Integrating Solar Corridors into Vermont Corn Silage Production Systems

Weather data were recorded with a Davis Instrument Vantage Pro2 weather station, equipped with a WeatherLink data logger at Borderview Research Farm in Alburgh (Table 1), in St. Albans (Table 2), and in Enosburg, VT (Table 3). In Alburgh, temperatures were below normal throughout the growing season. May was the only month that had warmer than average temperatures. From May through September, Alburgh received 23.89 inches of rain, which is almost twice as much precipitation received in 2021. The accumulated rainfall in Alburgh was 4.6 inches higher than the 30-year normal for May through September. This season, in Alburgh, there were 2500 Growing Degree Days (GDDs) which falls within the range of required GDDs for corn silage (2,200 to 2,800).

Unlike Alburgh, the temperatures at the St. Albans location were warmer than normal from May through September. May and August were 4.53 and 4.22 degrees above the 30-year average respectively. Like Alburgh, precipitation was higher than normal, and there was a total of 21.8 inches of rain, 2.66 inches above normal. Overall, there were 2597 accumulated GDDs. At the Enosburg location, precipitation was higher than normal as well, with above average rainfall in May, June, and September. There was a total of 26.3 inches of rain, 5.68 above normal. Overall, there were 2275 accumulated GDDs at the Enosburg location. Both of the on-farm locations had a sufficient number of GDDs for corn silage.

Table 1. Weather data for Trial 1 and 2, Alburgh, VT, 2022.

Based on weather data from a Davis Instruments Vantage Pro2 with WeatherLink data logger.

Historical averages are for 30 years of NOAA data (1991-2020) from Burlington, VT.

Table 2. Weather data for the on-farm trial in St. Albans, VT, 2022.

Based on weather data from a Davis Instruments Vantage Pro2 with WeatherLink data logger.

Historical averages are for 30 years of NOAA data (1991-2020) from St. Albans, VT.

Table 3. Weather data for the on-farm trial in Enosburg, VT, 2022.

Based on weather data from a Davis Instruments Vantage Pro2 with WeatherLink data logger.

Historical averages are for 30 years of NOAA data (1991-2020) from Enosburg Falls, VT.

Trial 1- The impact of corn row width on silage productivity

Harvest population and yield at 35% dry matter were significantly impacted by the row spacing treatments (Table 4). Corn populations were significantly greater in the 30” rows at harvest compared to the other row widths, with 31,363 plants ac^-1. All the other treatments had populations below the seeding rate target of 30,000 plants ac^-1. Harvest dry matter was not significantly different between the treatments, and all had a dry matter close to the target of 35% and ranged from 35.7-37.6%. Corn yield was highest in the 30” rows (25.5 tons ac^-1) but was not statistically different from the 20” rows (24.9 tons ac^-1). The 40” and 60” rows had the lowest yields, 18.1- and 18.5-tons ac^-1 respectively. The higher yields in the 20” and 30” rows are likely because of the higher plant populations at harvest. There were no significant differences in silage quality between the row widths (Table 5).

Table 4. Corn silage yield by row width in Trial 1, Alburgh, VT, 2022.

†Treatments within a column with the same letter are statistically similar. Top performers are in bold.

‡LSD –Least significant difference at p=0.10.

§NS- No significant difference at p=0.10.

Table 5. Corn silage quality by row width in Trial 1, Alburgh, VT, 2022.

‡LSD –Least significant difference at p=0.10.

§NS- No significant difference at p=0.10.

Light sensors were placed in between the rows of corn to measure the intensity of light reaching the soil surface and a control was placed outside of the corn rows. The light intensity, measured in accumulated lumens ft^-2, was similar for all row widths and the control during the first two weeks after the cover crop was interseeded (Figure 1). This figure provides a visualization of light intensity but does not, however, state that these differences are statistically significant. The 20” and 30” rows had the least amount of light reaching the soil surface, and there was little difference between the two treatments. Light intensity was greater throughout the season in the 40” rows compared to the 60” rows. Increased weed pressure in the wider row widths continues to be a challenge and may have resulted in this trend. Light sensors were removed approximately 3 weeks before harvest, and at that time, the rate of change of accumulated lumens ft^-2 had slowed down, and there would likely be little increase in accumulated lumens ft² in any of the treatments except for the control due to canopy closure.

