July 17, 1916 Influence of Calcium and Magnesium on Plant Growth 593 



Pisciotta (28), an Italian investigator, reports the analysis of 60 soils 

 which show a wide variation in the lime-magnesia ratio, due to the 

 variation in the lime content. Patterson (25) found that magnesian 

 lime, which is claimed to be poisonous, gave the highest yields. 



In summing up the literature studies previously mentioned, it will be 

 seen that Loew and his associates and Japanese students maintain the 

 theory of a definite lime-magnesia ratio, as do Ulbricht and Wartiadi, 

 whereas Dojarenko, Gossel, Konovalov, Meyer, Lemmerman, Haselhoff, 

 Gile, and Patterson claim that a definite ration of lime to magnesia is 

 not tenable and, furthermore, lacks substantiation. 



Lemmerman et al. have undoubtedly conducted the most extensive 

 investigations upon this subject and conclude that there is no correla- 

 tion between maximum crop productions and the ratio of lime to magne- 

 sia. Soils reported by Russell and by Gile show wide variations in the 

 lime-magnesia ratio, also in the percentages of these two elements, and 

 that there fails to be any correlation between the productivity of a soil 

 and its ratio of lime to magnesia. 



Solution cultures show that a specific ratio of lime to magnesia is not 

 equally effective in dilute solutions and in concentrated solutions. This 

 indicates that the effectiveness is dependent upon the total balance of all 

 the salts in solution instead of merely the ratio of calcium to magnesium. 



The preponderance of evidence appears to be against a definite ratio 

 of lime to magnesia, especially with respect to soil cultures in pots and 

 under field conditions. What really seems of first magnitude is the 

 resultant of all factors — that is, the climate, the plant, and structure, 

 reaction, micro-organic activity, and composition of the soil. 



EXPERIMENTAL WORK 



These experiments were planned with the idea of studying the effects 

 of calcium and magnesium upon plant growth when applied in different 

 natural and in artificially prepared forms. Studies were made to deter- 

 mine the amount of calcium and magnesium which the plants could 

 tolerate. The relation between the ratios of these two elements in the 

 plants, in the soils, and in the materials applied was also studied. 



Dolomite, limestone, magnesite, calcareous soils, and brown silt loam 

 were used as sources of the natural forms, while prepared materials, such 

 as the carbonates, chlorids, and sulphates, served as sources of the arti- 

 ficial forms. Increasing amounts of the various forms were used, also a 

 variance in the ratio of calcium to magnesium was employed. The 

 earlier applications varied from 0.1 to 0.6 percent of magnesium added 

 in magnesium carbonate and in magnesite. Later the following amounts 

 were employed: 2, 6, and 10 per cent of magnesium in magnesite; 10 

 and 12.7 per cent of magnesium in dolomite; 0.1, 0.01, and 0.001 per 

 cent of magnesium in the carbonates, chlorids, and sulphates. In each 

 series sand or soil was used as a control. 

 42719°— 16 2 



