Premium
Phosphorus in Fresh and Dry Dung of Grazing Dairy Cattle, Deer, and Sheep
Author(s) -
McDowell R. W.,
Stewart I.
Publication year - 2005
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2005.0598
Subject(s) - pasture , grazing , fractionation , phosphorus , zoology , bioavailability , chemistry , agronomy , nutrient , biology , bioinformatics , organic chemistry
Knowledge of phosphorus (P) fractions in dung of animals (dairy cattle, deer, sheep) grazing pasture is important for soil fertility and the potential for P transport in runoff and subsequent surface water quality deterioration. We used sequential fractionation and 31 P nuclear magnetic resonance (NMR) spectroscopy to determine P forms in fresh and air‐dried (to simulate field conditions during grazing) dung. Sheep dung was richest in P (8 g kg −1 ), and cattle dung poorest (5.5 g kg −1 ). Data for sequential fractionation indicated that most P was extractable by water (15–36%) and bicarbonate (36–45%) in fresh dung, and shifted toward recalcitrant, HCl (12–28%), and residual P forms (15–31%) with drying. Organic P concentration in dung was poor (maximum of 15% of total P), probably due to the poor concentration of phytate in pasture. The 31 P NMR spectra of NaOH‐EDTA extracts supported this by detecting a low concentration of monoesters (9–19% of total P in extracts), of which phytate is a major component. The 31 P NMR data also showed that changes in organic P concentration with drying could be due to the degradation of diesters. Data indicate the decreasing bioavailability of dairy cattle, deer, and sheep dung with drying and the need to consider this effect with respect to P returns for soil fertility and the potential for runoff.