ROTHAMSTED ROTATION 



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Now it has been demonstrated that the legumes peas, beans, 

 alfalfa, etc. when properly infected have the power of feeding on 

 this limitless supply of atmospheric nitrogen, while the non-legumes 

 barley, wheat, oats, etc. must depend upon the supply within 

 the soil, and the farmer must take advantage of this fact to supply 

 nitrogen for his crops, as the commercial fertilizer cannot be eco- 

 nomically used for the production of most crops, as is seen from the 

 fact that the nitrogen in a 50-bushel wheat crop would cost $14.40, 

 or 20 tons of sugar-beets $15.00, or 1 ton of alfalfa hay $7.50, if 

 bought as a commercial fertilizer. But will the legume draw nitro- 

 gen from the atmosphere while there is a supply in the soil, or will 

 it follow the line of least resistance and turn only to the atmosphere 

 when nitrogen is lacking in the soil ? If it does, it must first drain 

 the soil of its valuable nitrogen and thus leave it no richer than it 

 was before the legume was grown upon the soil. This is the prob- 

 lem which this chapter is to answer. 



Rothamsted Rotation. Crop rotation 'has been practised for 

 centuries, but the oldest system on which we have accurate infor- 

 mation is the one on Agdell Field at the Rothamsted Experiment 

 Station. This system was inaugurated in 1848 and is still being 

 carefully followed. It consists of a four-year rotation, as follows: 



First year: Swede turnips (rutabagas). 



Second year: Barley. 



Third year: Clover or beans. 



Fourth year: Wheat. 



Still another system has been running parallel and similar to 

 this, except that fallow cultivation is practised in the third year 

 instead of growing a legume. The average yields for twenty-year 

 periods are given below. These systems are of special interest to 

 western farmers, for when we substitute sugar-beets for the turnips 

 and alfalfa or peas for the clover or beans, we have nearly an ideal 

 rotation for our soils. 



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