Manure characteristics can influence the potential for P transfer in
runoff following land application of manures. This research assessed
the influence of manure characteristics on P solubility in calcareous
soils using manures from poultry (Gallus Domisticus) fed a variety
of grain-based diets with the manures containing a range of total P
(5.6-16.4 g P kg-1), water-extractable P (WEP, 0.9-4.7 g P kg -1),
phytic acid P (0.1-7.6), total N/P ratios (2.6-5.1), and total C/P ratios
(19.5-75.7). In addition, mono-ammonium phosphate fertilizer and
reagent grade inositol hexaphosphate (phytic acid [PA]), were included,
as well as a control treatment with no P additions. Treatments
were incorporated into two soils (Portneuf [Coarse-silty, mixed,
superactive, mesic Durinodic Xeric Haplocalcids] and Millville
[Coarse-silty, carbonatic, mesic Typic Haploxerolls]) at three rates
(10, 20, and 40 mg P kg -1) and incubated for a total of 18 wk with
subsamples taken at 2, 5, 9, and 18 wk. Soil samples were analyzed for
inorganic and organic NaHCO3 (Olsen) extractable P and select soils
were analyzed at 0 and 12 wk by 31P nuclear magnetic resonance
spectroscopy (NMR) for soil P characterization. The percentage of
WEP and PA (of total P) in the manures were linearly related (r 2 =
0.94). Increases in Olsen P over time were positively related to the
percentage of monoester P in the treatments. At 2 wk, there was a
strong negative correlation between the amount of PA added in the
treatments and increases in Olsen P. However, by 18 wk, Olsen P was
more closely related to the amount of C or N added with the treatments.
Changes in PA content of manures due to dietary modification may
influence P sorption on calcareous soils in the short-term while other
characteristics such as C/P ratio may exert a stronger influence over
changes in soil test P over longer time periods
