10 MASS. EXPERIMENT STATION BULLETIN 369 



besides calcium, it would seem that the hydroxyl ion also has an influence on 

 absorption by the plant. 



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

 J. Kucinski.) A plot of land known to be deficient in magnesium was divided 

 into four sections and treated as follows: no treatment, magnesium alone, mag- 

 nesium plus lime, and lime alone. Eleven species of plants were planted across 

 the sections and observations made as to the sensitivity of these plants to mag- 

 nesium deficiency and the relative intake of calcium and magnesium for the 

 different treatments. 



It was found that when only magnesium was added, all plants increased in 

 magnesium, and seven of the eleven decreased in calcium. When calcium and 

 magnesium were added, one of the eleven plants decreased in magnesium and 

 two in calcium. When calcium alone was added, five decreased in magnesium 

 and three in calcium. 



In general, magnesium seems to be much more easily introduced into the plant 

 than calcium when additional amounts are added to a soil. The addition of 

 magnesium plus calcium, on the other hand, may diminish the intake of both 

 elements by the plant. 



It was observed this year that calcium applications hastened the maturity of 

 certain cucurbits, as canteloupes and watermelon, by about two weeks; and 

 that those receiving lime were higher in sugar content at maturity than those 

 not receiving lime. 



The photograph on page 52 shows the marked response of celery to liming. 

 Cabbage, on the other hand, did equally well on the limed and unlimed portions 

 of the plot. 



Investigation witli Various Winter Cover Crops for Onion Fields. (Karol J. 

 Kucinski and Walter S. Eisenmenger.) Onion growers in the Connecticut Valley 

 do not as a rule use a winter cover crop on their onion fields. A winter cover 

 crop of rye, which is generally used on tobacco fields in the fall, if seeded on an 

 onion field would necessitate spring plowing. It is the practice of onion growers 

 to plow their fields in the late fall in order to have the fields ready for onion plant- 

 ing in the early spring as soon as the ground is free from frost. This practice of 

 fall plowing of onion fields is responsible for the sheet erosion and especially for 

 the excessive dust storms which are witnessed during late fall, winter, and early 

 spring. 



It is the object of this investigation to find a winter cover crop which, if seeded 

 in the late fall after the onion fields have been plowed, will produce a desirable 

 cover and yet winterkill so as not to interfere with the early planting of onions. 



Last year, buckwheat, spinach, barley, oats, spring wheat, and spring rye were 

 seeded on October 19, on a plowed onion field. Results showed that this date 

 was much too late for production of a proper cover which would prevent wind 

 and sheet erosion. This year, the same cover crops were seeded two weeks 

 earlier. Observations made during the middle of December show that buckwheat 

 and spinach did not produce sufficient growth for an adequate cover, while barley, 

 oats, spring wheat, and spring rye gave promise of a fairly good winter cover. 



In the future, it may be desirable to make the seedings somewhat earlier, 

 although with the increasing use of tractor power for plowing, the onion grower 

 has had a tendency in the past to let his fall plowing go until a short time before 

 the ground freezes. 



Onion Breeding. (Hrant M. Yegian.) The Connecticut Valley onion growers 

 follow the practice of planting seed sets for the production of market onions as 

 early in the spring as it is possible to prepare a proper seed bed. If the sets could 



