TRANSPIRATION 



91 



a normal rainfall a profitable crop will result in an average 

 year. 



Plants should be watered copiously but not frequently in 

 order that the water may soak some distance into the soil to 

 supply the deeper roots as well as the shallow ones. Most 

 soils respond more quickly and yields are increased more by 

 keeping optimum water content than by any other factor. 

 Since deep roots grow most readily through the air-filled 

 spaces in the soil watering should be delayed for most plants 

 until the available water has been depleted or until they 

 begin to wilt during the hottest part of the day. Many 

 plants will yield more and better flowers and fruit if allowed 

 to reach a low soil moisture for short periods. 



As explained in Chapter 7 water penetrates the soil only 

 as the field capacity is reached in the soil above. The most 

 economical way to water is to bring a considerable depth of 

 the soil to field capacity, because the roots grow more rapidly 

 in optimum conditions of moisture and air. Frequent light 

 watering encourages the growth of a poor root system of 

 shallow roots. A plant should have a root system in contact 

 with a large volume of soil to supply water and mineral food 

 (see Fig. 8). Most soils should have an inch or more of 

 water applied at a single application, following which the 

 plants should need none for a week. It is more economical 

 of water to apply it copiously but less frequently than to 

 water every day, since less is lost in evaporation. 



REFERENCES 



Maximov, N. A., The Plant in Relation to Water, Edited by R. H. Yapp, George Allen 



and Unwin, London, 1929. 

 Meyer, B. S., and D. B. Anderson, Plant Physiology, D. Van Nostrand Co., Inc., 1939. 

 Wilson, C. L., and J. M. Haber, Plant Life, Henry Holt and Co., 1935. 



