COMMERCIAL FERTILIZERS AND THEIR USE 245 



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they are omitted. Scant crops are as frequently due to 

 the want of proper tillage as to the absence of plant 

 food. Poor cultivation results in getting the soil out of 

 condition ; then, instead of thoroughly preparing the 

 land, commercial fertilizers are resorted to, and the 

 conclusion is reached that the soil is exhausted, when in 

 reality it is suffering for the want of cultivation, for a 

 dressing of land plaster, for farm manures, or for a 

 change of crops. There is no question but what better 

 tillage, better care and use of farm manures, culture of 

 clover and systematic rotation of crops would result in 

 greatly reducing the amount annually spent for com- 

 mercial fertilizers, without reducing the yield of crops, 

 as well as securing larger returns for the fertilizers used. 

 In general, the better the cultivation the less the amount 

 of commercial fertilizer required for average farm crops. 

 Cultivation cannot, however, entirely take the place of 

 fertilizers. 



293. Abuse of Commercial Fertilizers. When a soil 

 produces poor crops, a complete fertilizer is frequently 

 used where only an amendment is needed. Restricted 

 crop production on long-cultivated prairie soils is often 

 due to poor physical condition, deficiency of humus and 

 available nitrogen, or, in some cases, to lack of a mineral 

 element as potash or phosphoric acid. If the nitrogen 

 is supplied by legumes, and the one element of fertility 

 needed is added, improved cultivation together with the 

 chemical action of the humus on the minerals of the soil 



