4) with a high A value due to high contents of iron and clay and a
Latosol (sample No. 7) sand with a very low value for A. Samples of
the soils were prepared with several different water contents: 13 samples
of the Red soil (a range of water contents from 0.0 to 0.39 cm3/cm3
water content with 1.0 g/cm3 bulk density) and 6 samples of the
Latosol (a range of water contents from 0.002 to 0.24 cm3/cm3 water
content with 1.30 g/cm3 density). Actual water contents, OA, were
measured by weighing and the experimental water content, OE, was ob-
tained by the dual-energy gamma beam method, with eight determina-
tions per sample.
 Actual water contents were plotted against values obtained by the
dual-energy gamma method (Fig. 10). A linear regression equation of
the form


OA = -0.0059 + 1.0095 OE


E

E 4

CD
4. .3
C


0
v.2
L
4,
C<
5 K1

jo


 Experimental Water Content, eE(cm3/cm3)

Figure 10. Sensitivity of soil water content determinations. Actual water
content, 0A, were determined by weighing and experimental values, OE, were
determined by the dual-energy attenuation method (Ferraz, 26). Data are
presented for a Red soil and a Latosol, each for a range of water contents.
The straight line was determined by linear regression (r=0.995).
 30