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Enabling better global research outcomes in soil, plant & environmental monitoring.

Gypsum Block - G-BLOCK

G-Blocks are the most cost effective method of tracking your water and subsurface moisture by electronic means. The blocks have been designed to provide the largest resistance range possible at the moist end of use, where sensitive plants need monitoring. The large gypsum content of the block provides months of buffering soil solutions to ensure that you’re really reading water content and not salinity or fertilisers. They are easy to install and simple to read and provide a reliable method for subsurface moisture monitoring. The Model 5201F1 Gypsum Blocks feature a slim, 7/8" (2.2 cm) diameter design and come in a variety of lead lengths. Once buried, depending on soil type and conditions, the blocks have a life span of 2-5 years. Available with 3, 6, 9, 15, 25 and 50 foot leads.


The Model 5910A Soilmoisture Meter is designed for portable use in making rapid readings of Model 5201 Gypsum Blocks. The Model 5201 Gypsum Blocks feature a slim, 2.2 cm diameter design, and come in a variety of lead lengths.


Product No. Description Weight

  • 5201L03 SOILMOISTURE BLOCK, 0.9m leads 0.03 kgs
  • 5201L06 SOILMOISTURE BLOCK, 1.8m leads 0.04 kgs
  • 5201L15 SOILMOISTURE BLOCK, 4.6m leads 0.07 kgs
  • 5201L50 SOILMOISTURE BLOCK, 15.2m leads 0.19 kgs

Measuring Principle

Gypsum Blocks or G-Blocks are an evolution in design. They provide quick response and true sensitivity to conditions where moisture remains relatively high. All G-Blocks are wetted and checked for speed of response and ability to maintain overall consistency from block to block prior to shipping. The design of electrode spacing ensures a sensitive response to changing moisture conditions below 2 bars of matric suction with overall operating range to 10 bars of matric suction. G-Blocks provide significant improvements over any competitive or older style blocks.

Optimise water usage

There are several methods to optimise water use with G-Blocks. The first, and easiest, is the “Limits Method”. This simple, but effective, method requires that you determine the limits to which you want water to migrate. Plant maturity, rooting depth, rooting patterns and the system of irrigation will help you to determine these limits. Older and less effective irrigation, such as flood or furrow, will have a broader range of water limits; shallow rooting and precision applicators will have a narrower limit band. The G-Blocks are placed at the minimum water level (minimum refill point) and at the maximum water depth (maximum refill point) for irrigation cycles. Frequently another G-Block is placed at a depth past the maximum refill point to ensure irrigation water does not exceed the set minimum-maximum limits. The second method is the “Matrix/Segmental Method” which is simply an extension of the “Limits Method”. By placing additional G-Blocks between the minimum-maximum limits, you are able to more accurately monitor subsurface moisture due to root uptake, evaporation, and the water release characteristics of different soil types. This added information can be used to more accurately determine the precise level required for partial recharges.

Manually reading G-blocks

G-blocks are often read manually with a hand held reader. The reader is small, light weight, battery powered and has a digital readout. Typically a number of G-blocks (3 or more) will be buried in the soil at different depths across several sites depending upon the size of the farm or experiment. Each G-block has two bare wires which are left protruding from the soil surface. These wires are clipped onto the hand held reader terminals and then the read button is pressed to immediately display the current soil tension. The reading is manually recorded in a notebook, the wires unclipped and then moved to the next G-block.

Gypsum Blocks References
Burton, A.J., Pregitzer, K.S., Zogg, G.P. and Zak, D.R. 1998, ‘Drought Reduces Root Respiration in Sugar Maple Forests’, Ecological Applications, vol. 8, no. 3, pp. 771-778.

Hubbert, K.R., L., B.J. and Graham, R.C. 2001, ‘Roles of weathered bedrock and soil in seasonal water relations of Pinus Jeffreyi and Arctostaphylos patula, Canadian Journal of Forest Research, vol. 31, pp. 1947-1957.

Lof, M. 2000, ‘Establishment and Growth in Seedlings of Fagus sylvatica and Quercus robur: Influence of Interference from Herbaceous Vegetation’, Canadian Journal of Forest Research, vol. 30, no. 6, pp. 855-864.

Stenitzer, E. and Gassner, L. 2005, ‘Assessment of the Effect of Groundwater Lowering on the Capillary Rise in a Sandy Soil‘, in Monitoring and Modelling the Properties of Soil as a Porous Medium, eds W.M. Skierucha and R.T. Walczak, Institute of Agrophysics PAS, Lublin, pp. 179-187.

Stenitzer, E. and Gassner, L. 2005, ‘In Situ Estimation of Deep Percolation in a Dry Area by Concurrent Measurements of Soil Water Content and Soil Water Potential‘, in Monitoring and Modelling the Properties of Soil as a Porous Medium, eds W.M. Skierucha and R.T. Walczak, Institute of Agrophysics PAS, Lublin, pp. 188-195.

Timlin, D.J., Pachepsky, Y., Snyder, V.A. and Bryant, R.B. 2001, ‘Water Budget Approach to Quantify Corn Grain Yields Under Variable Rooting Depths’, Soil Science Society of America Journal, vol. 65, pp. 1219-1226.

Ulery, A., Stewart, S., Reid, D.A. and Shouse, P.J. 2000, ‘Vacuum Method for Field Installation of Pipes and Casings in Sandy Soils’, Soil Science, vol. 165, no. 3, pp. 269-273.