| Integrating pastured poultry with crop production is on the rise in California due to high demand for pastured products and desire by farmers to close on-farm fertility cycles. The rise of this practice has been accompanied by an increase in research, but there remain significant gaps in knowledge concerning pastured poultry/crop systems. This dissertation addresses those gaps using literature review, soil quality and crop growth investigation, grower surveys, and soil pathogen research. In Chapter 1, I summarize the literature on integrated crop/livestock agroecosystems in the United States. Chapter 2 investigates the experience of farmers raising pastured poultry in California. Growers reported positive results with soil fertility and marketing appeal and negative experiences with predation and feed cost. Pastured poultry were directly profitable to 50% of farmers, although 78% of respondents cited indirect profits through savings on items such as fertilizer and pest management. In Chapter 3, I present biological, physical, and chemical soil differences between pastured poultry fields and crop-only control fields. I found that poultry and pasture elevated soil quality parameters total C, total N, NH 4+, NO3--, Olsen P, K, organic matter, and cation exchange capacity relative to the control. These changes conferred greater biomass and height to plants grown in these soils and improved plant tissue concentrations of N, P, and K for most treatments. Soil Olsen P was elevated to potentially ecologically detrimental levels at one site. In Chapter 4, I present results from experiments assessing the prevalence of soil borne pathogens in pastured poultry and control fields. No incidences of E. coli O157:H7 or Campylobacter spp. were found in soils from any site. Soils from both pasture and control fields tested positive for Salmonella spp., making definitive interpretation of these results inconclusive. In summary, this research finds that pastured poultry/crop systems can be profitable to farmers and that certain crops can be grown in these agroecosystems without the addition of supplemental fertilizers. However, further attention to P management is critical, and integrated systems should be managed with care to avoid cross-contamination of crops by zoonotic pathogens. |
