Engineering, University of Nebraska-Lincoln; and
Alice J. Jones, Professor, Agronomy Department, University of
Nebraska-Lincoln. Corresponding author: Leonard L. Bashford,
University of Nebraska, Dept. of Biological Systems Engineering, 203 L.
W. Chase Hall, Lincoln, NE 68583-0726; voice: (402) 472-1627; fax:
(402) 472-6338; e-mail: email@example.com.
Transactions of the ASAE
© 1998 American Society of Agricultural Engineers 0001-2351 / 98 / 4105-1265 1265VOL. 41(5): 1265-1270
used. Even in areas where the soil temperature is not a
limitation, farmers still have problems dealing with residue
in no-till conditions, indicating that research for no-till
planting needs to be continued. The punch planter is an
alternative concept for no-till with precision as it rolls over
This research focused on some of the questions related
to punch planter performance with changes in corn
population and forward speed. The work was based on a
prototype punch planter designed and tested by Molin et al.
(1998). Seed spacings of 136, 165, and 210 mm were
tested, along with speeds of 1.5, 2.0, and 2.5 m/s, both in
the laboratory and in the field. The evaluation was based on
spacings between seeds or plants (quality of feed index,
multiples index, miss index, and precision). The soil
disturbed by the punch planter and by a commercial no-till
planter were measured to give an indication of difference
between the two systems. The emergence rates were
measured in all experimental fields.
MATERIALS AND METHODS
Plant populations based on different row widths and
distances between seeds are illustrated in figure 1. Three
seed spacings were selected considering population rates
normally used (fig. 1). The theoretical number of seeds
varied between 96,500 seeds/ha for 0.762 m row width and
the minimum seed spacing (136 mm), and 52,100 seeds/ha
for 0.914 m row width and the maximum seed spacing (210
A prototype punch planter designed by Molin et al.
(1998) was adapted for different punch wheels (fig. 2).
Three punch wheels were constructed using a metal ring
with fifteen punches welded around it. The length of the
channel that formed the punch was selected to give the
linear distance between tips corresponding to designed
seed spacing of 136, 165, and 210 mm. This resulted in
external wheel diameters of 650, 825, and 1,000 mm. The
punch planter was mounted on a tool bar at an angle of 22°
to the vertical and 7° of yaw. A John Deere MaxEmerge 2
commercial vacuum seed meter was used as the seed
A device consisting of a rubber wheel inclined 22° from
vertical in the opposite direction of the punch wheel (fig. 3)
was built to clean soil from the punches. The rubber wheel
was positioned slightly behind the punch wheel and almost
touching it with its relative position adjusted for each
punch wheel. The seed covering and firming device used
were two rubber wheels angled in a “V” shape.
Changes in length of the punches and forward speeds
resulted in different timings in the synchronization between
the seed meter and the punch wheel. The seed meter device
was allowed to rotate 40°, changing the dropping position
of the seeds. The adjusting mechanism consisted of an arc
slot shown schematically in figure 4. Preliminary tests were
conducted for each punch wheel operating at several speeds
to define the dropping position of the seeds.
Laboratory performance tests were performed on a
greased belt using the methodology described by
Molin et al. (1998). The punch wheels were tested at three
speeds (1.5, 2.0, and 2.5 m/s) using a 3 ×3 factorial
arrangement. Pioneer 3417 seed corn, size CD5 and
weighing 15.9 kg per 80,000 kernels was used. The
experiment was conducted in a completely randomized
design with seven replications of 36 seed spaces each (one
run on the greased belt). Quality of feed index, multiples
index, miss index and precision were the criteria used for
evaluation. These measures are based on the theoretical
spacing (xref), as specified by ISO 7256-1 Standard
(International Standardization Organization, 1984). The
1266 TRANSACTIONS OF THE ASAE
Figure 1–Theoretical corn populations based on seed spacings and
row widths with mark lines for seed spacings established for the
prototype punch planter.
Figure 2–Punch wheels with external diameters of 650, 825, and
1000 mm, all with 15 punches each.
