Air Seeder and Corn Planter Comparison for Corn for Silage

Air seeders are used primarily for seeding small grains and soybeans, but have the potential to plant corn as well.
Air Seeder and Corn Planter Comparison for Corn for Silage - Articles


Howard F. Schwartz, Colorado State University,

Conducted by: Greg Roth, Mark Antle and Scott Harkcom

Location: Rock Springs, PA

Collaborators: Penn State Farm Operations Staff

Sponsor: Doug Gammie, New Holland North America, Inc.

Research Objective:

To evaluate differences in stand establishment and yield of corn grown for silage in narrow rows using an air seeder or a narrow row corn planter.


Air seeders are used primarily for seeding small grains and soybeans, but have the potential to plant corn as well. Air seeders can handle bulk quantities of seed and fertilizer and are well adapted to planting large acreages very efficiently. Seed distribution in the row is generally less uniform for air seeders than with corn planters with finger pickup or vacuum seed distribution systems. Seed and plant spacing variability may be less important in corn silage production systems where high plant populations and narrow rows are being utilized. In our previous research, yields of corn grown for silage were maximized near 36,000 plants per acre. Narrower rows resulted in an average yield benefit of 5%.

Study Description:

Two planters were compared in this study. One was a Flexi-Coil air seeder with seventeen, 12-inch rows. We configured it to plant either 17 rows or to plant 15 rows with 2 rows shut off to provide two tramways through the crop approximately 60 inches apart. The second was a Monosem vacuum planter that was configured to plant either seven, 15-inch or four, 30-inch rows. These four planter configurations were evaluated in a replicated strip trial design with plots that were either one (Flexi-Coil) or two (Monesem) passes wide. Each plot width was increased in size by 10% to facilitate separation at harvesting. This resulted in plot widths that ranged from 18.7 to 22 feet wide and averaged 520 feet long. Each planter treatment was replicated 4 times in the field. All plots were planted on May 14, 2001 using Syngenta N58-D1 seed treated with Proshield insecticide. The target plant population was 44,000 seeds/acre. At a normal 90% emergence this should have resulted in a 40,000 plant/acre population.

At the four-leaf stage all plants in two, 100-foot row lengths were counted in each plot. Also, the spacing between individual plants was measured for 100 plant spacings in each plot. These data were used to calculate the plant population, the average plant spacing in each row and the standard deviation of the plant spacings.

The plots planted with the corn planter were then thinned by removing every sixth plant in the 15-inch row treatment and every tenth plant in the 30-inch row treatment. Plant populations and plant spacings were then recalculated to represent the field at harvest.

At harvest each plot was chopped at the half milk line stage of maturity using a six-row forage harvester equipped with a rotary head. The forage from each plot was dumped into a truck and weighed before unloading at the silo. A moisture sample of the forage was collected at the silo. The trucks were then weighed after unloading to obtain an accurate tare weight.

Yield plant spacing and moisture data were analyzed using SAS.


Initial plant populations (Table 1) of the air seeder plots were significantly lower than those achieved with the corn planter. This was not likely due to reduced emergence but possibly due to an error in the seed weight determination or the calibration of the planter. We used the seed count provided by the seed company and this may have been too high, resulting in fewer seeds/pound than actual. To compensate for this, we thinned the corn planter stands to a similar population to eliminate this effect on the final yield determination. The plant spacings in the rows were a function of the population and the row spacing.

The standard deviation of the plant spacings reflected the uniformity of the seed spacings. The air seeder resulted in values of 14.4 and 11.9 inches while the planter achieved spacings of 2.1 to 3.5 inches. These differences are considerable and Nielsen (1991) reported that grain yields decrease by about 2.5 bu/A for each inch that the standard deviation of plant spacing increases. Based on this formula, and a difference of 10.3 units in plant spacing variability we would anticipate a lower yield of 25.8 bushels/ acre (10.3 x 2.5 ) for the air seeder. This would translate into a silage yield reduction of about 3.5 tons/per acre @ 35% DM.

After the thinning process, the plant populations were similar for all treatments. The plant spacing variability increased slightly for the plots planted with the corn planter, especially in 15-inch rows, but the differences between the planter and the air seeder plots remained large.

Field observations confirmed the plant spacing deviation measurements. In the air seeder plots the within row variation was considerable and the stands resembled those obtained with a low seeding rate in a grain drill. Occasionally the skippers in adjacent rows coincided with each other, resulting in a small opening in the corn in these plots.

Yields in this study averaged 18.4 tons/acre, which is respectable but slightly below average for this site. This was due to the delayed planting date, some damage from western corn rootworm, and some mid season drought stress that also reduced the height of this crop somewhat. This corn crop responded well to the warmer and wetter than average August in our area and yielded more than we expected it would earlier in the season. Since this crop was not excessively tall and the leaf canopy closure was delayed, we would expect that narrower row treatments might have had an advantage in this environment because of their ability to capture more sunlight.

Yields were significantly higher for the air seeder treatments than the 30-inch conventional planter treatment and statistically similar to the 15-inch planter treatment (Table 1). Yields of the 12-inch row air seeder treatment averaged about 7.9% higher than the 30-inch row treatment. Adding the tramways to the air seeder plots had no effect on yield. The coefficient of variation for yield in this study was 3.8%, which is very low and indicates that the treatment effect was very consistent across the replications.

Dry matter concentrations of the forage were similar for all of the treatments. This indicates that the row spacing and planter had no effect on the maturity of the crop.

Table 1. Plant population, plant spacing in the row, standard deviation of plant spacings, yield and moisture of corn grown with a conventional corn planter and air seeders in two different configurations.
@35% DM
Corn Planter: 30 inch rows393782.12.73544036.717.6
Corn Planter: 15 inch rows425153.55.43542935.218.1
Air Seeder: 12 inch rows34848
Air Seeder:
12 inch rows with tramway
LSD (0.05)1.8


This study suggests that the impact of significantly higher within row variability associated with the air seeder in corn grown for silage has no negative impact on yield. In higher yielding and taller crops that reach full canopy earlier in the season, the effects of interplant spacing should be even less.

In this study there was no detrimental effect of the tramways on yield. In practice, tramways might only be necessary once in each 50 to 60-foot pass rather than in a 17-foot pass used in this study, so any impact on yield should be negligible.

The corn in this study exhibited moderate damage from the western corn rootworm. The seed treatment we used provided reasonable but not excellent control compared to granular products in the market place. Much of the corn grown for silage in the Northeast US is treated with a granular insecticide for rootworm control. Some method of distributing granular insecticide should be considered on the air seeder for use in the corn silage market to overcome this problem.

These results are encouraging regarding the potential of air seeders for planting corn for silage. Research should continue in more diverse environments to confirm the consistency of the treatment effects observed in this trial.