Soil pH - Soil Essentials: Managing Your Farm's Primary Asset - page 10

FUNGI

BACTERIA

Numbers

ALKALI TOLERANT WORMS

ACID TOLERANT WORMS

3 4 5 6 7 8 9 10 11

pH (water)

Figure 5 Influence of pH on soil organisms. ( Soil Sense C-03)

Response to pH test results
Results that indicate very low or very high pH levels show the soil has major
problems for supporting normal plant growth.

(1) Low pH (acid soils)
Some soils are naturally acid, while others have become acid over time through
management practices such as product removal, nitrate leaching and consistent use
of large amounts of nitrogen rich fertilisers, with the worst case being when the
subsoil becomes acid as well as the topsoil. Acidity in the topsoil can be corrected
by using one of a number of forms of lime and the economics of using lime should
be considered in terms of productivity and sustainability. The trend over a number
of years is the important issue, and soils that are becoming progressively more acid
indicate a change in management is required. A soil with a pH(w) of 5.5 or lower is
in need of special management to be sustainably productive, for example, by using
the short-term measure of growing acid-tolerant species and applying lime for
longer term benefits.

(2) Moderately to slightly acid soils
The important consideration is whether the trend in acidity over time is stable or
increasing. If it is increasing, occasional liming and/or a change in management
practices is needed.