Rothamsted Symposium on Trace Elements 18 



Conclusion:— The efiFectiveness of the technique outlined here 

 may be judged by the visual symptoms of the deficiencies that 

 have been produced with it in several crop plants, and some ex- 

 amples are illustrated here. 



The use of sand culture methods admittedly adds an extra 

 burden in the purification of this material but results suggest that 

 this can frequently be done eflSciendy enough to allow of much 

 useful work and its use has several advantages over solution cul- 

 tures as a rooting medium, including its adaptability for studies 

 where nutrients are given in solid form. Experience shows that 

 the limiting factor at present in the use of sand may be due to 

 the slow liberation of trace nutrients present as difficultly soluble 

 compounds or partly occluded in crevices and which are not al- 

 ways completely removed in the acid treatment. 



References 



1. Steinberg, R. A., 1935: J. Agr. Res. 51:413. 



2. Stout, P. R. and Arnon, D. I., 1939: Amer. J. Bot. 26:144. 



3. Scott, R. O. and Mitchell, R. L., 1943: J. Soc. Chem. Ind. 62. 



4. HiLLEBRAND, W. F. and LuNDELL, G. E. F., 1929: Applied Inor- 

 ganic Analysis. 



5. Piper, C. S., 1945: Private communication. 



Points from Discussion of Pa-per hy Dr. Hewitt 



Dr. Lohnis:— 



Have you gained any experience as to the degree of toler- 

 ance of lucerne for excess of Mn as in the neighbourhood of 

 Wageningen I have formerly noted that lucerne developed very 

 poorly on unlimed soil? Mn toxicity might be involved here. 



