54 IRRIGATION PRACTICE 



The chief protection against the great losses immedi- 

 ately after irrigation and before cultivation is possible, 

 is a loose, spongy top soil that absorbs the water the 

 moment it is applied and permits it to soak deeply into 

 the soil away from the immediate action of the sun's 

 rays. Occasionally it may be profitable to scatter a 

 mulch of some kind over the soil, immediately after an 

 irrigation, but this is of extremely limited application. 

 If water is applied by sub-surface methods this pre- 

 cultivation loss may be prevented, but sub-irrigation is 

 seldom profitable except in districts were natural sub- 

 irrigation is feasible. 



The soil should be cultivated just as soon as it is pos- 

 sible to do so after an irrigation, without doing injury to 

 the soil. If cultivation is performed too soon after irriga- 

 tion there is danger of leaving the top soil puddled or 

 in an otherwise undesirable physical condition for plant- 

 growth. By too early cultivation a soil may be perma- 

 nently injured for the season or even for several seasons. 

 The farmer who cultivates too early, and thereby leaves 

 the top soil in a poor physical condition, ultimately loses 

 more than does he who permits evaporation to go on a 

 day longer, to make sure that the soil is in the right con- 

 dition for cultivation. Whenever the soil is dry enough 

 to support the man and horse with the cultivating tool, 

 it is usually safe to begin cultivation. 



On the other hand, it must be said that, in the great 

 majority of cases, the farmer permits evaporation to go 

 on many days after the time of safe cultivation has been 

 reached. Few fields are injured from too early cultiva- 

 tion. Over the whole irrigated area, the farmers have 

 looked upon cultivation as an incidental matter, because 

 they have not realized the tremendously large quanti- 



