Correction

Soil Research ◽  
1993 ◽  
Vol 31 (2) ◽  
pp. 225
Author(s):  
IM Wood

Measurement of the Total Water Potential of Aqueous-Solutions of Polyethylene-Glycol - a Comparison Between Osmometer, Thermocouple Psychrometer and Equilibrated Soil Cores (Vol 31, Pg 7, 1993)

Soil Research ◽  
1993 ◽  
Vol 31 (1) ◽  
pp. 1
Author(s):  
IM Wood ◽  
IK Dart ◽  
HB So

This study examined two polyethylene glycol (PEG) polymers (PEG 6000 and PEG 10000) and compared measurements of water potential obtained with a thermocouple osmometer and thermocouple psychrometers at three temperatures (15, 25 and 35�C) and five osmdalities (50, 100, 200, 300 and 400 g/1000 g water). These were then compared with estimates of matric potential of three soils brought to equilibrium with PEG solutions of the same osmolalities. At the same osmolality and temperature the two PEG polymers gave essentially the same water potential. There was a significant effect of temperature on water potential which corresponded closely with changes in specific gravity of the PEG solution. There was a close correlation between the measurements of water potential of the PEG solutions obtained with the osmometer and the psychrometers (R = 0.99). However, the psychrometer gave increasingly lower values than the osmometer as water potential decreased. The differences in the measurements between the two methods are thought to be the result of design and calibration differences. The ease of use of the osmometer is such that it is recommended for routine use. The water potentials of the soil cores brought to equilibrium with the PEG 10 000 solution were linearly related to the water potentials of the PEG solutions estimated from both the osmometer and psychrometers (R2 = 0.84). However, there were clear deviations from a 1:l relationship. It was concluded that the results from the soil cores could not be used to determine which of the two instruments gave the more accurate measurement of water potential of PEG solutions.


Soil Research ◽  
1993 ◽  
Vol 31 (1) ◽  
pp. 1 ◽  
Author(s):  
IM Wood ◽  
IK Dart ◽  
HB So

This study examined two polyethylene glycol (PEG) polymers (PEG 6000 and PEG 10000) and compared measurements of water potential obtained with a thermocouple osmometer and thermocouple psychrometers at three temperatures (15, 25 and 35�C) and five osmdalities (50, 100, 200, 300 and 400 g/1000 g water). These were then compared with estimates of matric potential of three soils brought to equilibrium with PEG solutions of the same osmolalities. At the same osmolality and temperature the two PEG polymers gave essentially the same water potential. There was a significant effect of temperature on water potential which corresponded closely with changes in specific gravity of the PEG solution. There was a close correlation between the measurements of water potential of the PEG solutions obtained with the osmometer and the psychrometers (R = 0.99). However, the psychrometer gave increasingly lower values than the osmometer as water potential decreased. The differences in the measurements between the two methods are thought to be the result of design and calibration differences. The ease of use of the osmometer is such that it is recommended for routine use. The water potentials of the soil cores brought to equilibrium with the PEG 10 000 solution were linearly related to the water potentials of the PEG solutions estimated from both the osmometer and psychrometers (R2 = 0.84). However, there were clear deviations from a 1:l relationship. It was concluded that the results from the soil cores could not be used to determine which of the two instruments gave the more accurate measurement of water potential of PEG solutions.


1976 ◽  
Vol 54 (17) ◽  
pp. 1997-1999 ◽  
Author(s):  
W. T. McDonough

Seeds of smooth brome grass (Bromus inermis Leyss.) and alfalfa (Medicago sativa L. cultivar Ladak) were allowed to imbibe in water or solutions of polyethylene glycol (Carbowax 1540), mannitol, or sodium chloride. Seed water potentials were determined over a 72-h period after transfer of seeds to thermocouple psychrometer chambers. Seed water potentials were lower than osmotic potentials of the media, but these two potentials were not clearly related to each other. Possible reasons for the lack of gradation in response are discussed.


2020 ◽  
Vol 49 (8) ◽  
pp. 952-955
Author(s):  
Takahiro Fukui ◽  
Kenji Kubota ◽  
Yoshie Tarutani ◽  
Masaaki Akamatsu ◽  
Kenichi Sakai ◽  
...  

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