An introduction to the APLE-Lots barnyard runoff model
2021
- Biological Systems Engineering UW Madison
Project Media
Comprehensive nutrient management planning has become an increasingly important aspect for
agricultural land management throughout Wisconsin. Phosphorus (P) loss from agricultural lands can
adversely impact the quality of receiving water bodies. For dairy and beef farms, P loss originates from
cropland, grazed pastures, and open-air cattle lots, such as feedlots, barnyards, exercise lots, or overwintering
lots. From a whole-farm perspective, P loss from all sources should be evaluated to effectively
identify the major P sources to target remediation practices. Research shows cattle lots can be significant
sources of P loss for two reasons. First, the high concentration of cattle leads to high rates of manure
deposition and P accumulation relative to pastures and cropland. Second, cattle holding areas can be partially
or completely devoid of vegetation and have a compacted or impermeable (e.g., concrete) surface, which can
lead to high rates of runoff and erosion. This combination of a concentrated P source and active transport
pathways creates the potential for high rates of P loss. In areas with both non-point source P pollution issues
and a high prevalence of cattle farms with outdoor lots, there is a need to assess the P loss impact of lots
relative to other agricultural land uses to see if alternative lot management is needed. Computer models can
be cost- and time-effective tools to help quantify P loss from farms and identify alternative management
practices that reduce the impact of agriculture on water quality.