Rothatnsted Symposium on Trace Elements 28 



I) 6 g of potassium hydrate with g, 15 g, 30 g and 45 g 



of quicklime per pot respectively 

 II) 12 g of potassium hydrate with g, 15 g, 30 g and 45 g 



of quicklime per pot respectively 

 III) 18 g of potassiimi hydrate with g, 15 g, 30 g and 45 g 



of quicklime per pot respectively 



The following table illustrates the results obtained with oats. 



Table 2: Thi influence of increasing amounts of potassium hydrate and quicklime 

 on the development and yield of grain from oats (5 points = top development):— 



The principal results of this test may be summarised as follows: 



1) The grey speck disease can also be produced on a sound, marshy 

 soil by heavy fertilising with potassium hydrate. 



2) Where the disease is produced by moderate doses of potassium or 

 calcium hydrate, it can be reduced or suppressed by an increase of one or the 

 other of the hydrates. 



3) The occurrence or non-occurrence of the disease seems to be con- 

 trolled, in principle, only by the OH-ions concentration, the K:Ca -relation 

 is of no, or only of secondary, importance. 



4) The plant analysis confirms Lundegardh's findings, according to 

 which the manganese content of plants in acid soils, on one hand, and in 

 very alkaline soils, on the other, is higher than in neutral or slightly alka- 

 line soils. 



