The Effect of Nitrogen Fertilizers on the Yield and Nitrogen Content of Soybean Forage : I. On the amount of combined nitrogen requirement of soybean plants in sand and water culture : II. On the effect of fertilizing nitrogen in early and late stages of growth upon the green yield and nitrogen content of soybean plants

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Abstract
The effect of N-fertilizing on the yield and N-content of soybean forage was examined experimentally from 1950 to 1954, the results being as follows. 1. Most part of nitrogen stored in the cotyledons of soybean was transfer red to other parts of the plant in 2∼3 weeks after germination. Soybean seedlings had to take N compounds from soil with their roots after the cotyledon N had been exhausted, and N-fixation did not yet begin. 2. In sand culture, the forage yield of the plants supplied with N-fertilizers only for the first 5 weeks after germination, and depending upon symbiotically fixed N thereafter, was just as high as that of the plants supplied with N continuously through the entire season. 3. The effect of N-application upon the N-content of plant varied greatly according to the difference in soil conditions. Under certain conditions, such as low lime and sandy soil, the total amount of N per plant increased significantly : while in other conditions, such as loamy soil with rich lime, the increase was very small. 4. The recovery of N was greater in young stage of plant growth, and it decreased in later stages, especially after blooming. Therefore application of N fertilizers to soybean in early growth stage of the plants may be more effective than that in later stages for the forage production.

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