Use of gypsum blocks for measurement of soil water status : A dissertation submitted in partial fulfilment of the requirements for the Diploma of Agricultural Science in the University of Canterbury [Lincoln College]

Abstract

Considerable attention has been devoted to soil moisture studies by workers in agriculture, forestry, and engineering, and to a lesser extent by geographers. Methods range from age-old one of feeling a soil, to the recent neutron-scattering devices.

The Gravimetric method of soil moisture determination is still a standard reference method but it has the disadvantages of disturbing the sampling site and taking a long time to determine the soil moisture.

The Flask method is a very accurate and quick method of determining soil moisture, except for humic-rich soil, but it also has the disadvantages of disturbing sampling site.

There is a particular need for a quick and accurate method of measuring soil moisture in situ without undue damage to the site. Neutron-scattering devices have become increasingly accepted over the last decade because of the accuracy and speed of reading, but the main disadvantages include the high cost of the equipment, the maintenance cost, and the need for precautions in using radioactive materials.

Tensiometers have been used for measuring soil moisture .The tension range covered by tensiometers extends from zero to about 850cm of water. This is only a small fraction of tension range over which soil moisture is available for plant growth, since the wilting percentage corresponds approximately to the 15 atmosphere-percentage. Currently much of the interest in soil moisture is in terms of water potential which, because it is an energy concept , is valid for comparing water status through the soil -plant- atmosphere continuum