J une 2 ,1923 
Effect of Manganese on Plant Growth 
791 
SAND CUI^TURK EXPERIMENTS 
A quantity of quartz sand of medium sized grains was obtained for 
sand cultures. The sand, from external appearance, was good quality 
glass sand. Upon digesting 1,000 gm. in a mixture of i: i hydrochloric 
and nitric acids on a hot water bath for several hours, filtering out and 
washing the residue free of acids, it was found upon testing portions of 
the filtrate that the sand had contained small amounts of iron, manga¬ 
nese, zinc, arsenic, calcium, and magnesium. The residue of sand was 
snow white, except for a few black particles, which resisted further treat¬ 
ments of strong acids to dissolve them. A small amount of the black 
particles were separated, ground in an agate mortar, and fused with 
potassium bisulphate. The fused mass was extracted with dilute sul¬ 
phuric acid and tested for manganese, but none was found. 
Several hundred pounds of the sand were then washed with a mixture 
of nitric and hydrochloric acids and afterwards with distilled water until 
free of chlorids, as shown by a test with silver nitrate. The sand was 
then transferred to large, shallow, porcelain-lined agateware pans and 
dried. After the sand was dry 4,000 gm. portions were weighed into 
clean i-gallon earthenware pots. 
The sand prepared in this way possessed rather strong absorptive 
powers when wet with a Knop’s nutrient solution. It, therefore, was 
necessary to saturate the absorptive capacity of the sand with respect 
to the plant nutrients before plants could be j^own. This was accom¬ 
plished by adding the following amounts of manganese-free mineral 
nutrients to each i gallon of dry sand (4,000 gm.); 25 gm. of CaCOg, 
10 gm. of K2HPO4, 10 gm. of Ca(N03)2, 5 gm. of MgS04, 3 gm. of KCl 
and 3 gm. of Fe in the form of a suspension of Fe(OH)3. These chem¬ 
icals were all free from manganese and pots of sand receiving this treat¬ 
ment served as the controls. Equal numbers of other pots of the 
sand received 2 gm. each of manganese in the form of MnCOg and 
the above-mentioned nutrients. The mineral nutrients and the sand 
were thoroughly mixed by hand in a large porcelain-lined pan and re¬ 
turned to the respective pots. Equal numbers of plants of soybeans, 
cowpeas, and sweetcorn were grown in the purified sand, with and with¬ 
out manganese, until they approached maturity. They were then har¬ 
vested and the dry weights determined and chemical analyses made of 
the plant material. The results are given in Tables V and VI. 
Table VI. —Dry weights of the plants 
Spedes of plant. 
Manganese 
added. 
No man¬ 
ganese 
added. 
Increase 
due to 
manganese. 
Alaska peas (grown in water cultures). 
Gm. 
28. 10 
19. 80 
26. 50 
72. 00 
Gm. 
18. 80 
12. 25 
II. 30 
59.00 
Per cent. 
49-5 
61. 6 
134-5 
22. 0 
Soybeans. 
Cowpeas..-. 
Com. 
All the plants which grew in the pot cultures containing manganese 
made a very much better growth than did those from which manganese 
was withheld. The most striking result was obtained with cowpeas, in 
