BULLETIN OF THE BUSSEY INSTITUTION. 129 
It is to be inferred from the foregoing results, and from those ob- 
tained by the use of single fertilizers, that no mere manuring of the 
land of Section EE could have given a bean-crop much larger than 
six or seven kilogrammes to the square, or from thirty-six to forty 
bushels to the acre. It is plain, at all events, that crops so large as 
these last cannot be obtained economically, since the amount of fer- 
tilizing material expended in their production is out of all proportion 
greater than that which proved sufficient for the growth of crops 
very nearly as good. It has been seen already that the crops obtained 
by the use of comparatively small amounts of fertilizers, as in B 4 and 
B 7, must be vastly better in respect to cost than those from the 
squares that were heavily manured. Perhaps some happy combina- 
tion of farm-yard manure and the artificial fertilizers might have 
increased the crop a little ; but the number, thirty-nine bushels to the 
acre, may fairly be taken as that of the largest crop obtainable by the 
use of manure upon the land in question wnder the conditions that ob- 
tained in the year 1873. So many bushels of beans as this from the 
acre of poor land is undoubtedly a large yield, and the result is the 
more striking in view of the almost total failure of the contiguous 
barley crops; but it would seem to be sufficiently plain that the lavish 
expenditure of fertilizing materials, by which the largest crops were 
produced, would be wholly unjustifiable in the actual farming prac- 
tice of this region. 
It has been shown by the German chemist Hellriegel,* that in 
order to obtain a maximum crop, that is to say, the largest possible 
crop, of any plant, it is necessary, not only to supply the plant with 
the various chemical substances which serve as its food, but also to 
provide certain favorable conditions that are essential to the well- 
being of the plant, and to present the food under these conditions. 
Beside mere food the plant must have sufficient standing-room, and 
plenty of light, heat, air, and moisture. The experiments of Hell- 
riegel show most clearly the enormous influence that is exerted upon 
the quantity of a crop whenever any one of these conditions is left 
unfulfilled, or is only partially fulfilled. It is only when each and all 
of the conditions are favorable, and, as it were, in just proportion, and 
* In a most admirable series of researches made at the experimental station at 
Dahme. See Stockhardt’s Chemischer Ackersmann, 1868, 14, 13; Hoffmann’s 
Jahresbericht, 1866, 9, 146. 
VOL. I. 17 
