May a ,i9 Effect of Ferrous Sulphate on Chlorosis of Conifers 169 



A condition associated with chlorosis in Douglas fir which does not 

 appear in the measurements is its abnormally prompt loss of turgor on 

 the cutting off of the water supply. The leaves of chlorotic seedlings 

 wilted so quickly after the plants were taken up that measurements of 

 the width of the leaves could not have been accurately made for this 

 species. Another difference not shown by the measurements is in the 

 color of the terminal buds formed. The terminal buds of normal Douglas 

 fir are a reddish brown, while those of the chlorotic seedlings vary from 

 a light brown to a brown. 



No relation between the growth rate and the artificial supply of iron 

 was evident from an examination of the beds. As the treatments were 

 not begun until the latter part of the growing season, no material effect 

 was to be expected. 



SUMMARY 



Chlorosis has been the most serious problem encountered in the success- 

 ful production of coniferous nursery stock at a nursery in southern Idaho. 

 The disease affects all coniferous species grown in this nursery. With 

 chlorosis were associated poor growth of roots, stems, and leaves, failure 

 to form normal terminal buds, and susceptibility to winter injury. 



The importance of excessive soil moisture as a cause of chlorosis has 

 not been definitely determined. Preliminary experiments indicate, 

 however, that it is relatively unimportant. 



Chlorosis in western yellow pine at the Pocatello Nursery has been 

 definitely corrected by spraying with ferrous sulphate at lo-day inter- 

 vals. Similar, though less decisive, results were obtained with Douglas 

 fir. A i per cent solution in amounts sufficient to wet the tops thoroughly 

 proved the most satisfactory treatment. A 2 per cent solution ultimately 

 caused chemical injury to practically all the plants. In a region of more 

 frequent rains the stronger solution might be better. 



The control of chlorosis in jack pine and western yellow pine at the 

 Morton Nursery in Nebraska by spraying with a i per cent solution of 

 ferrous sulphate has given such evidence of success that it has been 

 adopted as a part of the regular nursery practice. 



The three soils on which conifers have been found decidedly chlorotic 

 all contain considerable amounts of carbonate and have been formed, 

 in part at least, from limestone. The nursery water supply at Poca- 

 tello also contains much calcium bicarbonate. No definite correlation 

 could be found between chlorosis and the amounts of calcium or of car- 

 bonate obtained by hydrochloric-acid digestion analysis. 



