1 HE IRRIGA TION A GE. 327 



the surface, which lessens the need of surface cultivation, and when 

 the vegetables are well grown obviates the decay which comes to fol- 

 iage by contact with a moist surface. The same is true of the use of 

 raised beds for strawberries when grown on the heavier loams or when 

 the light, shallow loams overlie hardpan and require frequent irriga- 

 tion. 



Another very important advantage of the raised bed lies in its 

 adaption to growth of vegetables and strawberries during the rainy 

 season of semi-tropical climates. Not only is the raised bed more re- 

 sponsive to the greater warmth which comes to the air at intervals, 

 and consequently promotive of winter growth of vegetables, but it al- 

 so escapes the supersaturation which long rains may occasion. The 

 deep ditches then act as opon drains for the escape of surplus water. 

 The system would seem to be widely available where there exists 

 both the need of irrigation and the danger of excessive rainfall, ac- 

 cording to varying weather conditions. 



SUBIRRIGATION AND UNDERFLOW. 



Subirrigation is the application of water under the surf ace by a 

 system of conduits. It has received so much thought and outlay and 

 has returned so little satisfaction that it must be looked upon as a 

 horticultural ignis fatuus, and only a passing reference need be given 

 to it. Various available publications 1 describe its different phases. 

 It seems fair to conclude that satisfactory growth is secured with less 

 water by subirrigation than by surface distribution, but it is done at 

 an outlay which is unwarranted either by the cost of water or by the 

 value of the crop. Results of greenhouse experiments are more satis- 

 factory than those from open-air work. Even if even distribution 

 could be had from any arrangement of underground pipes, which seems 

 doubtful in view of wide experience, it still remains true that for 

 shallow- rooting plants in open soils the water is applied at too low a 

 level. It also appears that the escape from the surface cultivation is 

 of doubtful advantage, contrary to the claims of advocates of subirri- 

 ation, and that thorough surface stirring, which is an indispensable 

 accompaniment of surface irrigation, is worth all it costs through the 

 superior thrift which it induces. It seems a fair conclusion from pre- 

 ent knowledge that subirrigation is practically unattainable because 

 of cost, inequality of distribution, etc., and possibly would be unde- 

 sirable even if these prohibitions were removed. 



Underflow irrigation is quite different from subirrigation, though 

 the former often goes in local parlance as "natural subirrigation." 



^ubwatering in Greenhouse, Farmers' Bui. 78. Irrigation in Fruit Grow- 

 ing, Farmers' Bui. 116. Surface and Subirrigation Out of Doors, New Hampshire 

 Sta. Bui. 34. 



