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MASS. EXPERIMENT STATION BULLETIN 351 



Calcium cyanamide was injurious to growth of all of the preceding species, 

 also to Anchusa myosotidiflora, when 15 gm. were applied to soil 10 to 14 days 

 before seeding. So applied, 10 gm. were not harmful, except to Calendula; and 

 12 gm. did not injure Anchusa, Alyssum argenteum, sweet pea and cucumber. 

 Six to 10 gm. improved the growth of Anchusa, Alyssum and Scabiosa and might 

 have so afifected other species had final readings been taken later, when seedlings 

 were older. 



If the necessary delay between soil treatment and seeding is not considered 

 too serious an objection, more use might well be made of calcium cyanamide as 

 a preventive of damping-off. It is not to be recommended, however, in the case 

 of Ericaceous plants or others which prefer an acid soil, for it is known (65) 

 to increase the pH value of soil, 100 pounds of calcium cyanamide having a lime 

 value equal to about 70 pounds of hydrated lime; and in a soil used by the writer 

 an initial pH value of 6.4 was raised to 6.7 by 14 gm. per square foot. 



One ounce for 2 to 4 square feet of soil is about 14 to 7 gm. per square foot, 

 and these are the amounts which may be used experimentally, with different 

 species, in different soils and at different lengths of time before seeding. For 

 increased safety, as a consequence of its more rapid decomposition (23), calcium 

 cyanamide should be thoroughly mixed with the soil. The soil should be moist; 

 and the poorer and more sandy it is, the longer should be the interval, according 

 to McCool (65), between soil treatment and seeding. 



The time interval necessary between soil treatment and seeding — during which 

 the nitrogen of the cyanamide is changing into the urea and the ammonia forms — 

 will also depend on the species of plant and, unless experience has shown that 

 it may be shorter, should probably be about 2 weeks in the case of the quantities 

 necessary to control damping-off. 



Table 12. — Effect of Calcium Hypochlorite on Growth of Seedlings 



i 



