38 Journal of Agricultural Research voi.xx, no. i 



{43), that lime-induced chlorosis is caused chiefly by a lack of potash in 

 the plant ash. This opinion is evidently based only on the analyses of 

 Fliche and Grandeau (9, 10, 11) and on those of Schulze (42). If a lack 

 of potash in the ash were the cause of the chlorosis, plants grown in non- 

 calcareous soils and in water cultures, under controlled conditions, with 

 an insufficient supply of potash, should show this type of chlorosis. In 

 such cases, however, the lack of potash is indicated by the appearance of 

 brown spots on the leaves and not by a yellowing. 1 However, it has not 

 been shown that a combined excess of lime and deficiency of potash 

 would not produce chlorosis. 



The reliability of ash analyses as the sole means of diagnosing the cause 

 of chlorosis is questionable. At the most, the results of ash analyses 

 should be taken as merely indicating the cause or as confirming other 

 evidence. The ash compositions of normal plants show such wide varia- 

 tions and are affected by so many conditions that it is sometimes unsafe 

 to assume that of two lots of plants those which have made the better 

 growth have an ash composition more nearly normal. • 



Aside from difficulties in properly interpreting the results of ash 

 analyses, it is sometimes doubtful whether the samples selected for 

 analysis are truly comparable, even when whole plants are taken. This 

 uncertainty was demonstrated in the analyses of rice, previously referred 

 to. The practice of taking only a portion of a plant for analysis is also 

 susceptible to error, especially where iron is to be determined. Since 

 iron appears to be relatively immobile in the plant after it is once trans- 

 ported to the leaves, certain leaves of a plant might contain a sufficiency 

 of iron while other leaves and the plant as a whole might lack iron (16). 



EFFECT OF APPLICATION OF IRON SALTS TO CHLOROTIC PLANTS 



Eusebe Gris, in 1845 (20), and later Sachs (41) and other investigators 

 (12, 21, 25, 26, 27) showed that various plants which became chlorotic 

 on calcareous soils could be cured by applying ferrous sulphate to the 

 leaves. This treatment and the improved one of Rassiguier (57), that of 

 brushing cut surfaces of pruned vines with a concentrated solution of 

 ferrous sulphate, have been rather generally used on grapevines which 

 became chlorotic on the calcareous soils of France and Germany. 



Various investigators have found that while iron salts were effective 

 in overcoming chlorosis when applied to the stems and leaves of plants, 

 they were ineffective when applied to the soil, even if used in considerable 

 quantity. Sachs (41), however, observed that where the roots of plants 

 were not completely surrounded by earth, as in the case of pot- bound 

 plants, applications of ferrous sulphate to the soil did cure the chlorosis. 



1 If potash is concerned in the formation of starch from sugars, a low percentage of potash in chlorotic 

 plants might be a secondary result of the chlorosis. With insufficient iron, chlorophyll formation is 

 depressed, less sugar can be synthesized, and little potash would be needed. 



