. Carnegie Institution of Washington publication. 106 Development and Activities of Roots of Crop Plants. mented by heavy, water-tight, cylindrical, galvanized-iron containers 2 feet in diameter and to 4 feet deep, while the one for corn measured 3 feet in diameter and 5 feet deep. Suflficient soil to fill the containers was secured from both the upland and lowland crop plats north of Lincoln (p. 40) on February 20 and stored in large piles in a dry place until March 30-31, when it was placed in the containers. These soils were chosen because they were from the same plats as those used in
. Carnegie Institution of Washington publication. 106 Development and Activities of Roots of Crop Plants. mented by heavy, water-tight, cylindrical, galvanized-iron containers 2 feet in diameter and to 4 feet deep, while the one for corn measured 3 feet in diameter and 5 feet deep. Suflficient soil to fill the containers was secured from both the upland and lowland crop plats north of Lincoln (p. 40) on February 20 and stored in large piles in a dry place until March 30-31, when it was placed in the containers. These soils were chosen because they were from the same plats as those used in the preceding experiments and both their mechanical and chemical composition had been determined (tables 8 and 9). Care was exer- cised to keep the soils from the several levels to 4 feet separated. When taken from the field they were in such excellent condition regarding water- content that it was unnecessary to add more water when working them over to break up lumps, etc. During storage they were kept well covered to reduce FiQ. 41.—Average daily temperature (long broken lines), humidity (upper solid line), and average daily evaporation at Lincoln, 1921. On March 30-31 a large trench was dug in the field where the 1921 crops were grown (p. 80), and the containers, 16 in number, placed close together in a row in such a manner that the tops were about 4 inches above the surface of the soil. The prepared soil from the deeper levels was then poured slowly into the containers, where it was tamped into place. When filled, the soil in each container (with certain exceptions to be noted) occupied the same relative position as regards depth that it had occupied in the field. Barley was grown in the lowland soil; potatoes in that from the upland. Sodium nitrate was added at certain sealed levels at the same rate as in the preceding experiment (viz, 400 p. p. m. of NaNOs based on the wet weight of the soil). In this series, however, the proper amount for the weighed soil
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