INJURY THROUGH EXCESS OF MANGANESE 



hy M. P. LoHNis, Ph.D. 



Laboratorium voor Microbiologie der Landbouwhogeschool, 

 Wageningen, Netherlands 



The investigations, about which I will report, were started 

 during the years of the German occupation of the Netherlands. 

 For a long time, literature from the Allied countries was unavail- 

 able, and I was unaware of the results obtained in other places. 

 The chemical analysis of the samples obtained in the summer of 

 1947 has not yet been completed, and the full results will be pub- 

 lished later. 



When the Netherlands were invaded by the German army, 

 in May 1940, the need for an increased production of food crops 

 was felt. In this connection, the experimental plots of the Labora- 

 tory for Microbiology at the Wageningen Agricultural College 

 were planted with beans CP^^seolus vulgaris') a crop which had 

 never before been grown there. The plots are 41 m^ each and are 

 well separated. They were originally established for the study of 

 a variety of problems in the microflora of the soil. In 1922 three 

 ranges of six plots each were dressed with different amounts of 

 limestone (60-30-15-10-5-0 kg). After 1922 two further plots 

 were fertilized with chilean nitrate and two with ammonium sul- 

 fate, as the only sources of nitrogen. In the later years of the 

 war, nitrate being unavailable, all plots had to be fertilized, how- 

 ever, with ammonium sulfate. Except for nitrogen, all plots have 

 been fertilized and planted in the same manner since 1922. 



From 1940 to the present, half of each plot has been planted 

 with beans and half with potatoes, the crops in the two sections 

 alternating yearly. In some years, a single row has been sown 

 with another crop. The first crop of Phaseolus vulgaris consisted 

 of kidney beans raised for the ripe seed. Later the variety 

 "Dubbele Prinsesseboon" has been chiefly grown. This is a 

 French dwarf bean, the unripe pods of which are used as a vege- 



