730 Journal o^ the GePartMbNT of AGHlctLTtlRfi. 



tobacco is properly yellow ; then the curing process is commenced and 

 is continued constantly to prevent " running " till the tobacco is 

 thoroughly dried. The relative amount of humidity and heat neces- 

 sary both during the yellowing period and the curing period are highly 

 important, as the results obtained depend largely on these factors. 



The ageing or fermenting process should not be attempted by tlie 

 farmer where a warehouse is available, as it is purely a warehouse 

 operation and can only be done projjerly where large quantities of 

 tobacco are brought together and where suitable buildings are avail- 

 able. 



Che/iitcal Clunujcs. — During the growing period there are certain 

 plant foods which become water soluble and are drawn into the plant 

 by means of fine root hairs on the plant. These plant foods, nitrogen, 

 potash, and phosphorus, in addition to certain other minerals such as 

 lime, magnesium, sulphur, iron, and carbon, are essential in building 

 up the cell-structure of the plant. During the growth, curing, and 

 fermentation of a crop of tobacco there are complex chemical changes 

 constantly going on ; starches are converted to sugars, alkaloidal 

 poisons are built up and broken down, nitrogen is probably used up 

 in this process and again liberated in the fermentation process. This 

 continuous chemical change is illustrated by the varying amounts of 

 nicotine found in tobacco at different stages. Generally speaking, as 

 a plant develops, there is a gradual increase in the nicotine. Seed- 

 lings at transplanting time will show approximately .25 per cent, of 

 nicotine, and at full maturity the plant may show 4 per cent, of 

 nicotine; if allowed to stand longer in the field and beconae over- 

 ripe it will show a slight falling off in the nicotine content. Likewise, 

 during the fermentation process, there is a reduction in the nicotine 

 content. 



If one follows these changes, we see starch form and disappear, 

 sugar form and disappear, nitrates and nicotine increase and again 

 decrease. Citric, oxalic, and malic acids are present in the growing 

 plants, and these partially disappear in the cured leaf. Butyric and 

 acetic acids are present in fermented leaf. During the fermentation 

 process gases are formed by the breaking down of certain compounds; 

 ammonia is one of these gases, which is easily detected by the odour 

 in the fermenting room. Thus it is apparent that after a crop of 

 tobacco reaches the curing-slsed it is highly important that the curing 

 and fermenting be carried out with the greatest care in order that 

 the best qualities may be obtained. 



Fertility of Soil. — The question of the fertility of the soil is one 

 which, though often discussed, is of such importance that I feel 

 justified in making a few comments on it before closing. I would 

 first like to impress the fact that the quantity of plant food in the 

 agricultural zone of the soil is a definite quantity, and every crop 

 grown on that soil takes away a portion of that definite quantity. So 

 it becomes a simple matter of reasoning, that if one continues to draw 

 on that stock of plant food without replacing it by means of fertilizers 

 or by growing deep-rooted manuring crops, he must expect in a few 

 years to see a falling off in yields. Again, constant cropping without 

 ploughing under manuring crops will reduce the humus or decaying 

 vegetable matter in the soil to such an extent that, although there 

 may be sufficient nitrogen, potash, and phosphorus to produce crops, 

 the soil niav be lifeless. This decaving vegetable matter acts like a 



