DRY FARMING CONGRESS. 



325 



Although the practice of fallowing land is almost as old as agricul- 

 ture itself, its extensive use to conserve soil moisture and to permit crop 

 growth in arid regions has not been so generally used until recent years. 

 It seems not to have been realized that the soil is capable of acting as a 

 storage reservoir for water when proper tillage is used, and that under 

 favorable circumstances enough moisture to mature an ordinary annual 

 crop can be stored in the soil before the crop is planted. Even if this 

 fact had been appreciated, it was not practicable to put it into general 

 use until farm machinery capable of cheaply getting the soil into proper 

 condition was devised and constructed. 



So far as American agriculture is concerned, effective summer fal- 

 lowing became possible only with the invention and general use of the 

 disc harrow. This implement, together with the plpw and the ordinary 

 smoothing harrow, makes an equipment cheap enough to be available 

 to every farmer, and efficient enough to make tillage for moisture con- 

 servation entirely practicable. The highest development of summer fal- 

 lowing for moisture conservation has probably been obtained, in this 

 country at least, in the region west of the Rocky Mountains. In all this 

 region, the greater part of the annual rainfall comes during the autumn, 

 winter and earl}^ spring months, when evaporation is at its lowest point, 

 and the greatest penetration of the rain into the soil is possible. Under 

 these conditions, a thorough summer fallow, established as soon as possi- 

 ble after the spring rains have ceased, can be cheaply maintained through- 

 out the summer and is wonderfully efficient in preventing evaporation 

 of water from the soil. 



Although it has been a well known fact for many years that a well 

 maintained surface mulch is very efficient in preventing evaporation of 

 water from the soil, definite facts as to just what this efficiency is are 

 extremely rare in our agricultural literature. Within the past two or 

 tliree years, however, experiments have been undertaken in a number of 

 places to ascertain just what this efficiency is under various conditions, 

 and we may now hope in the course of a few years to have a body of 

 knowledge on this subject from which to make deductions and upon 

 which to make generalizations. 



For practical purposes, however, it is sufficient to know that where 

 the annual rainfall conies during the colder months of the year, it is 

 possible to use a system of summer fallowing, together with growing 

 crops on alternate years, that will secure p'aying crops where the rain- 

 fall is altogether too light to permit farming without irrigation with the 

 ordinary cultural methods. 



It must be kept in mind that the best use and highest development 

 of summer fallowing and alternate year cropping is only possible where 

 the rainfall is largely concentrated in the cooler months. Where the 

 rain comes at frequent intervals during the summer months, the main- 

 tenance of an adequate surface mulch to retain this moisture is both 

 difficult and expensive. It must be remembered that there are some 

 conditions under which summer fallowing, together with alternate year 



