240 GREENHOUSES 



IRRIGATION.. 



There are two general methods of water- 

 ing greenhouse crops aside from hand water- 

 ing. One is by an overhead sprinkling sys- 

 tem ; the other is by an underground or sub- 

 irrigating system. Of these the overhead 

 system is by far the more popu- 

 lar. A census of a large number 

 of growers of greenhouse vege- 

 tables shows that practically 75 

 per cent, use some form of over- 

 head irrigation, while only two 

 out of the whole number con- 

 sulted were using sub-irrigation. 

 Practically the only system of 

 overhead irrigation used in 

 greenhouses is one in which 

 pipes, fitted with nozzles which 

 Fig. 125 A throw a rain-like spray, are run 



type of nozzle 1 . r - 1 - 



used in over- lengthwise of the house and so 



head irrigation arrange( J that they may be rotat _ 



ed to throw the spray on both sides of the pipe 

 line. The original system is known as the 

 Skinner system, but there are others now 

 on the market. Pipe lines for this system 

 should be about 16 feet apart and as far from 

 the foliage as possible. The nozzles should 

 be 3 feet apart. This system will operate 



