Elementary lessons in the physics Elementary lessons in the physics of agriculture elementarylesson01king Year: 1894 99 mospheric pressure affect slightly the level of water in wells, causing it to rise with a falling barometer and fall with a ris- ing barometer. The growth of crops appears also to affect the hight of the Avater-table when it lies near enough the surface to come within range of root action. This effect is shown in Fig. 43. The same figure also shows to what extent the water-table fell during a growing season. Fig. h3. Showing changes in the surface of the water-table under
Elementary lessons in the physics Elementary lessons in the physics of agriculture elementarylesson01king Year: 1894 99 mospheric pressure affect slightly the level of water in wells, causing it to rise with a falling barometer and fall with a ris- ing barometer. The growth of crops appears also to affect the hight of the Avater-table when it lies near enough the surface to come within range of root action. This effect is shown in Fig. 43. The same figure also shows to what extent the water-table fell during a growing season. Fig. h3. Showing changes in the surface of the water-table under alternate fallow plats and plats of growing corn. The straight lines connect the water-levels of wells 1 and 7 on the dates specified at the right, and the broken Une joins the water surfaces of wells 2, 3, 4, 5 and 6 on the same dates. 160. Best Hight of the Water-Table.—It is a matter of great importance, as bearing upon all questions of land drainage, to know at just Avhat distance below the surface of the ground the water-table should lie to interfere least, and at the same time to contribute most, to plant growth. In Eu- ropean cultivation it is held that the tillage of moors and bogs can only be successful when the water-table is maintained at least 3 feet below the surface in summer and 2 feet in winter. For light and gravelly soils in good condition a depth of 4 to 8 feet is held to be best for the majority of crops. The prob- lem is manifestly a complex one which cannot be simply stated. The case must vary with the character of the soil, with the season, and with the habit of the cultivated crop, as to whether it is naturally a shallow or a deep-rooted one.
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