Assessing the implications of chloride from land application of manure for Minnesota waterways

An emerging concern in Minnesota is increased chloride levels in ground and surface waters. Efforts to develop a statewide chloride-based fertilizer mass balance need research to better understand chloride concentrations in manure and pathways for movement. 

The objectives of the proposed project are to:

  1. Demonstrate the variability for chloride concentration in manure samples from Minnesota livestock and poultry farms based on species, geographical region, and correlating manure characteristics.
  2. Quantify the movement of manure-based chloride applied to Minnesota soils.
  3. Evaluate the leaching risk potential based on manure type (and chloride concentration) and soil characteristics.

The scope of this project is greater Minnesota, with manure and soil sampling drawing from livestock intensive areas across the state. The first activity leverages existing partnerships and collaborations to analyze manure samples from across Minnesota and enter that information into a newly created manure characteristic database. We will contract with a commercial laboratory to add chloride analysis to approximately 1,900 manure samples and share the anonymized data with us via the database. The Ph.D. student will use the database and related functions to summarize and analyze the data for spatial and temporal variation in chloride concentrations. The second activity explores interactions between different soil and manure types (also a synthetic fertilizer and no-nutrient control) on chloride leaching with in-tact soil cores representing coarse, medium, and fine-textured soils. The M.S. student will collect and analyze manure, soil, and leachate samples for chloride and other nutrients before and after multiple simulated rainfall events. The students and project team will collaborate on the third activity to assess the leaching risk potential for field scale application of manure. This analysis will include a sensitivity analysis of the chloride balance for soil systems to guide stakeholder discussions on mitigation options and future research directions.

The short-term expected benefits of this project are an increase in the quantity and quality of manure chloride data to support modeling efforts and a better understanding of if and how manure chloride leaching differs from that of synthetic fertilizer. Through this project, two graduate students will be trained within an interdisciplinary team, with opportunities to learn and practice team science and communication skills.