46 



been observed by Parr 1 and Friedersdorff 2 that crops 

 on drained land are improved by opening both ends of the 

 tile-drain lines to the atmosphere, thus increasing 

 air circulation in the drain-pipe. This improvement 

 may be due to increased soil aeration but such a rela- 

 tion is not immediately obvious. Indeed Mitscherlich 3 

 has pointed out that soil-aeration is not likely to 

 be increased very greatly for the reason that the 

 drain-tile is usually wet and impermeable to gases ex- 

 cept by solution in, and diffusion through, the pore- 

 water of the tile. 



If there is uncertainty as to the real cause 

 of the cultural benefits usually ascribed to soil 

 aeration, there is still less reason to regard this 

 evidence as importantly supporting the usual assumption 

 of the need of aerobic root respiration. It is quite 

 possible that adequate soil aeration might be a cul- 

 tural necessity even though all roots were fully capa- 

 ble of anaerobic respiration. Among the most important 

 reactions of the soil on plant life are those due to the 

 chemical nature of the soil solution and those due to 

 the nature of the microflora and fauna of the soil. 



1. Agr. Jour. India 7: 371-372 (1912). 



2. Deut. landw. Presse 39: 483-485, 493-498 

 (1912). 



3. Bodenkunde, 2nd ed. p. 248 (1913). 



