CULTIVATION. 25 



to support the leaves, making a total of 2360 Ib. of dry 

 vegetable matter. As new hay contains not less than one- 

 sixth of moisture, we increase the above dry weight of the 

 tobacco crop by one-sixth, to make a fair comparison, and 

 obtain as the yield of an average tobacco field 2750 Ib. of 

 air-dry vegetable matter, or more than 1J tons. The 

 matter stands then thus : An acre of first-rate grass 

 land yields as the result of 8 months' growth, 21 tons 

 of crop, while the tobacco land must yield 1J tons in 

 3 months. 



" If the above data are correct, the average rate of 

 growth of tobacco is greater than that of a corresponding 

 hay crop, in the ratio of 9 : 7. The real disparity is, how- 

 ever, much greater. The principal growth of tobacco is 

 accomplished in the hottest summer weather, and in a 

 period of some 40-50 days. Very heavy manurings are 

 therefore essential to provide for its nourishment, and 

 the more so because the best tobacco lands are light in 

 texture, and may suffer great loss by drainage, evapora- 

 tion, and decomposition." 



From these premises, Prof. Johnson advances to the 

 question of what should or should not be presented to 

 the plant in the form of manure. He commences with 

 a caution that, in general, growers must " avoid employ- 

 ing fertilizers which contain salt or other chlorine com- 

 pound in raising wrapping or smoking tobacco. It is 

 evident, also, that there is no occasion to use any fertilizer 

 for the special object of supplying phosphoric acid, since 

 the heaviest export of this substance does not exceed 10 Ib. 

 per acre, annually. It may be well to mention here that 

 phosphates which may be put upon a tobacco field, in 



