On Physiologically Balanced Solutions. 1 



By 

 0. Loew and K. A so. 



About half a century ago various authors have carried out 

 experiments in order to find a solution in which plants could 

 be grown to perfection which are cultivated in soil. After 

 many failures Knop succeeded to compose a culture solution of 

 the desired qualities, it was superior to all others, that of 

 Sachs not excepted. In other words, it was a physiologically 

 balanced solution; the injury by a one-sided nutrition was 

 prevented by the proper quantity of other nutrients. 



It must have been doubtless recognized by Knop, altho it 

 was not pronounced with emphasis, that the ratio of the dif- 

 ferent nutrients to each other is of fundamental importance for 

 the best development of the plants and that this principle of 

 the water culture must hold good also in regard to soil and 

 manure for the field crops. 2) In studying the cause of the toxic 

 action of magnesium salts we were led to infer that special 

 consideration is necessary for the regulation of the relative 

 amounts of lime and magnesia available to the roots. 



Numerous experiments have shown beyond any doubt that 

 the injurious action which magnesium salts exert on plants 

 from the higher algae upwards can only be prevented by- lime 

 salts and that the important function of magnesium salts can 

 therefore only be realised in the presence of lime salts. Our 

 investigations have further demonstrated, that the most favor- 



l) This article appears also in the Bulletin of the College of Agriculture, Tokyo 

 [mperial University, Vol. VIII. No. 3, 1907. 



-> It is true, some few adhere to the opinion, only holding good for aquatic plants, 

 that the osmotic laws determine the amount and kind of the necessary nutrients to 

 be absorbed. But the current of transpiration plays a more important role than that 

 for the land plants and it brings into the plant hody much more mineral matter 

 than needed. 



