6 MASS. EXPERIMENT STATION BULLETIN 398 



Where the individual plants were of the type that prevents the growth of weeds 

 — shade producing plants — the yield of tobacco increased after the late plantings. 

 In plots of small plants, such as barley, rape, and rye, the weeds in late summer 

 intrude and to a degree vitiate the results. 



There is no evidence, however, of a better quality of tobacco grown after im- 

 mature plants. This is not entirely new, for it is often the case that larger tobacco 

 plants do not cure as well as smaller tobacco plants. 



Tobacco Experiments with Application to Soil of Commercial Organic Materials- 

 Different types of carbon compounds were applied to the soil to study their effect 

 on the yield of tobacco. Because of prohibitive cost, there are not many such 

 compounds that can be used; but cane sugar, starch, dried skim milk, and char- 

 coal were each applied to duplicate plots at the rate of 100 pounds per acre. No 

 decided differences were noted in the tobacco although the check plots receiving 

 no additions of carbon were low in yield and crop index. The charcoal caused 

 more rapid growth in the early season, probably because of the more abundant 

 absorption of heat by the darker color induced, and also gave the highest yield, 

 suggesting the possibility of its use In early spring for frames where seedlings are 

 grown. The dried milk left a residual effect the following year for the cover crop 

 of rye. Increased growth on these two plots was pronounced, suggesting two 

 possible factors — the nitrogen in the milk, or the subsequent action of lactic 

 acid which may have influenced the soil flora. 



The Absorption by Food Plants of Chemical Elements Important in Human 

 Nutrition. (Walter S. Eisenmenger and Karol J. Kucinski.) Calcium, mag- 

 nesium, sodium, and potassium salts, at the rate of 200 parts per million of each 

 cation, w'ere added singly to soil growing vegetables. The increase of these 

 cations in plant tissue, when cations were added singly to the soil was as follows: 

 for cabbage — calcium 30 percent, potassium 127 percent, magnesium 543 percent, 

 and sodium, none; for celery — calcium 44 percent, potassium 256 percent, mag- 

 nesium 390 percent, and sodium 52 percent; for lettuce — calcium 12 percent, 

 potassium 132 percent, magnesium 346 percent, and sodium 72 percent; for carrots 

 — calcium 18 percent, potassium 24 percent, magnesium 42 percent, and sodium 

 106 percent; and for beet roots — calcium 22 percent, potassium 12 percent, 

 magnesium 85 percent, and sodium 356 percent. 



Larger amounts of magnesium, potassium, and sodium can be introduced mto 

 plants than of calcium. Also, more of the halides can be introduced into plants 

 than of phosphorus or sulfur. 



It mav be said that those elements which are abundant in sea water may be 

 introduced into plants more readily than the elements which are ?bundant in 

 land waters. 



The Intake by Plants of Elements Applied to the Soil in Pairs Compared to 

 the Intake of the Same Elements Applied Singly. (Walter S. Eisenmenger and 

 Karol J. Kucinski.) Cabbage, celery, lettuce, and string beans were grown after 

 application to the soil of 250 parts per million each of calcium, sodium, and potas- 

 sium, singly and also in all possible combinations. Results show that when these 

 ions were applied in pairs, the amounts taken in by the plant were lower than 

 when they were applied singly. This behavior is suggestive of the well-known 

 premise that up to a certain point one of these elements can serve the function 

 or purpose of the other. 



Magnesium Requirements of Plants. (Walter S. Eisenmenger and Karol J. 

 Kucinski.) Nearly one hundred species of plants have been grown on a mag- 

 nesium deficient plot, one-fourth of which receives magnesium sulfate; one fourth. 



