Rotational grazing systems are a great alternative to confined farming, especially for small farms. Initially, capital expenditures can be a concern, but financial assistance (e.g., Environmental Quality Incentives Program) is available to establish fencing, watering systems, and other practices. Many farmers in Wisconsin realize the benefits of rotational grazing for farm finances, agronomics, and soil/ecosystem health. Timely applying nitrogen (N) fertilizers to rotationally grazed dairy pastures increases pasture yields, extends spring grass growth into the early summer and maximizes fall pasture production. N-fertilizer application requires soil testing and planning for the operation to be timed to minimize N losses through leaching (nitrate (NO3-)), denitrification (NOx, N2O), and volatilization (NH3). With the increased fertilizer prices, split N fertilizer applications to rotationally grazed pastures are recommended to make the best use of the nutrients and reduce the risk of losses due to seasonal weather events (e.g., rain, drought, heat). Although there are studies in the literature, the most efficient timing for N applications to rotationally grazed pastures in Northern and South Central Wisconsin has not been established yet. This study will comprehensively assess soil NO3- levels following fertilizer applications and aerial mapping of N-containing gas emissions from the surface of fertilized dairy pastures. As good pasture management improves soil and water quality, the proposed study addresses two major topics stated in the RFP: soil management (directly) and surface or groundwater problems (indirectly).

Nutrient contamination in groundwater has been a concern for Wisconsin residents since the 1960s and the risk has shown an increasing trend over the past decade (Cox, 2021 from the National Academy of Sciences). A recent article from the New York Times has put pressure on Wisconsin agriculture to reduce nitrate leaching to groundwater. Collecting nitrate leaching information from cropland over the growing season is cumbersome and expensive. Unlike other Midwestern Universities (e.g., Iowa State, Purdue, Ohio State, Minnesota), UW-Madison (and thus the state of Wisconsin) does not have a long-term monitoring network to study nitrate leaching under different cropping systems and various management practices. Such a network is crucial for assessing on-farm management and improving biogeochemical models that can be used to develop best management practices to reduce negative environmental impact of agriculture while maintaining or increasing soil productivity.

Turfgrass is an important specialty crop that impacts nearly every citizen in Wisconsin. The uses of turfgrass are highly diverse and include athletic fields and golf courses; home, commercial, and institutional landscapes, parks and public recreation areas; and cemeteries and roadsides. Turfgrass landscapes provide numerous extensive ecosystem services to urban and suburban communities (Thompson & Kao-Kniffin, 2017). Turf protects and enhances our environment through climate regulation, nutrient and pollution filtration, dust reduction, and other ecosystem services. Despite these services, there has been increasing attention drawn to the negative aspects of inputs to turf, including the use of water, fertilizers, and pesticides. 

In this project, we propose adapting a world-renowned global dynamic ecosystem model, Agro-IBIS (Agricultural Integrated Biosphere Simulator), specifically for turfgrass and its ecosystem services. Through over 20 years of research and development, Agro-IBIS has simulates both natural and agricultural ecosystem processes accurately by integrating models of land surface physics, vegetation dynamics and phenology, and belowground biogeochemistry within a single consistent framework (Foley et al., 1996). 

There is little, if any, nitrogen (N) response research conducted for corn silage in Wisconsin. This is somewhat surprising as 25% of the corn grown in the state is harvested as silage (2021 Wisconsin State Agriculture Overview). Current N recommendations for corn silage are to use the maximum return to N (MRTN)-based recommendations for corn grain, and then select a rate toward the higher end of the recommendations to minimize purchased feed (Laboski & Peters, 2012). However, with biomass-based crops, expected yield may be a valuable metric to developing N recommendations. In fact, Penn State University has N recommendations for corn silage based on expected yield (https://extension.psu.edu/nitrogen-fertilization-of-corn). Current N recommendations in Wisconsin are also based on the premise that corn silage and corn grain N response is the same, but there does not appear to be any data to support this statement. Corn silage is also assessed for quality, so quality should be an important consideration in developing N recommendations. In addition to just N recommendations, the manure N credits and the cover crop fertilizer adjustments may also be different for corn silage compared to corn grain. 

The Central Sands region of Wisconsin is an intensively farmed highly productive growing region for high value vegetable crops, notably potatoes. However, the Central Sands has coarse grained soils and shallow depth to groundwater, making it particularly vulnerable to leaching of agricultural chemicals into groundwater. Additionally, potato crops have a high water demand and typically require 25-40cm of irrigation annually to supplement rainfall. Well sampling by the Wisconsin Department of Agriculture, Trade and Consumer Protection have found numerous sites with elevated levels of nitrate in this region. While it is known that regional use is leading to nitrate infiltration into groundwater, the contributions of individual field-scale operations for a complete crop rotation cycle have not been quantified in detail. Additionally, common farm management practices (companion cropping and variable irrigation rates) that may mitigate nitrate leaching have likewise not been quantified in this region.