29 



Gisiger: Deficiencies Caused by Excesses 



Summary:— An unfavourable concentration of OH-ions, and 

 not a higher fixation of boron, is the immediate cause of disturb- 

 ances in plant growth after excessive use of lime in acid soils. In 

 these soils, boron does not react in the normal way as a nutrient, 

 but rather as a medicine; it strengthens the roots against the hy- 

 drating effect of the excessive concentration of OH-ions. Soils 

 retaining a detrimental excess can be leached by watering. The 

 grey speck disease of oats can be produced in an originally acid, 



4fSssCaO 

 ^Ojs - 



a ff GrO 



18 gs KOH per pot 



Textfigure 3.— Influence of increasing quantities of potassium and 

 calcium hydrate on the manganese content of oat straw. 



marshy soil by adding calcium carbonate and also by calcium or 

 potassium hydrate. When the dressing with these hydrates is 

 very heavy the soil shows a strong alkaline reaction and the disease 

 does not occur. It can also be prevented by manganese. Small 

 quantities of boron favour, while large doses suppress, the grey 

 speck disease. The K:Ca relation has no appreciable effect on 

 this disease. The manganese content of oat straw reveals that the 

 availability of manganese is greater in acid and very alkaline soils 

 than in neutral and slightly alkaline soils. 



'P\.e\erences 



Gerretsen, F. C., 1937: Manganese deficiency of oats and its relation 

 to soil bacteria (Annals of Bot. N.S. 1:207-230). 



Gisiger, L., 1944: Kalk und Kali (Landw. Jahrbuch d. Schweiz 

 58:515-589). 



Hudig, J., 1911: Ueber eine eigentiimliche Bodenkrankheit (Land- 

 wirtsch. Jahrbiicher 40:613-644). 



