NEWER SOIL PROBLEMS 57 



as best we can, the amount returned from various sources, in legume 

 crops, farm manures, and several forms of commercial nitrogen, it 

 seems impossible to reach a total of more than two million tons; this 

 leaves an annual deficit of about one million tons of nitrogen. When 

 we remember that production is based on the use of a small percentage 

 of the total supply each year, we can realize better the importance of 

 having a large total supply in order that the small percentage may be 

 adequate for profitable production. I am aware that some of these 

 calculations have been made from rather crude data ; but it is one of 

 the problems of agriculture to ascertain the truth, and to either dis- 

 prove or confirm the calculations already made. 



THE PROBLEM OF MAINTAINING AND INCREASING THE 

 NITROGEN SUPPLY 



The problem of the nitrogen supply naturally divides itself into 

 two lines ; one, the conservation of the natural supply ; the other, a res- 

 toration through new supplies. As the nitrogen is included in the 

 organic matter of the soil, it is a frequent custom to apply various 

 agents to those soils low in organic matter that will hasten the de- 

 composition of the organic matter, so that more nitrogen can be re- 

 covered than under natural processes. The agents so used are acid- 

 ulated fertilizers, green cover and catch crops plowed under, lime in 

 caustic forms ; and sometimes even clover and farm manures are used 

 for the purpose. On much of the poorer land, where the amount of 

 available nitrogen is the measure of crop growth, it is being found 

 more profitable to continue the process of breaking down the organic 

 matter by using more and more of these agents designed to secure 

 nitrogen, than it is to supply nitrogen. In the end, and the end is 

 coming soon on much of the land, the organic matter becomes so low 

 that stimulation is not effective, and complete fertilizers must be used 

 to provide each deficient element in the quantity needed for the crop. 

 In general, such crops do not pay the cost of the fertilizer. It is not 

 contended that there is no legitimate use for these various stimulating 

 agents, for some of them have great value, and there is a proper place 

 for them; but it is one of the problems of agriculture to determine 

 their proper use and their improper use. 



A common reply to the problem of restoring nitrogen to the soils 

 has been to let the legumes do it. It is true that nitrogen can be added 

 to soils by means of legume crops ; but it is also true that legume plants 

 prefer available soil nitrogen to air or bacterial nitrogen, and are 

 likely to use the soil nitrogen before using the other source. If this 



