SOILS. 



19 



been impossible for any large amount of organic matter to accumu- 

 late. The aridity of the climate has not permitted a heavy growth 

 of vegetation and has hastened the burning out of the decomposed 

 matter. No large quantity of organic matter is usually present, 

 much less than is found in soils of humid sections.^ There is, how- 

 ever, in all the better soils of the region, where the rainfall is 15 inches 

 or more, sufficient humus and nitrogen to produce a number of large 

 crops. As yet the question of fertility has usually not entered into 

 the problem of crop production in the semiarid region. The amount 

 of moisture has not been sufficient to enable the farmers to use the 

 fertility present. Lack of moisture has been the one problem. The 

 writer does not say that if general farming becomes successful and 

 well established fertility will not very soon become a problem or that 

 it might not now be a problem if an abundance of water were avail- 

 able, but that in the past lack of moisture has been the one limiting 

 factor. Under the heavy cropping of irrigation farming, fertility has 

 in many sections become a problem within a very few years after 

 breaking the sod. In fact, in some of the more arid regions more 

 organic matter is needed from the start, as at Wheatland, Wyo. 

 Any system of agriculture to be permanent must provide for the 

 maintenance of the fertility of the soil, but in the territory here dis- 

 cussed the average farmer has not learned how to exhaust this, 

 so its maintenance does not give him any immediate concern. The 

 problem now at hand for the average farmer is to learn how to use 

 profitably the fertility already present and how to produce crops 

 with the limited amount of water received. When this is done, 

 when he lias learned how to utilize the native fertility of the soil 

 under the prevailing climatic conditions, then attention may well be 

 given to soil maintenance and improvement. It is altogether proba- 

 ble, however, that the addition of humus would so change the water- 

 holding properties of the soil as to enable a crop to be produced with 

 less rainfall. 



The large crops produced in wet seasons and the large crops grown 

 under irrigation all attest the value of the soil. The size of these 

 crops is probably due in no small measure to the very dryness of the 

 climate, contradictory as this may seem. 



A severe and long-continued drought ^ usually leaves the soil in excel- 



lent shape for a crop the following season, indicating that a complete drying out of 

 the soil for a prolonged period brings about beneficial changes in the soil. Indeed, 

 in keeping soils of poor or average fertility in an air-dry condition in the laboratory 

 for several months they are usually found more productive when tested with plants 

 again. ^ 



1 Bulletin 55, Bureau of Soils, pp. 27 and 28. 

 215 



2 Bulletin 55, Bureau of Soils, p. 63. 



