MADISON, WI, FEBRUARY 2, 2009--Phosphorus is one of the key nutrients that can cause algal blooms and related water quality problems in lakes, rivers, and estuaries worldwide. Phosphorus entering waters originates from a variety of sources. Agricultural land receiving long term applications of organic by-products such as animal manure is one of the major contributors. Such soils often become enriched with P, leading to elevated P loss through erosion and runoff. Information on the chemical characteristics of P in these soils is essential to improving our understanding of how P behaves in soils and how it is transported in runoff to devise better management practices that protect water quality.
A group of scientists in the USA and Australia have identified the chemical forms of P, using 31P nuclear magnetic resonance (NMR) spectroscopy, in soils receiving organic by-products for at least eight years (treated) as compared with soils not receiving P application (untreated). Results from the study were published in the January-February issue of the Soil Science Society of America Journal.
Regardless of the type of organic materials applied (dairy, swine, poultry, or spent mushroom compost), orthophosphate (inorganic P) was the single dominant P form, more so in treated soils (79-93% of total P) than in untreated soils (33-71%). Orthophosphate was also the only P form that differed dramatically between paired soils, three to five times greater in treated than untreated soils. Other P forms included condensed inorganic P and various organically bound P groups; however, their amounts were relatively small and differences between each paired soils were insignificant.
Surprisingly, the study revealed no evidence of phytate-P accumulation in any of the soils receiving organic wastes. Phytate is an organic storage form of P that is known to be present in animal manures, in particularly large proportion (up to 80% of total P) in pou
|Contact: Sara Uttech|
Soil Science Society of America