Establishment and Evaluation of Deep-Rooted Perennial Cup Plant and Gamagrass as a Corn Silage Alternative in Dairy Systems

 Problem: 

Dairy farmers who rely on annual cropping systems as a significant part of their forage harvest are at much higher economic risk than those who do not. The trade-off is that annual crops such as corn silage are high yielding, resulting in more tonnage per acre. For example, on the well-drained soils of the Pawlet valley where my farm is located, average corn silage yields are 20-25 tons/acre. However, dairy economics, climate variation, and water quality regulations add challenges. Milk prices continue to fluctuate while input costs such as corn seed continue to increase. Additionally, the availability of non-neonicotinoid treated seed becomes almost non-available. Extremely wet spring weather can delay critical timing of field work and planting and wet fall weather can delay harvest affecting crop quality. More regulations on soil and nutrient management mean more planning for manure applications and cover cropping which can be difficult with variable weather conditions. If nutrients are put on at the wrong time or rate and a cover crop is not established in a timely way, soil erosion and runoff is a significant risk.

Solution:

While extensive work has been done on cover cropping trials and short season corn variety trials to address soil health in annual cropping systems, this project explores the feasibility of a perennial alternative. The working hypothesis is that farmers can transition a portion of their corn silage production to a perennial mix of cup plant (Silphium perfoliatum), Eastern gamagrass, birdsfoot trefoil, plantain, and alsike clover and obtain similar yields and quality without a negative impact on milk production. This perennial mix has the potential to decrease annual tillage, erosion, water and nutrient runoff, chemical use, and costs, while increasing biodiversity, pollinator and other wildlife habitat, soil health, and water infiltration, all while maintaining or improving forage quality and quantity. These are all wet-tolerant, deep rooted species, which would be more appropriate than corn to plan in field areas and soil types that are marginal or less conducive to annual crop planting.

Cup plant is a native perennial of wet-mesic prairies of North America and is highly productive for biomass in soils too wet to maintain dependable production of alfalfa or corn crops. The crude protein concentration and digestibility suggest that cup plant produces sufficient forage quality to be considered as a feed source for ruminant livestock. Cup plant can serve as a buffer crop between fertile crop land and wetlands, capturing nutrients. It is also a crop attractive to pollinators. Overall, it is an an ecologically attractive crop to incorporate into forage systems in North America.

Establishment and management trials will include seeding a base of low-growing, diverse forbs comprising birdsfoot trefoil, plantain and alsike clover which is first planted as one would establish a pasture. We will then use a specialized subsoiler-seeder, called a ripsower, which is used to shatter compaction pan layers common in previously annually cropped ground. It will also be used to interseed cup plant and eastern gamagrass late in the growing season to enable winter seed stratification and spring emergence. Over time, increasing amounts of cup plant and gamma grass can be established within the field, using the ripsower. 

Establishment of the perennial would keep soil covered year round, reduce the costs and risks inherent in annual cropping systems such as fuel use and annual seed costs and the risk of repeated or delayed plantings. Research from the University of Wisconsin demonstrated that there is opportunity to replace up to 30% of the corn silage in a conventional dairy cow ration with perennial cup plant and not observe any impact on milk production or animal performance.

Overall a perennial crop that has the potential to produce yields roughly equivalent to corn silage would reduce environmental risks, reduce annual planting costs, and improve soil and water quality.