only in the arid western areas, for there it is absolutely 

 necessary. But irrigation to supplement generally ade- 

 quate rainfall is being developed in the humid eastern part 

 of the country. Its benefits in the production of vegetable 

 crops, even where the total annual precipitation is ample, 

 may be summarized as follows : 



(a) To tide over periods of drought which might otherwise materially 

 reduce or wipe out the yield. 



(b) To make it possible, through control of moisture conditions 

 throughout the growing season, to produce a larger yield. 



(c) To secure a better quality of crop by making possible continuous 

 growth, which is essential to high quality. 



(d) To make it possible to apply water at critical periods of growth. 



(e) To obtain a good start for plants transplanted into a dry soil. 



(/) To obtain prompt germination of seed at the time of sowing, 

 especially important in the case of a succession of crops. 



(g) To make possible the preparation of soil which without irrigation 

 would be too dry for plowing or pulverizing. 



(h) To protect especially vulnerable and valuable crops from light 

 frosts by overhead irrigation. 



[7] Swamps, Marshes, and Wet Lands. 



While designed and regulated restoration of the different 

 classes of wet land as a social asset is undoubtedly, because 

 of the scale on which it usually must be done, a responsibility 

 of organized communities, especially the States and the Fed- 

 eral Government, there are many farms on which the owners 

 might advantageously make the beginnings of such restora- 

 tions. On many farms are considerable areas which were 

 once marsh or wet but have been drained dry. While in 

 the greater number of instances fertile, tillable soils have 

 been uncovered, in some other instances the soil has proved 

 to be unsuitable for cropping, even for the preferred forage 

 crops and grasses, and the condition of dryness is unsuitable 

 for the return of the original marsh hays, huckleberries and 

 other natural cover. The stoppage of the drainage outlets 

 of many of these plots would lead to restoration of their 

 natural wetness and encourage the spontaneous reestablish- 

 ment of the grasses and other cover which they would then 

 favor. 11 Marsh hays have some value for pasturage and for 



11 For the dominating importance of health considerations see p. 44. 



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