| Autor: |
Feldhake, Charles M., Glenn, David M., Peterson, Donald L. |
| Zdroj: |
Agronomy Journal; July 1996, Vol. 88 Issue: 4 p652-656, 5p |
| Abstrakt: |
Forage persistence during severe drought is dependent on the plant's ability to maintain, at the soil surface, a viable crown from which growth regenerates upon renewed availability of water. The objective of this study was to evaluate the surface soil temperature under a tall fescue canopy during the progression into severe drought. A 2.5‐ by 2.5‐ by 2.0‐m weighing lysimeter was shielded from precipitation during rainy weather from the summer solstice through the fall equinox of 1992 at Kearneysville, WV. As evapotranspiration decreased to 23% of the calculated potential rate, there was no increase in midday soil heat flux relative to net radiation but a 2.3‐fold increase in surface soil temperature relative to levels of net radiation. During severe water stress, daytime surface soil temperatures remained from 0 to 3°C cooler than canopy temperature; however, nighttime surface soil temperatures were typically around 5°C warmer than canopy temperature, suggesting that surface soil temperature was poorly coupled to canopy temperature. Surface soil temperature under complete canopy cover may be useful for quantifying forage water stress by evaluating the magnitude of daytime changes relative to net radiation. The forage canopy provides shielding for the crown from daytime radiation and high temperatures during water stress; however, this is in part offset by the insulation provided and the resultant higher nighttime temperatures. |
| Databáze: |
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