No. 7. DEPARTMENT OF AGRICULTURE. 371 



knovvu to lead to the rouclusiou that the larger pan tomes from the 

 air and is by so much a net gain to the soil. The probability is 

 that these proportions will vary with the varying quantities of the 

 soil nitrates. It is also a well established fact that the plant is 

 enabled to secure its nitrogen by the bacteria, or micro-organisms, 

 resident in the nodules on the roots, though their modus operandi 

 is not certainly known. However, the conditions of such activity 

 are well understood. Moisture, heat, alkalinity and the presence of 

 air are some of the prime conditions that must be secured in order 

 to promote rapid nitrification by means of the bacteria. The pres- 

 ence of phosphate and potash, with frequent cultivation, has been 

 found to greatly promote their activity. These leguminous plants 

 may exist in a feeble state without showing the existence of nodules, 

 and presumably without their specific bacteria, especially in soils 

 rich in nitrates; but in the measure of the existence of the root 

 nodules, and hence of their bacterial action, will thev fix the free 

 atmospheric nitrogen and reach a full development. 



Though the fertilizing value of the clovers may not yet be fully 

 appreciated, they are coming into favor more and more; yet many are 

 discouraged by their failures in attempting to produce it. How 

 to secure a clover stand and bring it to maturity is the anxious and 

 important question. My own experience and rather extensive ob- 

 servation leads me confidently to the conclusion that when we un- 

 derstand the nature and demands of the clover plant as well as 

 we understand those of our common farm plants, we will have no 

 more difficulty in growing it than we have in growing them. Poor 

 soil will produce but poor crops of any kind. Unfavorable climatic 

 conditions will injure any crop. Any other crop treated as un- 

 wisely as we have usually treated the clovers will result in as many 

 failures as we experience in growing this. The fact is that clover 

 is one of our hardiest plants. It takes hold on the earth, the air 

 and the sun more fully than do the non-leguminous plants, and with 

 the aid of its bacteria has a distinct advantage over the latter; and 

 when its deep-root system is once developed can more successfully 

 cope with frost and flood and drouth. 



There are at least four supreme conditions of securing a full 

 growth of clover. 



1. The soil must be cleared of stagnant water, and this for two 

 reasons: 



First, because water in a compact clay soil will form ice that will 

 ruin the plant by heaving. When water freezes it expands and 

 must bulge upward. When this occurs the plants caught in it are 

 lifted out of the soil or are broken. This, and not the low tempera- 

 ture, is what destroys the plant. If no stagnant water is present 

 and the soil is loose when the ground freezes and the pressure is 

 put upon it, the earth crumbles and the plant escapes injury. But 

 in the second j^lace, the water should be removed to admit air. As 

 has been already stated, the bacterial activity cannot go on without 

 the presence of air. Nitrification or the chemical union of oxygen 

 and nitrogen cannot take place, of course, without the air contain- 

 ing oxygen. Hence the absolute necessity of an open soil free from 

 stagnant water. Surface drainage will not always be sufficient. It 

 must be remembered that the clover roots need a foot or two in 



