Alfalfa in Kansas. 465 



ments. In selling or buying alfalfa hay these differences in composition 

 should never be overlooked. 



The raw materials used in the manufacture of commercial fertilizers 

 could be furnished, just before business was demoralized by the Great 

 War, at prices that were the basis for the following valuation of the ele- 

 ments: Potassium, 6.02 cents a pound; phosphorus, 9.16 cents; nitrogen, 

 16.5 cents. Leaving the calcium out of account, the alfalfa crop per acre 

 for the season, obtained by cutting the plant when about one-tenth in 

 bloom, carried potassium that in a commercial fertilizer would have cost 

 $11.42, phosphorus worth $1.25, and nitrogen worth $30.06, besides the 

 cost of manufacture of the fertilizer, marketing it, and transporting it to 

 the point of consumption. These figures give a fair idea of the actual 

 fertilizing value of a crop of less than three tons of alfalfa hay cut when 

 one-tenth in bloom, if the elements could all be returned to the land. 



In the preceding paragraph data derived from the alfalfa crop cut 

 when one-tenth in bloom have been used, as that stage is one frequently 

 taken for cutting the crop. Comparison of these data with those for 

 alfalfa cut at other stages shows that in respect to percentage com- 

 position the calcium varies least, indicating that, on the College soil, as 

 the plant matures the calcium, or lime, compounds continue to be absorbed 

 at about the same rate. With nitrogen, phosphorus and potassium there 

 is a steady diminution in the percentages present as the crop advances in 

 maturity. As the total yield for the season is less the more mature 

 each cutting is permitted to become, the conjunction of lower yield and 

 lower percentage of the several elements causes very great differences 

 in the total quantities removed. Thus the six cuttings of alfalfa in the 

 bud removed more than twice as much nitrogen, phosphorus and po- 

 tassium as did the three cuttings made when the plant was in seed. At 

 the same time the calcium removed was over 50 per cent greater. 



It is seen, thus, that the actual quantity of the elements of fertility 

 removed in the alfalfa crop will vary with yield and time of cutting, and 

 it also varies with the soil. Since all agriculture works toward the re- 

 moval of as large crops as can be obtained, it will be seen that the ten- 

 dency is toward a system that removes much fertility from the land, and 

 that the actual money value of the fertility in an alfalfa crop is very 

 large. 



The element in the alfalfa that contributes most to its fertilizing value 

 is the nitrogen, and we should be making a grave mistake if we con- 

 sidered that this element is all drawn from the soil. As is now 

 well known, leguminous plants harbor bacteria on their roots which have 

 the power to absorb nitrogen from the air in the soil and to build it 

 into their organic tissues, and later these tissues undergo changes and 

 their nitrogen becomes available to the host plant. Alfalfa possesses 

 this power to a high degree, and by means of it a large part of the 

 nitrogen of the crop is obtained indirectly, but with little delay, from the 

 limitless store of the atmosphere. 



The extent to which the nitrogen of the alfalfa crop is supplied by 

 the air can not be stated with any degree of certainty. Observations 

 and analyses directed towards the solution of this problem are very 

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