PRECAUTIONS IN IRRIGATION 237 



3reated. It has been noted (page 204) that in arid 

 -egions soil mulches are relatively more efficient and 

 more easily managed than in humid regions. 



Soils of intermediate fineness lend themselves most 

 eadily to the practice of irrigation. Excessively heavy 

 ;lay is generally to be avoided, because of (a) the slow 

 liffusion of water, by both capillarity and percolation, 

 mtl (b) the danger from puddling after an irrigation, 

 inless cultivation is delayed so long that a large amount 

 ->f water is lost. On the other hand, very light sand should 

 )e avoided because of its leachy character, and the great 

 oss of water by percolation or surface evaporation, 

 ,he former, if a large amount of water is added at once; 

 /he latter, if it is added very frequently. 



But in humid regions it is wise to practice irrigation 

 'or crops easily injured by an excess of water except on 

 ;hose light and porous soils which have thorough 

 Irainage, because of the possibility of a rainfall following 

 closely upon the application of water, thereby rendering 

 he soil over- wet, to the injury of the crop. On the porous 

 Soil the excess quickly drains away. In the Sumatra 

 -obacco region of Florida, for example, where there is a 

 arge rainfall, irrigation has been found successful only 

 lpon the lighter sandy loam and sand soils. This crop 

 s particularly sensitive to an unfavorable soil condition, 

 rhen too, the heavy soil, the clay loam, or clay, has a 

 arge water capacity, which makes possible the storage 

 )f a large amount of water against the needs of the crop- 

 growing season. Consequently it is on these latter that 

 lry farming of grains is most generally practiced in the 

 iiVestern states. 



