Phosphorus speciation in calcareous soils following annual dairy manure amendments
Weyers, E., Strawn, D.G., Peak, D., Moore, A.D., Baker, L.L., Cade-Menun, B. (2016). Phosphorus speciation in calcareous soils following annual dairy manure amendments, 80(6), 1531-1542. http://dx.doi.org/10.2136/sssaj2016.09.0280
Plain language summary
Applying manure to crops can change the forms of phosphorus (P) in the soil. This can change the availability of P for plant uptake, and can also affect whether this P will be transported to water bodies, where it can contribute to harmful and nuisance algal blooms.
This study investigated the effects of three years of manure additions (at two levels)
on the forms of P in calcareous soil, compared to chemical P fertilizers and no fertilizer. Total P concentration in the manure-amended soils increased over 3 yr. The highest soil test P concentrations were in the soils receiving the highest rate of manure. Most P in these soils was associated with calcium minerals, regardless of fertilizer. This study will provide a baseline to compare the effects of long-term fertilizer application on P cycling, and will be useful for planning manure applications to calcareous soils to limit excess soil Pthat could leach into water.
© Soil Science Society of America. Applying manure to crops may alter P speciation in the soil profile and thus affect its availability for plant uptake and transport to surface waters. The goal of this research was to determine how repeated manure amendments affect P speciation within calcareous soil. Soil samples were collected in 2013, 2014, and 2015 from two depths to analyze differences in P composition following annual applications of 17 Mg ha-1 manure, 52 Mg ha-1 manure, or NH4H2PO4 fertilizer, and control plots (no P). To speciate the soil P, sequential chemical extraction, P K-edge X-ray adsorption near-edge structure (XANES) spectroscopy, 31P nuclear magnetic resonance spectroscopy, and microprobe element mapping were used. Total P concentration in the manure-amended soils increased over 3 yr. The highest soil test P concentrations were in the 52 Mg ha-1 plots. Most extractable P in the sequential extraction procedure was removed with the most aggressive extractant, suggesting that the predominant form of P is associated with Ca-P minerals. The XANES results showed that P species were similar among all amendments and years: 54 to 74% Ca-P minerals (e.g., hydroxyapatite), 25 to 35% adsorbed P, and 0 to 19% organic P (predominantly phytic acid). Despite the poorly soluble Ca-P species predominating in all soils, soil test P increased in the manure-amended soils. The P speciation results provide a baseline to compare how long-term changes affect P availability and will be useful for designing long-term scenarios in manure-amended calcareous soils to limit excess soil P that could leach into water.