Effect of dairy manure-based fertilizers on nitrous oxide emissions in a semi-arid climate

Manure treatment technologies are of interest to dairy operations to improve nutrient management, although there are little data related to nutrient availability and environmental impacts of these manure-based fertilizer products. This field trial experiment investigated the impact of two manure-based fertilizer sources (phosphorus enriched solids [PE] and mechanical vapor recompression solids [VR]) on soil nutrients, crop yields, and N₂O emissions in a forage rotation. The study was a factorial random complete block design, with two main factors: manure history (with [M]; without [NM]) and manure-based fertilizer product (control [Con], PE, VR), under a continuous corn and triticale rotation. M had greater soil organic carbon, total carbon, total nitrogen, and M3-P (30%–128%) and reduced NH₄-N (15%) than NM, with no other treatment differences. Corn silage yields were greater in NM versus M (7%) treatments only in 2021, while in 2022 VRNM was 17% greater than ConNM only. Triticale yields were 14% greater in M plots versus NM treatments only in 2021. In 2022, triticale yields were 1.7 times lower in ConNM versus all other treatments, and PENM was 71% greater than ConM. The greatest N₂O fluxes occurred in May, June, and July with M having 69% greater average cumulative fluxes than NM, while average VR cumulative fluxes were 102% greater than PE and Con. Over both years, net loss of N_applied as N₂O-N was 1.9%–2.2% for VR and 0.4%–0.8% for PE solids. While manure-based fertilizers performed well as a nutrient source, their susceptibility to N₂O loss needs to be considered in management strategies.