Maintaining Persistence and Productivity of Perennial Forages in a Changing Climate

Livestock farms of all sizes and production systems depend on high-quality forage crops to support the health and productivity of their livestock. Regardless of the production system, feed is one of the highest expense categories for a livestock operation. Purchasing substantial quantities of off-farm feeds, such as grain, impacts farm economics and can present increased risk to the environment from nutrient loading. In addition, perennial forage crops can provide additional environmental benefits including reducing soil erosion, improving soil health, and increasing soil carbon stores. Enhancing on-farm forage production therefore can help improve farm economics and environmental impacts. Through conservation efforts, farmers have made substantial changes in corn silage cropping management to include soil health and environmental priorities, recognizing their long-term benefits to farm productivity and resilience. However, the same shifts have not occurred for perennial forage crop management. Despite their potential and importance, perennial forage crops continue to be an underutilized resource on the farm.

In the northeast, dairy farmers are under immense pressure to produce enough forage during a relatively short growing season that will sustain their herd through the year before the next crop is harvested. This often leads to farmers managing their forage crops in ways that prioritize short term returns over long term productivity and profitability. Two common examples are harvest height and frequency. While it seems obvious that mowing lower to the ground would allow you to harvest more of the crop and therefore increase yields, this mentality ignores the quality or value of the resulting forage and the impact on the longevity and persistence of the stand. Modern mowers can create incredible amounts of vacuum at the soil surface when harvesting. The lower to the ground the mower head is, the more vacuum force is exerted onto the soil which can result in substantial forage contamination. When fed to a dairy cow, this high-ash feed fills the rumen without providing adequate nutritive value and therefore could cost the farmer more money in supplemental grain to obtain the necessary level of milk production. From the plant’s perspective, the bottom few inches of a grass plant are where it stores energy and initiates new growth from. If this area is damaged and damaged repeatedly and often, the plant’s energy reserves will be diminished requiring it to mobilize root stored energy. This will likely also cause the root biomass to be reduced making the plant less resilient and less productive. Currently, most farms also harvest frequently trying to optimize yield and quality. Frequent harvest means mowing the forage every 28 to 30 days regardless of weather conditions. If stands are damaged repeatedly, they will thin allowing weedy plants to establish further reducing forage yield and quality. Therefore, optimal harvest management must balance quantity and quality needed to meet the goals of the herd while maintaining growing conditions that support robust, productive, and persistent forage crops. Between low mowing heights and short frequencies between harvest the perennial forages are under significant stress. Now add climate change to that stressful situation and both plant productivity and farm resiliency are at risk. 

Climate change threatens our cool season perennial forages. Rainfall has and will continue to become more variable. For example, the northeastern US will experience greater variability in precipitation, including more frequent extreme rainfall events, reduced snow cover and greater winter precipitation, drier growing seasons, and increased temperatures (Jay et al. 2023). Prolonged dry periods, hot temperatures, and excessive moisture are all adding stress to our forage stands that prefer cool and relatively wet growing conditions. However, farmers continue to manage their forage stands "as normal" likely because they have limited information and reason to do otherwise. Climate, weather, and environmental variability will continue to challenge our forage systems. It is unclear which management practices, or combinations thereof, represent the greatest opportunity to increase farm resiliency. Based on our observations, research, experience, and conversations with farmers we believe modifying harvest management may possibly improve forage productivity and possibly build resiliency in the face of climate change. 

This project seeks to quantify the forage yield, quality, and economic impacts of various harvest height and frequency regimes in perennial forage stands in the northeast. We believe harvesting at higher cutting heights will help the stand regrow more quickly especially under adverse weather conditions. We believe leaving more stubble will also allow the soil to remain wetter and cooler especially during the hot summer months. Lastly, we believe mowing at higher heights will improve forage quality and persistence both providing benefit to the farmer. Harvest frequencies have been shortened to produce higher quality forage, however there is no recent research to determine the range of harvest frequencies that can provide highest quality forage while minimizing stress on the plants. Updated research that evaluates the impact of frequency on forage quality (digestible nutrients per acre), regrowth potential, and persistence are factors farmers need to help improve farm viability and resiliency.

Finding the frequency of harvest and cutting height that will allow farmers to produce the feed they desire while also building large root systems will ultimately provide more long term protection to the farm. Farmers will be able to realize reduced costs associated with importing feed, wear and tear on equipment, and re-establishing damaged forage stands thus improving farm economics. Avoiding the importation of feed into the region can significantly reduce the potential for nutrient loading in soils and potential contamination of surrounding natural resources. In addition, maintaining stands that provide adequate soil surface cover and below-ground root biomass can help build carbon and stabilize soils reducing the risk of soil erosion and resulting nutrient runoff. In this way, this project will help farmers meet their own farm’s production and economic goals while enhancing environmental conservation.