. Soil physics and management. ° C. Yellow ° C. ° C. ° C. ° C. White ° C. ° C. °C. ° C. A very interesting demonstration is to fill a tray three by sixfeet with soil, plant an equal number of seeds in each half of thetray, and cover one-half with very dark soil and the other half withwhite soil and place in the sunshine (Fig. 134). For best resultsthis should be carried on in spring or fall. Plants come up from 24 TEMPEEATURE 303 to 72 hours sooner in the part of the tray covered with dark table following gives the temperature in the two
. Soil physics and management. ° C. Yellow ° C. ° C. ° C. ° C. White ° C. ° C. °C. ° C. A very interesting demonstration is to fill a tray three by sixfeet with soil, plant an equal number of seeds in each half of thetray, and cover one-half with very dark soil and the other half withwhite soil and place in the sunshine (Fig. 134). For best resultsthis should be carried on in spring or fall. Plants come up from 24 TEMPEEATURE 303 to 72 hours sooner in the part of the tray covered with dark table following gives the temperature in the two parts ofthe tray: Effect of Color on Soil Temperature Time Thermometer bulb1 inch belowsurface Thermometer bulb 2 inches below surface Thermometer bulb 4 inches below surface Light Dark Light Dark Light Dark 6 Maximum 6 ° F. ° 5° F ° F. 82 ° 5° F ° F. ° 5° F. ° F. ° ° F. ° F. ° °F. ° F. ° °F. Increase ° F. ° F. ° Fig. 134.âDifference in growth on light and dark colored soils. A, corn; B, wheat; C, water-melon. The time and the number of plants coming through the soilare governed to some extent by the color of the soil, as is shown inthe following table. 304 SOIL PHYSICS AND MANAGEMENT Time Required and the Number of Plants that Came Up in the Soils of DifferentColors. One Hundred Seeds Were Planted in Each ^ Wheat Oats Corn Melons Days after planting Light Dark Light Dark Light Dark Light Dark 7 s 2951586265 4 758686868686 27 707575 75 6 80100100100100100 1 66 7272 684 959595 4 3257 8 9 10 21 11 60 12 85 13 86 With black the absorption is almost complete. The soils of what-ever color tend to cool to the temperature of the surroundingatmosphere during the night or in cloudy weather. The table onpage 302 shows that the lowest temperatures of the dark-coloredsands were not as low as the light-colored ones.
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