juiy 17. 1916 Influence of Calcium and Magnesium on Plant Growth 605 



EFFECT OF MAGNESITE AND DOLOMITE UPON WHEAT AND SOYBEANS 



(SERIES I AND j) 



Series I had wheat grown in the pots and then turned under, and wheat 

 was then replanted in the same pots; while series J had cowpeas grown 

 and turned under and then soybeans planted, except in pots 182 and 183, 

 from which the cowpeas were removed before the soybeans were planted. 

 The cowpea hay grown in pots 182 and 183 contained 0.4 per cent of 

 calcium and 0.179 P er cen t of magnesium, in a ratio of 5 to 5.7, and 

 removed from each pot 32 mgm. of calcium and 14.32 mgm. of magnesi- 

 um. In 10 seeds planted there was 0.58 mgm. of calcium and 1.59 mgm. 

 of magnesium. The above pots contained extracted sand. 



Figure 1 of Plate LXXXV shows the effect of succeeding crops when 

 grown upon extracted sand. The pot at the left marked "sand only" 

 has had no other crop preceding it, while in the middle pot cowpeas 

 were grown and removed, taking out some of the most readily available 

 calcium and magnesium. From the pot at the right three crops of alfalfa 

 were removed, taking out 164.5 mgm. of calcium and 90.72 mgm. of 

 magnesium. 



Dolomite has no detrimental effect upon the crops used throughout 

 these experiments. However, the addition of larger quantities of mag- 

 nesite — for example, 35 per cent — caused considerable yellowing of the 

 leaves, and the plants were able to mature but few seeds. Plate 

 LXXXV, figure 2, shows that the plants growing in dolomite have quite 

 a number of bean pods, while in the magnesite pot none are visible and 

 the uppermost leaves are sickly. This yellowing of the uppermost leaves 

 while the lower ones remain green differs from true translocation and 

 accompanies high magnesium applications. The yellow leaves have a 

 higher magnesium content than do the healthy ones, as sickly leaves 

 from the plants taken from pot 185 show 0.955 P er cen t of calcium and 

 1. 1 1 per cent of magnesium, while the healthy leaves from the same 

 plants showed 0.896 per cent of calcium and 0.88 per cent of magnesium, 

 respectively. 



Schulze and Godet (31) found more calcium in the husk and more 

 magnesium in the seed of lupine, pine, pumpkin, castor bean, sunflower, 

 and various nuts. 



Plate LXXXVI, figure 1, shows the comparative growths of soybeans 

 in brown silt loam and dolomite. Evidently the brown silt loam would 

 have been improved by applications of some limestone or dolomite. 



The differences of yields of duplicates in Table XI are due chiefly to the 

 differences in the duration of growth. In the wheat, series I, pots 173, 

 l 75> l 77> an d 179 were harvested 65 days after planting, while their 

 duplicates were harvested 12 days earlier. In the soybean, series J, pots 

 181, 184, 186, and 188 were harvested 53 days after planting, while their 

 duplicates were permitted to mature, standing until 80 days after 

 planting. 



