100 GROWING LEGUMES FOR SOIL BETTERMENT 



rich in both nitrogen and mineral plant food. The main- 

 tenance of fertility may almost be said to consist in keep- 

 ing the soil well supplied with humus. 



The cultivation of leguminous crops is one of the most 

 important and economical means of maintaining a supply 

 of nitrogenous plant food in the soil. Nitrates may, of 

 course, be supplied in commercial fertilizers ; but fer- 

 tilizers containing nitrogen are very expensive, and it 

 usually pays better to supply nitrogen by growing 

 legumes or by the application of stable manure, which is 

 rich in nitrogen when properly handled. In good farm 

 practice both stable manure and leguminous crops are 

 used as sources of nitrogen. 



Improper methods of tillage add very greatly to the 

 evil effects that result from lack of humus. In many 

 parts of the country the land is plowed only 3 or 4 inches 

 deep. Below the plowed stratum the soil becomes sour, 

 densely packed, and unfit for plant roots. When such 

 soils are plowed deep and this sour packed subsoil is 

 mixed with the upper portion, the growth of many crops 

 is greatly retarded. This has led many farmers to be- 

 lieve that deep plowing is ruinous. Some farmers have 

 tried to remedy the difficulty by subsoiling. The subsoil 

 plow breaks up the packed layer but does not throw it 

 out on top. But while subsoiling does break up the hard 

 layer into chunks it does not pulverize it or put humus 

 into it. In most cases work done in subsoiling is prac- 

 tically wasted, and it is doubtful if it ever pays. A much 

 better method is to plow a little deeper each year until a 

 depth of 8 or 10 inches is reached. This gives a deep 

 layer of good soil, particularly if the supply of humus is 

 kept up. 



When new soil, or that which has lain undisturbed for 

 several years, is broken up, it is always best to plow deep 

 from the beginning, for the deeper layers will be about 

 as fertile as any, except the top inch or two. It is wise, 