Figure 3–Schematic view of the cleaning wheel and its relative
position to the punch wheel.
quality of feed index is the proportion of spacings between
0.5 and 1.5 xref. The multiples index is the proportion of
spacings equal or less than 0.5 xref, and the miss index
represents the percentage of spacings greater than 1.5 xref.
The precision of seed spacing was defined as the ratio
between the standard deviation of the seed spacings
between 0.5 and 1.5 xref and the theoretical spacing (xref).
The precision was not affected by missing or multiple
Field tests were performed with the same 3 ×3 factorial
design and same treatment levels (three wheels at 1.5, 2.0,
and 2.5 m/s). Three no-till plots were used, one with corn
residue, one with grain sorghum residue and one with
soybean residue. All residue was left from the previous
cropping year. All three areas, located at the Rogers
Memorial Farm east of Lincoln, were planted on 7 and
8 May 1996. Three 50-m-long rows were planted as
replications for each treatment. Pioneer 3394 seed corn,
size CD4, weighing 22.7 kg/80,000 kernels and having a
certified 95% minimum germination, was used in the field
tests. The bulk density of the top soil was determined using
54 mm diameter ×60 mm high cylinders. Four replications
of bulk density on each plot were collected. These same
samples were used to determine moisture content by using
the oven-dry method. The cone index of the top layer
(between 35 and 105 mm) was also determined. An
electronic cone penetrometer was used. The penetration
resistance was measured at intervals of 35 mm. The tip was
a standard cone of 12.8 mm diameter (ASAE, 1994). For
each block, 12 locations were sampled for cone index.
Residue amounts were determined using the line-transect
method described by Dickey et al. (1986).
The plot with the soybean residue was selected for soil
disturbance measurement. Punch wheels with 650 mm
and 1000 mm external diameters were used in this
experiment. The prototype punch planter was run at a
constant forward speed of 2 m/s. The seed covering and
firming device were removed for those tests. The same
was done with two of six rows of a commercial no-till
planter (International planter equipped with double disk
openers and no row cleaning device) running at the same
conditions and adjusted for the same planting depth. Soil
volume displaced by the punches was measured by
placing a plastic wrap into the holes after removing the
loose soil. Each hole was than filled to the top with water
using a 100 mL burette, with the water needed to fill the
hole used as an index of soil disturbance volume. Six
holes were randomly used for this test in each treatment.
The volume of soil displaced per meter of row by the
punch wheels was calculated based on the spacing
between holes. For the commercial no-till planter, a
special device comprised of two parallel aluminum blades
50 mm apart was used. Each blade had a triangular
contour similar to that of the transverse section of the slot
made by the double disc opener. They were used as walls
for holding the plastic wrap after removing the loose soil
so the volume of a 50-mm section of the slot could be
measured. In the same way, six measures were taken and
the mean was multiplied by 20, giving the volume of soil
disturbed per meter of row.
The emergence rate was determined by counting a 20-m
section of the plots every two days in the first two weeks
after emergence began. Final count was made at the end of
the third week. The final count was assumed to be the
established stand and was used for computing the
intermediate emergence rates.
Field test parameters of quality of feed index, multiples
index, miss index, and precision were measured after the
last count of emergence. Three weeks after planting, the
spaces between plants were measured. Seventy sequential
spaces were measured between plants on each replication
for each treatment resulting in 280 spaces for each
Although the prototype planter had just one row and
was limited in some of its features like depth control, seed
depth was adjusted to 50 mm and was measured so any
abnormality related to emergence could be recorded. Three
weeks after planting, seed depth was measured on each
treatment for each area. Nine seedlings in each row,
randomly selected, were cut off at the soil surface. Each
seedling location was then excavated and the distance
between the surface and the center of the seed was
measured. The objective was to determine if forward speed
affected the planting depth with the limited depth control
available on the prototype. Each wheel was analyzed for
the three speed levels in each of the experimental areas.
RESULTS AND DISCUSSION
The first approach to the statistical analysis of the
laboratory data was to fit a second-order response surface
for each variable tested against forward speed and wheel
diameter. However, since most analyses had significant
lack of fit, a response surface analysis was not suitable.
