Nutrient over-loading in many dairy manure-amended soils in the dairy
producing areas of Texas has led to environmental problems as such eutrophication of
local surface water bodies. One of the nutrients contributing to eutrophication problems
is phosphorus (P). This project focused on fractionation and solubility of selected P
forms in an effort to determine a relationship with P found in runoff from dairy manureamend
soils. Ten soils (5 calcareous, 5 noncalcareous) were collected from the dairy
producing areas of Texas. Triplicate soil samples were analyzed for 0-5 cm and 5-15 cm
depths. An acid-base extraction method was used to determine total P (TP), inorganic P,
and organic P. Sequential extractions were used to determine the loosely-bound P, iron
(Fe) phosphates, aluminum (Al) phosphates, reductant soluble P, occluded apatite P, and
calcium (Ca) phosphates for calcareous and noncalcareous samples. The ammonium
oxalate method was used to determine extractable Fe, Al, and silicon (Si). Potassium
chloride extraction was used to determine soluble Ca, Al, Fe, Mg, and P. A weak NaOH
extract was used to determined the amount of bioavalible P. Dissolved P in runoff
events and soil pH were collected in a previous study. Calcareous and noncalcareous soils displayed varying concentrations of P
indifferent fractions and with separate comparisons, stronger relationships could be
achieved. It was also determined that KCl soluble Mg could be used as a predictor for
dissolved and total P in runoff for calcareous soils (r2âÂÂs ranging from 0.865 to 0.928 and
0.801 to 0.886, respectively). Ammonium oxalate extractable Al also yielded high
correlations in calcareous soils for dissolved and total P in runoff (r2 ranging from 0.798
to 0.991 and 0.766 to 0.973, respectively). In noncalareous soils, pH resulted in a less
correlated relationship with dissolved P (r2 = 0.600). This study shows that there are
simple and effective ways of predicting dissolved and total P in runoff to improve best
management practice recommendations for manure-amended soils.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/4888 |
| Date | 25 April 2007 |
| Creators | Harstad, Laura Elizabeth |
| Contributors | Feagley, Sam |
| Publisher | Texas A&M University |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Thesis, text |
| Format | 638328 bytes, electronic, application/pdf, born digital |
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