The Story of the Soil; from the Basis of Absolute Science and Real Life, by Cyril G. (Cyril George) Hopkins
page 158 of 371 (42%)
page 158 of 371 (42%)
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"If they rotate their crops, they would probably yield as well as ever," said the Chief. "No, that, too, has been tried," replied Percy. "The Illinois Experiment Station has practiced a four-year rotation of corn, cowpeas, wheat, and clover on an experiment field on the common prairie soil down in 'Egypt,' and the average yield of wheat has been only twelve bushels per acre during the last four years, but when legume crops were plowed under and limestone and phosphorus applied, the average yield during the same four years was twenty-seven bushels per acre." "Probably the increase was all produced by the green manure," suggested the Chief. "Organic matter has a great influence on the control of the moisture supply." "That was tested," said Percy. "The green manure alone increased the average yield to only fourteen bushels while the green manure and limestone together raised the average wheat yield to nineteen bushels, the further increase to twenty-seven bushels having been produced by the addition of phosphorus." "Well, Sir," said the Chief, "we have made both extensive intensive investigations concerning the chemistry of the soil solution by very delicate and sensitive methods of analysis we have developed, and we have also conducted culture experiments for twenty-day periods with wheat seedlings in the water extract of soils from all parts of the United States, and the results we have obtained have changed the thought of the world as to the cause of the infertility of soils." |
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