II. DESERT SOILS
63
in the deserts of North and South America (personal observations). Inorganic phosphorus moves downward in desert soils only very slowly but
has been shown to move in organic form (Hannapel et al, 1964). Organic
phosphorus represents a significant proportion of total phosphorus of native desert soils even though organic matter is low (Fuller and McGeorge,
1950b) (see diagrams in Fig. 13).
Organic phosphorus (ppm)
KX)
200
300
0
100
2 0 0
300
4 0 0
0
100
200
300
4 0 0
0.1
0.2
0 3
01
0.2
0.3
0.4
100
2 0 0
300
4 0 0
Q.
ω
a
2.5
7.5
1.5
3.0
4.5
6 0
&y>4
% t
P
>
*
A
A
/
(
/
/ Toltec
/ loam
/
'
0.1
0.2
0.3
0.4
0
0.1
100
200
300
400
500
0
0.2
0.3
0.4
TOO 800
900
1000 1100
0.1
0.2
0 3
0.4
0.5
0.
Organic carbon (%)
10
2.0
3.0
4.0
Fig. 13. Relationship between the soil organic phosphorus and organic carbon
in some desert soils of the Southwest United States.