RECLAMATION OF ARID LANDS NEWELL. 179 



giving all the necessary elements required for the growing crop. 

 This, however, is true in part only. The soils of Egypt for best 

 results must be fertilized by supplying the lack of some of the ele- 

 ments of plant food not brought by the Nile. 



As a matter of fact, irrigation can not take the place of cultivation, 

 and it is not a lazy man's form of agriculture, but quite the reverse. 

 Cultivation may take the place of irrigation to a certain extent, and 

 it has been found that thorough cultivation reduces the need of 

 water, but neither cultivation nor application of muddy waters will 

 bring to the soil all the needed constituents which must be had to 

 obtain the largest and best growth of plant or "fruit. 



During the first few years the crop returns from the formerly un- 

 worked soil are frequently large, but to preserve the valuable quali- 

 ties experience has shown that some of the constituents of the soil 

 must be conserved and others added. In other words, it is impos- 

 sible to take large crops away from the fields year after year unless 

 the necessary food is supplied to the plants. The successful irrigator 

 must not only cultivate his fields, apply water sparingly, but must 

 fertilize, supplying those materials which experience has shown are 

 most beneficial to the crops. He should strive to retain or renew in 

 the soil the useful constituents placed there by nature and supplement 

 these where needed. 



Most' of the soils of the arid region contain a large proportion of 

 soluble mineral salts. The rains have not been sufficient to wash 

 these entirely away and they remain fairly uniformly diffused 

 throughout the soil. Some of these salts are extremely valuable as 

 plant food, but if at any point in the field they are in excess, there 

 plant life is destroyed. The chief deficiency among these, however, 

 appears to be in the phosphates. It is sometimes essential to supply 

 this lack, even though there is a large quantity of the salts of soda 

 and potash. 



The problem of obtaining the phosphates should not be a very 

 difficult one as throughout the arid region are large deposits of the 

 rock carrying the necessary supply and the smelters or other in- 

 dustries, as a by-product, can produce unlimited quantities of the 

 acids necessary to put this phosphate into soluble or accessible form. 

 The development of the industry has, however, not proceeded to a 

 very notable degree, because of the slowness of the farmers to recog- 

 nize the fact that fertilizers of this kind are valuable and the fear 

 that, if it is generally known that fertilizer should be used, this will 

 add to the discouragement of the new farmers. 



ALKALI. 



The excess of what is otherwise a valuable fertilizing element is 

 also a matter which must be of serious concern. The natural salts. 



