Nutrient mass balance and fate in dairy cattle lots with different surface materials

Authors: Vadas, Peter; Powell, Joseph

Submitted to: American Society of Agricultural and Biological Engineers
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/14/2018
Publication Date: 2/2/2019
Citation: Vadas, P.A., Powell, J.M. 2019. Nutrient mass balance and fate in dairy cattle lots with different surface materials. American Society of Agricultural and Biological Engineers. 62(1):131-138. https://doi.org/10.13031/trans.12901.
DOI: https://doi.org/10.13031/trans.12901

Interpretive Summary: On dairy farms, outdoor cattle lots can be a place of high nutrient deposition in manure. This represents an inefficient use of farm nutrients and potential loss to the environment. Management of barnyards to recover nutrients can have environmental and production benefits. We monitored nitrogen (N) and phosphorus (P) fate over five years in dairy heifer barnyard plots constructed with soil, sand, or bark mulch surfaces. Of total N inputs to plots through cows, only 6 to 19% of inputs were lost in runoff, leaching, and gas emissions. Of total P inputs to plots by cows, only 4 to 6% of inputs were lost in runoff and leaching. Therefore, most nutrients deposited by cows onto barnyards could be recovered and used as fertilizer for crop growth by removing surface materials and spreading them on cropland, or including animal lots in land used for crop rotation so crops can recover nutrients.

Technical Abstract: On dairy farms, outdoor lots where cows spend substantial time can be a place of high nutrient deposition in manure. This represents an inefficient use of farm nutrients if nutrients are not recovered and a potential for nutrient loss to the environment. Management of barnyards to recover nutrients can have environmental and production benefits. We monitored nitrogen (N) and phosphorus (P) fate over five years in dairy heifer barnyard plots constructed with soil, sand, or bark mulch surfaces. Barnyards were stocked with dairy heifers several times per year, for about a week at a time. We monitored N and P loss in runoff (soil plots only), leachate, and gas emissions. Of total N inputs to plots through cow excretion, 6 to 8% of inputs were lost in runoff (~2%), leachate (~3-4%), and gas emissions (~3-4%) from soil and mulch plots. The majority of N inputs remained in the surface material. For sand plots, more N inputs were lost in leachate (~13%) and gas emissions (~6%), but most N still remained in surface materials. Of total P inputs to plots by cow excretion, 4 to 6% of inputs were lost in runoff and leachate, with most P remaining in surface materials. Results suggest most nutrients deposited by cows onto barnyards could be recovered and used as fertilizer for crop growth by removing surface materials and spreading them on cropland, including animal holding areas in land used for crop rotation so crops can recover nutrients, or corralling animals directly on cropland.