With the introduction of new tools to measure soil moisture, agricultural research took a major step forward in the development of efficient crop irrigation techniques. In this 1960 article, researchers explain how tensiometers work and give specific, practical advice on where to place them in the field.

1960

“The moisture sensing unit — a porous cup — of tensiometers must be reached by the irrigation water if the moisture measuring instruments are to be of practical value as guides to irrigation practices.

“In most soils a good location for a tensiometer station is often next to the furrow, but it may be necessary to locate the porous cup under the furrow in orchard soils with little or no lateral movement of water during irrigation. In sprinkler-irrigated orchards the cup must be in soil that is re-wetted by the sprinkler at each irrigation but is not shielded by a low hanging branch nor is flooded by runoff from a branch. Also the porous cup should be in areas of active feeder roots as determined by root density studies, or by digging at different sites until a general pattern of root densities is apparent.

“Some traffic between the tree rows is necessary in most orchards, so the soil moisture measuring instrument must be in a protected spot reached by irrigation water and where feeder root density is average for the tree. In general, a good location for a tensiometer is at the drip line on the tree side of the first furrow, south or west of the tree.”