Exportation 



ever increasing quantities, and they have not 

 been restored completely by farmyard manure. 

 Therefore it is necessary to import them. 



Exportation. 



A more or less important part of the crops pro- 

 duced on the farm does not return to the soil — thus 

 a portion of the wheat, oats, barley, potatoes, etc., 

 grown is sold as such. These cereals and roots 

 contain nitrogen, phosphates, potash, and lime 

 extracted from the soil by the plants. Therefore 

 the total quantity of fertilising elements which these 

 products contain are taken from the farm. 



Hay and straw are also sold sometimes, and all 

 this represents an exportation of fertilising matter. 

 On dairy and breeding farms the crops obtained are 

 consumed on the spot. But then they are exported 

 in the animals sold — in the shape of meat, skins and 

 blood, bones, or in the sale of milk — and, further, 

 there is the loss in fertilising matter between the 

 consumption of produce by the animal and its 

 restoration in the form of manure. These losses 

 which are considerable, as we shall see further on, 

 especially in nitrogen and potash, are caused by 

 exposure to air, by fermentation, by dilution, by 

 rain water, and by the loss of urine. The loss of 

 fertilising elements in the air and by drainage is 

 considerable. Those in the drains are carried to the 

 sea and irretrievably lost. 



All these depletions, by sale and loss, going on 

 practically for hundreds of years on some soils, 

 have ended by impoverishing them to a point where 

 the usual restitution is not sufficient to maintain 



