. Elementary lessons in the physics of agriculture . Fig. Jf8. Showing differences of temperature of rolled and unrolled soil and associated air temperatures. Further than this, the lumps, being in poor connection with the soil below, conduct their heat slowly downward, while at the same time they shade the, lower soil; and by exposing a very large surface to the sky they cool rapidly by radiation. The measured differences of soil temperature due to this cause have been as high as ^ to IC^ F., the lower figure having been observed at a depth of three inches and the higher at' inches. The
. Elementary lessons in the physics of agriculture . Fig. Jf8. Showing differences of temperature of rolled and unrolled soil and associated air temperatures. Further than this, the lumps, being in poor connection with the soil below, conduct their heat slowly downward, while at the same time they shade the, lower soil; and by exposing a very large surface to the sky they cool rapidly by radiation. The measured differences of soil temperature due to this cause have been as high as ^ to IC^ F., the lower figure having been observed at a depth of three inches and the higher at' inches. The heating effect of fermenting manures in the soil has been observed to produce a rise in temperature of nearly 1^ F. In the case of well drained soil the percolation of warm summer rains often carries rapidly and deeply into the soil considerable heat and thus raises the temperature di- rectly, and as this water must evaporate more slowly from the drained soil, if at all, than from the undrained, it is not cooled as much as it might have been had percolation not occurred, thus leaving all the water to evaporate in a short time.
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Keywords: ., bookcentury1800, bookcontributorthe, bookdecade1890, bookyear1891
