Procedure for the filter paper method of measuring soil water suction

The filter paper method offers a simple routine method for measuring matric suction over the full range of soil water content from field saturation to almost air-dry. Although the method was developed several decades ago it has not widely accepted. This was probably due to erratic results, the reasons for which were not fully understood. Inaccuracy due to condensation, the most serious problem, can be avoided; error due to mechanical pressure during equilibration is unimportant. Salinity effects are important only at high suctions, while at low and moderate suctions the salt content of the paper can provide information on the osmotic potential of the soil water. An in situ method of using the filter paper avoids problems associated with overburden pressure and, in soft wet soil, mechanical disturbance caused by sampling. -Authors