Agriculture Reference
In-Depth Information
Box 4.4 Measuring Bulk Soil Strength in the Vineyard
Bulk soil strength in the vineyard is measured by the resistance offered to the
entry of a penetrometer, an instrument consisting of a steel rod about 1 m long
withasharp,conicaltipandapressuregaugeatthetop(igureB4.4.1).Asthe
tip is pushed into the soil, the pressure applied to overcome the soil's resistance is
recorded by the gauge. The rod has a graduated scale so that the pressure can be
recorded at known intervals down the profile. Readings are most reliable when
the rate of entry of the rod is constant. Penetration resistance and hence bulk soil
strengthvaryspatiallysothatalargenumberofreadingsarerequiredtoobtain
an acceptable average value. Because soil strength depends on wetness, as shown
in figure 4.7, measurements should be made at the same water content, usually
around
FC
.
Figure B4.4.1
A handheld
penetrometer in use.
(Photocourtesyof
Dr. Jonathan Holland,
NewSouthWales
Department of Primary
Industries,Australia.)
Penetrometers are valuable for detecting where compacted soil and hard
layers occur in the profile and how serious they are. This information allows the
most appropriate ameliorative treatment to be determined, whether it be deep
ripping, sowing a permanent cover crop, applying gypsum, mulching, or some
combination of these.
