INVESTIGATIONS ON MICROELEMENTS FROM 

 A PRACTICAL POINT OF VIEW 



hy F. Steenbjerg, Dr.Agr., 



Kgl. Veterinaer- ir Landbohtpjskole, Copenhagen, Denmark 



During the past fifteen years chemical investigations on the 

 relation of manganese and copper in the soil and in plants have 

 been made in Denmark. In recent years, it has, moreover, been 

 shown by Bendixen and Pedersen that a cobalt deficiency dis- 

 ease occurs in young cattle (heifers) on the sandy soils of Judand. 

 As far back as about 1910, and before that time, comprehensive 

 investigations on the visual symptoms and etiology of those plant 

 diseases which we now know to be caused by lack of microele- 

 ments were started at the State Plant Pathological Laboratory at 

 Lyngby. 



Both iron and manganese deficiency very often occur in Dan- 

 ish agriculture and horticulture. While manganese deficiency 

 is generally known and causes losses on nearly all soils in Den- 

 mark copper deficiency is known particularly on the sandy soils 

 of Jutland where it causes severe losses. 



As early as 1932 it had been shown that a determination of the 

 exchangeable manganese of the sandy Danish soils, which are 

 rather uniform in physical condition, gave some measure of the 

 power of the soil to supply the plants with manganese. The 

 amount of exchangeable manganese in the soil is regulated by 

 the pH value and by the conditions of oxidation and reduction 

 of the soil. At the same time it was shown that manganese is 

 absorbed in a different degree in acid and alkaline soils. More- 

 over alkaline soils, rich in humus, seem to fix the manganese in a 

 non-exchangeable state with a very considerable energy. 



For a determination of the exchangeable manganese a one 

 molar solution of magnesium nitrate is used as the displacing solu- 

 tion. The sodium, potassium and ammonium ions give smaller 



