Sub-Irrigation 



percolates upward through the soil, affording the roots of the plant a steady 

 supply of moisture. It is upon such lands that the finest crops of celery 

 are grown. 



In many parts of Europe, notably in Holland, and to a small extent in 

 the cauliflower districts near Erfurt, Germany, crops are grown largely upon 

 sub-irrigated land. This is particularly true in the reclaimed districts of 



Sub-Irrigation Benches 



Testing the Cement Tanks for leaks 



Holland, which produce such enormous crops of fine bulbs and such quan- 

 tities of various plants and shrubs. In these districts, which lie beneath the 

 sea level, and which would be overflowed were not the water kept down by 

 a system of pumps in constant operation throwing the water over the 

 dykes into the sea, plants never suffer from lack of moisture, as within a 



