14 DRY LAND FARMING 



with the dews are heavy and the air is moist. The rain- 

 fall is frequently so excessive that drainage in one form 

 or another must be given the most careful attention by 

 those who till the soil. In such areas the precipitation 

 is 27 inches in the year and upwards. In some maritime 

 areas it is as much as 70 inches and upwards. Where 

 the precipitation is very heavy the loss to the soil in 

 fertility through leaching is considerable, and the remov- 

 al of soil by denudation is quite frequently very serious. 

 Notwithstanding, in nearly all even of the areas that are 

 humid there is a dry season in which the crops may suf- 

 fer in the absence of measures to protect the moisture, 

 that is, in the absence of some of the operations that 

 apply in tilling semi-arid areas. 



The influences that affect aridity. Foremost among 

 the influences that affect aridity is the amount of the 

 precipitation. When this is too low for successful crop 

 production under the conditions present, no matter how 

 favorable the other qualifying influences are, the effort 

 to grow paying crops must fail. These qualifying influ- 

 ences include: (1) the character of the precipitation; (2) 

 the season of the same ; (3) various influences that affect 

 moisture evaporation, and (4) those which affect filtra- 

 tion and the leaching of moisture in the soil and sub- 

 soil. Because of these qualifying influences, the results 

 to be expected from a given amount of precipitation 

 cannot by any means be definitely forecasted. They will 

 vary greatly. The amount that would suffice to produce 

 a given result in one instance would be wholly inade- 

 quate in another instance, and yet it would seem safe to 

 make the statement that crop production would be vir- 

 tually quite safe and remunerative where the , rainfall 

 is not less than 15 inches on ordinary soils, and that it 

 should be generally safe and remunerative where the 

 rainfall is not less than 9 to 10 inches. These statements 

 are based on experience and observation. Where the 