Trial 2- The impact of corn row width on silage productivity and establishment of interseeded forages

Interactions

There was a significant row spacing by forage type interaction (p=0.033) for percent ground cover just before corn harvest (Figure 2). All three forage types performed best in the 60” rows compared to the 30” and 40” rows. In the 30”  rows, alfalfa and the orchardgrass/alfalfa mix had higher ground over than the orchardgrass alone. The inverse of this trend was observed in the 40” rows where the orchardgrass treatment performed better than both the alfalfa and the orchardgrass/alfalfa mix. The orchardgrass alone performed better in the wider 40” and 60” rows, whereas the alfalfa was able to establish better in the narrow 30” rows. These results indicate that different forages react differently to the various row widths, and therefore it is important to continue to study the optimal row spacing for interseeded forage establishment.

Impact of Row Width

There was a significant difference in ground cover, corn harvest population, and corn yield between the row widths (Table 6). The 60” rows had significantly higher ground cover from the interseeded forages, 28.2%, and the 30” and 40” rows had ground cover of only 6.19% and 3.91% respectively. The wider row spacing allows for better establishment of the interseeded crop, but overall, the forage yields were low and therefore not measured. Corn populations at harvest were highest in the 40” rows, 30,774 plants ac^-1, and that was statistically greater than the 30” and 60” rows, both of which were below the target population of 30,000 plants ac^-1. Corn yield was highest in the 30” rows, 28.0 tons ac^-1, and that was significantly more than the other row spacings. Interestingly, the 40” rows had the highest harvest population but the lowest corn yields, 15.9 tons ac^-1, which is 1.3 and 1.8 times less than the 30” and 60” rows.

Table 6. Ground cover, corn silage yield and population by row width in Trial 2, Alburgh, VT, 2022.

†Within a column, treatments marked with the same letter were statistically similar (p=0.10). Top performers are in bold. 

‡LSD –Least significant difference at p=0.10.

Impact of Forage Type

The interseeded forage type had no impact on the ground cover at harvest, corn harvest population, or corn yield (Table 7). All three forage types had low ground cover at the time of corn harvest; the trial average was 12.8%. With the poor establishment observed in this trial, it is not surprising that the interseeded forages had no impact on corn yields at harvest.

Table 7. Ground cover, corn silage yield and population by forage type in Trial 2, Alburgh, VT, 2022.

‡LSD –Least significant difference at p=0.10.

§NS- No significant difference at p=0.10.

On-farm research trials to evaluate the effect of row width on corn yields and establishment of interseeded forages

 Statistical analyses were not done on data collected at either on-farm trial location, therefore any differences between treatments cannot be considered statistically significant. At the St. Albans location, corn population and yield were greater in the 30” rows compared to the 60” rows (Table 8). Corn silage in the 30” rows produced 5.5 more tons ac^-1 in 2022 than in 60” rows at the same location. The harvest population in 30” rows was 33,106 corn plants ac^-1, above the target seeding rate of 30,000 plants ac^-1. The harvest population in 60” rows was only 24,829 corn plants ac^-1, which is 8,277 less plants ac^-1 than the 30” rows and 5,171 plants ac^-1 below the target seeding rate. Alfalfa was only harvested in the 60” rows due to poor establishment in the narrower 30” rows. The average dry matter yield of interseeded alfalfa at the time of corn silage harvest was 174 lbs ac^-1.  Overall, the interseeded alfalfa produced little biomass, but the dry matter yield observed in this year’s trial was comparable to the biomass production of alfalfa interseeded into corn silage in last year’s trial conducted at the Alburgh, VT location.

At the Enosburg, VT location, corn silage yield was slightly higher in the 20” rows (18.8 tons ac^-1) than in the 40” rows (18.4 tons ac^-1). Harvest populations were also higher in the 20” rows; there was approximately 2,900 more plants ac^-1 in the 20” rows (Table 9).. The alfalfa interseeded into 20” rows did not establish well and was not measured, but in 40” rows, the dry matter yield of interseeded alfalfa just after corn harvest was 51.2 lbs ac^-1. 

Table 8. Harvest characteristics of corn silage and alfalfa, St. Albans, VT, 2022.

