56 



Journal of Agricultural Research 



Vol. XX, No. i 



soil adapted to its growth. Each pot received 9 gm. sulphate of potash, 

 6 gm. double superphosphate, and 22.5 gm. sulphate of ammonia divided 

 in two applications. Twenty rice plants were planted in each pot, but 

 these were thinned to 10 when growth was well established. The results 

 are given in Table XIII. 



Table XIII. — Effect of varying degrees of moisture on the availability of iron to rice 

 plants in calcareous and noncalcareous soils 



Maxi- 

 mum 

 water 

 capac- 

 ity of 

 soil ex- 

 pressed 

 as per- 

 centage 

 of dry 

 weight 

 of soil. 



Amount 

 of soil 

 per pot. 



Amount of water main- 

 tained in soil during 

 growth of plant. 



36. 2 



Pounds. 



69 ! 



69 



22.3 per cent 



26.3 per cent 



30.3 per cent 



34.3 per cent 



Water at surface of soil. 

 Water 3 inches above 



surface of soil 



20.2 per cent 



24.2 per cent , 



28.2 per cent 



32.2 per cent 



36.2 per cent 



Water 3 inches above 



surface of soil 



1 1 per cent 



18 per cent 



25 per cent 



Water 3 inches above 



surface of soil 



Oven-dried yield of plants 

 per pot. 



Aver- 

 age. 



Gm. 



U5-3 

 124.4 

 137-6 

 137-6 

 160.4 



163.8 

 55-7 

 74-3 

 67.8 

 69- I 

 79-3 



123.3 

 10.5 

 11. 1 



4.0 



18. 1 



The different water contents maintained during the experiment were 

 made up when the plants were 4 days old, except that the pots to receive 

 3 inches excess water were made up with water at the surface at this 

 time, the water being raised to 3 inches when growth permitted it. 

 When n days old, the plants in soils No. 1647 and 1648, where water 

 was at the surface or above it, were markedly chlorotic, as well as all 

 the plants in soil No. 1194. After 31 days' growth, all the plants in soil 

 No. 1 1 94 were still markedly chlorotic; the submerged plants in soil No. 

 1647 were normal green and were growing rapidly, as were all other plants 

 in this soil; in soil No. 1648 the submerged plants and those in pots with 

 20.2 and 24.2 per cent water were normal green, while those in pots with 

 28.2, 32.2, and 36.2 per cent water were plainly chlorotic. At 72 days' 

 growth, when the plants were cut, the appearance in regard to chlorosis 

 was similar to that at 31 days, except that in soil No. 1 194 the few plants 

 that had not died in the pots with 3 inches excess water were normal 

 green and far larger than the others. 



The temporary chlorosis affecting the plants where the excess water 

 was added is entirely distinct from the lime-induced chlorosis. A similar 

 yellowing takes place in the field when the fields are flooded following 



