Oct. i, i 92 o Cause of Lime-Induced Chlorosis 55 



and thickness of the films depending somewhat on the amount of moisture 

 in the soil. The substances in solution in a film surrounding one particle 

 will therefore react with those in films surrounding adjacent films. One 

 particle of carbonate of lime would affect the soluble iron in the films of a 

 certain number of adjacent particles. 



While the moisture films are to a certain extent continuous, we know 

 that the composition of the films is not uniform throughout the soil. 

 This is evident from certain well-established facts, such as the slight 

 lateral movement of fertilizers. If the composition of the films were 

 uniform and conditions were analogous to those in a solution with rela- 

 tively few solid particles, a slight amount of carbonate of lime would 

 have the same effect as a much larger amount. This, however, is not 

 the case. 



It might be expected that the effect of carbonate of lime in depressing 

 the availability of iron and in inducing chlorosis would be influenced 

 somewhat by the amount of water in the soil, since the aggregation of 

 the soil particles and their moisture films would be affected by the water 

 content. It was, therefore, of interest to observe the manner in which 

 the growth and chlorosis of rice would be affected by different percentages 

 of moisture in calcareous soil. 



A preliminary test was conducted with four pots, each of which held 

 36 pounds of soil containing 15 per cent of calcium carbonate. Twelve 

 rice plants were grown in each pot with abundant fertilizer. The plants 

 were grown 30 days with 22 per cent of moisture in the soil. Water was 

 then added to two of the pots until there were 2 inches of water above 

 the surface of the soil, and the other two pots were maintained unchanged 

 at 22 per cent moisture. After 67 days' growth the plants were cut. 



The plants in all four pots were very slightly chlorotic at 30 days, but 

 a few days after the extra water was added the submerged plants became 

 intensely chlorotic and remained so for about 10 days. They then 

 quickly improved in color, and a few days later the submerged plants 

 were a perfectly normal green, while the plants in the soil with 22 per 

 cent moisture were markedly chlorotic. This difference persisted until 

 the plants were cut. The plants grown for the whole period with 22 per 

 cent moisture gave an average green weight of 175 gm. per pot, while 

 the plants grown for 30 days with 22 per cent moisture and then sub- 

 merged for 37 days yielded 424 gm. per pot. 



Experiment X. — An extended test was conducted from January 2 to 

 March 22, 191 8, using one noncalcareous soil and two calcareous soils 

 (one a beach sand with practically no organic matter and the other a 

 loam) ,* The noncalcareous soil was used as a control to determine how 

 the growth of rice would be affected by different amounts of water in a 



1 The calcareous loam was the same as the noncalcareous soil except for the addition of the carbonate 

 of lime some years before. 



