Lecture53-55(2008)

Lecture53-55(2008) - m + o is within the available water...

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AVABILITY OF SOIL WATER TO PLANTS Chapter 19 in Introduction to Environmental Soil Ph ysics Water infiltrates into soil then redistributes under gravity and matric potentials. The amount of recharge determines plant available water Some water is taken up by plants as it drains/redistributes Field moisture capacity (FMC) = water remaining is soil after excess water has drained. Drainage take place 2-3 days Soil is at -333 cm of water or (-1/3 bar). The following conversions are useful: 1 bar = 0.987 atmosphere = 1,017 cm of H 2 O = 10 -1 megapascal, MPa (10 6 Pa). ALSO 1 cbar = 1 kPa = 10 cm of H 2 O. We will use: 1 bar = 1,000 cm of H 2 O and recall 1 kPa = 10 cm of H2O .
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Available water (AW) = soil water that is readily taken up by plant roots AW = FMC – PWP However, if the for
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Unformatted text preview: m + o is within the available water range, conditions may not be suitable for maximum plant growth. Plants stress is a function of the transpiration rate. If transpiration exceeds the rate at which water can move to the rootsplant is stressed. Stressed causes turgor to decrease, stomates close, transpiration is decreased, --no CO 2 for photosynthesis and growth stops. Permanent wiltin g point (PWP) = soil moisture content at which the soil is not capable of maintaining plants in an unwilted condition. PWP considered to take place at -15000 cm of water (-15 bars, for m + o ). Some plants can exist at potentials well below -15,000 cm, but they might not grow at these potentials....
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This note was uploaded on 08/08/2008 for the course SS 322 taught by Professor Lowery during the Spring '08 term at Wisconsin.

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Lecture53-55(2008) - m + o is within the available water...

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