| dc.description.abstract | Soils from Gitunmba, Kabete, Katumani and Lanet areas
of Kenya were sampled for analysis. The major objectives
of the investigation were to determine the quantities of the
inorganic and organic forms of phosphorus and to determine
the fate of applied water soluble phosphorus in these soils
and their phosphorus adsorption properties using Langmuir
adsorption isotherms. Gituamha soil had the highest amount
of iron and aluminium phosphates, followed by Kabete, Lanet
and Katumani soils in that order. Calcium phosphate was
found to be low in most of the soil samples analyzed.
Gituamba soil had higher levels of organic phosphorus
than the other three soils. OrgRnic phosphorus in Kahete
soil decreased sharply with depth. In Lanet and Katumani
soi Is organic phosphorus decreased gradually with depth.
The distribution of organic phosphorus was closely related
to the distribution of organic matter. High organic
phosphorus in Gituamba soil was associated with high soil
acidity which most likely decreased microbial mineralization
of orga~ic phosphorus.
(viii)
The amount of phosphorus fixed as aluminium and iron
phosphates increased between 3 to 30 days, while calcium
phosphate decreased in all the soils. Phosphorus fixed was
correlated with oxalate-extractable Al203 and Fe203.
Gituamba soil sorbed the highest amount of phosphorus
and its phosphorus adsorption max~mum was 99 ~g pig and
the constant related to bonding energy (k) was 4.4 x 10-3
M-1. Phosphorus adsorption maximum for Kabete soil was
49 ~g Pig and the k value was 6.3 x 10-3 M-1. For Katumani
soil phosphorus adsorption maximum was 14 ~g Pig and the
k value was 34 x 10-3 M-1. Phosphorus adsorption maximum
for Lanet soil was 33 ~g Pig and the k value was
10 x 10-3 M-1. Phosphorus sorption was strongly influenced
by oxalate-extractable Fe203' AI203 and organic carbon
(their correlation copfficients being 0.96, 0.79 and 0.93
respectively, thtlS being highly significant for Fe203 and
organic carbon). The T,angmuir constant, k was not corrected
for the inita1 surface phosphate. | en |
