\viii;at soils oi- rwi; .\i.e\\S])R\ \ divisjox. J33 



'I'liis sliows how ra])i(lly tobacco deprixes llic soil, whereon 

 it is grown, of its potash, and if there is any ihonght of putting 

 ihe lands down to tobacco, tiiis aspect of the problem sliould 

 receive due attention, i^ven for wheat (unless the straw be all 

 ploughed in again) the proporticMi of potash in at least five of 

 the culti\ated soils is not high, and this dehcienc\- would be 

 much moi-e severely felt in tiie case of tobacco. The fact that 

 tobacco grown on some of the Alexandria soils is reputed to 

 burn badly, nia\- quite easil\- be due to lack of potash therein. 

 Mayer says* : — 



The more ashes there are in tobacco and the more potash there is 

 in these ashes, and the smaller the amount of non-volatile acids in com- 

 bination with the potash, so mucii the better will the tobacco I)urn.''= 



I have already referred to the losses that wheat soils undergo 

 if all the produce, i.e., both grain and straw, is constantly re- 

 moved from the farm, and the increased loss in potash due to 

 tobacco culture, as above indicated, would also be felt in its 

 ftiU intensity if the entire crop were sold ofif year by year. In 

 v/heat cultttre. however, the soil would not only save two-thirds 

 of its yearly loss of potash if the straw were regularly ploughed 

 in again, but would at the same time gain in organic matter, 

 w hich subsequentl)' becomes changed into htimus ; and so, too, 

 in tobacco culture, a great deal of the potash and other plant- 

 food constituents is saved by ploughing in the stems and w'a.ste. 

 Tobacco steius contain, on an average- 

 Nitrogen 2T'j to 3 ])er cent. 



Lime About T,y2 



Potash 5 to 8 



Phosphoric Oxide .... 3^ to i 



This means that if the tobacco production on one acre (stems 

 and refuse as well as leaves) totals 3.ooolb., and would, if 

 removed in it^- entirety from the farm, deprive the soil of 20olb. 

 of potash, the stems, aggregating in weight i,40olb., would again 

 restore to the soil about 931b. of that potash, and would also 

 supply it with a considerable runount of organic matter capable 

 of conversion into httmus. 



Manurial Needs of the Soils. 



For the cultivation of wheat without further manuring, 

 sandy loams of the general type of the Alexandria soils should 

 contain, per acre, to a depth of one foot, at least 5,ooolb. of 

 nitrogen. 3,ooolb. of potash. 2.ooolb. of phosi)horic oxide. t 



From these data it may easily be calculated what quantities 

 of these plant foods should be added to the defective soils to 



* Storer; •"Agriculture in some of its relations with Chemistry" ( 1897). 

 3, 504. 515. _ - , I 



t Approximately .14 per cent, ot nitrogen. .09 per cent, ot polasli, and 

 .06 per cent of phosphoric oxide. 