Seed distribution parameters (multiples index, miss index,
quality of feed index, and precision) of the laboratory tests
are presented in table 1, as well as the probabilities of F
and least significant differences (LSD) at 5% probability.
Probabilities of F were significant for all the variables
1267VOL. 41(5): 1265-1270
Figure 4–Schematic view of the seed meter and its adjustment
position relative to the external wheel.
The smallest wheel (650 mm) had the best results at
2.0 m/s, with a quality of feed index of 95.1% and
precision of 14.0%. The multiples index and miss index,
not always significant, as complementary of quality of feed
index, were the lowest at 2.0 m/s. In previous work,
Molin et al. (1998), using only the small wheel and before
performing some major changes in the prototype, observed
similar results. However, no effect of speed between
1.0 m/s and 3.0 m/s was observed.
Almost the same response occurred with the largest
wheel (1000 mm). Precision was even better (12.1%), but
the multiples index was high at all three speeds. Also, a
high miss index was observed at 2.5 m/s, resulting in the
lowest quality of feed index of all treatments.
For the intermediate size wheel (825 mm) the results
were opposite, with the poorest results at 2.0 m/s. This
behavior may be related to the dropping position angle of
the seed meter. The results show that the synchronization
between seed meter and punch wheels is a major factor that
needs special attention for accurate results.
Overall, despite the variability, some high values for
quality of feed index were observed. They were not directly
related to speed and punch wheel diameter, suggesting that
synchronization between seed meter and punch wheel has
to be improved. The length of the punches, with punch
wheel diameters up to 1000 mm, did not represent a
technical limitation for the range of forward speeds
between 1.5 and 2.5 m/s.
Soil moisture content was considered high (table 2) for
field operations, especially in the corn residue. A very
dense coverage of residue on that area (table 2) and
frequent rains were reflected in the test results. The top soil
cone index of the three areas (fig. 5) was consistent with
the no-till system in use at the site for several years.
The volume of soil displaced by the smallest punch
wheel (650 mm), as presented in table 3, represented
45.7% of the soil disturbed by the commercial no-till
planter. The largest punch wheel (1000 mm) displaced
29.9% of the volume of soil displaced by the commercial
planter. The volume of soil disturbed per unit area for
0.76 m (30 in.) rows and the smallest punch wheel resulted
in 8.48 m3/ha. The largest punch wheel displaced
5.54 m3/ha compared with 18.55 m3/ha for the
1268 TRANSACTIONS OF THE ASAE
Table 1. Seed spaces distribution from the laboratory tests
for each punch wheel and forward speed
Punch Wheel Multiples Quality of Miss
Diameter Speed Index Feed Index Index Precision
(mm) (m/s) (%) (%) (%) (%)
1.5 6.5 86.1 7.4 19.0
650 2.0 4.1 95.1 0.8 14.0
2.5 4.9 91.8 3.3 16.9
1.5 1.6 98.4 0.0 14.4
825 2.0 6.5 88.6 4.9 17.9
2.5 2.5 95.9 1.6 15.6
1.5 8.6 88.6 2.9 12.9
1000 2.0 6.9 92.2 0.8 12.1
2.5 9.8 83.3 6.9 18.9
LSD (0.05) 3.91 5.05 3.24 0.024
Pr > F (%) 0.0012 0.0001 0.0001 0.0001
Table 2. Soil and residue characteristics for each of the field areas
Residue Type Area
Corn Grain Sorghum Soybean
Soil gravimetric moisture (%) 29.5 25.7 24.4
Soil bulk density (Mg/m3) 1.30 1.19 1.21
Residue cover (%) 91 46 73
Figure 5–Cone index from the top layer (between 35 and 105 mm) of
the three areas of field tests.
