362 



possible only a full production. Thus oats often fail on parcels of land, 

 which have gradually been too heavily fertilized. Measurements of the 

 amount of transpiration show that in concentrated solutions, the plant needs 

 less water, for the production of one gram dry weight, than it does in very 

 dilute ones. From this it is evident that, up to a certain degree, fertilizing 

 signifies a saving of water\ 



The structure and size of the root system is changed gradually by con- 

 centration, corresponding to the change in the root hair, already mentioned. 

 Schwarz's- experiments with pines demonstrated this very well. He found 

 a gradual decrease in the extent of the roots of conifers with an increase 

 of the nutrient content of the soil, as had already been determined for 

 other plants. Here the relation between the aerial and underground axes 

 was changed. While, in unfertilized sand, the weight of the root system of 

 the pine seedlings was greater than that of the aerial parts, with an abun- 

 dant supply of nutritive salts the weight of the root system amounted to 

 only one-fifth that of the aerial axis. 



Even in cabbage plants, which have been gradually accustomed by cul- 

 tivation to the highest admissible concentrations, an over-nutrition finally 

 takes place and with it a retrogression in production. Thus kohlrabi plants 

 were found to be especially susceptible to large additions of phosphorus, 

 while they require high nitrogen and potassium fertilization, together with a 

 corresponding addition of calcium^. 



Changes in Meadows. 



The method of improving sour and sandy meadows by fertilization, 

 depends essentially on an increase of the nutrient concentration. The acid- 

 loving grasses, or those of sterile soil, which withstand only weakly con- 

 centrated solutions, then disappear and our good fodder grasses, demand- 

 ing higher nutrient content and producing more nutritive substance are 

 established. Very instructive experiments on permanent meadows are 

 found in Lawes and Gilbert*. We w^ill cite from them only one example, 

 in order to show that those different grass species gradually prevail in those 

 nutrient solutions, of which they can endure a higher concentration. With 

 the stated fertilizers, the percentages of the various grass species in 100 

 hay plants were found as given in the following table. 



From this table of grasses, we see how the rapidly spreading Festuca 

 duriuscula disappears on sterile sandy soil, if the concentration of the ni- 

 trate solutions and the mineral substances increase simultaneously. Agrostls 

 julgaris and Anthoxanthum odoratnm behave similarly, while, conversely, 



1 Sorauer, P., tJbef Mifsernten bei Hafer. Oesterr. Landwirtsch Wochenblatt. 

 Nos. 2, 3. 1888. 



2 Schwarz, F., t)ber den Einfluss des Wasser- und Nahrstoffgehaltes des Sand- 

 bodens auf die Wurzelentwicklung von Pinus silvestris im ersten Jahr. Zeitschr. f. 

 Forst-u Jagdwesen. January, 1892. 



3 Otto, R., Vegetationsversuche mit Kohlrabi etc. Gartenflora, 1902, p. 393. 



4 From "Journal of the Royal Agric. Soc. of England" and "Proceedings of the 

 Royal Hort. Soc. 1870," cit. in Biedermann's Centralbl. 1876, II, p. 405. 



