3 July 2016
As reported recently in the online magazine No-till Farmer, a study led by Ohio Northern University chemistry professor Christopher Spiese links the popular herbicide glyphosate to dissolved reactive phosphorus (DRP) desorption in soils. Mobilization and runoff of phosphorus to streams and lakes is associated with toxic algae blooms in Lake Erie and the Gulf of Mexico Dead Zone.
For decades, soil scientists have understood phosphorus to form low-solubility compounds or to be tightly bound to soil particles. To control phosphorus, it was important to reduce soil erosion. Control erosion and we could control phosphorus runoff. Here is an example of this well-worn but, in my opinion, somewhat outdated understanding from PennState Extension:
Phosphorus is not lost into the atmosphere—rarely does it leach beyond the reach of roots…The concentration of soluble phosphate in the soil solution is very low, and phosphorus is relatively immobile in the soil…Because phosphorus is very immobile in the soil, it does not move very far in the soil to get to the roots. Diffusion to the root is only about 1/8 of an inch per year, and relatively little phosphorus in soil is within that distance of a root.
To the contrary, recent studies (1, 2, 3, 4, 5) indicate significant leaching of phosphorus from agricultural fields. The Agronomy Society of America reports here:
http://blogs.agu.org/terracentral/2016/07/03/lake-erie-watershed-soil-phosphorus-study-shows-glyphosate-link/
There is a wealth of information out there about Christopher Spiese and this particular study.
https://www.onu.edu/user/12601
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