Bahiagrass (Paspalum notatum Flugge) pasture fertilization recommendations
have traditionally been based upon clipping studies. Inclusion of P from ma
nure, not originally considered when P recommendations were developed for p
astures, may minimize the need for P fertilization without reducing bahiagr
ass production or P uptake. The objective of this research was to determine
if manure contributes greatly to the P crop nutrient requirement. A 2-year
field study utilized a factorial arrangement of 0 and 6.9 Mg air-dried man
ure ha(-1) with 0, 17, 34, 51, and 68 kg inorganic P ha(-1) from triple sup
erphosphate to evaluate bahiagrass yield, root distribution, and P uptake r
esponse on a Myakka fine sand (sandy, siliceous, hyperthermic Aeric Alaquod
). Because air-dried manure was used in the field study, a greenhouse study
was employed to confirm that there were no differences in bahiagrass yield
or P uptake from either air-dried or fresh cattle (Bos spp.) manure source
s. There were no manure or manure by P interaction effects on yield or P up
take of bahiagrass indicating that manure source did not effect grass produ
ction in the greenhouse. In the field study, bahiagrass roots were distribu
ted into the Bh horizon, and the Bh horizon had at least four times more Me
hlich-1 extractable P than that of the Ap horizon. This horizon was most li
kely acting as a main source for P-uptake by the grass. This observation wa
s further confirmed by no yield response to levels of inorganic P applicati
on in 1989. A linear-response-and-plateau (R-2=0.196) relationship with a c
ritical point of 15.4 kg P ha(-)1 was found in 1990. Bahiagrass yield and P
uptake were not dependent on P fertilization, either from manure or inorga
nic P, due to the availability of P from the Bh horizon.