Archive image from page 54 of Development and activities of roots. Development and activities of roots of crop plants; a study in crop ecology . developmentactiv00weav Year: 1922 Investigations at Peru, Nebraska. 37 soil was quite too low for maximum root development during the cold rainy month of April (cf. Lehenbauer, 1914). During May, a slow but uniform rise occurred, while differences between the temperatures on June 9 and 23 were quite pronounced. This ushered in a hot, dry period which extended to July 4. It is interesting to note that the deeper soils into which the new roots were ext
Archive image from page 54 of Development and activities of roots. Development and activities of roots of crop plants; a study in crop ecology . developmentactiv00weav Year: 1922 Investigations at Peru, Nebraska. 37 soil was quite too low for maximum root development during the cold rainy month of April (cf. Lehenbauer, 1914). During May, a slow but uniform rise occurred, while differences between the temperatures on June 9 and 23 were quite pronounced. This ushered in a hot, dry period which extended to July 4. It is interesting to note that the deeper soils into which the new roots were extending were progressively colder. Undoubtedly temperature has a marked influence upon crop-root development under field conditions. April 14 May 12 20 June / / 3' / / / / 3' r s '//'/ Fig. 15.—Soil-temperatures at various depths during 1919. May June 5 12 19 26 2 9 16 23 July August 15 22 29 7 12 20 25 Fig. 16.—Average day and night temperatures (solid lines) and average maximum and minimum temperatures. Indeed, it has been suggested (Shepperd, 1905) that in northern latitudes, where the ground freezes deep in the winter, the soil may be too cold for the roots of cereals to penetrate to a depth greater than 3 feet before midsummer (cf. Pulling, 1918). The average weekly day and night temperatures are shown in figure 16, which also includes the average weekly maximum and minimum tempera- tures. The average for the day temperatures was determined from the
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