Table 3. Volume of soil displaced by the smallest punch wheel
(650 mm), largest punch wheel (1000 mm), and commercial
no-till planter on the soybean residue area at 2.0 m/s
Volume of Soil Displaced
Punch Wheel Per Sample* Standard Per meter of
Diameter (mm) (ml) Deviation Row (mL/m)
650 89 3.30 646
1000 88 5.52 423
Commercial no-till planter 71 1.97 1413
* A sample means one hole for the punch planter or one measurement
for the commercial no-till planter. The numbers represent a mean of
Table 4. Seed planting depths of corn plants in each of the residue
cover areas for each punch wheel and forward speed
Punch Wheel Seed Depth (mm)
Diameter Speed Corn Grain Sorghum Soybean
(mm) (m/s) Residue Residue Residue
650 1.5 47 a* 38 a 34 a
2.0 39 b 43 a 38 a
2.5 36 b 41 a 40 a
Pr > F (%) 0.007 0.368 0.437
825 1.5 53 a 47 a 52 a
2.0 56 a 47 a 49 a
2.5 51 a 49 a 50 a
Pr > F (%) 0.381 0.904 0.850
1000 1.5 44 a 37 b 48 a
2.0 44 a 41 ab 43 a
2.5 44 a 44 a 47 a
Pr > F (%) 0.997 0.044 0.647
* Means for a residue and punch wheel diameter followed by the same
letter are not significantly different by Fisher’s Protected LSD (α =
commercial no-till planter. The soil disturbed by the punch
planter was proportional to the population rate and was
much lower than that disturbed by planters with row
Each punch wheel showed a relatively uniform seed
depth among forward speeds and residue conditions
(table 4). The target depth was 50 mm on each wheel, but
the adjusting system was very limited in its precision. Only
in the corn residue did the smallest punch wheel (650 mm)
have a significant change in depth between 1.5 m/s and the
other two speeds. The intermediate punch wheel (825 mm)
produced no significant differences in seed depth at the
three speeds in any of the three residues. For the largest
punch wheel (1000 mm), only the grain sorghum residue
produced a significant depth difference between 1.5 m/s and
2.5 m/s. From these observations, depth was not considered
a major concern. As mentioned, each wheel had a different
setup for depth control. This resulted in some average
differences in depths among the three punch wheels.
A good and uniform emergence rate depends on factors
such as seed quality, soil temperature and moisture and
depth and its uniformity. The corn residue consistently
delayed emergence (fig. 6). This difference was three to
four days longer than the other two residues. The cause of
the delay may be related to the low soil temperatures and
high soil moisture content due to the heavy residue cover
Field test results showed similar trend as those observed
in the laboratory. A significant lack of fit was observed for
at least one parameter in each field area. All the parameters
were related in some way, so the response surface analysis
was considered unsuitable. The results of quality of feed
index, multiples index, miss index, and precision are
presented in table 5. The F probabilities for those
parameters showed significant differences among
treatments in the corn and grain sorghum residue areas, but
not in the soybean residue. Thus, in the soybean residue,
the punch planter speed or wheel diameter had little
influence on the seed spacing.
The quality of feed index tended to be higher for the
smallest punch wheel (650 mm). Quality of feed index
greater than 80% was observed. This occurred with the
other punch wheels and independent of ground speed, on
the grain sorghum and soybean residue. As the miss index
and multiples index are complementary to quality of feed
index, they had the tendency to increase with the size of the
punch wheel. The multiples index was lower than that
observed in the laboratory tests. However, a peak on
multiples index, even higher than that from laboratory tests,
was observed for the largest punch wheel (1000 mm) at 2.0
m/s in all three residue areas. The same was true for the
miss index at that point. Like shown by the laboratory test
results, this lack of tendency may be related to the dropping
position angle of the seed meter.
When analyzing the miss index in the field, all factors
related to seed-soil system have to be considered because it
may mean seeds that did not germinate, even if correctly
placed. Evidence is shown by the different residues. The
corn residue, with its dense coverage, resulted in a higher
miss index when compared with the other two areas.
However, the prototype also left a few seeds on the surface.
1269VOL. 41(5): 1265-1270
Figure 6–Corn emergence rates from field tests where each curve
represents one area (all nine treatments) with different residue (corn,
grain sorghum, and soybean).
