148 HORTICULTURE FOR SCHOOLS 



In a few localities water may be obtained in considerable 

 quantities without pumping, since artesian wells may be 

 secured merely by tapping the underground supply. It is a 

 cheap method of obtaining water but is usually unreliable, 

 for when any considerable number of wells is sunk, the flow 

 is likely to dwindle or cease in all of them. Artesian wells 

 are caused by the water being held in the ground under 

 pressure by impervious strata of soil or rock material; and 

 when this is pierced the water is allowed to escape. If the 

 supply is exhausted faster from the wells than it flows into 

 the underground reservoir, the flow will, of course, soon cease. 



243. Application of water. Water is applied to the 

 ground by flooding, basins, furrows, sub-irrigation, or over- 

 head sprinkling. The method depends primarily on the crop 

 and the soil. Vegetables are frequently grown in beds pro- 

 vided with systems of underground tiles through which 

 water is introduced into the soil. The method is practicable 

 only for crops grown on a relatively small scale or for green- 

 house irrigation, but it is an efficient means of applying the 

 water and it leaves the surface of the ground loose and 

 pliable. 



Sometimes vegetables are grown in beds depressed below 

 the general level of the ground, and are irrigated by flooding. 

 This is on a small scale the basin method of application of 

 water. Sometimes, also, vegetables are grown on narrow 

 flats somewhat higher than the ground level, and are irri- 

 gated by lateral seepage from either side. 



Irrigation by sprinkling has come into extensive use in 

 recent years. Permanent pipes are used, and large areas 

 are watered by the simple process of opening a valve. The 

 method is very successful. The only question is the original 

 cost of installation. 



Orchards are most frequently irrigated by the furrow 

 method. Water is conveyed through a head-ditch along the 

 highest side of the land, and then distributed over the 



