44 DRY LAND FARMING 



that may or may not be farmed on the dry farming plan, 

 that each of the factors named exercises an important 

 influence on production. But it must be conceded, never- 

 theless, that the actual amount of the normal precipita- 

 tion is the most potent influence in production in dry 

 areas. Where the precipitation is below a certain 

 amount, dry farming cannot be practised, though all the 

 other considerations mentioned should be satisfactorily 

 present. 



The precipitation that will grow a good crop of grain 

 depends: (1) on the preparation that has been given to 

 the land ; (2) on the season at which the precipitation falls 

 as well as on the amount of the same ; (3) on the extent 

 of the evaporation ; (4) on the temperature, and (5) on the 

 soil. Of these influences the preparation that has been 

 given to the land is the most important. If moisture 

 has not been properly stored in the soil and subsoil, and 

 a dry season follows, the favorable influence that may 

 be exerted by all the other agencies combined will not 

 insure a crop even under semi-arid conditions. Much less 

 will these insure the same under arid conditions. It is 

 very evident, therefore, that the amount of the precipi- 

 tation alone does not determine the capacity of the land 

 to grow crops in these areas. 



It is also evident that the amount of precipitation 

 that will suffice to grow a crop in one locality may not 

 grow the same in another. Without knowing all the at- 

 tendant conditions it is not possible to determine the 

 amount of precipitation that will suffice to grow a good 

 crop. It would seem safe to say, however, that on the 

 parallel 45 north latitude a good crop of wheat may be 

 grown on an annual precipitation of 6 to 8 inches on care- 

 fully summer-fallowed land, providing it has been sum- 

 mer-fallowed for one year. On an annual precipitation 

 of, say, 12 to 15 inches, good crops of certain kinds of 

 grain may be assured on properly summer-fallowed land. 



