C - Lublin

metal concentrations were determined using the atomic absorption method. To
obtain the HA and FA fractions, the 0.1 N NaOH extracts were acidified to pH 1.5
with 1 N H 2 SO 4 . After the separation of precipitated HA from acid FA solution, the
P content in two fractions was determined by the Murphy-Riley method. The
contents of C, Fe, and Al were determined as noted above.
Difference electronic spectra of the alkaline extracts, HA and FA were
obtained using the solvent (0.1 N NaOH for soil extracts and HA, a mixture of 0.1
N NaOH and 1 N H 2 SO 4 for FA) as a reference.
The HA obtained from initial soil was used to prepare Fe-HA complex. The
treatment of HA with FeCl 3 provided C:Fe ratio of 1:6. The Fe-HA complex
prepared was treated for five weeks with KH 2 PO 4 solution added to have a C:P
ratio of 1:17. The pH value for systems was 4.1. Control complex and its P-
modified organic product were used for the IR examination (KBr – technique). IR
spectra of HA and FA from initial soil were also obtained.
RESULTS AND DISCUSSION
Table 1 shows that extractability of C and M by 0.1 N NaOH tended to
increase with increase in incubation period of P-enriched soil. Under these
conditions, the difference in distribution of alkali-soluble C and M between the HA
and FA fractions became more and more obvious. The amount of C associated with
HA was greater, the greater was the incubation period of P-enriched soil. On the
contrary, the amount of M associated with HA decreased sharply after one-year
incubation of soil enriched in P.
Table 1. The contents of C org , metals (Fe+Al), and P, mg/100 g soil
Soil treatment
1 year incubation
without P
with added P
0.1 N NaOH
extract
HA
FA
C org M C org M P C org M P
628
570
170
210
369
365
87
114
10
24
259
205
83
96
10
29
3 years incubation
without P
with added P
657
745
190
250
403
552
107
73
4
3
254
193
83
177
11
58
99