466 Kansas State Board of Agriculture. 



complicated and difficult. Alfalfa roots penetrate to such depths that it 

 is not possible to know how great a mass of soil is subject to draft. 

 Accurate sampling of soils, and especially taking account of the alfalfa 

 roots, etc., in the soil, is very difficult. The relation of the weight of the 

 roots left in the soil to that of the crops removed is a vital part of the 

 problem, but it is practically impossible to handle this satisfactorily for 

 field conditions. One thing well established is that on soils rich in 

 nitrogen alfalfa will get much of its supply of that element from the 

 soil, but on soils poor in nitrogen it depends more upon the help of the 

 bacteria. We may say with comparative safety that alfalfa grown on 

 soils poor in nitrogen will, by means of the robots, and stubble and dropped 

 leaves, add to the soil more nitrogen than it removes, and that, therefore, 

 although much nitrogen may be removed in the crops, the soil will be 

 enriched in that element. On the other hand, soils rich in nitrogen will 

 lose some of their store even when planted to alfalfa or other legumes. 

 With a certain intermediate composition there would be equilibrium, and 

 on the whole neither gain nor loss of nitrogen. 



This capacity of alfalfa to add nitrogen to soils that are deficient in 

 that element constitutes one of the most important characteristics that 

 the plant possesses in relation to fertility. Nitrogen is likely to be the 

 element that is first to become deficient in Kansas soils, and alfalfa cul- 

 ture is in many parts of the state the most readily available means of re- 

 storing it. To do this most effectively, however, one should not depend 

 merely upon the residues of roots, stubble, etc., left in the ground, but 

 should feed the alfalfa crop on the place as much as possible, and apply 

 the manure produced to the farm. This procedure has the additional 

 merit that the potassium, phosphorus and other elements will also be 

 largely returned at the same time. 



Another important benefit to the soil accompanying alfalfa produc- 

 tion is due to the addition of organic matter or humus that takes place. 

 Organic matter is the storehouse of nitrogen, and to an extent of mineral 

 substances, and it confers highly important physical and chemical prop- 

 erties. Soil well supplied with humus deports itself more favorably 

 toward drouth, flood, heat and cold. By its decay it yields acids that 

 attack the silicates, phosphates and other difficult soluble mineral con- 

 stituents of the soil, and brings them into a condition to be used by 

 plants. A complete discussion of the relations of humus to soil value 

 would require many pages, but here it must suffice to have pointed out 

 the important function that alfalfa serves in adding this substance to 

 fields on which it grows. 



In respect to potassium and phosphorus, which are taken wholly 

 from the land on which the crops grow, inspection of Table 53 shows 

 that alfalfa removes two, three, four, or even more, times as much as 

 do most other crops. Hence, whatever may be the capacity of a soil to 

 supply these elements, it is taxed much more by alfalfa than by ordinary 

 crops. This is a fact very frequently unrecognized by farmers. Their 

 attention is so closely fixed upon the beneficial results accruing to a soil 

 by the addition of humus and nitrogen that they fail to attend to the 

 equally important fact that calcium, potassium and phosphorus are 



