IMPORTANCE OF COPPER AND MOLYBDENUM 



IN THE NUTRITION OF HIGHER PLANTS 



AND MICRO-ORGANISMS 



hy E. G. Mulder, Ph.D. 



Landbouwproefstation, Eemskanaal, Groningen, Netherlands 



Copper:— Copper deficiency in cultivated plants may occur on 

 sandy and peaty soils in Europe as well as in the U.S.A. and Aus- 

 tralia. In Holland and other countries of Western Europe the 

 deficiency symptoms are known as reclamation disease. 



Since the discovery of Hudig and Meyer in 1925 (4) that 

 reclamation disease can be prevented for a number of years by 

 adding one dressing of 50-100 kg CUSO4 per ha, many farmers in 

 the affected areas of Holland have treated their land with copper 

 sulphate. As a result of this the pronounced symptoms of the 

 disease are seen rather sporadically in Holland nowadays. The 

 mild cases, however, which are recognized less easily, still occur 

 frequently. 



To prove that the reclamation disease was due to a lack of 

 available copper in the soil, three series of experiments were 

 carried out: 



1) The symptoms of copper deficiency in various species of 

 plants growing in nutrient solutions were compared with those of 

 the reclamation disease. These symptoms appeared to be quite 

 similar. This was not only so in the case of pronounced cases in 

 which dead, white tips appeared at the youngest leaves while no 

 ears emerged, but also of the mild cases in which the ears emerged 

 normally, but grain production was reduced (Plates 4, 5 and 6). 



Plant species less susceptible to the reclamation disease (pota- 

 toes, rye) required considerably less copper than highly susceptible 

 plants such as wheat, barley and oats. 



2) Copper determinations according to the carbamate method 

 (5) were carried out on plants grown in normal and diseased 

 soils. Grain and straw of ripened plants, and leaf and stem mate- 

 rial of young plants were analysed. In the latter instance the 