Table 5. Field spaces distribution of corn plants from tests performed
in each of the residue cover areas for each punch wheel
and forward speed
Punch Wheel Multiples Quality of Miss
Diameter Speed Index Feed Index Index Precision
(mm) (m/s) (%) (%) (%) (%)
1.5 3.6 64.3 32.1 14.4
650 2.0 2.0 76.7 21.3 12.7
2.5 0.4 78.3 21.3 12.9
1.5 7.6 52.6 39.8 12.1
825 2.0 3.2 65.1 31.7 9.3
2.5 1.6 72.3 26.1 11.0
1.5 3.6 57.4 39.0 10.3
1000 2.0 11.2 38.6 50.2 9.2
2.5 0.8 63.1 36.1 11.1
LSD (0.05) 4.38 14.46 11.80 3.231
Pr > F (%) 0.0011 0.0004 0.0011 0.0458
Grain Sorghum Residue
1.5 0.8 81.5 17.7 11.5
650 2.0 2.8 67.9 29.3 10.5
2.5 1.2 80.3 18.5 11.2
1.5 2.8 63.9 33.3 8.1
825 2.0 0.8 68.7 30.5 8.6
2.5 1.2 81.1 17.7 9.3
1.5 5.2 53.0 41.8 7.6
1000 2.0 8.8 49.8 41.4 6.7
2.5 0.8 75.5 23.7 7.9
LSD (0.05) 3.92 15.41 12.55 2.392
Pr > F (%) 0.0051 0.0017 0.0020 0.0046
1.5 2.0 82.3 15.7 12.5
650 2.0 1.2 78.7 20.1 11.8
2.5 0.4 81.9 17.7 10.6
1.5 4.4 75.1 20.5 11.4
825 2.0 0.4 82.7 16.9 11.3
2.5 2.4 75.5 22.1 11.3
1.5 3.6 72.7 23.7 9.1
1000 2.0 7.6 60.6 31.7 8.1
2.5 0.8 82.3 16.9 7.7
LSD (0.05) 5.38 21.92 18.12 3.393
Pr > F (%) 0.1642 0.5101 0.7182 0.0749
Some penetration problems were observed on corn residue
which suggests a lack of ballast.
Overall, both the field and laboratory results showed
favorable potential for the punch planter prototype. Planter
performance did not have a consistent trend for punch
wheel diameter and forward speed and part of the
variability may be attributed to limitations on
synchronization between the seed meter and punch wheel.
Best results were observed for the smaller punch wheel, but
good results were observed for both low and high speeds
and the largest punch wheel. This shows that the length of
the punches in the tested range did not affect the
performance of the prototype. The results also indicate the
necessity of improved synchronization between the seed
meter and punch wheel.
This research was designed to observe punch planter
performance with varying corn population and the effects
of forward speed. A prototype punch planter was adapted
for different punch wheels with external wheel diameters of
650, 825, and 1000 mm, resulting in linear distances
between tips of 136, 165, and 210 mm, respectively. Tests
were run at speeds of 1.5, 2.0, and 2.5 m/s, both in a
laboratory (greased belt) and in the field (corn, grain
sorghum and soybean residue). The spacings between seeds
or plants were measured and analyzed for quality of feed
index, multiples index, miss index, and precision.
Emergence rates were measured in all experimental fields.
The soil disturbed by the punch planter was measured and
compared with a commercial no-till planter.
Overall, despite the variability, high values for quality of
feed index were observed. The results were not related to
speed and punch wheel. The length of the punches, with
punch wheel diameters up to 1000 mm, did not represent a
technical limitation for the range of forward speeds
between 1.5 and 2.5 m/s. The results indicated the
necessity for improved synchronization between the seed
meter and punch wheel.
With the help of a soil cleaning device, the smallest and
the largest punch wheels displaced, respectively, 45.7% and
29.9% of the soil displaced by a commercial no-till planter
equipped with double disk openers under the same
Only the 650 mm wheel operating in corn residue and
the 1000 mm wheel operating in grain sorghum residue
presented significant differences in planting depth, despite
the tests being made with a single row prototype with
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