Rothamsted Symposium on Trace Elements 136 



well known that in arable land, on sandy areas, the pH values in- 

 crease accordingly. In hay the differences are hardly noteworthy. 



A considerable increase in manganese in young pasture grass 

 on clay was observed following manuring with Thomas phosphate 

 containing 6 per cent manganese, the average figures being 8.6 

 and 19.0 mg, respectively. In hay the difference is small. On 

 sand and peat the differences in manganese between young pas- 

 ture grass and hay after manuring with Thomas phosphate were 

 also small. 



Evidence has further been obtained that coarse, young pasture 

 grass from sandy soils contains less manganese than ordinary, 

 young grass. 



Supplementary Research on Copper, Cobalt, Molybdenum* 

 and Selenium (m collahoration with J. de Wael):— A low con- 

 tent of copper in pasture grass and hay, formerly reported from the 

 northeastern diluvial part of the Netherlands, has also been ob- 

 served recently in alluvial parts. Values as low as 3-5 mg of Cu 

 per kg (dry matter basis) are not exceptional. However, in the 

 majority of the cases examined normal values of 10-25 mg were 

 found. As pointed out, a low copper content of the blood serum 

 of cattle grazing on these pastures, indicating a "conditioned 

 deficiency," was repeatedly recorded. 



Small amounts of cobalt were determined in pasture grass, hay 

 and liver of cattle in numerous cases. In pasture grass and hay 

 from alluvial soils figures of about 300-500^ per kg (dry matter 

 basis) were found to be quite normal. The amount of cobalt in 

 grass and hay originating from diluvial soils may be considerably 

 lower, about half of the amount mentioned above or even lower. 

 Signs of cobalt deficiency are repeatedly reported for those areas. 

 Evidence has been obtained that the affected animals— cattle and 

 goats— will show a favourable response to the oral administration 

 of cobalt or a mixture of cobalt and copper. The liver of normal 

 cattle was shown to contain about 300-400y of cobalt per kg (dry 

 matter basis). The liver of catde from affected areas may show 

 less, e.g. 120y. 



Selenium was found occasionally in pasture grass, hay, drink- 



» Grass, from sandy soils of the North East diluvium, showed a very low molyb- 

 denum content — as a rule less than 1 mg per kg (dry matter basis), the highest 

 values being about 2 mg. Grass from peat soils contained more molybdenum, the 

 maximum found amounted to about 10 mg. This suggests that, in addition to the 

 pU value of the soil, other factors play a role in the absorption of molybdenum by 

 plants. For clover, values up to 30 mg per kg were determined. 



