cision has been reached as yet as to how this effect is produced. It is thought 

 that in this, physical, chemical and soil bacteriological processes interact 

 supplementarily. The frequent thawing and freezing in the winter serves 

 to break and loosen the soil. Thus the action of the atmospheric processes 

 is favored and the soil opened for the beneficial species of bacteria. It has 

 not been determined with certainty to which genera these belong. Hiltner 

 has proved first of all, that they are not the Alinit bacteria. In the end the 

 usefulness will be decided by the greatest accomplishment of the nitrifying 

 bacteria; for, according to Reitmair^ the nitrification in good mild soils with 

 sufficient heat begins immediately after the fall harvest in such a way that 

 the nitrate requirement of the subsequently planted grain will be met until 

 the next spring. In this, however, a suitable friability and a definite calcium 

 content is taken for granted". (See also the statements under Drain Water.) 

 Naturally it must be emphasized with Stutzer^ that the land may be al- 

 lowed to lie fallow only under certain fixed circumstances. It is thought 

 that this may be done if it seems financially most advantageous for the agri- 

 culturalist to do without the field for the long time while it is lying fallow, 

 rather than to use the more quickly acting green manure and stable manure. 

 When working with soils tending to unripeness, emphasis should be laid on 

 this lying fallow only because it loosens the soil mechanically and does not 

 affect the fertilizing salts. The nitrogen of the organic fertilizing masses 

 seems, as Pfeiffer* especially emphasizes, to be held fast in the soil, capita- 

 lized as it were, and then shows a long subsequent action. This author is, 

 however, an opponent of the theory of letting ground lie fallow, which he 

 characterizes as a robber cultivation, so far as the stock of nitrogen is con- 

 cerned. He sees in this an incomplete restitution of the amounts of nutri- 

 ment removed from the soil by the crops. In Pfeiffer's opinion, the soluble 

 nitrogen compounds obtained by letting the land lie fallow are lost again in 

 great part from uncultivated soils by the water which soaks through. Such 

 considerations, in my opinion, are entirely justifiable for light soils, Init do 

 not hold good for heavy soils provided with an abundant absorptive power 

 by the clay and weakened by the harvests. 



2. Relation of the Nutritive Substances to the Plants. 



The phenomena treated in this and the following division, are rarely the 

 result of only a lack or an excess of the nutriment in the soil. They are 

 usually the result of the co-operation of numerous factors, among which 

 atmospheric humidity plays an especially decisive role. We will not forget 

 that almost all diseases are produced by an unsuitable combination of the 



1 Reitmar, O., Die Stellung der Brache und der Griindiingung- in unsern moder- 

 nen Fruchtfolgen. D. Landw. Presse. Sond. 1903. 



2 Wohltmann, F., Fischer, H., and Schneider, Ph., Bodenbakteriologische and 

 bodenchemische Studien aus dem Poppelsdorfer Versuchsfelde. Journ. f. Landwirt- 

 schaft 1904, p. 97. 



3 Stutzer, A., Die Nutzbarmacliung des Stickstoffs der T-.uft fiir die Pflanzen. 

 D. Landw. Presse 1904, Nos. 10-19. 



4 PfeifCer-Breslau Stickstoffsammelnde Bakterien. Brache und Raubbau. Berlin, 

 P. Parey, 1904. cit. Centralbl. f. Agrik. Chem. 1905, p. 599. 



