McQueen and Miller (1966, 1968) revived and improved a method described by Gardner in 1937, which measures the soil moisture tension based on the amount of water ate-sorbed by filter paper in contact with a soil sample.
Williams and Sedgley (1965) used a filter-paper method to estimate the 15-atmosphere percentage of soils, and Fawcett and Collis-George (1967) expanded that method to construct entire soil moisture retention curves.
Del Valle and Cadavid (1970) who tested the variability of McQueen and Miller's method also constructed soil moisture retention curves for several profiles of soils derived from volcanic ash.
SUBSTANCE: method comprises using microscopic chlorella algae as a biological test, distributing the suspension of the cells of chlorella over the paper filter on the surface of the soil plate in the Petri caps, obtaining chlorophyll extract, determining optical density of the extract, and comparing it with the reference one. The 20-ml volume of the suspension of the chlorella cells are distributed inside the Petri caps. The caps are covered and set into a greenhouse. The caps are exposed to light during seven days, and then the filters are removed from the caps, dried at a temperature of 38-42°С, grinded, and extracted. The allelopathy activity of the soil is expressed in per cents of the optical density of the extract on the reference one, in which chlorella is grown on the filter, which is set onto four layers of moistened filtering paper or cotton.
It is my purpose here to summarize a recently improved method for measuring soil moisture stress through the use of filter papers and to list some of the applications, since these are quite scattered in hydrology writings.
SUBSTANCE: method involves taking samples for refraction metering of cellular sap of indicating organs of vines from different parts of vineyard; determining cellular sap concentration by means of field refractometer; working out regression analysis diagram of dependence between content of soil moisture accessible for plants and refractometric factor value of cellular sap concentration of indicator organ for obtaining of "soil-sort" combination, said diagram being provided with additional irrigation norm scales for different vine growing periods. Indicator organs are 2-3 apex top internodes of green sprouts selected on the basis of refractometric factor value of cellular sap concentration and allowing moisture content of plants to be determined. According to diagram, irrigation time for vineyard is designated without allowing cellular sap concentration of indicator organ to be increased to critical level.