Linking Nutrient Transport to Soil Physical Processes During Freeze/Thaw Events to Promote Wintertime Manure Management, Nutrient Use Efficiency, and Surface Water Quality

View the project final report

• 2015 annual report
• 2016 annual report

Commodities

• Agronomic: corn
• Animal Products: dairy

Practices

• Animal Production: manure management
• Crop Production: no-till, nutrient cycling
• Education and Training: demonstration, extension, workshop
• Production Systems: agroecosystems
• Soil Management: soil chemistry, soil physics, soil quality/health
• Sustainable Communities: sustainability measures

Wintertime manure applications are a fundamental practice for dairy producers in the Midwestern United States and other temperate regions, yet nutrient losses in agricultural runoff are a major environmental concern, thus a key focus in manure management. Field- and watershed-based models are intended to guide surface applications of manure to minimize nutrient losses to the environment, however, these models are less effective during freeze/thaw conditions. Nutrient transport during the winter is sensitive to weather and the complex conditions of frozen soils. Therefore, this study aims to 1) quantify a winter water balance that 2) partitions nutrient movement from runoff and infiltration to elucidate the underlying freeze/thaw mechanisms that control soil infiltration potential, thus dictate surface nutrient transport after dairy manure applications. Specifically, soil infiltration potential will be tested on till versus no till corn silage fields with fall versus late-winter manure applications and unmanured controls. Runoff volume and nutrient load, snow-water equivalents, frost depth and type, sublimation, soil moisture, temperature, and vertical soil water fluxes will be monitored. Data from this field study will be used to develop and test winter routines for prediction tools that evaluate nutrient loss from agroecosystems (e.g. SurPhos, SWAT, APEX). These models will be used to update nutrient management software that directly benefits producers (e.g. SNAP-Plus). Moreover, findings will be used to produce fact sheets and workshops that highlight best management practices under frozen soil conditions and maximize on-farm nutrient use efficiency from winter manure applications. Increasing the knowledge of winter processes and nutrient transport through field research and model validation allows researchers and producers to improve agricultural sustainability by balancing environmental and economic viability.

The overall goal of this study is to improve the understanding of nutrient transport on and in frozen soils after wintertime dairy manure applications, as well as identify practices that minimize on-farm nutrient losses. A field approach will be used to quantify the complex relationships between wintertime soil physical processes, weather, and land management. Through calculating a water balance, we will link tillage and the timing of wintertime dairy manure applications to changes in infiltration potential, hence runoff risk, of frozen and thawing soils. Analyzing variables such as snowmelt rate, runoff volume, nutrient load, and soil permeability in relation to the timing of manure applications will help uncover the underlying mechanisms that drive nutrient retention in frozen soils. Therefore, the specific objectives of this study include:

1) Test the effect of wintertime manure applications on nutrient cycling and soil conditions on till and no till corn silage fields under fall spread, late-winter spread, and unmanured controls.

2) Quantify a winter water balance and partition nutrient losses to link differences in runoff volume and load from manure treatments to the infiltration potential of frozen and thawing soils.

3) Improve wintertime manure management guidelines and maximize on-farm nutrient returns for subsequent growing seasons.

Data will be used to develop and evaluate a new manure phosphorus runoff model for winter conditions (SurPhos), which will be integrated into field- and watershed-scale models (e.g. SWAT, APEX) to assess the impact of agricultural practices on environmental quality. The Wisconsin Phosphorus Index in SNAP-Plus, a nutrient-management program widely used by Wisconsin farmers to fulfill the state’s agricultural runoff management rules (NR151) will also be updated. Findings from this study will be integrated into dairy manure management programs for producers in Wisconsin through the use of fact sheets, nutrient management guides, surveys, presentations at Arlington Research Station Field Days, and UW-Extension workshops.