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The vacuum within the Sampler causes the water to move from <br />the soil, through the pores of the porous ceramic cup, and into the <br />Sampler. The rate at which the soil solution will collect within the <br />Sampler depends on the capillary conductivity of the soil, the soil <br />suction value within the soil (as measured with tensiometers), and <br />the amount of vacuum within the Sampler. In moist soils of good <br />conductivity, at field capacity (10 to 30 cb of soil suction as read on <br />a tensiometer) substantial soil water samples can be collected <br />within a few hours. Under more difficult conditions it may require <br />several days to collect an adequate sample. <br />Recovering a Sample from In general, a vacuum of 50 to 85 cb is normally applied to the Soil <br />the Soil Water Sampler Water Sampler. In very sandy soils, however, it has been noted <br />that very high vacuums applied to the Soil Water Sampler seem to <br />result in a lower rate of collection of the sample than a lower <br />vacuum. It is our opinion that in these coarse, sandy soils, the high <br />vacuum within the Sampler may deplete the moisture in the im- <br />mediate vicinity of the porous ceramic cup reducing the capillary <br />conductivity, which creates a barrier to the flaw of water to the <br />cup. In loams and gravelly clay loams, users have reported collec- <br />tion of 300 to 500 ml of solution over a period of a day with an <br />applied vacuum of 50 cb, when soils are at field capacity. At waste <br />water disposal sites, users have obtained 1500 ml of sample solu- <br />tion in 24 hours following cessation of irrigation with 1 to 2 inches <br />of waste water on sandy or clay loam soil. <br />To recover a soil water sample, remove the Pressure-Vacuum tube <br />from the vacuum port of the pump, and attach the tube to the <br />pressure port. Place the discharge access tube in a small collection <br />bottle and remove both clamping rings. Apply a few strokes on the <br />hand pump to develop enough pressure within the Sampler to force <br />the collected water out of the Sampler and into the collection bottle <br />(see Fig. 11). <br />t900K3 <br />Figure 11. <br />Subsequent samples are collected by again creating a vacuum <br />within the Sampler and following the steps as outlined above. <br />SOILMOISTURE EQUIPMENT CORP. 14 ~ \® <br />P.O. Box 30025. Sonto Borboro. ColiFornia 93105 USA / \ <br />Phone: (805) 964-3525 • fox: (805) 683-2189 soiiM\ oisrsae <br />e-moil: soles©soilmoisture.<om ~ Web: hltp://wwwsoilmoislure.<om ~/ <br />