WATER OF SOIL IN ITS E ELATION TO PLANTS 258 



the distances through which this movement may be 

 effective in properly supplying the plant.^ It must be 

 understood, however, that the rate of water supply is 

 the controlling factor in plant nutrition. It has been 

 shown also that the longer the capillary column, the less 

 is the amount of water delivered from a water table to 

 any given point. Therefore capillarity, although it 

 may act through a distance of ten feet, may be important 

 for only three feet as far as plant nutrition is concerned, 

 since water beyond that point is moved too slowly to be 

 of any great value in time of need. No rehable data are 

 available as to this particular phase, but the knowledge 

 of the factors governing capillary movement clearly 

 indicates that capillarity of the soil is of greatest im- 

 portance in a restricted zone immediately around each 

 absorbing root surface. 



176. Influence of water on the plant.^ — In general, 

 as the amount of water available to a crop is increased, 

 the vegetative growth also is increased, the plant be- 

 coming more succulent. The percentage of moisture in 

 the crop, even at harvest time, is usually high. Quality 

 practically always suffers with such a stimulation of 

 vegetative activity. This is especially noticeable with 

 such crops as barley and peaches. Shipping qualities 

 also are depressed with increased water, especially if 

 the water available is excessive. With an enlargement 

 of the plant cell a change probably occurs in the cell 

 contents, tending toward a greater susceptibility to 

 disease. Ripening is delayed, tillering is diminished, 



1 Warington, R. Physical Properties of Soil, p. 105. Ox- 

 ford. 1900. 



2 Mitscherlich, B. A. Das Wasser als Vegetationsfaktor. 

 Landw. Jahr., Band 42, Seite 701-717. 1912, 



