102 



IRRIGATION PRACTICE 



make the draft of the plant upon the soil so small as to 

 extend greatly the productive power of the soil. 



73. Physical effects of sediments. The physical 

 effects of the addition of river silts to the soil are not, 

 however, always uniformly beneficial. On a sandy soil, 

 the river silts usually bind the soil together and make it 

 more firm, of better water-holding power and of easier 



FIG. 22. Deposit in field of suspended matter from irrigation water. 



cultivation. On a heavy clay, if the river sediment is of 

 a loamy character, the clay is mellowed and lightened 

 and, therefore, improved. However, if the silt is very 

 fine or of a clayey nature, its application to a clay soil 

 or even to a loam soil might be disadvantageous, because 

 of the finer texture that it would produce. Herein lies 

 the danger in using irrigation water that carries consider- 

 able quantities of suspended matter. River mud is usually 



