Rothamsted Symposium on Trace Elements 24 



entirely prevented. It is possible that here and in the following 

 pots a few plants were enabled to grow, because the injurious 

 exchanging matter was washed into the deeper layers. 



In the leached series, serious damage is shown only by the 

 highest amount of lime. 



The growth in the boron series is very similar to that in 

 the non-leached series; it shows a quick improvement through the 

 first lime treatments and then a sudden decrease which is mod- 

 erated by boron. The leached series, surprisingly, shows better 

 growth than the boron series. 



The mustard reacts similarly to flax, as illustrated in Plate 1 

 which shows three test series with increasing lime quantities on 

 an acid soil. In the first series the mustard was sown immedi- 

 ately after liming. The growth shows an improvement through 

 the small lime doses, but after the fifth dose there is a progressive 

 decrease. In the next two series the same soil is used as in series 

 one; the second series was treated with 3 1 mg of boric acid, whilst 

 the third was leached during one winter. With this leaching a 

 noticeable reduction of the so-called lime damage was again 

 achieved. 



Experiments with new soils led to similar results, as can be 

 seen from Plate 2; all the 6 pots had been filled with the same 

 soil rich in lime. 



The Mitscherlich pots (the three on the right) were well 

 leached for a period of a fortnight. Then the same base manure 

 of P N K was given to all pots. Into the second and the fifth 

 pot a supplement of boric acid, and into the third and sixth a 

 strong dose of soluble phosphate (mono calcium phosphate) was 

 mixed. A similar advantage resulted from the leaching and from 

 the boron dressing, the latter did not produce a further noticeable 

 effect in the leached soil. 



The illustration is clear enough without any further explana- 

 tion and these experiments may be summarized as follows: 



J ) On very acid soils the growth can be noticeably improved by liming. 



2) Injuries to the growth of plants, "sensitive" to lime, are only ob- 

 served when lime is added in excess of the quantity needed for the satu- 

 ration of the soil up to jjH 7. 



3) The injury is probably caused by alkaline calcium compounds, which 

 arise from transformation. The injury can be traced to a too high con- 

 centration of hydroxide (OH)-ions. 



4) These damaging compounds can be washed out almost entirely, so 

 that such sensitive plants as flax and mustard are less hindered in growth. 



5) In soil rich in calcium, if the water table is high, the enrichment 



