SOIL TEMPERATURES OBSERVED AT AUBURN, ALA. 66 As an illustration of soil temperatures in a southern locality I have chosen the following record for 1889 at Auburn, Ala., where the agricultural experiment station has maintained three sets of buried thermometers, two of them in sandy soils on hills and one in moist bottom land near the banks of a small stream. It appears from these records that the difference in temperature in the growing season between the so-called "cold wet" and warm dry" soils averages but a few degrees; in fact, I doubt whether it is appreciable from observations having the accuracy of those here given. Thus at 3 inches depth and during the warm half of the year the maximum temperatures on the hill average 1° F. above those in the bottom land, while the minimum temperatures on the hill average 2° F. colder than those of the bottom lands. The temperatures here given are the averages of the maxima and minima and are taken from successive monthly reports and from Bulletin No. 18 of the Alabama Agricultural Experiment Station. In these, as at most other United States stations, the correction for the temperature of the long stem of the thermometer still remains to be applied. A comparison of the temperature at 3 inches depth with the maximum and minimum air temperature shows that the soil is warmer than the air in the daytime from April to October, inclusive, and warmer than the air at the minimum temperatures throughout the year. This latter is true for the minimum temperatures of the soil down to a depth of 96 inches, but the excess of maxima temperatures of the soil over those of the air during the daytime in summer ceases a little below 6 inches. Evidently the temperature of the soil is sufficiently high to allow of the growth of some form of vegetation throughout the year. Extremes and means of soil temperatures for 1889, as observed at Auburn, Ala. [Lat. 32°.6 N.; long. 85°.4 W.; altitude, 732 feet.] Jan. Feb. Mar. Apr. May. June. July. Aug. Sept. Oct. Nov. Dec. Minimum terrestrial ra diation temperature.. 21.0 24.0 32.0 37.0 43.0 43.0 60.0 62.0 48.0 36.0 22.0 30.5 Extremes and means of soil temperatures for 1889, etc.—Continued. Jan. Feb. Mar. Apr. May. June. July. Aug. Sept. Oct. Nov. Dec. Soil temperature. SANDY SOIL ON A HILL; OFTEN CULTIVATED 3-inch depth: Maximum Minimum 6-inch depth: Maximum. Minimum 24-inch depth: Maximum. Minimum 48-inch depth: Maximum.. Minimum 96-inch depth: Maximum. Minimum BOTTOM LAND ON BANK 3-inch depth: Maximum. 6-inch depth: Maximum. Minimum 24-inch depth: 53.5 53.0 56.5 63.0 71.5 75.0 79.5 79.0 84.5 74.5 69.0 60.5 58.0 56.5 58.5 65.0 36.0 Maximum.. Minimum 48-inch depth: Maximum Minimum 54.0 57.5 58.0 67.5 76.0 80.0 85.5 82.0 82.5 74.5 66.0 60.0 48.5 46.0 51.0 58.5 65.0 69.5 77.0 78.5 72.5 63.0 52.5 50.C 54.5 54.0 57.0 64.0 71.0 75.0 79.5 79.0 79.0 75.0 68.0 61.C 57.0 SOIL TEMPERATURES OBSERVED AT PENDLETON, OREG. Among the United States experiment stations for which soil temperatures have been published, I quote the following observations made by Mr. P. Zahner, voluntary observer at Pendleton, Oreg., (lat. 45°.7 N.; long. 112°.2 W.; altitude, 1,122 feet), because it represents a climate so different from that found in the same latitude east of the Rocky Mountains. A number of observations of diurnal periodicity are given by Zahner, and a shorter series is at hand for Corvallis, Oreg. (lat. 44°.5 N.; altitude, 150 feet). The comparison between these shows that the Pendleton air and soil are appreciably warmer than the Corvallis in July, August, and September, but colder in November and probably also in December. In general the maximum soil temperature at Pendleton at all depths follows that of the daily maximum air temperature. Rainfall lowers the temperature of the soil, as on March 18, 1890, at 8 inches depth by 2° F., but at 24 inches depth by 0.5° F. At 12 inches depth the soil was not frozen throughout the year, but at 8 inches it was frozen up to the 7th of March. The soil temperatures were read daily at 3 p. m.; the soil was naturally dry and light, and was covered with a thin grass. The thermometers were maximums and minimums, apparently read from above ground without being disturbed in their positions. Observations at Pendleton, Oreg., in 1890. [From the Monthly Reports of the Oregon State Weather Bureau.] Air temperature. Absolute maximum temperature... Absolute minimum temperature.. Mean of maximum temperature Mean of minimum temperature.. Monthly mean temperature. Precipitation. Total monthly rainfall. 4-inch depth: Jan. Feb. Mar. Apr. May. June. July. Aug. Sept. Oct. Nov. ° F. • F. ° F. • F. • F. ° F. °F. ° F. ° F. ° F. ° F. Soil temperature. 