Silage corn is a popular crop among New Hampshire dairy producers since it has the potential to produce high yields of digestible dry matter. However, silage corn production often requires significant inputs, and many NH dairy farms are not located in areas well-suited for growing the crop. Planting corn in these areas compromises both farm profitability and farm sustainability by using farm resources inefficiently, or by degrading them. There may be other crops better suited to these farms that will allow for efficient forage production without degrading soil and water resources.
Brown midrib sudangrass-sorghum hybrid (BMR-SS) is one crop with the potential to provide high yields of high-quality feed. An annual crop, it gives producers flexibility in rotating crops, and it is planted to form a dense ground cover that minimizes soil erosion and runoff. Initial investigations in Cheshire County in 2003 show that dry matter yields of up to six tons per acre are possible, with a forage quality profile similar to that of cool-season grasses.
This project set out to evaluate BMR-SS as a possible alternative to silage corn on NH farms.
- Evaluate the yield potential and forage quality of BMR-SS grown in a variety of conditions
Compare the dry matter yield, forage quality, cost of inputs, and labor involved for growing BMR-SS to those involved with growing silage corn.
Demonstrate BMR-SS production practices to area producers
Four dairy farms that currently grow silage corn in southwestern New Hampshire participated in this project. The cooperating dairy farms range in size from 43 to 500 milking cows, and from 180 to 1900 acres of cropland. The dominant soils on each farm vary from moderately well-drained upland soils to well-drained and highly productive alluvial soils in the Connecticut River Valley.
Each farm planted between three and five acres of BMR-SS when the soil temperature reached approximately 60oF; two farms planted on May 20, another farm planted June 10, and the fourth planted on June 14. Participants aimed for a seeding rate of 60 lb. per acre, with the actual seeding rate ranging from 48-67 lb. per acre. Each farm was able to harvest two cuttings, mowing once the crop reached a height of 36-48 inches and ensiling it either in bunker silos or in wrapped round bales. After the first harvest, participants topdressed BMR-SS plantings with 225 lb. urea to apply 100 lb. of nitrogen per acre.
We recorded crop yields for both BMR-SS and silage corn. For BMR-SS, we weighed five 5’sections of the mowed swath in random locations in each field to calculate tons of forage per acre, then adjusted for the crop’s moisture content to determine dry matter yield. For silage corn, producers either measured the dimensions of the bunker silo upon completing harvest, or they kept track of the number of loads of silage from each field, then multiplied this by the average load weight to determine corn yield per acre. These figures were adjusted for moisture content in order to determine dry matter yield.
From participants’ records, and through personal communication, we recorded the cost of purchased inputs (i.e. seed, fertilizer, and herbicides), hours of labor required for field operations involved in growing both BMR-SS and silage corn crops, and other expenses (e.g. equipment rental, custom application acreage charges).
We sampled both BMR-SS and corn silage for forage analysis at least three weeks after ensiling. Three of the participating farms, however, did not have the ability to segregate BMR-SS from grass and alfalfa crops they were harvesting at the same time and storing in the same bunker. In those cases, unensiled BMR-SS samples were submitted for analysis. All samples were sent to Dairy One forage laboratory in Ithaca, NY; analyses included crude protein (CP), acid-detergent (ADF) and neutral detergent fiber (NDF), non-fiber carbohydrate (NFC), net energy lactation (NEl), 30-hour in vitro dry matter digestibility (DMD) and neutral detergent fiber digestibility (NDFD).
Yields of BMR-SS ranged between 3.0 and 4.9 tons of dry matter per acre, with the two farms that were able to plant in May having the highest yields. The first cutting yielded approximately twice as much forage as the second cutting, possibly due to cooler than normal temperatures in August and September. Silage corn yields ranged from 3.6 to 7.5 tons of dry matter per acre, with corn giving higher yields than BMR-SS across all farms. BMR-SS yields were lower than expected; an initial demonstration plot planted in 2003 indicated that the crop could produce as much as 6 tons of dry matter per acre. However, the 2004 growing season featured higher than normal rainfall in the spring and cooler than normal cooler temperatures later in the summer, and plots were located in moderately well-drained soils. These factors may have kept yields low; a warmer or drier growing season, or planting on soils with better drainage may have provided higher yields.
