Daily and seasonal air and soil temperatures at Davis, California
Author AffiliationsAlfred Smith was Associate Professor of Soil Technology and Associate Soil Technologist in the Experiment Station.
Hilgardia 4(3):77-112. DOI:10.3733/hilg.v04n03p077. May 1929.
Abstract does not appear. First page follows.
Since 1924 certain phases of soil temperature have been studied at Davis, California, in order to ascertain the influence of various soil conditions, of moisture, and of the shading effect of crops upon soil temperatures.
The data herein reported will show that the ranges in thermal environment of various parts of a growing plant-top, stems, and roots are apparently very great. For example, the leaves and branches on July 17, 1925, were in atmosphere heated to 116° Fahrenheit; the stem (unshaded) just below the ground surface was in soil having a temperature of 143°; while the roots would be in a medium at 107° for the 3-inch depth, and 84° for the 24-inch depth.
Bacteria and fungi of many varieties may live at low temperatures in the soil. The limit below which most cultivated plants are practically inactive lies in general between 40 and 45° F. Bacterial activity which increases the supply of available nitrogen is stimulated by relatively high temperatures while at extremely high temperatures this activity is reduced to a degree as unimportant as when too low temperatures prevail.
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