12-inch depth: Maximum Minimum Mean 34.0 41.0 46.0 62.0 67.0 71.0 78.0 85.0 70.0 63.0 51.0 27.0 33.0 33.0 46.0 58.0 60.0 69.0 71.0 64.0 51.0 40.0 30.4 37.1 39.8 52.2 63.1 65.8 73.7 73.3 65.7 54.7 45.2 24-inch depth: Maximum 38.0 33.0 34.6 40.0 45.0 58.0 64.0 66.0 74.0 73.0 70.0 64.0 54.0 35.0 36.0 45.0 58.0 61.0 68.0 71.0 64.0 54.0 44.0 38.1 40. 1 50.1 60.9 63.7 30.7 71.7 66.7 57.3 48.5 a Inches. SOIL TEMPERATURES OBSERVED AT MONTREAL, CANADA. As illustrating temperatures of the ground in a very cold locality, I quote the work of Messrs. C. H. McLeod and D. P. Penhallow, of McGill College Observatory, Montreal, who have maintained a series of observations of the temperature of the earth by Becquerel's method, in which the temperature of a coil of wire in the laboratory is brought to equality with the temperature of a similar coil buried in the earth. The following table gives the mean temperature for the tenday periods ending on the dates given in column 1 and at a depth of 1 foot below the surface of the ground. Temperatures are given. by them for other depths, as also for the air; the total rain and snow is also given. An investigation of the connection between earth temperature and the development of vegetation is being carried on by them, but as no results have as yet been published I give merely their soil temperatures at a depth of 1 foot, which usually agree, within a degree centigrade, with the average temperature of the air for ten days. Mean temperature of the soil at a depth of 1 foot for periods of ten days at Montreal, Canada. This series seems to show the powerful influence of a snow covering to keep the ground from cooling to very low temperatures during the winter. The minimum temperatures at 1 foot depth were -0.5° F. g the twenty days March 22 to April 10, 1889, and +0.4° F. during the ten days March 17 to 26, 1890. METHODS OF MEASURING SOIL TEMPERATURES. As it is very important that there should be numerous observations of soil temperature available for agricultural study, and as many persons are deterred by the expensiveness of the deep-earth thermometers, I would call attention to the fact that agriculture does not need to consider temperatures at depths below 4 feet and that the inexpensive, excellent system of thermometers, made by Green, of New York, has been recognized as the standard at stations in the United States; but for accuracy and convenience nothing can exceed the thermophone devised by Henry E. Warren and George C. Whipple, of the Massachusetts Institute of Technology. Several methods of measuring deep-earth temperatures have been most thoroughly studied in the memoirs of Wild and Leyst, of St. Petersburg, a summary of which I have prepared and will submit at another time. The soil thermometers constructed by Green are made in accordance with suggestions made by Milton Whitney, of the South Carolina Experiment Station, and have been used by him. Whitney has published a description of this new self-registering soil thermometer as follows (see Agr. Sci., Vol. I, p. 253; Vol. III, p. 261): This is a modification of Six's form of thermometer in which the maximum and minimum temperatures are registered in one and the same instrument. The essential features of the thermometers are as follows: A cylindrical bulb 6 inches long, filled with alcohol. The bulb is protected by a somewhat larger cylindrical metal tube, containing numerous holes, and is to be placed 3 inches below the surface of the soil-i. e., so that the bulb will extend vertically between the depths 3 and 9 inches, respectively, in the soil. The tube carrying the alcohol extends some 6 or 8 inches above the surface of the ground, when it bends twice at right angles and descends again to the surface, bends at right angles twice, crossing the main stem, and is carried up about 6 or 8 inches again, where it terminates in a bulb partially filled with alcohol. The lower bend in this stem carries a column of mercury which is drawn back toward the bulb when the alcohol contracts, and pushes a steel index up to the minimum temperature on a scale which reads downward. This index is held supported in the alcohol by a little spring when the alcohol expands and the mercury leaves it, while another index is pushed up to the maximum temperature by the other end of the column of mercury. The indices are set by the help of a magnet. The advantages claimed for this instrument are that it gives at once, without any calculation, the mean temperature of a definite depth of soil, for which we now use at least three thermometers, while it gives in addition the maximum and minimum temperatures, and need only be read once a day instead of three times, as at present. * * * 2667-05 M- -5 |