Abstract
The investigation concerned variations in the plant oestrogen content of red clover-timothy swards receiving the same basic fertilization, but with different plant compositions and levels of nitrogen fertilizing. The oestrogen content of pure red clover was high in the early spring and declining by midsummer. The oestrogen content in aftermath remained high and compared to the age of the growth was greater than that of the spring crop. The age of the aftermath from the preceeding harvest, as well as the time of harvesting affected the content.
The plant oestrogen content of red clover grown in the mixed swards was on average somewhat higher that from a pure red clover sward. The plant oestrogen content of a pure timothy sward was usually negligible.
Nitrogen fertilization diminished the share of red clover in the mixed swards and thus the plant oestrogen contents of those swards as well. The effect was very notable in the spring crop. The average content of aftermath was consistently higher than that of the spring crop.
Nitrogen fertilizer had a loowering effect on the estrogen content of pure red clover as well as on the percentage of crude protein in clover. The study found a strong correlation between the plant oestrogen and crude protein contents of red clover. Apparently both are due much to the same factors despite their divergent chemical compositions.
Changes occurring in the total plant oestrogen content are determined predominantly by alternations in the contents of formononetin and biochanin-A, which were usually parallel. Compared to these changes, the quantities and respective variations of daidzein and genistein were insignificant.
