July 22, 1918 
Salt Requirements for Buckwheat Plants 
161 
A comparison of the solutions which produced the highest average 
yields of tops in the two series representing the two different physio¬ 
logical growth periods here considered, indicates the best proportions of 
the salts to be markedly different for the two growth periods in question. 
The highest yield of tops for series A occurred with culture R4C2, which 
is characterized, as previously stated, by having four-tenths of its 
osmotic value due to monopotassium phosphate, and two-tenths and 
four-tenths due, respectively, to calcium nitrate and to magnesium 
sulphate. The yield from this culture was 34 per cent higher than the 
corresponding yield from culture R1C1. The best physiological balance 
for series B is shown for culture R3C5. This culture derived three- 
tenths of its total osmotic value from monopotassium phosphate, five- 
tenths from calcium nitrate, and two-tenths from magnesium sulphate. 
It produced a yield of tops which was 80 per cent higher than the corre¬ 
sponding yield from culture R1C1. It thus appears that the greatest 
production of dry weight of tops in this series of 3-salt solutions, with 
total osmotic concentrations of 1.75 atmospheres, and for buckwheat 
plants during the period of growth between the flowering stage and the 
ripening of the seeds, may be expected with the salt proportions of 
solution R3C5. Thus, the maximum yield of tops was produced during 
the later period of growth (series B) in a medium having a lower osmotic 
proportion of monopotassium phosphate, a much higher proportion of 
calcium nitrate, and a much lower one of magnesium sulphate than the 
solution which produced the highest yield of tops during the early 
growth period (series A). 
A comparative study of the diagrams of the two series thus brings out 
the fact that there is no similarity between the two series with respect to 
the distribution of the areas of high and of low dry-weight yields of tops. 
This is a clear indication that the response of the plants to the osmotic 
proportions of the salts in the solutions here employed is markedly 
different for the two different stages of development. Furthermore, a 
comparison of the total ranges of the average relative yields of the two 
series clearly shows that the buckwheat plants here employed respond 
just as readily to the variations in the proportions of the salts in the 
different solutions during the later period of development (series B) as 
they do during the early stages of growth (series A). The variation in 
the average relative yield values for tops in series A extends from 0.60 
to 1.34, showing a total range of 0.74 from the lowest to the highest 
value. In series B the corresponding total range from the lowest to the 
highest is 0.80, extending from 1.00 to 1.80. The variations in the 
average yield values as given for series B must, of course, be taken as 
the results of the approximate differences in the growth rates of the 
cultures, during the time period of this series, in response to the differ¬ 
ences in the salt proportions in the various solutions. Since, however, 
the cultures were carefully selected and, so far as could be judged, were 
