TOBACCO INVESTIGATIONS. 37 



mold growth. Seed preserved in cloth bags in a cool, dry place will retain 

 its vitality longer, and give higher percentage of germination, than seed 

 stored in air-tight containers. 



Top-dressing Tobacco Seed Beds U'ith Dry Ground Fish. 



It is the custom of many growers to top-dress the tobacco seed beds 

 occasionally with some quick nitrogen fertilizer, such as ammonium 

 sulfate, nitrate of soda, commercial "starter," or fish. The danger of 

 using an excess of the three former is pretty well recognized by the growers, 

 but in the use of dry ground fish not so much attention has been paid to 

 the amount used, as it has been claimed that it is impossible to apply an 

 excess of this material. 



This view is erroneous, as at least three cases have been noted where an 

 excess has been applied, the "burning" of the plants taking place four to 

 six days after application. In all cases the plants were thoroughly sprayed 

 and the fish well washed off the leaves. Experimentally, the same appli- 

 cations proved injurious in all three cases. The mechanical condition 

 of the fish seems to play a very important part in the injury, as in all three 

 cases the fish was very finely ground, and in all probability the nitrogen 

 was more quickly available than with other coarser or less nitrogenous 

 fish. 



Xo set rule as to the amount to be applied can be given, but as much 

 discretion should be used with fish as with the ammonium sulfate or sodium 

 nitrate, as the loss of the beds from top-dressing is a very serious matter. 



As a matter of fact, beds properly fertilized should not need any appli- 

 cation of nitrogen except, perhaps, after they have been pulled over several 

 times. While a large, apparently vigorous growth is obtained when the 

 bed is repeatedly top-dressed with nitrogenous fertilizers, the plants are 

 apt to be tender and succulent, and will not stand transplanting so well. 



Summary. 



1. The yield of tobacco in Massachusetts has not been gradually decreasing 

 during the past ten years. Since 1914 the yield has been loiv, but this is due 

 to adverse climatic conditions primarily. 



2. In general, rainfall is the major limiting factor of growth {and this neces- 

 sarily includes soil moisture along ivith it), together irith temperature. 



3. Excessive seasonal rainfall is invariably followed by a reduction 'in yield, 

 independent of temperature. 



4. Subnormal rainfall, when accompanied by temperatures excessively above 

 normal, reduces the yield. 



5. Subnormal rainfall, when accompanied by subnormal temperatures, does 

 not apparently reduce the yield to any extent unless the rainfall is very much 

 below normal. 



6. There are, undoubtedly, in many localities specific problems to be worked 

 071, such as the effects of improper fertilization, methods of culture, and control 



