200 MASSACHUSETTS HORTICULTURAL SOCIETY. 



large extent, in another way. Those who so strongly insist that 

 clover feeds upon the air foiget that in every arable soil, such as 

 clover is usually raised in, there are many hundreds and often some 

 thousands of pounds of nitrogen in chemical combination, although 

 in forms not readily assimilable. But, for all that, it may not be 

 denied that, with the breezes almost constantly bringing fresh por- 

 tions of air in contact with the foliage, at least a little and per- 

 haps more than a little of their nitrogen may be gained in this 

 way. But it should be noticed in this connection that man}' of 

 Boussingault's first trials were made under very much the same 

 conditions as those fixed by Prof. Atwater. In nearly all cases 

 there wore slight gains of nitrogen wh6n the plants were grown 

 with exposure to free air ; but ihej were ver}' small, falling very 

 far short of those made by Prof. Atwater's plants. 



But this ammonia of the air can also reach the plant by way 

 of the roots, through the power possessed b}' the soil of absorbing 

 gases within its pores. That such absorption of ammonia does take 

 place has been proven by experiment. It is an operation that may 

 go on all the time, day and night alike, and during as much of the 

 year as the soil is open to the access of the air. It cannot be told 

 how much combined nitrogen may be brought within reach of the 

 crops in this way, for it is about impracticable to determine with 

 any degree of accuracy the rate of this absorption. Koenig in Ger- 

 many estimated it at about thirty pounds per acre and year ; but 

 in such a manner that his result was not after all much better than 

 a pretty reliable guess. It the quantity is as large as this, how- 

 ever, it is a valuable contribution to the nitrogen suppl}*. 



Perhaps you are acquainted with the history of that rather re- 

 markable system of culture, that was carried on for a dozen years 

 or more by Rev. Mr. Smith, on the Lois Weedon farm in England 

 — the results of which furnish such a striking illustration of what 

 can be accomplished by tillage alone. The fields were divided off 

 into strips three feet wide. In the first year of the course, every 

 alternate one of these strips was planted with three rows of wheat, 

 a foot apart ; the spaces thus left between the rows being wide 

 enough to permit full and complete culture by hand, during a 

 large part of the growing season. The unoccupied three-foot 

 strips were most thoroughly cultivated during the whole season ; 

 largely by hand labor. In the following year these unoccupied 

 strips were in their turn planted with wheat, in rows a foot apart. 



