Soil Nutrient Availability and Soil Health Indicators in Long-Term Swine Manured Production Fields of North Dakota

Recycling livestock manure in crop production may reduce dependence on synthetic fertilizers while influencing soil nutrient availability and soil health. The objective of this study was to compare soil nutrient concentrations and selected soil health indicators between farms receiving swine manure and neighboring non-manured production. Six fields located within an 18-km radius in Towner County, North Dakota, including three fields with a history of swine (Sus scrofa) manure application and three fields managed with synthetic chemical fertilizers only, were evaluated in 2022. Surface soil samples (0–15 cm) were analyzed for aggregate stability, nutrient availability, soil organic carbon (SOC), total nitrogen (N), and permanganate oxidizable carbon (POXC). Average soybean (Glycine max) and spring wheat (Triticum aestivum L.) yields during 2013–2022 were similar between manure (M) and non-manure (NM) fields. Manured fields had greater available phosphorus (P) and zinc (Zn) concentrations compared with NM fields (p = .02 and p = .04, respectively). Differences in aggregate functions were observed between M and NM fields, although these responses were likely influenced by inherent soil texture differences among sites. Results suggest that periodic swine manure application under on-farm conditions can maintain crop productivity while increasing the availability of selected nutrients without negatively affecting measured soil health indicators. However, field scale variability in soil properties and management histories should be considered when interpreting manure effects under on-farm conditions.