ROTATION OF CROPS 2/3 



as the South with her depleted cotton and tobacco lands 

 testifies; as the West learns as the wheat field moves still 

 farther West, depleting the land as it goes, finally to 

 forsake it and to leave its rescue to clover and dairying 

 and diversified farming. 



And so it is throughout the world : the progress of 

 vegetation tends constantly to impoverish the soil, unless 

 crop rotation is permitted to adjust the unhappy condi- 

 tion. Where crop rotation is practiced, the demand on a 

 particular element is met with a less demand by a differ- 

 ent crop. For example, alfalfa gets its nitrogen from the 

 air, but feeds heavily on potash : and corn, coming after 

 alfalfa, feeds largely on nitrogen which has been accumu- 

 lated in the soil during the growth of the alfalfa; but the 

 potassium which alfalfa largely uses is less in demand by 

 the corn plant, and hence there is a readjustment by the 

 rotation: a readjustment such as Nature can handle 

 without denying any element to any crop. 



All plants do not exhaust the soil equally. And so we 

 get this principle : all plants do exhaust the soil, but they 

 do not do it equally. Thus some plants get their nitrogen 

 from the soil only, others get it from the air. Some plants, 

 like potatoes, use a great deal of potassium ; and others, 

 like corn, a less amount. Our grain crops use a great deal 

 of phosphorus, a great deal more than the potatoes or the 

 legumes. And so all along the line. While this range is 

 not so great as one might think, still, it is sufficiently large 

 to make one-crop farming a barbarous treatment to the 

 land. 



In this connection it should be said that a wisely- 

 planned crop rotation includes a legume somewhere in the 

 scheme, that the nitrogen supply may be maintained with 

 no shortage at all. 



Take the practice that is getting into favor so generally : 



