western-queensland-gardening-guide.pdf - South West NRM

At the neutral pH level, that is 7, all nutrients are available. As the soil increases in
alkalinity nutrients including nitrogen, iron and copper become unavailable; at the
other end of the scale, the acid end, the availability of nutrients tapers off. Therefore,
the closer the soil is to neutral, the wider the range of nutrients available and the better
your plants will grow.
Plants respond differently to pH. The majority of species grow well between 6.5 and
7.5, that is, in the neutral range. Some are quite adaptable and will tolerate a pH from
6 to 8. Bulbs like daffodils and jonquils are in this category. However, some plants
have very special requirements and a narrow range; for example, azaleas require a pH
of 4.5 to 5.5, that is very acid, making them quite unsuitable for the alkaline conditions
produced by bore water. When the pH is greater than 8.5, which is common when
bore water is used, the range of species able to be grown is very restricted.
The salts in bore water cause a build-up of salts in the soil which causes changes in the
soil structure. This leads to hard setting of the soil and impermeability to water as
mentioned earlier. When the concentration of salts in the soil is too high the plants can
actually perish for want of water, even if the soil is moist. This happens because the
membranes which convey water from the soil through to the plant are adapted to a
certain solution strength of salts. n there is too much salt, the water cannot pass
through the membrane resulting in the plant's death.
Some plants are better adapted than others to salty conditions. These are mentioned in
the list of salt-tolerant plants at the end of this chapter. Plants which are included in
both salt-tolerant and alkaline-tolerant lists are the most valuable plants to use when
gardening with bore water.
With problem water it is easier to use species which tolerate salt and alkalinity rather
than struggling with less suitable species and having to use expensive chemical
methods or time-consuming mechanical measures. There are also a number of species,
particularly native shrubs and trees, which after the establishment phase require little
water (see Table 4). Some of these are quite attractive and are certainly worth
consideration. It is best to choose plants which are adaptable to their surroundings
rather than trying to drastically change the environment.
Steps for growing less well-adapted plants
In small, special purpose areas, there are some steps which can be taken to grow less
well-adapted plants.
A necessary addition to most gardens is vegetables. Where there is a real problem
with clay soils and bore water, it is often beneficial to form raised beds of well-drained
sandy soils on top of the heavy clay soil. This improves the drainage and keeps the
salt content to a minimum. Do not mix the sandy soil into the clay. A bed 20 to 30 cm
high is adequate for annual vegetables and flowers and some ornamental trees and