MANURES. 37 



tloubt that at one period of growth, a greater proportion of inor- 

 [ranic matter is necessary than at anotlier — that the straw and the 

 jeed, although requiring the same materials, at the same time 

 [equire the different elements in different quantities. The well 

 tnown fact that the soil is more exhausted during the formation of 

 he seed than at any other period of the growth of the plant, is 

 ■xplained upon this principle. 



From the analysis- of Sprengel it appears that the ash from 1000 

 hs. of wheat contains more than 2 lbs. of potash, and 4 lbs. of 

 ilica, whilst the straw contains but one-fifth pound of potash and 

 iiearly twenty-nine pounds of silica. The great quantity of the 

 atter substance in the straw is necessary to give strength to sup- 

 lort its burden of grain. The variation is similar in other grains, 

 nd a like variation is seen in all the elements, in comparing the 

 institution of the straw and the seed. 



i The practical inference from all this would seem to be, that by 

 ccommodating the manures to the demands of the plant at different 

 eriods of growth, the straw or the grain might be improved at 

 leasure, or that we might at least expect a great control over the 

 evelopment of one or the other. How far this may be true it is 

 ppossible to decide, without more full and true experiment, 

 [his would consist in its simplest form in applying the same 

 ianure to two portions of the field at different times, to one por- 

 on when planted and to the other just before the crop goes to seed. 

 j The experiments of Mr. Campbell, of soaking seeds in saline so- 

 Itions, are very interesting in this connection. His object is to 

 turate the seed with the solutions, and, if v^e understand him, to 

 lus supply them with all of those substances that they need for 

 ^e, for he tried the experiment without the use of other manures, 

 id in another instance in pure sand. It is to be presumed, bow- 

 er, that his expectation of reaping a tenfold crop by this means, 

 j conjunction with other manures, has not been fulfilled, as we 

 jive never seen any statement of such a result. It has been sta- 

 ll before, that the probable good effects arise in this case from the 

 "gorous start given to vegetation in the outset, by which the plant 

 i| early placed in a condition to appropriate large quantities of 

 ibd, and also to obtain it under unfavorable circumstances. 

 If such is the case, great practical use may be made of the prin- 

 <^le, and especially when in other respects, such as preparation 



