150 VEGETABLE FORCING 



Amount of water required. An enormous amount of 

 water is required to grow good greenhouse crops. As 

 previously stated, it enters into the composition of the 

 plants, but most of the water which enters the roots 

 escapes by transpiration from the leaves. There is also 

 rapid evaporation from the soil. Wright, after making 

 a survey of this question in nearly 75 commercial green- 

 house establishments, estimates that the average daily 

 requirement of water during the months of May and June 

 is 280 gallons per 1,000 square feet of bed surface in crops, 

 or over 12,000 gallons to the acre. Expressed in differ- 

 ent terms, 243 gallons of water would be required daily 

 per acre during the months of May and June, and under 

 certain conditions more than that amount might be 

 needed, to meet the requirements of the crops. 



Much more water is required during the late spring 

 and early summer months than through the winter. The 

 heat rays of the sun are then intense, and with the ven- 

 tilators and doors open there is the most rapid escape of 

 water from both the plants and the soil. Again, at this 

 season of the year the days are longer and there is much 

 more sunshine than during the winter months. 



The character of the weather at any particular season 

 of the year is also an important factor. It is readily 

 understood that less water will be required on cloudy 

 days than in bright, sunny weather, and this matter 

 should have the most careful consideration of the grower. 



The kind of crop under cultivation is also an important 

 factor to be considered. Generally speaking, tomatoes 

 and cucumbers require more water than does lettuce. 



Crops which are well advanced or approaching ma- 

 turity, necessarily require more water than young plants, 

 though there may be diminished evaporation from the 

 surface of the beds because they are shaded by the crops. 



Soils which are very open and porous, due to a large 



