SOURCES OF NITROGEN OF PLANTS. 97 



HUMUS IN THE NATUKAL CONDITION. 



The Clawsoii wlieat (1882) gave an increase of crop 60 times that of the 

 seed, and the nitrogen increased 25 fold ; while the clover for 1883 gave an 

 increase 3,188 times that of the seed, and the nitrogen was increased 1068 

 fold. 



In 1885 the Minnesota spring wheat gave an increase of crop 200 times that 

 of the seed, and 116 times the quantity of nitrogen, while clover the same year 

 gave an increase in crop of 11,405 times the weight of the seed, and the 

 nitrogen was increased 3,892 times. 



HUMUS DEPRIVED OF NITROGEN. 



The wheat (1882) grown in a soil where the humus had been deprived of its 

 nitrogen gave an increase of entire crop 8 times that of the seed, and tlie nitro- 

 gen just doubled, while clover the same year and in same conditions gave an 

 increase of 1,597 times the weight of seed in the total crop, and 566 fold increase 

 •of nitrogen. 



It is thus seen that the clover has a wonderful power of taking up nitrogen 

 from the humus of the soil in circumstances where wheat has a far inferior 

 power. This is shown alike in humus in the natural condition as found in 

 arable soils, and the " inert and inactive" nitrogen that has been supposed to 

 be of no worth to growing plants. 



Why this difference between wheat and clover? Some will say that nitrifica- 

 tion took place during the season of growth; that the distilled water with which 

 they were watered during the season of growth may have contained a little 

 ammonia, or the plants may have absorbed ammonia from the air, and thus 

 in one or all of these ways the plants may have obtained their suj^ply of 

 nitrogen. 



Grant all these possibilities the question still comes back. Why did not the 

 wheat take advantage of tliese sources of active nitrogen as well as the clover? 

 The soil was the same for both plants, they shared the same distilled water and 

 grew side by side. These plants, so to speak, sat at the same table and had 

 the same bill of fare. Why was one lean and hungry, while the other waxed 

 fat, unless the one had the power to eat and digest some article on the table 

 for which the other plant had no stomach? Can we explain these results 

 except upon the assumption that clover has a power of taking from the com- 

 bined nitrogen of the vegetable matter of the soil a supply of nitrogen under 

 circumstances where wheat fails to obtain a sufficient supply? Is the great 

 value of clover as a manural crop to be explained by its power to accumulate 

 from this source a supply of nitrogen which may supply a cereal crop following 

 where the cereal would fail but for the intervention of the clover ? 



When the clover has taken up this soil nitrogen and made it a part of its 

 •own structure; the nitrogen is no longer inert and useless; it has become active 

 and available: it has "enlisted for three years or during the war." When the 

 clover is returned to the soil either as a whole crop, or as clover sod, or as ' 

 manure of stock fed on the clover, this accumulattd nitrogen is available for 

 any subsequent crop. This is a fact which demands your thoughtful considera- 

 tion. If clover has the power of appropriating and assimilating this most 

 costly and precious element of plant growth from sources most abundant, but 

 practically unavailable for plants of highest agricultural value, this becomes a 

 question of high import to the practical farmer. " The power of one plant to 

 accumulate and store up in the soil the materials for the sustenance and 



13 



