Oct. i, 1920 



Cause of Lime- Induced Chlorosis 



53 



and ferric tartrate which were applied to the soil every other day. 

 Results of the test are given in Table XII. 



Table XII. — Comparative availability to rice plants of organic and inorganic iron com- 

 pounds in calcareous and noncalcareous soils: Experiment I 



Special additions 

 to the soil. 



Amount 

 added. 



Oven-dried yield of plants per pot. 



Calcareous soil. 



Series 

 A 



Series 

 B 



Series 

 C. 



Series 

 D. 



Series 

 E. 



Aver- 

 age. 



Noncakareous soil. 



Aver- 

 age. 



None 



None 



Ferric oxalate 



Do 



Ferric tannate. . . . 



Do 



" Ferric humate". 



Do 



Ferric citrate 



Solution of ferric 



citrate 



Ferric tartrate. . . . 

 Solution of ferric 



tartrate 



Tobacco stems 



Do 



Stizolobium vines. 



Do 



Dried blood 



"Mixture" 



Citric acid 



Tartaric acid 



Gm. 



2-43 

 4.86 



16.36 



Gm. 



28 

 30 

 18 

 19 

 19 



38 



Gm. 



Gm. 



23 



Gm. 



26 



Gm. 



26 

 28 

 24 

 24 

 25 

 28 

 16 

 16 

 24 



Gm. 



Gm. 



After three weeks the plants in noncalcareous soil were about twice 

 the size of those in calcareous soil. Later the plants in calcareous soil 

 were all more or less chlorotic, but the plants in pots receiving the larger 

 applications of tobacco stems, cover crop, or "mixture" were less chlo- 

 rotic than others. All the plants in the noncalcareous soil were a good 

 green throughout growth. 



In the noncalcareous soil none of the materials significantly affected 

 growth except the "mixture," which depressed the yield about 20 per 

 cent. In the calcareous soil the "ferric humate " was distinctly injurious, 

 while the larger applications of tobacco stems and Stizolobium vines were 

 plainly beneficial, although they did not induce a normal growth. 



Summary. — All organic iron compounds tried in the two preceding 

 experiments failed to increase appreciably the growth of rice in the cal- 

 careous soils. It is, therefore, probable that organic iron is no more 

 available than inorganic iron in such soils. 



While concentrated or soluble organic materials, such as dried blood, 

 citric and tartaric acids, molasses, and a humus extract, failed to ameli- 

 orate the chlorosis, bulky organic materials, such as tobacco stems and 

 velvet bean plants, when used in considerable quantities measurably 

 improved the growth and color of the plants. Also, in previous work with 

 pineapples and sugar cane large amounts of stable manure ameliorated 



