AUTHOR=Laan Maggi , Strawn Daniel G. , Kayler Zachary E. , Cade-Menun Barbara J. , Möller Gregory TITLE=Phosphorus availability and speciation in soils amended with upcycled dairy-waste nutrients JOURNAL=Frontiers in Chemical Engineering VOLUME=5 YEAR=2024 URL=https://www.frontiersin.org/journals/chemical-engineering/articles/10.3389/fceng.2023.1303357 DOI=10.3389/fceng.2023.1303357 ISSN=2673-2718 ABSTRACT=

The excessive application of dairy manure to soils to supply plant nutrients can result in increased offsite nutrient transport and degraded water quality. However, by concentrating nutrients from dairy-waste onto biochar or as biosolids, a viable alternative fertilizer can be produced that will benefit soil health, promote carbon sequestration, and decrease nutrient leaching into surface waters. In this study, a greenhouse experiment was conducted to assess soil phosphorus (P) speciation and barley plant growth in soils amended with dairy-waste treated biochar and fermented manure. Phosphorus characterization in the post-harvest soils was determined using selective extractions, 31P-NMR and XANES spectroscopy, and isotopic tracing (P-δ18O). Selective extractions and NMR spectroscopy revealed that most of the P in the amended soils occurred as inorganic species (>85%). XANES spectroscopy further showed that the soil P occurred as either calcium-P minerals (54%–87%) or adsorbed P (0%–46%) species. Analysis by P-δ18O in water and sodium bicarbonate extractions of the treated soils showed that the water-extracted P pool is cycled much faster than the sodium bicarbonate extracted P. Although less than 10% of the total P in the dairy-derived bioproducts was extracted using water, plant productivity in the soils treated with these amendments was the same as that in soils treated with equivalent amounts of conventional nitrogen and P fertilizer. This suggests that dairy-derived bioproducts are good soil amendments to supply nutrients and limit leaching.