40I 



The poisonous effects of an excess of magnesium and the associated 

 theory given by Loew, as to a definite quantitative relation between calcium 

 and magnesium in the soil for obtaining good harvests, have been con- 

 sidered already in the section on "Lack of Calcium" (p. 301). Recently 

 Loew^ has supplemented his earlier statements by calling attention to the 

 fact that the favorable quantitative relation between calcium and mag- 

 nesium in the soil cannot always be fixed by definite figures. It changes as 

 soon as the two bases are made accessible in different degrees for absorp- 

 tion by the plant. 



Loew's theory is contradicted by experiments made by Meyer-. The 

 emphatic fact here is that heavy additions of calcium as well as of 

 magnesium can greatly impair the yield. Naturally the various plant species 

 behave very differently with the same fertilizer. Given the same quantity 

 of magnesium, the grain and straw yield of oats was lessened, but that of 

 rye was not decreased. 



GosseP, on the basis of his own experiments, also considers Loew's 

 point of view to be Incorrect, yet we think it, nevertheless, worth consider- 

 ation. Too much faith must not be put in definite figures because each 

 cultural experiment offers different conditions. A constant effort must be 

 made to overcome the injurious effects of the magnesium compounds when- 

 ever brought into the soil in great quantities in the fertilizer. Qf first im- 

 portance is the great quantity of magnesium chlorid spread on the field with 

 the so-called "waste salts" which reduces the sugar content of beets, the 

 starch content of potatoes, etc. An effort must be made to combine the non- 

 absorbable chlorine with a base, especially calcium, so that it can be washed 

 easily into the subsoil. 



Finally attention must be called to the fact that the same amount of 

 calcium acts injuriously at one time and beneficially at another, according 

 to whether it is added in the forms of calcium carbonate or calcium sulfate. 

 Thus, for example, Suzuki*, found in vegetative experiments with moun- 

 tain rice, that the yield was considerably reduced by an excessive ad- 

 dition of calcium carbonate (the proportion of calcium to magnesium was 

 as 3:1), even if phosphoric acid was present in an easily soluble form. On 

 the other hand the addition of an equivalent amount of gypsum caused an 

 unusual increase in the yield, especially of grain. From this experiment, 

 however, it is evident that the injurious action of an excess of calcium is not 

 always to be sought in a decrease in the looseness of the soil as compared 

 with that found after the use of slightly soluble phosphoric compounds, but 

 probably has its foundation also in the neutralization of the root acids. 



1 Loew. O., and Aso, K.. tJber verschiedene Grade der Aufnahmefahig-keit von 

 Pflanzennahrstoffen durch die Pflanzen. Bull. College of Agric. Tokyo. Imp. Univ. 

 Vol. VI. No. 4, cit. Centralbl. f. Agrik.-Chemie 1905, p. 594. 



2 Meyer, D., Untersuchungen iiber die Wirkung- verschiedener Kalk- und 

 Magnesiaformen. Landw. Jahrbiicher Vol. XXXIII, 1904, p. 371. 



3 Gossel, Fr., Bedeutung- der Kalk- und Magnesiasalze fiir die Pflanzenernah- 

 rung. Vortrag- auf d. 75. Naturf. Vers. (s. Chemikerz. 1903, No. 78). 



■i Suzuki, S., iiher die schadliche "Wirkung einer zu starken Kalkung- des 

 Bodens. Bull. College of Agric. Tokyo, Imp. University. Vol. VI. cit. Centralbl. 

 f. Agrik.-Chem. 1905, p. 588. 



