To evaluate the effect
s of di
ssolved organic carbon (DOC) on pho
sphate retention (including both
sorption and/or precipitation reaction
s) on
soil
s, experiment
s were performed by u
sing two typicalcalcareou
s soil
s from
southea
stern Spain (Calcic Rego
sol and Luvic Xero
sol) and two different type
sof DOC: (1) extract
s from a commercial peat (DOC-PE) and (2) high-purity tannic acid (DOC-TA).The experiment
s were carried out from a 0.01 M CaCl
2 aqueou
s medium at 25
![](/image<font color=)
s/entitie
s/deg.gif">C. The re
sult
s obtained
show that the pre
sence of both DOC-PE and DOC-TA, over a concentration range of 15 (DOC-15)to 100 (DOC-100) mg L
-1, produce
s in all ca
se
s a decrea
sing amount of pho
sphate retained in the
soil
s studied, the decrea
se ob
served being higher when DOC-PE i
s u
sed a
s source of DOC. Thevalue
s of the decrea
se ob
served when DOC-PE wa
s added ranged between 19.9% (DOC-15) and15.6% (DOC-100) for the Calcic Rego
sol and between 17.3% (DOC-70, DOC-100) and 14.6%(DOC-15) for the Luvic Xero
sol. The variation ob
served when DOC-TA wa
s added ranged between8.5% (DOC-100) and 0.5% (DOC-35) for the Calcic Rego
sol and between 7.0% (DOC-100) and1.0% (DOC-15) for the Luvic Xero
sol.Keyword
s: Pho
sphate;
sorption; precipitation; calcareou
s soil; di
ssolved organic carbon