This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from ...
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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1933 Excerpt: ...and additional lime is applied every fourth year if needed. Both rock phosphate and superphosphate are used. Rock phosphate was applied at the rate of 1 ton an acre once in a 4-year rotation prior to 1925, when the application was changed to 1,000 pounds an acre. Since 1932, 500 pounds an acre has been used. Superphosphate (16 percent) was applied annually at the rate of 200 pounds an acre at first; in 1923 a reduction to 150 pounds annually was made for all grain crops and the application was omitted for the legume crop; and since 1929, 120 pounds of 20-percent superphosphate has been used. Complete commercial fertilizer--a 2-8-2 10 mixture--was used in the arlier experiments, at the rate of 300 pounds an acre annually, and disked in. From 1923 to 1929 a 2-12-2 mixture at the rate of 200 pounds an acre, which has the phosphorus equivalent of 150 pounds of 16-percent superphosphate, was applied. In 1929 this was changed to a 2-12-6 mixture used at the rate of 200 pounds an acre. Potash was applied as muriate of potash at the rate of 50 pounds annually on all grain crops, and was omitted only on the legume crop. Five experiment fields located on Marshall silt loam in northwestern Iowa are representative of this soil in that section of the State. These fields are located in Cherokee, Woodbury, Sioux, and O'Brien Counties. Table 7 gives the average acre yields and increases due to manure, lime, and fertilizer treatments on Marshall silt loam for the fields located in the counties named above. Percentages, respectively, of nitrogen, phosphoric acid, and potash. Table 7.--Average acre yields1 of crops and increases due to fertilizer treatment on Iowa experiment fields' on Marshall silt loam in northwestern Iowa 'Corn yields averaged from 22 crops on 5 fiel...
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