Top performers are in bold.

Table 9. Harvest characteristics of corn silage and alfalfa, Enosburg, VT, 2022.

Top performers are in bold.

DISCUSSION

In 2022, the UVM Extension Northwest Crops and Soils Program conducted two research trials at Borderview Farm in Alburgh, VT and two on-farm trials in St. Albans and Enosburg, VT. At all three research sites, there were sufficient Growing Degree Days (GDDs) for corn silage, which ranges from 2,200 to 2,800 GDDs. Precipitation was high throughout the 2022 season and all the sites received above average rainfall. Temperatures fluctuated by site. It was unseasonably cool in Alburgh throughout the season, but temperatures in St. Albans were above average from May through September. At all three sites however, May was a particularly warm month, with average temperatures above the 30-year normal.

Trial 1 in Alburgh studied the impact of corn row width on silage productivity, and included 20”, 30”, 36”, 40”, and 60” row widths. The 30” rows had s statistically greater harvest population and silage yield than the other row widths. One of the challenges that arises when planting corn in alternative row widths is that most equipment that is available is designed for conventional 30” row widths. To reach a target seeding rate of 30,000 plants ac^-1 in 60” rows, the seeding rate must be doubled to make up for the loss of rows, but not all equipment is capable of accurately planting at such high seeding rates. The increased yield observed in the 30” rows could be due to the statistically lower harvest populations in the other row widths or the increased competition within the row with higher plant populations. There were no observed differences in corn silage quality between the different row widths.  Unsurprisingly, the wider row widths, 40” and 60”, had higher light infiltration to the soil surface compared to the narrower row widths (20”, 30”, and 36”).

Trial 2 evaluated the impact of row width on silage productivity and interseeded forage establishment. The row widths in this trial were 30”, 40”, and 60” and the forages included alfalfa, orchardgrass, and an alfalfa/orchardgrass mix. The different forages reacted differently to the row widths. For example, orchardgrass alone does not establish well in narrow 30” rows but does better in wider row widths with increased light availability. Alfalfa established well even in the 30” rows, and there was little difference in dry matter yield between the alfalfa and orchardgrass/alfalfa mix when interseeded into 30” rows. This indicates that most of the biomass in those mixed treatment was from the alfalfa and not the orchardgrass. Expectedly, all the interseeded forages performed best in the 60” row widths, and ground cover at the time of corn harvest was highest in the wider rows. Corn populations at harvest were statistically greater in the 40” row widths, but that did not result in high yields. The 40” rows had a statistically lower corn silage yield compared to the other treatments and was likely due with difficulties harvesting this row spacing with a standard corn chopper. More research still needs to be done on selecting hybrids that will perform well at high seeding rates. Flex ear hybrids have the potential to make up for lower populations and still produce adequate yields by increasing ear size when planted at those low seeding rates. Nonetheless, majority of corn silage yield comes from the stover and less plants per acre, or smaller plants, will likely result in less overall biomass. In 2022, the interseeded forages had no impact on silage yields. In years with suboptimal conditions (i.e., drought) an interseeded forage could potentially compete with the cash crop for resources which may result in lower yields.

The two on-farm trials studied to impact of row width on silage productivity and interseeded forage success. At both locations, the narrow row width (20” and 30”) produced higher yields than the wider row widths (40” and 60”). Corn populations were also lower in the wider row widths. Like what was observed in the two research trials done in Alburgh, establishing a good corn population is crucial, and the alterative row widths had lower corn populations resulting in lower yields. Alfalfa was interseed into the corn silage at both locations, and overall establishment was poor. At both sites, alfalfa biomass could only be collected in the wider row width, and average dry matter yields were low. Alfalfa is a perennial forage species that is commonly grown in Vermont and a growing number of farmers and researchers are interested in using interseeded crops as forage. While the alfalfa did not establish well while the corn crop was growing, it may continue to grow next spring, increasing ground cover in 2023 prior to corn planting. More research needs to be done on the long-term success of interseeded forages like alfalfa. But if silage yields can be maintained, then farmers can begin to select their interseed cover crops for more targeted benefits. It is important to remember that these data represent only one year of research at three sites. The UVM Extension NWCS program plans to repeat these research trials again in 2023.