CHAPTER XVII 



Sub-Irrigation 



ABOUT the year 1890 the attention of florists was aroused by a new 

 method of watering greenhouse plants grown in benches, which was 

 originated by the Ohio Experiment Station, and called "sub-irriga- 

 tion." Various modifications of the original system have been evolved by 

 other experiment stations, chiefly those of Wisconsin, New Hampshire, and 

 Indiana. Briefly described, this system consists of introducing water under 

 the soil, either by the use of porous tiles laid at intervals throughout the 

 soil, or by constructing the bench so as to form a shallow, water-tight tank, 

 in the bottom of which are placed porous tiles of various forms ; the prin- 

 ciple in each case being that these tiles form a number of canals, through 

 which water is introduced to the bottom of the bench, under the soil, and 

 is absorbed by the tiles, and passes upward and evaporates through the sur- 

 face of the soil by capillary attraction. This method of watering plants 

 has been vised to some extent by the forcers of vegetables with con- 

 siderable success. It seems to be gradually gaining ground and coming 

 steadily into use, although its universal adoption will be very much hin- 

 dered by the large expense attending the construction of practical sub- 

 irrigation benches. 



Sub-irrigation exists in a state of nature wherever water is either stand- 

 ing or moving underneath the soil ; and it also takes place at the banks of 

 rivers or streams by the percolation of water upward through the soil by 

 capillary attraction. It is probable that a considerable percentage of the 

 fertility of river bottoms, or of lands lying along, and contiguous to, constant 

 streams of water, is due in some measure to the steady source of moisture 

 furnished the adjoining soil by capillary attraction, herein named sub-irriga- 

 tion. 



The success of the growers of celery in the famous celery districts of 

 Michigan is due in a large degree to sub-irrigation, as the best celery grounds 

 are reclaimed swamps, or low lands lying along creek bottoms, which have 

 within a few feet underneath the surface a constant flow of water, which 



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