BMR-SS required more labor per acre, but corn had greater input costs per acre. Field preparation and planting required generally the same number of man hours for both crops, except for farm #3, which needed to spend much longer picking stones prior to planting BMR-SS. However, because harvesting BMR-SS requires separate mowing and chopping/baling operations, and because there are multiple harvests during the season, there is substantially more labor involved with harvesting that crop than there is for silage corn, with a single harvest with a single pass over the field. Because BMR-SS doesn’t require the use of herbicides for managing weeds, input costs are generally $30-40 less per acre. However, fertilizer costs are similar for the two crops; where corn is planted with a starter fertilizer, with a single sidedress later on, BMR-SS is topdressed with a significant amount of nitrogen fertilizer, with two applications possible in the event of three harvests.
We calculated the number of man hours and money for inputs spent to produce a ton of dry matter for each crop. For the yields reported, BMR-SS consistently required more man hours per ton of dry matter. Despite lower input costs per acre for all farms, two farms had higher input costs per ton of dry matter with BMR-SS.
BMR-SS offers good feed quality and strong dry matter yields. However, it did not provide a consistent advantage in crop yields or feed quality for all farms. Farm #3 features upland soils that periodically cause delays in planting, and dry matter yields for BMR-SS and silage corn were similar. Here, BMR-SS may be a more productive crop than corn. Farms #1, and #2 are located along the Connecticut River, with significant acreage of productive agricultural soils, and they were able to harvest more dry matter per acre with less labor on their cornfields. Such farms with level, well-drained soils that allow them to complete field operations in a timely manner are suited to corn production, and they may not see any advantage with regards to crop yields or forage nutritive value by planting BMR-SS.
BMR-SS is often presented as an alternative to corn, but such a comparison may not be appropriate. Despite no clear advantage over corn in terms of yield or quality, BMR-SS has qualities that make it a good forage to include in the crop mix. Though not included in the scope of this project, the crop has the potential to reduce soil erosion. As an annual crop it allows for flexibility in a crop rotation that may disrupt pest life cycles and reduce overall pest pressure in the field. Moreover, under certain conditions, such as spring or fall rainfall that delays corn planting or harvest, BMR-SS may even provide higher dry matter yields or better quality feed than corn. The ability to harvest during the summer, when drier conditions prevail, is an advantage over the risk of delaying harvesting in a rainy fall, especially on farms with wet soils.
Education & Outreach Activities and Participation Summary
We held a Field Day at one of the cooperating farms in August to educate area producers on growing practices and considerations related to growing BMR-SS. Eight people attended the event, though there would have been more if the event hadn’t been held during one of the few intervals of good drying conditions where farmers could harvest dry hay.
Results from this project will be presented to area farmers at the Spring Crops meetings sponsored by UNH Cooperative Extension; based on prior attendance, we should be able to reach an additional 50-60 farmers. Information will also be written into an article in a forage crop newsletter mailed to forage producers in southwestern New Hampshire, and in UNH Extension newsletters throughout the state.
In interviews conducted after the growing season, two of the participants said they were interested in growing BMR-SS again on their own, while the other two said they had little interest in growing it again. Those with an interest in growing it saw possible roles as a nurse crop for new seedings, as a rotational crop following corn for a year prior to seeding to a perennial forage crop, or as a crop dedicated to feeding dry cows. They also reported that the forage they harvested had good quality, and that it appeared to be palatable when fed to animals.
The farmers with little or no interest saw some of these benefits, but they also saw drawbacks. Even farms that were still interested in the crop expressed some surprise that yields were not greater, though they attributed this to the growing season or the particular field where the crop was planted. Perhaps growing the crop under different conditions would yield more tonnage. One farm mentioned that harvesting BMR-SS conflicts with harvesting other perennial forages, whereas harvesting silage corn in the fall helps to spread harvesting operations over a greater part of the growing season. Another farm seemed satisfied with the quality of BMR-SS but concluded that they probably wouldn’t plant it again because they’re more familiar with silage corn and they perceive growing BMR-SS as somewhat risky. The farm did indicate that more familiarity might lead to greater acceptance in the future.
Areas needing additional study
- Continued demonstration plots will increase farmer awareness of BMR-SS as a forage crop and farmer comfort with growing the crop. As mentioned earlier, a lack of familiarity with the crop is an impediment to more widespread adoption. Additional years of study would provide more reliable information about the yield potential of the crop over several growing seasons.
Refining growing and harvesting practices, particularly in the areas of nitrogen and weed management.
Evaluating BMR-SS as a forage crop on other livestock operations. While feed quality may not be high enough to support high-producing dairy cattle, it may meet the nutritional needs of other livestock, such as beef cows or sheep.
Other uses of BMR-SS. In particular, BMR-SS may have value as a rotational crop for managing weeds and diversifying forage production on organic livestock operations.