No. 6. DEPARTMENT OF AGRICULTURE. 489 



air or not, makes it important to use care, in order to prevent too 

 large accumulations of this element. The danger, particularly in 

 the case of certain cereal crops and fruits, is that the excess of 

 nitrogen would be likely to cause an abnormal growth, that is, an 

 undue leaf and wood growth. As in all other lines of farm practice, 

 it is the judicious use of nitrogen that results in maximum returns. 



Practical Application of Principles. 



In order to give the most practical information to the farmer, 

 the discussion of the use of the various plants described will be 

 considered, first, in reference to those grown for the primary object 

 of preventing losses in soils, and their consequent indirect improve- 

 ment, due both to the saving of valuable soil constituents, and to 

 the addition of vegetable matter; and second, in which the object 

 of use is primarily to build up wornout or run-down soils, both in 

 their physical character and their nitrogen content. In order that 

 the matter presented may be directly applicable in present practice, 

 it is necessary to select a method of practice now largely followed 

 and which if continued will result in loss, and point out how the 

 plants may be used and losses may be prevented, and what the gains 

 are likely to be other than the saving of the food in the soil. 



The Losses that Mav Occur in Rotation. 



The common rotation of corn, oats, wheat or rye, and clover, may 

 be taken as an example, because as usually conducted it is wasteful 

 of fertility, due to the fact that no improving crops are introduced 

 between the cereals, and only one in the rotation, and if the clover 

 fails there is no renovating crop grown. By this practice it is im- 

 possible to prevent losses due to leaching, since the land is left 

 bare for a part of two years. The sod land is used for corn, if 

 it happens to be clover, the striking benefit of the clover in fur- 

 nishing an abundance of nitrogen is apparent. The corn crop is 

 usually harvested in early September, at a time in the season when, 

 because of favorable conditions of weather preceding, namely, warm 

 and moist, there has been an accumulation in the soil of nitrates 

 due to the breaking down of the vegetable matter contained in the 

 clover crop. After the removal of the corn, the land is left bare, 

 except possibly a few annual weeds, the nitrates that have been 

 formed and are ready to immediately feed another crop, and which 

 are freely movable are carried away into the drains by the 

 heavy rains liable to come in the fall. If heavy rains do not come 

 in the fall, then the spring rains, which come before another crop 

 is planted, carry at least a part of the nitrates so essential for the 



